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Last update Jan 10 2016 This AskSam database has three main indexes:

GEOLOGY INDEX   - an alphabetical listing of geological topics of interest to me, e.g. GIS; Gold.....

People                  -  geological contacts grouped according to University or Country or topic,

e.g. Appalachians, Caledonides....

TECTONICS and other topics  -  an alphabetical listing of Tectonic topics, e.g. Cordillera, Pan-African.....

Prof. W.R. Church's geologic database:

http://instruct.uwo.ca/earth-sci/fieldlog/ -  pdf, jpg, dwg, txt, etc files

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FAQ   Temp_Geology    Chronostratigraphic chart = c:\fieldlog\chronostratchart2012.pdf

Time scales   Geological Time Scale - http://instruct.uwo.ca/earth-sci/300b-001/cordtimescale.jpg

http://johnbetts-fineminerals.com/jhbnyc/referenc.htm - mineral listings with chemical formulae

Documentation_Maps

Current topics:  converting Android Google lollipop_back_to_Kitkat

Anthropogene/Anrhropocene   Correspondance re Global Warming

Publications-WR Church   Dad geology   Personal_HISTORY   Jordan_Laarman

Riccio_Bay_of_Islands    Sharpe_Thetford      Nexus_Maps     Thesis Regulations

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Ontario Geological Survey

Ontario Digital maps    Paleozoic Ontario   Ontario OGS

Ontario Ministry of Northern Development and Mines - http://www.mndm.gov.on.ca/en

http://www.mndm.gov.on.ca/en/mines-and-minerals/applications/geologyontario - Geology Ontario data

files

Geological Society of America

http://community.geosociety.org/home - GSA 'My Connected Community'

http://community.geosociety.org/communities/community-home?CommunityKey=5485bcb6-4859-402d-9283-d85ee36ccb4c - Climate Science Group

http://community.geosociety.org/communities/community-home?CommunityKey=854eb289-f0f9-4cd2-a91b-67ddb18362ac  - Open Forum

Structural Geology & Tectonics Division featured essay schedule for 2013

Essays will be published on GSAs Speaking of Geoscience blog on the 28th of each month.

"Speaking of Geoscience blog =  http://geosociety.wordpress.com/

http://www.geosociety.org/ - Geol Soc America  GSA Fellow name = # 1156554 ; pwd = Church

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Institutional Teaching and Research at UWO

http://uwo.ca/earth/ - website of the UWO Earth Science department

Prof. W.R. Church's database:

http://instruct.uwo.ca/earth-sci/fieldlog/Asksam/Geology.htm - this asksam database as an on-line htm file (asksam documents are represented as items in a single htm file.)

http://instruct.uwo.ca/earth-sci/fieldlog/ -  pdf, jpg, dwg, txt, etc files

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/   -   to .../fieldlog/cal_napp = location of pdf and jpg files

specifically related to Appalachian Geology

2nd year Field Camp, Whitefish Falls

http://instruct.uwo.ca/earth-sci/fieldlog/aaGE/Southern_Province/Whitefish_Falls/Plane-Table_Lake/ -

kmz files relevant to the 250y Field Camp mapping area at Plane Table Lake. The file PTL.kmz is the       generalized kmz (maps, waypoints, photographs) suitable for viewing on Microsoft computers (XP, 7, 8),       whereas the file aPTLphotos.kmz contains a map image of the road-side diabase locality at Plane Table Lake       along with a set of photographs attached to waypoints marking localities with information pertinent to the       tectonic/structural/impact history of the area. To be viewed in Windows the files can be downloaded to the local       computer or run directly from the 'instruct' site, whereas in Android systems the files can be run directly from the 'instruct' site.  To download and view the PTL.kmz file in Google Earth running on a Windows machine:

a), right click on the PTL.kmz file and select 'Copy link address'. e.g.

http://instruct.uwo.ca/earth-sci/fieldlog/aaGE/Southern_Province/Whitefish_Falls/Plane-Table_Lake/PTL.kmz -

To run the kmz directly from the 'instruct' site,  right click on the PTL.kmz file and select 'Open link in new window' -> click Save -> your Browser window appear and Google Earth and the kmz file will load. (The first time this is done you may have to signal 'Open' in the bottom left download box.)

On an Android tablet, e.g.  go to:

http://instruct.uwo.ca/earth-sci/fieldlog/aaGE/Southern_Province/Whitefish_Falls/Plane-Table_Lake/

and simply click the kmz file.

There are other Whitefish Falls kmz files at:

http://instruct.uwo.ca/earth-sci/fieldlog/aaGE/Southern_Province/Whitefish_Falls/ and

http://instruct.uwo.ca/earth-sci/fieldlog/aaGE/Southern_Province/  for the Southern Province in general.

UWO Library

Library off-campus access - need to logon and first go to the Catalog and then select ONLINE resource

Call numbers    On-Line Journals

Geo-Tectonics Newsgroup Archives

http://www.jiscmail.ac.uk/lists/GEO-TECTONICS.html   -  Geo-Tectonics

http://judithcurry.com/    - Climate_etc, Judith Curry

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Askam data files not accessible online:

Monique_Toshiba    Snug_Toshiba

C:\ directories : Church-3     Asus_EEE   C:\-local

OCR documents are saved by Epson to CHURCH-3 (not available on line)

C:\Documents and Settings\churchlap\Application Data\EPSON\Smart Panel\ScanImg\mailfile

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Do's and Dont's

Don'ts: Snark; Partisan hackery; Ethnic pride; Political Correctness ; Ostentatious appeals to authority;

Obnoxious appeals to expertise; Specialization tunnel-vision; Social constructionism.

Cite facts others can check; Always wonder "what-if I am wrong"; Consilience (act of concurring);

Methodological naturalism.

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THU 11/18/2004 07:45 AM  key[ index ]

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Click to go to the index  Tectonics and other topics

GEOLOGY OF NORTH AMERICA - http://instruct.uwo.ca/earth-sci/300b-001/300outlold.htm

Recent - reply from lee   Melezhik aerobic biosphere

1.44 diskettes

250y

350y

aaGE

aawhere?_UWO_Folder_locations    -   Norm's room 48

Analyses

Anthropogene

Arabian Journal of Geoscience

Australia     Australia_isotopes

BGS  British Geological Survey

Cairo University

Chemistry

Chromite Chromitite  Riccio  Sharpe

Climate change_Global Warming_Atmosphere

Computers_Geology

Conferences

Consulting - Round Table Group

Continental Drift - History of Plate Tectonics   Cont_Drift_Sea_floor-Spreading_Hess_Dietz_DuToit

Cosmology - Astrophysics

Courses   200 300

Diamonds

Dinosaur_extinction

Drawing software  Inkscape_Irfan_Photodraw

Dropbox

Earth_Science_Dpt  Geology

Earth Systems - Tectonics, Earth Chemistry

Environment

Equipment Inventory

Evernote

Evolution/Origin_of_Life

Experimental

Fieldlog       C:\fieldlog

Field Trips/Guides (Norm's Lab)  250y    350y     UWO_Field_Trips (= Norm SWUSA)

Finnigan_Kaminak

First Nations

Foreland Basins

Foreland basins_Tectonics

Fracking

Geography

Geological_Society_of_America (GSA)

Geological Survey of Canada - Geoscan Search

Geology Earth_Science_Dpt

Geophysics (Sanchez)

Geosphere (New GSA electronic journal)

GIS   GPS   GSA Meetings Cartography

Global Warming_Atmosphere   science geology environment environmental_links global warming atmosphere

Gold

Goldschmidt Conference_2012

Historiography    -   boninites    History of Plate Tectonics

IUGS

Jim Renaud

Kompozer

Life - paleontology

Kimberlites

Mantle

Mapping

MapTrack

Meetings

Mendeley

Metamorphism

Meteorites - Impact structures  (Ludovic)

Microscope_camera_1025

Minerals  http://johnbetts-fineminerals.com/jhbnyc/referenc.htm - mineral listings with chemical formulae

Mineral Deposits

Miscellaneous

MORB

Nexus 7 2nd Generation  For a primer on the use of the Nexus 7 in association with Google Maps, Google

Nickel_Olivine Olivine-Ni

Norm folders_Suffel

Ocean_crust-ophiolites - Plate Tectonics

Oil and Gas

Olivine-Ni

One_Geology

OneNote

Ontario Digital maps; Berdusco; Paleozoic

Ophiolites - see Ocean_crust-ophiolites, and MORB

Origin of the Earth   chondritic iron core and oxygen

Paleontology

Panther permissions Unix

Papers_Discussions personal\home

Pazner

People

Photographs   - record of geology  photos in geolphotos.ask

PHOTOS IN CAROUSELS and Books

(=-photo.ask) - for  Egypt 1980, Egypt 1981, Egypt 1988, and Brazil

Plate Tectonics - see Ocean_crust-ophiolites    History of Plate Tectonics

Plotting software

Powerpoint

Printer_scanner_Earth_Science

Projector, digital

Quebec

References, Geology - also, Geology_general in main index

References, Panafrican - also Geology_Panafrican in main index

References, Students

ResearchGate

Samples

SeaMonkey - HTML editor

Sedex

Steve_Johnston

Student seminars

Teaching  Wayne State University

Temporary

Theses

Thinsections / Photography)

Time scales

Trespass_Staking

USB - SDXC cards

Volcanism

Wales_Mining (Great Orme Cu; Dolaucothi gold)

Web sites and journals  + record of 35 mm photographs associated with the web sites

Welsh coal

WinSCP see Internet Links - What was said

What was said

Zaplab

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THU 11/18/2004 07:48 AM key[ FAQ ]

SeaMonkey - HTML editor

If the computer has a user whose name is different to that archived on the department server, e.g. admin_church rather than wrchurch, then:

START -> Search -> person or computer -> search for earthsci.es.uwo.ca -> double click on search result -> enter user as wrchurch@uwo.ca and password as 54..........  The printer files will than become available.

Front Page  - how to use Front Page

Dad geology  - history of research concerning Appalachian eclogites and ophiolite

Publications-WR Church  -

Where are the geology photos on church-3 and in 'instruct'

Instructions for the Dept. projector

Departmental copier - 98142

Geological map of the USA - http:\\www.geosociety.org/bookstore/ select maps and charts

http://www.gsajournals.org/perlserv/?request=get-document&doi=10.1130%2F0016-7606(2000)112%3C4:PATHAT%3E2.0.CO%3B2

How to change NAD27 values to WGS84

there is a calculated standard difference in WGS84 (NAD83) and NAD27 datum readings for latitude (Y, Northing) and longitude (X, Easting); add 223 meters to the NAD27 Northing (Y), and 10 m to the NAD27 Easting (X) values to change from NAD27 to WGS84.

http://freegeographytools.com/category/google-earth - free geography tools; convert and import maps with worldfile data into Google Earth; also import xls

http://freegeographytools.com/2007/microdem-a-swiss-army-knife-of-terrain-and-gis-tools

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THU 11/18/2004 07:49 AM key[ geology photographs ]

E:\aaMy Photos\Geology - jpg, tif images

Photos-Geology_I - = 35 mm geolphotos.ask in c:\archives

Southern Province photographs

Grenville photographs

Appalachians - Southern photographs

Appalachians - Northern photographs

Caledonides photographs

Morocco photographs

Egypt-Sudan photographs

Saudi Arabia photographs

Alps photographs

SW-USA photographs

Cordillera photographs

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THU 11/18/2004 11:01 AM key[ Field Guides ]

UWO_Field_Trips (= Norm SWUSA)

http://www.lib.utexas.edu/geo/onlineguides.html - Virtual and On-line Geologic Field Trip Guides

Aug 18 2006 - PDAC Bursary and Scholarship programme/Field Trip funding

Submit to Teresa Barrett, PDAC 34 King St. East 9th Floor, Toronto M5C 2X8 tbarrett@pdac.ca up to $3000 - app to be made by a student group contact information incl school, reasons, dates, location of field trip http:\\www.pdac.ca Documentation_Maps - maps, guides and papers in Norm& Duke's lab For on-line field expenses go to misc\uwo http://www.canadiangeologicalfoundation.org/nl/FTpdf.html - pdf's of GAC Newfoundland section field guides New England Intercollegiate Geological Conference Hon and Hepburn NEGSA 2007 field trip http://neigc.org/NEIGC/2004/index.html - NEIGC 2004 field trips to the Avalon, Nashoba terranes http://neigc.org/NEIGC/Guidebooks.html - reference list of all NEIGC guidebooks 1988 to present http://neigc.org/NEIGC/PreviousMeetings.html - list of all NEIGC meetings Jan 23 2011 The Interrelationships Between Deformation and Metamorphism to be held at Granada (Spain), from 23-26 May, 2011. The meeting will mark the occasion of the retirement of professor Tim H. Bell. A special volume is planned to be published by the Journal of Metamorphic Geology. The period for REGISTRATION AND ABSTRACT SUBMISSION is now open. Please visit the conference web site for more information about research topics, preliminary conference program, online registration and abstract submission. http://www.ugr.es/~aerden/conf/index.htm Deadline for early registration and abstract submission: 15 April, 20 http://www.ucm.es/info/petrolog/personal/arenas_ricardo.html Maroc http://194.204.205.38/Des/Universites - Moroccan Universities http://www.um5a.ac.ma/etablissements/Facultes.htm - Rabat Sciences de la Terre Ressources minrales, ressources en eau et environnement dans le Maroc msetien et le gharb (Mohamed EL WARTITI) - Les bassins sdimentaires ; analyse godynamique et ressources naturelles (Mohamed BOUTAKIOUT) - Gosciences appliques lenvironnement et lamnagement (Mohamed EL HATIMI) - Gologie du quaternaire applique lenvironnement et ressources naturelles (Mhamed ABERKAN) - Gologie Structurale et applique (Ahmed CHALOUAN) - Les environnement marins de plate formes actuels et anciens (Naima HAMMOUMI) http://www.israbat.ac.ma/geologie/depgeologie.htm#composition http://www.usmba.ac.ma/formation/FPT/FSTU.html - Fes earth Science France - Toulouse; Paris Clermont Ferrand - Nicollet http://christian.nicollet.free.fr/ Corsica (Corse) Portugal - Spain - Wales - Cardiff Scotland - Glasgow Egypt - Saudi Arabia - Ireland - Oman http://www.dstu.univ-montp2.fr/omanophiolite/omantrip/pages/1_sommaire/1_sommaire.htm - the Oman ophiolite http://www.isteem.univ-montp2.fr/TECTONOPHY/ridge/ophiolite-ridge.html - Nicolas http://www.uoregon.edu/~drt/Oman/mhhoman/omanemplacement.html - Hemphill Mark Hemphill-Haley (mark@newberry.uoregon.edu) http://darkwing.uoregon.edu/~markhh http://www.bris.ac.uk/Depts/Geol/vft/oman.html - photo quiz Norwegian Caledonides http://pangea.stanford.edu/groups/SAP/Great%20Britain%20Itinerary.htm - field trip to Britain Printing colour photographs/airphotos/Google Earth images: If the computer has a user whose name is different to that archived on the department server, e.g. admin_church rather than wrchurch, then: START -> Search -> person or computer -> search for earthsci.es.uwo.ca -> double click on search result -> enter user as wrchurch@uwo.ca and password as 54.......... The printer files will than become available. London and east http://www.uh.edu/~jbutler/anon/coursesandresources.html **************************************************************************************************************************** WED 11/24/2004 01:11 AM key[ geology sapp ] http://instruct.uwo.ca/earth-sci/fieldlog/Sapp/sappft.htm - FIELD TRIP Southern Appalachians Blowing rock desciption http://carolinageologicalsociety.org/GB%201998/Output/Gillon.html - url for a comprehensive site dealing with the Ridgway Mine - The Ridgeway Gold Deposits: A Window to the Evolution of a Neoproterozoic Intra-Arc Basin in the Carolina terrane, South Carolina http://minerals.usgs.gov/east/staff.html - list of geologists at Reston with telephone #'s and e-mail addresses Avery Drake, Scientist Emeritus 703-648-6931 has no e-mail address Wrote to John Slack - he provided a guidebook reference but otherwise was not able to help. "You might also want to look at field trips that were held in conjunction with the '89 ICG meetings here in Washington, which may have included one to this area (I'm not sure)." http://www.mgs.md.gov/esic/geo/lgepm.html - Maryland Geological Survey http://www.mgs.md.gov/esic/geo/index.html - online maps of Maryland http://www.mme.state.va.us/DMR/home.dmr.html - Virginia Dept of Mines, Minerals and Energy https://www.agu.org/cgi-bin/agubookstore?topic=FT Geological Cross-Section Through Part of the Southern Appalachian Orogen P. M. Hanshaw Field Trip Guide Book, Volume T365, 1989; , softbound, ISBN 0-87590-602-8, AGU CODE IG3656028. AGU Member Price -$ 14.70 | Nonmember Price - $21.00 | AGU Student Member Price -$ 14.70

Valley and Ridge and Blue Ridge Traverse, Central Virginia P. M. Hanshaw

Field Trip Guide Book, Volume T157, 1989; , softbound, ISBN 0-87590-591-9, AGU CODE IG1575919. AGU Member Price - $14.70 | Nonmember Price -$ 21.00 | AGU Student Member Price - $14.70 AGU Member Price -$ 14.70 | Nonmember Price - $21.00 | AGU Student Member Price -$ 14.70

Southern Appalachian Windows P. M. Hanshaw  Field Trip Guide Book, Volume T167, 1989; , softbound, ISBN 0-87590-616-8, AGU CODE IG1676168. AGU Member Price - $14.70 | Nonmember Price -$ 21.00 | AGU Student Member Price - $14.70 Tectonics of the Virginia Blue Ridge and Piedmont P. M. Hanshaw Field Trip Guide Book, Volume T363, 1989; , softbound, ISBN 0-87590-655-9, AGU CODE IG3636559. AGU Member Price -$ 9.10 | Nonmember Price - $13.00 | AGU Student Member Price -$ 9.10

Stratigraphy and Structure Across the Blue Ridge and Inner Piedmont in Central Virginia P. M. Hanshaw Field Trip Guide Book, Volume T207, 1989; , softbound, ISBN 0-87590-579-X, AGU CODE IG207579X. AGU Member Price - $9.10 | Nonmember Price -$ 13.00 | AGU Student Member Price - $9.10 Metamorphic Rocks of the Potomac Terrane in the Potomac Valley of Virginia and Maryland P. M. Hanshaw Field Trip Guide Book, Volume T202, 1989; , softbound, ISBN 0-87590-587-0, AGU CODE IG2025870. AGU Member Price -$ 9.10 | Nonmember Price - $13.00 | AGU Student Member Price -$ 9.10

Petrology and Structure of Gneiss Anticlines Near Baltimore, Maryland

P. M. Hanshaw Field Trip Guide Book, Volume T204, 1989; , softbound, ISBN 0-87590-585-4, AGU CODE IG2045854. AGU Member Price - $9.10 | Nonmember Price -$ 13.00 | AGU Student Member Price - $9.10 Ultramafite-Associated Cu-Fe-Co-Ni-Zn Deposits of the Sykesville District, Maryland Piedmont P. M. Hanshaw Field Trip Guide Book, Volume T241, 1989; , softbound, ISBN 0-87590-595-1, AGU CODE IG2415951. AGU Member Price -$ 4.20 | Nonmember Price - $6.00 | AGU Student Member Price -$ 4.20

Titanium-Mineral Deposits of the Roseland Anorthosite-Ferrodiorite Terrane, Blue Ridge Province of Central Virginia Field Trip Guide Book, Volume T244, 1989; , softbound, ISBN 0-87590-626-5, AGU CODE IG2446265. AGU Member Price - $4.20 | Nonmember Price -$ 6.00 | AGU Student Member Price - $4.20 The Adirondack Mountains- A Section of Deep Proterozoic Crust P. M. Hanshaw Field Trip Guide Book, Volume T164, 1989; , softbound, ISBN 0-87590-592-7, AGU CODE IG1645927. AGU Member Price -$ 14.70 | Nonmember Price - $21.00 | AGU Student Member Price -$ 14.70

Tectonostratigraphic Terranes in the Northern Appalachians P. M. Hanshaw

Field Trip Guide Book, Volume T359, 1989; , softbound, ISBN 0-87590-560-9, AGU CODE IG3595609. AGU Member Price - $14.70 | Nonmember Price -$ 21.00 | AGU Student Member Price - $14.70 Northern Appalachian Transect: Southeastern Quebec, Canada, Through Western Maine, U.S.A. P. M. Hanshaw Field Trip Guide Book, Volume T358, 1989; , softbound, ISBN 0-87590-559-5, AGU CODE IG3585595. AGU Member Price -$ 19.60 | Nonmember Price - $28.00 | AGU Student Member Price -$ 19.60

Dr. Alexander E. Gates: agates@andromeda.rutgers.edu    Tel: 973-353-5034

Gates, A.E., Muller, P.D., and Valentino, D.W., 1991, Terranes and tectonics of the Maryland and southeast Pennsylvania Piedmont, in Schultz, A., and Compton-Gooding, E., eds., Geologic evolution of the Eastern United States: Field Trip Guidebook for the Northeast-Southeast Sectional Meeting of the Geological Society of America, Virginia Museum of Natural History, v. 2, p. 1-28.

See misc.ask  for letter to Alex Gates and to John Slack

http://geoweb.tamu.edu/Faculty/Miller/BREclogite/BREclogite.html - Lick Ridge eclogite is 459 Ma; titanite 394; rutile 335

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WED 12/01/2004 03:26 PM key[ logan stevens ]

"Proud Heritage - People and Progress in Early Canadian

Geoscience", GAC Reprint Series Number 8

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WED 12/01/2004 03:34 PM key[ papua eclogite ]

Papua eclogite Figures:

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/eclogites/papuaeclogite2.jpg - extrusion model

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/eclogites/papuaeclogite3.jpg - Explanation to Fig 2

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/eclogites/papuaeclogite.jpg - D'Entrecasteaux map

Nature article on Papuan eclogite is in c:\aahtm\wrc\papuaeclogite.pdf

Suzanne L. Baldwin, Brian D. Monteleone, Laura E. Webb, Paul G. Fitzgerald, Marty Grove & E. June Hill, 2004, Pliocene eclogite exhumation at plate tectonic rates in eastern Papua New Guinea. Nature, Sept, v. 431, p. 263-267

http://su-thermochronology.syr.edu/baldwin/baldwin.html

http://su-thermochronology.syr.edu/nature02846.pdf

Professor Suzanne L. Baldwin

Dept. of Earth Sciences

204 Heroy Geology Laboratory

Syracuse University

Syracuse, NY 13244-1070 USA

Phone: 315 443 4920

Lab: 315 443 4917

Department: 315 443 2672

Fax: 315 443 3363

http://www-hl.syr.edu/depts/gol/scott.html - Scott Samson sapp cadomian thermogeochronology

Dear Suzanne,

Just a short note to apologise for the delay in acknowledging your reply to my earlier e-mail - I have a large family and over Xmas it gets even larger!!

Furthermore just before Xmas I had to give up my office at the University and the move to other 'quarters' was rather chaotic. Nevertheless, I can now say that I indeed do have thin sections as well as samples of the Fleur de Lys material, and I intend to move along and get them all sorted out, as soon as the weather lets me get out again - my means of transportation is my bicycle! Syracuse is not too far away, so you must be getting similar kind of weather.

The age data on the Irish material appeared in "Max, M.D., O'Connor, P.J., and and Long, C.B., 1984, New age data from the Pre-Caledonian basement of the northeast Ox Mountains and Lough Derg inliers, Ireland. Bull. Geol. Survey of Ireland, 3, 203-209.", and "Sanders, I.S., Daly, J.S., and Davies, G.R. 1987. Later Proterozoic high-pressure granulite facies metamorphism in the north-east Ox inlier, north-west Ireland. Journal of Metamoprhic Geology, 5, 69-85". I attempted to use these data in "Church, W.R. 1991. Discussion on a high precision U-Pb age for the Ben Vuirich granite: implications for the evolution of the Scottish Dalradian Supergroup, Jour. Geopl. Soc London, 148, 205-206.", as well as tentatively point out that the eclogite-bearing part of the Fleur de Lys Supergroup in Newfoundland could form the core of an extensional core complex." There has been some progress recently on this front, and I will, as soon as I can, assemble a coherent set of links to the relevant papers and send them on to you - I am still wading though the published and unpublished data. In the case of the Fleur de Lys, the paper to read is Dallmeyer, R.D.1977. 40Ar/39Ar age spectra of minerals from the Fleur de Lys terrane in northwest Newfoundland: their bearing on chronology of metamorphism within the Appalachian orthotectonic zone. Jour. Geology, 85, 89-104.

I was last in touch with Hugh Davies in 2001 regarding the structure of the Owen Stanley south of the ophiolite belt. I was interested in the fold architecture of the Owen Stanley ( ) because the passive margin sediments of Huronian of the Southern Structural Province (north of Lake Huron here in Ontario) are deformed into a set of tight, upright but culminating (canoe shaped) folds with fold intensity decreasing towards the foreland. The folding was a singular event at about 2.2 Ga or earlier that was accompanied or followed by intrusion of low-Ti basalt. Significantly later collisional Penokean age folding in association with granite intrusion shows the reverse tendency with higher grades of metamorphism and folding associated with granite intrusion more intense towards the foreland. (The Australian Hamersley (Hamersley Iron Fm ) of more or less the same age as the Huronian seems to exhibit a similar structural architecture:

In at least a superficial sense the fold structure of the Southern Province looks like that of the Owen Stanley and I was looking for Hugh to confirm that the sections he had presented in his earlier papers on the geology of Papua were indeed realistic. The other link I have with Papua concerns the similarity of the high grade dynamothermal aureole beneath the ophiolite in comparison with the dynamothermal aureole of the Bay of Islands ophiolite. In the latter case the cpx-garnet granulites form the top of an inverted upper part of an ophiolite which is overlain by mylonitized lherzolites with garnet, kaersutite, and Ti-biotite growing in the spinel pyroxenite layers, a nice example of element migration from the rocks of the aureole into the overlying lherzolite. Interestingly, it would seem that it is the mantle lherzolite/harzburgite section between the aureole/untramafic reaction zone and the upper dunite/gabbro that has accomodated all the thinning of the mantle section. At some point in time I plan to have a web page for this occurrence, as well as for a Late Proterozoic example in the southern Eastern Desert of Egypt. (A colleague of mine, Norm& Duke, is thinking of running a Southern Appalachian mineral deposits field trip sometime next term and I am hoping it will include a visit to the Bakerville eclogite 'olistostrome' locality. Should you ever be interested in this occurrence, the information I have gleaned is available as a set of links on the above excursion web site.) There is also a remnant 'dynamothermal aureole beneath parts of the Baie Verte ophiolite belt above the Fleur de Lys, but it is separated from the eclogite-bearing Fleur de Lys by a 'lower' sequence of inter-sheared psammites (staurolite grade) and ultramafic (serp and chrome actinolite schist) and mafic (clinopyroxenite/gabbro) material, and an upper unit of mafic schists (Birchy Schist complex).

Superficially, this belt has some features in common with the D'Entrecasteaux occurrence.

I will send a thin section as soon as I get my affairs sorted out.

Hope this is useful,

Regards,

Bill Church

http://www.nature.com.proxy.lib.uwo.ca:2048/cgi-taf/DynaPage.taf?file=/nature/journal/v411/n6840/full/411930a0_fs.html -

FERNANDO MARTINEZ, ANDREW M. GOODLIFFE & BRIAN TAYLOR, 2001. Metamorphic core complex formation by density inversion and lower-crust extrusion. Nature, 411, (21 June 2001), p.930 - 934.

These calculations are intended to illustrate general features of the proposed mechanisms of core complex formation by lower crustal flow and buoyant extrusion rather than constitute a rigorous modelling of the details of this area. We summarize below these features and their more general implications for continental rifting.

(1) Geological and geophysical observations indicate that the regional crustal structure surrounding the D'Entrecasteaux islands consists of ophiolite overlaying less-dense continental crust, creating a two-layer inverted crustal density profile.

(2) Overall crustal thinning is seismically observed in the area of the Goodenough basin and D'Entrecasteaux islands and is necessary to explain the subsidence of the basin, but uniform crustal thinning is inconsistent with heat-flow values, estimates of extension by faulting, and relative uplift of the islands.

(3) Low heat-flow measurements in the basin interior relative to model predictions for uniform crustal thinning suggest that preferential thinning of the lower crust relative to the upper crust occurs across the basin. We infer that this thinning occurs both by stretching and by crustal flow into the core complexes.

(4) Formation of the island core complexes is explained by buoyant extrusion of ductile lower crust enabled by splitting and pulling apart of the ophiolite layer, locally focusing the regional extension. The buoyancy of the lower crust alone would not probably be sufficient to breach the stronger upper layer.

(5) Because the core complex emplacement accommodates the locally focused extension it does not generate compression, as in gravity sliding models29, nor does it generate purely radial shearing patterns implied by models of forceful plutonic emplacement.

(6) A narrow zone of extension can produce very rapid vertical advection of the lower crust, and account for the nearly isothermal ascent of material followed by rapid cooling inferred from the metamorphic pressuretemperaturetime studies. The rapid ascent of lower crust also produces a local heat-flow 'high' in broad agreement with the high thermal regime near the islands.

(7) Although lower crustal flow, implying a weak lower crust, is proposed to occur beneath the basin and islands, significant Moho relief, implying a strong lower crust, is nevertheless maintained between the peninsula and basin. We suggest that this dual behaviour is related to the subduction of the Solomon Sea slab (Fig. 2) that locally introduces heat associated with the arc line and hydrates the mantle and lower crust beneath the basin and islandsthis makes these areas weaker than those under the peninsula and cold forearc region.

(8) The mechanism of buoyant lower crustal extrusion may occur in other areas of extension and core complex formation where earlier obduction or thrusting has emplaced layers of greater density over less dense ones (Fig. 3a). It may also occur in areas of more uniform crustal composition where increasing temperatures with depth lowers crustal density by thermal expansion (Fig. 3b). In this case a cooler and more brittle surface layer may locally rupture in extension, allowing the deeper, hotter, less dense, and plastic layer to be rapidly extruded.

Norwegian eclogite

****************************************************************************************************************************

FRI 12/03/2004 02:07 PM key[ Blowing rock description ]

South on 221 to junction with 221/321. Turn left and continue north towrds Boone. Pass under the Blue Ridge Parkway.

Stop 2 - Tweetsie Railroad. Park in Tweetsie Railroad Parking lot on east side of 321/221. Continue along the highway 150 meters south towards Blowing rock. Outcrop is composed of Blowing Rock gneiss (1.06 Ma), a dark augen gneiss with megacryst fo of K-feldspar forming small shear pods within an anastomosing shear. The gneiss is cut by a felsic vein and a diabase dike, both of which are also involved in the shear deformation.

Stop 3 is a roadcut opposite the Payne Branch road intersection on the east side of 221/321. Park on grassy shoulder on east side of road at south of the outcrop.  Outcrop is after the Country Crafts Antique shop towards Boone.  Outcorp is composed of massive gritty turbidites, possibly graded, with conglomeratic channels

Go up hill by Wahoos Whitewater Rafts and come down other side on Highway 321 towards Boone. large outcrop on right is Granfather Mountain conglomerate.

****************************************************************************************************************************

SAT 12/04/2004 10:41 AM key[ Web sites ]

Instruct web site

W.R. Church - personal internet file  http://publish.uwo.ca/~wrchurch/  index.htm is archived in c:\aahtm\

http://www.jiscmail.ac.uk/lists/GEO-TECTONICS.html - Geo-Tectonics Newsgroup Archive

GENERAL

http://64.207.34.58/StaticContent/3/TPGs/2007_TPGNovDec.pdf - The Professional Geologist (added Jan 21 2010)

http://virtualexplorer.com.au/VEjournal/  - journal, Virtual Explorer

http://www.geoscienceworld.org/ - GSW Geoscience World

http://www.geologynet.com/ - Geologynet (Australia)

http://www.geologynet.com/news3.htm - News

APPALACHIANS

Northern Appalachians

Directory Burlington Peninsula - \fieldlog\cal_napp\newfoundland\burlington

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/newfoundland/burlington/burlington.htm

Directory Western Newfoundland - \fieldlog\cal_napp\newfoundland\westnewf

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/newfoundland/westnewf/westnewf.htm

Directory Quebec - \fieldlog\cal_napp\quebec

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/quebec/southern_qubec.htm

Directory New England - \fieldlog\cal_napp\new_eng

http://instruct.uwo.ca/earth-sci/fieldlog/cal_napp/new_eng/new_england.htm

Logan - archived in c:\aahtm\logan  http://publish.uwo.ca/~wrchurch/logan/logan.htm

Logan and the Taconic Problem - archived in c:\aahtim\logan with figures logan1.jpg, logan2_3.jpg, and logan4.jpg

Southern Appalachians - archived in c:\fieldlog\sapp

http://instruct.uwo.ca/earth-sci/fieldlog/Sapp/sappft.htm = Field Trip; see Southern Appalachians Field Trip

Directory \fieldlog\sapp Directory \fieldlog\sapp\expertgismaps

Directory \fieldlog\sapp\expertgismaps\airphotos - airphotos of selected areas in the Southern Appalachians used in sappft.htm

Directory of course 300  \aacrse\300\htm

Course notes for the Southern Appalachians - \aacrse\300\htm\300\sapp.htm -

(If modified this .htm file should be copied to instruct.uwo.ca/earth-sci/300b-001/sapp.htm via SSH secure file transfer)

CORDILLERA

Directory Nevada, Arizona, SE California - c:\fieldlog\cargo

http://instruct.uwo.ca/earth-sci/fieldlog/cargo/indexcargo.htm

Dear Dr. Church, (the recommended changes have been made!)

GREAT web sites you have.

Just a note to say that URLS for parts of our National Geologic Map Database project have been changed. For some reason, our IT-security people wouldnt allow us to provide redirects from our old pages, so Im going through various web sites and informing those, like yourself, of our new URLs

National Geologic Map Catalog State Maps Search page near the bottom of your page--

USGS map index

The new URL is

*****************

Your long list of maps from the catalog is probably really really old.

--Search of National Geologic Map database for "California" "Imperial" county--

Unfortunately, all links to the product description pages are out of date

For example, your link to Manganese deposits in the Paymaster mining district, Imperial County, California should be

***********

The "Geologic Mapping in Progress" database lists areas that are now being mapped, and describes who to contact for more information.

US geologic map data model activities are changing over to http://nadm-geo.org

Thank you very much for linking to our sites.

Were adding a Cartographic Resources page (map templates, etc) Its still under construction, but will be officially added to our project site shortly http://ngmdb.usgs.gov/Info/cartores/

We have the standards and guidelines page http://ngmdb.usgs.gov/Info/standards/

Weve added a search for DMT papers page http://ngmdb.usgs.gov/dmt/search.html

Last, but not least, you wouldnt happen to know off the cuff if the Bolsa Quartzite extends into California would you?? I have a bit of a discrepancy in lexicon records that Im having difficulty in resolving.

Cheers!

-Nancy Stamm

NUBIAN SHIELD

Photographs

Directory Egypt - c:\fieldlog\pan_african\egypt

http://instruct.uwo.ca/earth-sci/fieldlog/pan_african/egypt/egypt.htm

http://www.traveljournals.net/explore/egypt/locations/h/1.html - lat longs of all locations in Egypt

Directory Saudi Arabia - c:\fieldlog\pan_african\saudi

http://instruct.uwo.ca/earth-sci/fieldlog/pan_african/saudi/saudi.htm

Directory Morocco - c:\fieldlog\pan_african\maroc

http://instruct.uwo.ca/earth-sci/fieldlog/pan_african/maroc/maroc.htm

****************************************************************************************************************************

gerf12:08 AM12:08 AMSUN 12/12/2004 04:31 PM key[ panafrican geology age dates ]

Chronology

523 Um Aud diorite (unpublished)

575 Rb-Sr, 579 zircon - Gebel Qattar granite (Stern and Hedge, 1985)

578 +/-15 - Nakhil Granite (Sultan et al. 1990)

580-570 - the Jibalah group deposited in small, isolated, pull-apart basins caused by strike- and dip-slip movements on faults of the Najd fault system.

583? Gattarian granites

583  Salah El Belih granodiorite (571 Rb-Sr) cuts the Hammamat (Stern and Hedge 1985)

585 +/- 13 Hammamat; youngest detrital ziron; U-Pb age peaks at 640and 680 Ma;

also 750 to 2630

585 +/-15 R-Sr Hammamat (Willis et al. 1988)

589 +/-9 - Rb-Sr dikes cutting the G Qattar granite

590 +/-11 Um Had granite (Ries and Darbyshire, unpub) cuts the Hammamat

592 +/-26 Rb-Sr Dokhan Gebel Dokhan (Stern & Hedge 1985)

593 +/-13 - youngest Dokhan volcanics (Wilde and Youssef, 2000);

602 +/-9 - oldest Dokhan volcanics (Wilde and Youssef, 2000);

606 - Hadabah pluton 606 2 Ma Shearing on the Ibran shear zone in the central part of the terrane, constrained by the age of the Hadabah pluton, may have occurred as late as 605 Ma.

610 - Ar/Ar amphibole Ar Ridaniyah shear zone

610 - movement on the Umm Farwah shear zone, which cuts the eastern margin of the Ablah group, occurred about 610 Ma or later.

613 - Ablah group rhyolite. 613 7 Ma (but see 641 below);

*616 +/-9 Dokhan? at Wadi Sodmein (Ries and Darbyshire, unpub)

*********634 zircon maxima in Hammamat H2

639 - Tathlith gneiss.  Crops out on either side of the Nabitah fault zone, represent magmatic events approximately 100 million years later than the Tabalah shearing. Zircons from these plutons range in age from 710-361 Ma and 711-451 Ma, respectively, suggesting complex evolutionary and isotopic histories, including inheritance and lead loss. ****************************************************************************************************************

641 - age of rhyolite in the Ablah molasse basin;

620-640 - the Jurdhawiyah group and Hibshi formations were deposited in fault controlled basin (isolated fault-controlled lake). East-west convergence conceivably accounts for the creation of the Jurdhawiyah and Hibshi basins as a result of concomitant northward extension or tectonic escape. Basins closed and inverted during subsequent north-south shortening and north- and south-vergent reverse faulting.

****************************************************************************************************************

640 - Ash Shawhatah pluton 640 3 Ma The Ash Shawhatah pluton (ID# 7) intrudes the Nabitah fault zone, indicating cessation of Nabitah orogeny ductile deformation in the eastern part of the terrane by 640 Ma, although brittle deformation occurred after 640 Ma, as evidenced by faulting at the contact of the granite.

640 - peak regional granulite facies metam. in Tanzania S. Muhongo et al. Jour Geol 2001 p. 171

645 - Ar Rayn Trondhjemite

646 - Junaynah granite 646 10 Ma The Junaynah granite (ID# 4) has undergone brittle deformation by the Junaynah fault zone, and is considered as an evidence for brittle deformation in the central part of the terrane after about 645 Ma, comparable to the brittle faulting on the Nabitah fault zone.

*********646 zircon maxima in Hammamat

650 - The basins were closed and inverted by folding. Northerly trend of Murdama and Bani Ghayy folds implies bulk east-west shortening.

650 - Ar Rayn tonalite

651 -Abss granodiorite 651 4 Ma  The Abss granodiorite and Tathlith gneiss which crop out on either side of the Nabitah fault zone, represent magmatic events approximately 100 million years later than the Tabalah shearing (>755 ma).  Zircons from these plutons range in age from 710-361 Ma and 711-451 Ma, respectively, suggesting complex evolutionary and isotopic histories, including inheritance and lead loss. The Abss and Tathlith results in Table 1 are preferred formation ages, implying that the plutons belong to the suite of syn-Nabitah orogeny intrusions well known in the eastern part of the terrane (Stoeser and Stacey, 1988).

654 - Musayrah pluton 654 3 Ma The Musayrah pluton has the same age, within error, as the Abss granodiorite. It intrudes the Abss granodiorite, but is evidently part of the same Nabitah -654orogeny magmatic event as the granodiorite.

******************************************************************************************************************

650-670 - 8000 m sandstone, conglomerate, bimodal volcanic rocks, and limestone(Murdama basin) and in narrow grabens (Bani Ghayy basins). Possibly >10 km uplift and erosion in parts of the region prior to deposition. Much of the region was at a low elevation soon after terraneamalgamation and orogeny. The two basins are foreland basins at subsided and extended parts of a newly amalgamated crust in the center of the study area that was downflexed (foreland basin) by the overthrusting of an ophiolite complex and other terranes from the east.

******************************************************************************************************************

667 - Ar Rayn trondhjemite

******** *671, 693 zircon maxima in Hammamat H1 and H2, respectively (Wilde & Youssef 2002)

686 +/- 56 Rb-Sr Dokhan? volcanics at Gebel Nuqrah (Stern & Hedge 1985)

685 +/- 16 (Wilde & Youssef, 2000) upper Dokhan weighted mean inherited zircon cores

690 single grain zircon with inheritance of 1.9-2.1; Uweinat, Gebel El Asr  (Sultan et al. 1994)

694 - Urdd ophiolite

******************************************************************************************************************

710-725 Midyan diorite; tonalite

711 - tonalite, Dixon 1981, Um Samiuki area

712 - Shadli (Um Samiuki) volcanics of southern Egypt (Stern et al. 1991)

720 - lower intercept (down to 663 Ma) of 2650-1065 Sabaloka granulite gneiss & migmatite

(Kroner et al 1987)

720 - lower intercept Duweishat 2.6 -1.23 gneisses (Wadi Halfa) (Stern et al. 1994)

728-782 Al Qarah tonalite

731 - Murat tonalite

740 - Late Precambrian (740 Ma) charnockite, enderbite, and granite from Jebel Moya, Sudan; a link between the Mozambique Belt and the Arabian-Nubian Shield

743 +/-24 Al Wask, Sm/Nd age, Claesson, Pallister and Tatsumoto 1984

743 (Ledru) - 696 (Pallister) - Jar and Salajah tonalites

750 age of Nubian Wadi Gerf ophiolite, Eastern Desert

*********750  zircon maxima in Hammamat , both H1 and H2

750 - Siham arc (Khida region) (Whitehouse et al. 2001) old ages of 2.6-2.4, 1.9-1.65, 950-800

755 - Al Khalij pluton 755 7 Ma, intrudes the Tabalah shear zone. Its age indicates that shearing occurred prior to 755 Ma and defines, in the west-central part of the terrane, the earliest deformation event documented. 760-780 Ma. The shear zone dates the onset of arc-arc convergence in what eventually became the Arabian-Nubian shield. Marks the beginning of the complex, heterogeneous process of terrane amalgamation and continental accretion that led to the eventual convergence of East and West Gondwana.

760 - lead loss Al-Mahfid 2550 granite gneiss with older components at 2938-2730;

coeval granite sheets (Whitehouse et al. 1998)

768 +/-61 - Abu Swayel (S&H, 1985), rhyodacite

779 +/-4 Um Ba'anib granite gneiss (Meatiq; has 1149 Ma orthoamphibolite xenolith)

(Loizenbauer et al 2001)788 +/-13 sediments overlying Meatiq gneiss

780 - J. Ess ophiolite (782+/-38, Sm/Nd age, Claesson, Pallister and Tatsumotom 1984)

**********804 , 823 zircon maxima in Hammamat H1 and H2 respectively

821 Iqwaq tonalite

816-847 Asir Terrane arc.

843  to 665 - oldest sed-volc in Pan-African of Tanzania S. Muhongo et al. Jour Geol 2001 p. 171

820-870 Ma - the Bir Umq-Nakasib suture zone, 5-65 km wide and over 600 km long.

900 - Abas terrane (Yemen)  zircons w. weighted average age of 939+/-47; inherited core 2605+/-15

also met at 760 (Whitehouse et al 1998)

945 - Rabigh (Asir)

*********962 zircon maxima in Hammamat

Kroner, A., Stern, R.B., et al. 1987. The Pan-African continental margin of northern Africa: evidence from a geochronological study of granulites at Sabaloka, Sudan. EPSL, 85, 91-104.

Sultan, M., Chamberlain, K.R., Bowring, S.A., and Arvidson, R.E. 1990. Geochronologic and isotopic evidence for involvement of pre-Pan-African crust in the Nubian Shield, Egypt. Geology, 18, 764-761.

Stern and Dawoud;   Univ. Tex. at Dallas, Programs Geosci., Dallas, TX, United States; Univ. Khartoum, Sudan.  Late Precambrian (740 Ma) charnockite, enderbite, and granite from Jebel Moya, Sudan; a link between the Mozambique Belt and the Arabian-Nubian Shield? Journal of Geology 99, no. 5 (199109): 649-659

Kroener, A.; Todt, W.; Hussein, I. M., and others Universitaet Mainz, Institut fuer Geowissenschaften, Mainz, Federal Republic of Germany; Max-Planck-Institut fuer Chemie, Federal Republic of Germany; Geological Research Authority, Sudan; Egyptian Geological Survey and Mining Authority, Egypt. Dating of late Proterozoic ophiolites in Egypt and the Sudan using the single grain zircon evaporation technique. Precambrian Research 59, no. 1-2 (1992, 11): 15-32

Stern and Kroener.  University of Texas at Dallas, Programs in Geosciences, Richardson, TX, United States;  Johannes Gutenberg-Universitaet, Federal Republic of Germany. Late Precambrian crustal evolution in NE Sudan; isotopic and geochronologic constraints.  Journal of Geology 101, no. 5 (1993 09): 555-574

Stern, R. J.; Abdelsalam, M. G. Univ. Texas at Dallas, Center Lithospheric Studies, Richardson, TX, United States  Formation of juvenile continental crust in the Arabian-Nubian Shield; evidence from granitic rocks of the Nakasib Suture, NE Sudan.  Geologische Rundschau 87, no. 1 (1998): 150-160

El-Sayed, M. M.; Furnes, H.; Hassanen, M. A., and others. 1999. Crustal evolution of the Egyptian Shield; a proposed new geotectonic model. Geological Society of America, 1999 Annual meeting Abstracts with Programs - Geological Society of America 31, no. 7, p. 179

Fowler, T. J.; Osman, A. F. Gneiss-cored interference dome associated with two phases of late Pan-African thrusting in the central Eastern Desert, Egypt. Precambrian Research 108, no. 1-2 (20010501): 17-43

Loizenbauer, Juergen; Wallbrecher, E.; Fritz, H., and others Structural geology, single zircon ages and fluid inclusion studies of the Meatiq metamorphic core complex; implications for Neoproterozoic tectonics in the Eastern Desert of Egypt. Assembly and breakup of Rodinia Precambrian Research 110, no. 1-4 (200108): 357-383

Whitehouse, M.J., Stoeser, D.B., and Stacey, J.S. 2001. The Khida terrane - geochronological and isotopic for Paleoproterozoic and Archean crust in the eastern Arabian Shield of Saudi Arabia. In Diva, R.S. and Yoshida, M., Tectonics and Mineralization in the Arabian Shield and its Extensions. IGCP 368 International Conference Abstracts, Jeddah, Saudi Arabia. Gondwana Research, 4, 200-202.

Genna, A.; Nehlig, P.; Le Goff, E., and others Proterozoic tectonism of the Arabian Shield. Precambrian Research 117, no. 1-2 (2002 07 31): 21-40

Neumayr, P.; Hoinkes, G.; Puhl, J. The Migif-Hafafit gneissic complex of the Egyptian Eastern Desert; fold interference patterns involving multiply deformed sheath folds. Tectonophysics 346, no. 3-4 (2002 03 15): 247-275

09:41:25  07 APR 98 key[ mailbase geo-tectonics geotectonics ]

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08:19:09  28 APR 98 key[ geology Tanner Glasgow ]

Discussion of Henderson et al Highland Workshop field excursion  is in C:\fieldlog\cal_napp\napp_cal_correlation \Henderson et al.doc (Chew ; Ian Alsop)

C:\fieldlog\cal_napp\napp_cal_correlation\Henderson et al.doc

sent    11/10/2009 in Geology/people/Harris_Henderson; he replied 11/10/2009

Peach and Horne abstract - Tay Nappe

Dear Geoff,

Just caught your latest JGS paper on the Highland Border complex, and I have a question for you.

(We corresponded briefly back in 1998 a short while after which I started to have health problems, eventually traced to prostate cancer. However I am now in remission after years of treatment, and so able to take an interest once again in what has been happening in Scotland and Ireland.)

In our earlier correspondance I broached the possibility that the chromite-bearing quartzo-feldspathic HBC  clastic rocks and black shales (Loch Lomond, Balmaha, North Esk, Aberfoyle, Loch Fad), the olistostromal (?) phyllitic melange at Toward, and perhaps the Aberfoyle 'Basement Breccia' of Jehu and Campbell (1917), were potential foreland basin sediments deposited in front of and overthrust by the southerly derived obducting Highland Border ophiolite. We agreed that the Highland Boundary may have no particular paleogeographic significance.  You didn't make these points in your recent paper, and I wonder therefore whether they have now gone by the board?

I notice that Draut and Clift have made the Tremadocian Lough Nafooey Gp allochthonous relative to the Dalradian - I have always preferred this, but is there any field evidence to support the idea?  I also know that there are debris flows in the lower Murrisk loaded with ophiolite debris - as is also the case at Ballantrae, Baie Verte and Betts Cove in Newfoundland, and Thetford in Quebec.  Are there any such rocks stratigraphically above the Highland Boundary ophiolite?  This material could be coming from the leading edge of the obducting ophiolite or from blueschist/eclogite extrusions penetrating through the rear of the ophiolite, as per Papua-New Guinea, Oman, Cuba, etc..  Has anybody really searched for blueschist debris in the Murrisk olistostromes?

I have also been reading the views of Flowerdew and colleagues on the Irish Moinian, and of the older paper by Peter Friend et al on high pressure rocks associated with the Naver nappe in northern Scotland.

eclogite-bearing psammites are continental derived and pre- 475

The tectonic history of the Dalradian seems to have got a lot more complicated, with events at c.7-800, c. 600, 475, and 430 - even unconformities.

To: wrchurch@julian.uwo.ca

From: G.Tanner@geology.gla.ac.uk (Geoff Tanner)

Subject: Highland Border Complex

Date: Tue, 28 Apr 1998 13:06:43 +0100

Dear Prof Church,

Firstly, my sincere apologies for the long delay in responding to

your e-mail message to me on this topic in January.  We are having a major

upheaval in the Glasgow Department, still not finally resolved, which

coupled with heavy teaching has distracted me from more important things!

outset that I agree with most of your inferences about the structure etc.

of the Highland Border Complex in Scotland.  Incidentally, I have a great

respect for J. G. C. Anderson's work and use his paper on the Highland

Border Complex as a 'bible' to refer to, when I am doing reconnaissance

work in an unfamiliar part of the zone.  Unlike some others, he actually

states what can be seen at these various places.

I have been interested in the chromite-bearing arenites for some

time and have mapped and sampled those at Loch Lomond, Aberfoyle, and Bute

(the Loch Fad conglomerate and its equivalents), in the Loch Ard Forest SW

of Aberfoyle, and in the North Esk section.   They are quite separate from

the pale arenites which have been previously classified with the HBC, but

which I believe are  represent the upper part of the Dalradian

Neoproterozoic-Cambrian succession.

New petrographical and geochemical work on the Keltie Water Grits

has convinced me that they are part of the autochthonous Dalradian

sequence; they are probably separated by a tectonic break from the

chromite-bearing grits etc.(which could well represent foreland basin

deposits, as you suggest), with a further tectonic break between them and

the overlying HB ophiolite.  The pale grits with limestones and black

slates are probably equivalent to the similar sequence found immediately

south of the Dalradian s.s. outcrop on Bute (as previously inferred by

Anderson). This area will be one of my mapping targets in the next few

weeks. There is certainly evidence of an upward-deepening to black shale

and chert in the 'Dalradian', if one includes in the latter those rocks

presently labelled as an 'L.Ordovician component' of the HBC, and there are

excellent olistromal melanges.  I stumbled on a fine example of the latter

near Toward Point at the end of last season, not realising that it had

Despite a lot of careful searching (having seen the blueschists on

Achill Island) of some well-exposed sections such as at Stonehaven on the

NE coast, no high P assemblages have been found within the HBC in Scotland,

and I doubt that they are still preserved.    With this exception, your

analogy with the internal obduction front in Quebec and Newfoundland is an

excellent one.

The earliest cleavages in the Dalradian and the HBC certainly

appear to be contemporaneous (with a possible pre-D1 cleavage being

recognised in both units - discussion and reply to appear in the Geol. Mag.

for July). D2 could represent a back-thrusting event, but there is at

present an unresolved dispute between those who interpret the S2 shear

bands as representing NW-directed shear, and those who consider that they

resulted from  NW-directed shear. Regarding your final point, I agree

entirely that the present location of the outcrop of the HBC along the

'Highland Boundary Fault' is controlled by the geometry of, and interaction

between, the major structures to either side of it, and has no particular

paleogeographical significance.

I apppreciate your having taken time to share with me your ideas on

the evolution of the HBC, and will keep you posted on future findings and

developments.

With best wishes,  Geoff Tanner

____________________________________________________________________________

__

Dr.P.W.G.Tanner (Geoff Tanner)

Department of Geology & Applied Geology, Lilybank Gardens,

University of Glasgow, GLASGOW G12 8QQ, Scotland.

Tel.No.Direct:+44-(0)141-330-5465; Secretary:+44-(0)141-339-8855 ext.5436

Fax No.+44-(0)141-330-4817.  e-mail:G.Tanner@geology.gla.ac.uk

Dear Dr. Tanner,

I have been following your work in the Dalradian and the consequent discussions with Brian Bluck over the significance of the Highland Border complex with some interest (I was a student of JGC Anderson!!), and particularly as it concerns the analogy of the HBC to the ophiolite belts of Newfoundland and Quebec. I think your arguments are impressive, and making the Dalradian deformation relatively late rather than relatively early, as I have been too willing to accept, certainly forces a re-evaluation of many other aspects of Appalachian-Caledonian geology. Looking at the problem from an Appalachian perspective, however, I wonder whether more consideration should not be given to the possibility that the chromite-bearing quartzo-feldspathic HBC  clastic rocks and black shales (Loch Lomond, Balmaha, North Esk, Aberfoyle, Loch Fad), the olistostromal (?) phyllitic melange at Toward, and perhaps the Aberfoyle 'Basement Breccia' of Jehu and Campbell (1917), are potential foreland basin sediments deposited in front of and overthrust by the southerly derived obducting Highland Border ophiolite. From this point of view the  Keltie Water unit should be considered autochthonous relative to the Dalradian, whereas the foreland basin and ophiolite units are potentially, but not necessarily in the case of the foreland basin material, far travelled allochthonous units assembled during the ophiolite obduction process.

One of the characteristic features of foreland basins formed during ophiolite obduction (e.g. Papua-New Guinea, the Alps, the Western Newfoundland and Quebec Appalachians, and the Late Proterozoic Eastern Desert of Egypt and Saudi Arabia), is the antithetical association of clastic grains of chromite or clasts of ultramafic rock with quartz-rich or arkosic sedimentary material, sometimes with K-feldspar clasts, of continental derivation. In explanation the chromite is thought to have been obtained from the dunitic component of the ophiolite and the quartzose material from continental-derived slope and rise sandstones dragged back up onto the continent during the obduction process. Consequently, the presence of chromiferous sediments at many localities within the HBC might suggest that part of the HBC also represents an obduction-related foreland basin. There are no preserved samples in Scotland of the autochthonous 'northern' LATE STAGE distal parts of the foreland basin (e.g. the Utica shale facies of Quebec and New England), and the DISTAL region could lie either much further to the north above or beyond the Dalradian, or to the south in the subsurface of the Midland Valley and the Southern Uplands. Similarly, the PROXIMAL region of the foreland basin during the INITIAL stage of its development may have been located at the Highland Border or  even beyond the Southern Uplands. If the foreland basin succession is transitional with the Dalradian, the transition should be marked by an upwards-deepening to black shales and cherts succession in the Dalradian, followed by upward coarsening through distal flysch to coarse olistostromal melange in the HBC. There is perhaps a hint of this in the HBC??

By analogy with the internal obduction front in Quebec and Newfoundland, there should also be a zone of highly tectonized material (in places with high-pressure mineral assemblages) representing subducted slope and rise sediments (and perhaps continental basement). This unit should be located oceanward of the foreland basin and below the proximal ophiolite belt, and  may have been in part the source of the quartzose clastic material in the foreland basin. As far as I know there are no surface exposures of this tectonic facies in Scotland, but it could be buried in the subsurface north of the Ballantrae ophiolite, and in Ireland could be represented by the allochthonous? Deer Park ophiolite - South Achill Group of the Clew Bay region. Since the age of the oldest back-basin olistostromes overlying the obducted Ballantrae ophiolite are Tremadocian, obduction must have been initiated by this time, and would have continued until at least mid-Ordovician time.

If the cleavage in the HBC including the ophiolitic and foreland basin rocks is congruent with the S1 cleavage of the Dalradian, as you would prefer, it would seem that the earliest deformation of the Dalradian must then post-date development of the foreland basin, and could  be related to the southeast under northwest translation of the foreland basin coeval with the southeast to northwest subduction flip recorded by the arc volcanics of Bail Hill in the Southern Uplands and Slieve Aughty in Ireland. The Dalradian S2 would then represent a local shear contemporaneous with the the imbricate deformation of the Southern Uplands.  Similar style movements (back folding) also occurred during the Ordovician in the Sutton-Bennet Taconic tectonites of the Quebec Appalachians, contemporaneous with post-obduction northeast directed subduction in the Newfoundland Notre Dame Bay region and the western Taconic margin of New England (as mentioned in my relatively recent discussion of Pinet and Tremblay's paper in Geology). The localization and preservation of the HBC must then be related to the HB downbend and the post-ORS movements that developed the Strathmore syncline; in other words, the HB fault zone has no special paleogeographic significance.

Should the above be of interest to you, I would be happy to receive any comments on any of the above raised points.

Kind regards,

Bill Church

10:47:44  05 JUN 98 key[ Gondwana Pan-African ]

- A new insight into Pan-African tectonics in the East-West Gondwana collision zone by U-Pb zircon dating of granites from central Madagascar

Jean-Louis Paquette, Anne Ndlec

EPSL 155(1-2): 45-56

The assembly of Gondwana was the result of a major collision orogen, the East African Orogen, between East and West Gondwana during Neoproterozoic times. Madagascar, which represents a fragment of East Gondwana, is located in a key area of this Pan-African orogen. Granites of unambiguous tectonic setting have been dated using the U-Pb zircon method in order to constrain the timing of orogenic events. The central part of Madagascar is characterized by syntectonic alkaline granitic sheets, referred to as "stratoid" granites. These are of both mantle and crustal derivation. Their U-Pb zircon ages are well defined between 627 and 633 Ma for both plutonic suites, regardless of either mainly mantle or crustally origin. It is not surprising that the crustally-derived suite contains inherited zircons in the 2.2-2.4 Ga range attesting to the existence of Lower Proterozoic crust in northern central Madagascar. The generation of huge amounts of granitic magma is regarded as the result of post-collision extension under a high heat flow regime. Therefore, an age between 700 and 650 Ma is inferred for the beginning of Gondwana assemblyalong the collision zone between central Madagascar and Kenya, i.e., in the central part of the East African Orogen. Following this, brittle fracturing of the stratoid granite series permitted the emplacement of the Ambatomiranty granitic dyke swarm at a minimum age of 560 Ma, in possible connection with a nearby shear belt. The strike-slip tectonic regime at ~570-560 Ma is well known in southern Madagascar and in its Gondwana connections. This stage corresponds to intracontinental reworking and the final suturing of Gondwana.

08:38:04  08 JUN 98 key[ 350Y Fred]

Fred,

I do not think 350Y as it is presently conceived is effective. Based on this year's experience, here are some reasons why?

In the geology component of the course, it was assumed that virtually all students had taken a basic course in structural geology and had attended the 2nd year field camp (use of compass, air photos, dips and strikes; Huronian stratigraphy).  The first two days of the course were nevertheless used to instruct the students on the lithologies and structures present in and around the Sudbury basin and the Front region of the Grenville Province. (In spite of elaborate precautions, one of the vans representing 1/3 of  the class, missed the rendez-vous at Parry Sound on the first day, and they therefore remained uninstructed with respect to structures present in high grade Grenville structures; for this reason no import was given to student evaluation as it concerned the mapping of the area of Grenville rocks east of Sudbury.)  Students were also provided with reminders on the use of a compass to measure dips and strikes, to orient an air photo, and to determine locations on the photo.

The students were then divided into groups of four and asked to make a reconnaissance map of a well exposed area of folded sedimentary and mafic igneous rocks, and a preliminary assessment of a second area of high grade Grenville metamorphic rocks, both operations to be carried out within the time limit of 3 1/2 days (a half day was lost because of an unscheduled non-geological INCO mine tour that took up a morning). The first area contained cross bedded quartzites (rocks with younging criteria), variably textured gabbros, Sudbury breccias, two generations of diabase, a fold structure, and a fault with associated drag folds.  The second area was composed of highly deformed high grade pelites, psammites, various kinds of amphibolite and felsic gneiss, all complexly folded, brecciated, and disrupted by anastomosing shear zones. The students had already prepared a coloured copy of the airphoto used for the first mapping area during the 300B course, and had been shown how to view stereo pairs of photographs.  (However, only 2 studentsout of 16 had developed this ability by the time of the course.). The dip and strike data collected by each student was entered into the computer in the evening (two groups per day), and over the time of the mapping period an image of the variation in dip and strike across the whole area was gradually generated. Students were expected to analyse the image and incorporate their evaluation into their reports.

Although for logistical and safety reasons the students mapped in groups of four under the surveillance of myself or a TA, they were expected to make their own observations, interpretations, and generate their own map report. For this reason it was deemed likely that the student reports would not be uniform and would contain varying interpretations of the geology of the area. This indeed proved to be the case, and in this respect it it important to note that the methodology of the geology component of the course was  different from that of the geophysics part.

Problems:

1)  The geology and geophysics parts of the course have nothing in common.  The geophysical survey largely involved a GPR experiment over an unexploited ore body  in a sand covered area with no outcrop. While a valid exercise in the detection of solid rock beneath sand, it has no real bearing on the geology of the Sudbury Basin or the geology of the areas selected for geological mapping.

There was therefore confusion on the part of the students concerning the methodologies and aims of the geophysics and geology components of the field camp. The geophysics experiments followed a cook book procedure leading inevitably to the same 'correct' result.  The results generated by each student group tended therefore to be the same, and because the experiments were group efforts the data reduction also tended to reflect the competence of one or two dominant persons in the group. It was difficult therefore not to produce a 'correct' report, and all marks therefore clustered in the 80-90% range. The same remarks apply to the non-analytical components of the GIS module. In contrast, in the geology part of the course the students were expected to make a subjective  interpretation of geological observations they had recorded on their  maps. Some students held  that the methodology should have been the same in both cases.

2) Three days of mapping is an  inadequate amount of time to spend on a course involving both the instruction of students with poor geological backgrounds, and the testing of a students ability to map.  Where most students have inadequate backgrounds and who therefore exhibit a high anxiety quotient, the ratio of 16 students to 1 instructor is far too high to be able to provide all-day attention to individual students.

3) While there was no problem concerning the partition of time during the day between Geology and Geophysics, there was competition for the computers at night between Matlab and Fieldlog, and some students were still doing their geophysics data reduction up until the last moment on the day they were supposed to have been doing their geology report. Some students resented having to enter data after 9 pm. Clearly, geology and geophysics were competing for the students' attention.

4) Many students did not know  how to use a compass, how to measure dip and strike, how to determine their location on an an airphoto (some even managed to walk the wrong way, off the photo??), or understand the rudiments of structural and igneous geology. For example, after three days in the field, and after having been reminded that their report would need to include a section on the relative age of the rocks units, some otherwise seemingly very good students wondered how they would know the relative age of sediments and gabbro, since the instructor hadn't actually told them - and this despite the gabbro having being mapped as cross cutting folded quartzites, and the gabbros having fine grained margins close to their contact, with the same kind of sediment on both sides of the gabbro!! After three years of geology courses!! Leading questions were often not considered an adequate response to a request for the 'right answer', and there was often a reluctance to ponder questions and the significance of observations.

5)  Some students questioned the necessity of making the general orientation traverse across the Sudbury structure and the Grenville Front, since this trip had been made with them by Dr. Plint during 200Y. This complaint seemed to be related to the question of  'value for money' and perhaps to resentment at the imposition of the 200 course fee. (For some reason there was some tendency for this imposition to be blamed on the course instructor! Shoot the messenger syndrome, perhaps!) The complainants however were not actually able to identify what it was that they had learnt during their trip with Dr. Plint. 6) Students were differentiated in terms of the program in which they were registered (geophysicists, hydrogeologists, Hon. geologists, BA's, with some using the course as a fill-in rather than as a core requirement). They also differed in their physical ability and their enthusiasm for the outdoors - always complicating factors in these kinds of courses. There may also have been some resentment at the 'sergeant-majoring' required to get people into the vans at 8.10 am each morning (although I have to be up at 6 am!), and some were not entirely happy with the physical effort required in mapping. Others (but two only!) revelled in it. The weaker groups tended to wander around as a group, even mapped on a 'group airphoto' rather than their own photos, and betrayed their collusion when exactly the same tortured syntax and conclusions appeared in the reports of students from the same group. They tended to be slow in the field because every move required a consensual group decision. Other students tended to map as individuals, and relatively early in the day would become divorced from their group, travel further, and make more observations. Some students wanted everthing explained , that is, they wanted only to be instructed, and appeared resentful if they weren't, whereas others (unfortunately the few!) enjoyed having to carry out the exercise in logic required in geological interpretation. Similarly, some students were 'active' when entering data into the computer, others were disinterested, and others were actually annoyed at being taken away from the television program they happened to be watching! Some students were unwilling to be persuaded that the field mapping exercise beyond the first two days of demonstrations was not uniquely a 'show and tell' on the part of the instructor, but rather an opportunity for the student to demonstrate their observational and data collection skills, and their interpretive abilities. 7) There were no logistical problems concerning vehicles, accomodation, food, or equipment. All but one student used the cooking facilities at the motel. Clearly, however, while some were relatively skilled cooks, others were disinclined to have to fend for themselves and found feeding themselves a chore. I do not have a solution for this. 8) When students go to field camp resentful at some perceived injustice, one loses the sense of camaraderie and willingness to cooperate. Then every scenario that fails to meet someone's subjective very highest standard may end up being judged as the 'worst possible' rather than as the 'best possible under the circumstances'. We have to live with it I suppose. Some days you're the dog, some days you're the hydrant! I would recommend that next year the geology and geophysics components of 350Y be held separately, allowing a normal 12 days for the Geology field camp as per: 1) Travel to Sudbury - deformation in high grade metamorphic terranes 2) Geology of the Sudbury region - stratigraphy, sedimentology, mafic and felsic intrusive igneous rocks, low to medium grade metamorphism, impact structures, Trap and Sudbury dikes, folding, faulting, cleavage formation, mylonites, mineral deposits, environmental impact of mining. 3) Mapping instruction - use of the compass, locating yourself on an aerial photo, pacing, dips and strikes, etc. 4) Mapping 5) Mapping 6) Mapping 7) Mapping 8) Archean overnight Noranda/Kirkland Lake Cu, Ni 9) Timiskaming/Cobalt Silver Camp 10) Grenville assessment map, compile mapping data, start to write report 11) Write report 12) Return to London Since the 4th year field trip is located in the Maritimes region, and since 250Y and 350Y covers Southern and Grenville Province, Paleozoic Platform, and Sudbury geology only, there is little chance for our students to examine the fundamentally important Archean volcanic geology of the Superior Province of Ontario. I would suggest therefore that two days of 350Y be assigned to a visit to the Archean. These two days would also provide a buffer in the case of bad weather. The 350Y course should be restricted to students in the geology and applied geology programs, and allowed as an option for geophysics students. The geophysical experiments could just as well be given as labs in the 3rd year geophysics course, and carried out on campus. Bill c. 14:25:33 22 MAR 99 key[ Geology Paul Lindberg SEG Seminar March 18-20 1999] 205 Paramount Drive Sedona, Arizona 86336, Tel: 520 282-1247, palindberg@sedona.net Thursday March 18 1999 - Lower Proterozoic Gogebic iron formations (there are some, although rare carbonate horizons in the iron formations, which are not replaced by haematite), Hotchkiss Superdip Magnetometer, Lindberg thinks the haematite is primary and the magnetite secondary becase as one approaches the Duluth gabbro the ores become magnetic; Archean age Two Mile Lake, Nakina iron formation - cycles from magnetite rich through chert to clastic zones, seem to be unique to the Nakina; Britannia (Bonanza) copper, Fig 2., PAL Jan 29, 1968; Guichon copper (Cu disappears from outside to inside but Cu concentrations are in the depleted centre. Friday March 19 - West Shasta (East Klamaths Devonian arc); Jerome; Nome, Alaska, Au and Alexander terrane Greens Creek Au; Con Mine shear zone, Yellowknife.. Saturday March 20 To remember: Cretaceous in depresssions in the enriched Gogebic 'soft' iron gossans = silica removal (Gruner, 1946) If pyrrhotite is not present there is no magnetic signature, therefore EM-Mag surveys without a magnetic signature is no guarantee that the EM signature is carbon - although of course it might be. Jerome has a strong linear fabric and therefore does not appear to be foliated. 16:52:39 23 MAR 00 key[ Grenville Easton review of Davidson 2001 ] Davidson. A. 2001.The Chief Lake complex revisited, and the problem of correlation across the Grenville Front south of Sudbury, Ontario. Precambrian Research. v. 107, 5-29 pdf can be accessed as Davidprecambres2001.pdf at c:\fieldlog\Grenville\Grenville_Front\Davidson\brodil Map Fig 8 of the area between Highway 69 and Baby Lake is in ...\brodil\davidsonmaps\David01fig8.jpg. It has been linked in GEarth Davidson - Rivers files in C:\personal\HOME\AAMANUS\GRENVILL Brodil map is in F:\OGS\Geology\brodil28_1, brodil83_1.dwg; was originally registered using NAD27; modified NAD83 version is saved as brodil83_1.dwg; fueten.htm is in aarev\pub2\fueten Maps and figures are in c:\fieldlog\mapimagesjpg Mike, Just a note to let you know that I have today mailed Davidson's manuscript to you. With respect to his main conclusions there is little to disagree with, nor are they are very novel either. Now if he had actually solved the problem of the isotopic age discrepancy? The other deficiency in the paper, which I have not discussed in the report is that Lumbers placed the Grenville Front Boundary Fault as separating a western panel within which the foliation trend has relatively regular NE-SW trend from an eastern panel within which the foliation trends outline large Z-shaped fold structures which are continuous with similar folds east of the boundary of the granite with the gneiss, and which are also generally contiguous with other meso-scale folds mapped by Lumbers in eastern Tilton Township. The foliation trends shown on Henderson's map of the Brodil Lake area, which are shown in more detailed than on Davidson's map, do not seem to be offset across the Grenville Front boundary as delineated by Davidson, and the importance of the mylonite zone designated by Davidson as the Grenville Front may therefore be illusory. It is perhaps merely a late Grenville high strain singularity. Furthermore, contrary to the impression given by Davidson (3rd sentence of the abstract) it is Lumbers Grenville boundary that marks the abrupt disruption in the continuity of southeast-trending Sudbury Diabases, and not the granite-gneiss boundary. This criterion was also used by Bethune and Davidson to define a Grenville Front in the Tyson Lake area to the west of that of Lumbers and Card. I may be able to get a student to look into this during field camp in May. You wouldn't happen to have available an airphoto of the area around Brodil Lake, would you?? Hi Bill: I received your review about a month ago now, and everything was sent back to Tony who is working in revisions. The other reviewer was Nick Culshaw. The only days I am tied up from 8AM to 6PM over the next couple of weeks are May 3, 8 & 9. I will be arround the office otherwise (705-670-5995; home phone 705-523-0948). Thus, it shouldn't be a problem getting together with you either in the PM or in the field when you are in town. I don't have a photo covering Brodil Lake, but I can check the Resident Geologist's Office, as they do have some local photo coverage available. In your message you noted "One point I didn't discuss is that Lumbers placed the Grenville Front Boundary Fault as separating a western panel within which the foliation trend has a relatively regular NE-SW trend, from an eastern panel within which the foliation trends outline large Z-shaped fold structures which are continuous with similar folds east of the boundary of the granite with the gneiss, and which are also generally contiguous with other meso-scale folds mapped by Lumbers in eastern Tilton Township." This seems to be how Lumbers placed the Front in the River Valley area as well (east of Hwy 805), at the change between a western panel showing dominant NE-SW trends and an eastern panel showing no dominant trend in the anorthosite, but which contains large folds in the host gneisses. I had trouble understanding why he placed the Front where he did last summer (since there wasn't an obvious change in metamorphic grade, there was no major fault, no mylonite zone), but based on your comment, it seems clear that this change in structural pattern was an important factor in his positioning of the Front not only southwest of Sudbury, but to the east as well. This boundary may also mark the abrupt disruption in the continuity of Sudbury diabase as well, unfortunately, we don't have dikes right near the boundary to know this for sure. The area of the River Valley intrusion and its country rock gneisses north of the Sturgeon River and east of Highway 805 (Dana Township) are within the Grenville Province according to Lumbers. Unlike much of the area to the SW, however, strain and metamorphic recrystallization are not penetrative. Deformation and metamorphic recrystallization are largely restricted to high-strain zones, although the development of coronas in both the 2475 Ma River Valley gabbronorite to norite and in Sudbury diabase attests to regional Grenvillian metamorphism (after 1240 Ma at least). Something we can discuss further when you are in town. Good PGE numbers are coming out of some of the prospects in the River Valley intrusion and it will be receiving lots of exploration work over the summer. Have a good trip. Mike Easton ***************************** Precambrian Geoscience Section Ontario Geological Survey B7064, 933 Ramsey Lake Road Sudbury, Ontario P3E 6B5 705-670-5995, Fax 705-670-5905 eastonrm@vianet.on.ca sent June 15 2000 Mike, Just a short note to express my regret that I didn't get to see you during our Spring field camp. I got completely tied up keeping the field camp going in the rain and trying (and mostly failing!!) to get the computer hardware and software working. I did make a quick visit to the Survey while bringing Norm& and Dave to a meeting they had with the Laurentian people, but it was unfortunately on one of the days you were unavailable. Re the Grenville, the only new observations we made are that the mylonitized granite at Alice Lake is cut by an equally deformed 1 ft thick dike that has a 'trap' dike trend, and that about 1.5 km south of the SE corner of Silver Lake on the road to Rheault, the deformed Huronian is cut by an undeformed dike of microgranite. There is also a small swarm of N-S garnet-bearing felsic dikes cutting the Huronian north of the Sudbury water treatment plant near Coniston. Recently I have been busy teaching myself and writing up a course module on 'heads-up' georegistration and basemap\landsat\airphoto\mag integration in Autocad (for the Sudbury region), and have appended a .jpg of a NAD83 georegistered .dwg version of Henderson's map of the Brodil/Chief Lake area. I hope to find some time in August to break down and overlay Davidson and Ketchum's data onto the same map, as well as enter the data from this years fieldcamp - but as of next Wednesday it is cycling time in Wales, France, and Spain!! Regards, Bill Church - The Chief Lake complex revisited, and the problem of correlation across the Grenville Front south of Sudbury, Ontario. A. Davidson. Points Made: Lower age limit for the Huronian is constrained by 2.47 age of the East Bull Lake intrusive suite Krogh et al 1984. Fahrig, W.F., Gaucher, E.H., and Larochelle, A. 1965. Paleomagnetism of diabase dykes of the Canadian Shield, CJES 2, 278-298. Small occurrences of ultramafic rock in hanging wall adjacent to the Chief Lake complex; also common to the NE - see Davidson, A., 1998 Current Research, and Easton et al., 1996 and 1999- Guide Book with Davidson. Ultramafic rocks have zircons coeval in age with the East Bull Lake body at 2.47 Ga (Corfu and Easton 1998, Institute of Lake Superior Geology. River Valley anorthosite data at 2.475 (Heaman, L.M. 1999, pers. comm to Davidson) p. 10 few tight folds in Huronian at the Front, cites Fueten but should cite Henderson. p. 10 conglomerate to south of Ramsay Lake was assigned by Colins 1936 to the Ramsay Lake. p. 10 states that Nipissing cuts axial planar foliation p. 11 close to the Front Huronian folds have been tightened and Nipissing diabase has been competently boudinaged. p. 11 U-Pb titanite in granodiorite cutting Huronian at Long Lake is 1749+12/-8 Davidson and Van Breemen 1994. p. 11 Eden Lake is 1747+/-3, Sullivan and Davidson 1993 p. 11 Killarney is 1742+/- 1.4 zircons Van Breemen and Davidson, 1988. p.11 Cutler titanite is 1740+16/-6, Davidson et al 1992. p. 32 " ..progressively deeper crustal level being exposed to the southeast. Displacement that brought this about was concentrated on faults, the greatest displacment being on the master fault referrred to as the Grenville Front Boundary fault." Davidson's placing of the Grenville Front at the boundary between granitic rocks and 'Grenville' gneisses relocates the Front to where it was assigned by Phemister and Grant in 1958, and to approximately the same position as Henderson's 'Western Limit of Completely recrystallized Rocks'. He also confirms Henderson's western limit of penetrative fabric in the plutonic rocks, and the location of Henderson's garnet isograd in the 'Grenville'. Lumbers however placed the Grenville Front Boundary Fault as separating a western panel within which the foliation trend has relatively regular NE-SW trend from an eastern panel within which the foliation trends outline large Z-shaped fold structures which are continuous with similar folds east of theboundary of the granite with the gneiss and which are also generally contiguous with other meso-scale folds mapped by Lumbers in eastern Tilton Township. The foliation trends shown on Henderson's map of the Brodil Lake area are not offset across the Grenville Front boundary as delineated by Davidson, and the importance of the mylonite zone designated by Davidson as the Grenville Front may therefore be illusory. It is perhaps merely a late Grenville high strain singularity. Furthermore, contrary to the impression given by Davidson (3rd sentence of the abstract), it is Lumbers Grenville boundary that marks the abrupt disruption in the continuity of southeast-trending Sudbury Diabases, and not the granite-gneiss boundary. This criterion was also used by Bethune and Davidson to define a Grenville Front in the Tyson Lake area to the west of that of Lumbers and Card. Krogh (Yearbook 65) reported a whole-rock Rb-Sr age of 1750 Ma for samples collected along the Brodil Lake road crossing the Linton Lake granite as defined by Davidson. Muscovite from a small northeast trending granite dike that intrudes the Huronian section at the northwest margin of the granite gave a Rb-Sr age of 1600 ma and a zircon from the same rock an age of 1655 Ma. Krogh concluded that the granite underwent plastic and brittle deformation at 1700 Ma or at some time earlier than 1450 Ma. Krogh's isotopic studies in the Bell lake region also showed that deformation occurred between the time of intrusion of the 1700 Ma granites and intrusion of c. 1500 Ma granites at Bell Lake. More recently he has shown that undeformed in situ pegmatites that cut the front-parallel geneissic foliation have ages of c. 1450 Ma and contain monazite or zircon whose degree of discordance towards a Grenville age intercept varies according to their distance from the 'Grenville Front'. In the vicinity of the Front at Highway 69 muscovite from an undeformed (non-mylonitized) dyke has a Rb-Sr age of 1630 Ma, whereas a cataclastically deformed pegmatite contained monazite with an age of 988+/-2. Davidson and Van Breemen also reported a titanite age of 1749 for the Little Raft Lake granodiorite, but zircon from the Raft lake megacrystic granite has an age of 1464 Ma. A granitic dike also cuts deformed Huronian in exposures on the east side of the road south of the Murray fault. The granite is however not deformed??? Review of paper: The Chief Lake complex revisited, and the problem of correlation across the Grenville Front south of Sudbury, Ontario by A. Davidson. Davidson's paper is a useful statement of his recent work in the Broder-Dill Township region of the Sudbury District, and the maps will be of interest at least to local workers: map Figure 3 does contain some revisions to map Figure 2 of Davidson and Ketchum (1993) - diorite-monzonite agmatite reappears as massive diorite comingled with granite, coarse pink granite is in some places now massive hornblende gabbro, medium to fine granite becomes equigranular granite, and 'grey tonalite, granodiorite' less informatively becomes Eden lake suite. On the other hand Davidson's maps do not show the large horseshoe-shaped screen of quartzite mapped by Henderson as occuring in the Linton Lake granite east of Brodil Lake, and which is even shown on Lumbers Burwash sheet. The conclusions are not novel, since I doubt that anyone in this day and age would pretend that the Grenville Front is a Grenvillian terrane boundary. To be certain that the foliation in the Raft lake megacrystic granite is not a non-penetrative Grenville fabric would require demonstration that undeformed Sudbury dykes transect the foliation in the granite. However, the pattern of distribution of Sudbury diabase in Fueten and Redmond's map of the area show that the Sudbury diabase extending NW from the northeast end of Long lake shows the same sinistral stepped displacement pattern as the dykes mapped by Bethune at Tyson Lake. The existence of Grenville age faults and shear zones cannot therefore be ruled out as an element in the structural history of the rocks between Brodil Lake and the Murray Fault. Davidson's map does shows a Sudbury diabase cutting the north-west margin of the Raft Lake granite east of the NE end of Raft Lake, but no specific comment is provided on its relationship to deformation in the granite body. Davidson (p. 14) reiterates an earlier suggestion that the samples of granite that gave a 1.75 Ga age (Krogh 1967) for the Linton Lake granite may have been collected from unrecognized rafts of older granitoid rock. However, this would imply that the older granite is lithologically unrecognizable from the Linton granite. There is no indication of which outcrops were sampled by Henderson (1967, GAC Guidebook, p. 279) other than a statement that Krogh collected his samples between locations 6 and 8 on Henderson's field guide map. The contradiction between the isotopic ages and Davidson's assertion that the Linton Lake granite intrudes the Raft Lake granite could however be explained as a remobilization phenomena involving the intrusion of a mafic relatively high temperature Raft lake magma into a lower temperature melting Linton Lake. This would not be incompatible with Davidson's description of mafic phases of the Raft Lake incorporating crystals detached from partly consolidated granite. 18:30:42 17 APR 00 key[ geology GIS Sudbury air aerial photos airphotos photographs ] Coloured orthophotos of the Sudbury region: Firstly, full tiles were captured with Snagit from the above website, and placed on layers in Autocad, where the layer name includes the coordinates of the bottom left corner. The tiles were then registered. Secondly, smaller higher resolution images were captured and registered to locations on the full tile, including where possible one of the corner locations. The Tiles are: col490_5145, 495000, 5150000 copper col490_5150, 495000, 5155000 azilda col495_5145, 500000, 5150000 clara col495_5150, 500000, 5155000 frood col500_5145, 505000, 5150000 ramsey col500_5150, 505000, 5155000 north col510_5145, 515000, 5150000 coniston col510_5150, 515000, 5155000 testmap area col515_5145, 520000, 5150000 wahnapitei col515_5150, 520000, 5155000 east of test area see c:\arcfolders\orthophotomap.jpg map showing tiles with numbers Geology 350Y - Aerial Photos - Sudbury Grenville Front region. Return to 350y Field Trips Coloured orthophotos of the Sudbury region: The orthophotos are downloaded as MrSid files and can be added directly to an ArcGIS document without any need to georeference. "The U.S. Geological Survey (USGS) provides the Microsoft TerraServer site with images and maps of the United States. The images are in the public domain, and are freely available for you to download, use and re-distribute. If you download and use any images, the TerraServer team and the USGS appreciate a reference to our work on this project." See http://terraserver-usa.com/about.aspx?n=aboutaboutimages Airphotos for Brodil Lake and NW Sudbury have now been received (Nov 17th 2000) and are all in envelope marked Sudbury: year =89 flight line = e.g. 4615 Roll e.g. 20 photos that have been scanned are marked (scan) Brodil Lake 89-4613 18-152, 18-154(scan) 89- 4614 20-157(scan) Sudbury NW 89-4615 20-25(scan) 89-4616 18-24(scan), 18-26(scan) 89-617 32-22(scan), 32-24(scan), 32-26 89-4618 32-194(scan), 32-196(scan) Ordered airphotos for Hyman and Drury, and 1 photo each for Broder, Capreol and Falconbridge. Photos have now been received (June 6th 2000) and are all in envelope marked AGNEW LAKE: Agnew Lake 90/I-4615 27-58 27-60 27-62 27-64 27-66 90/I-461421-119 21-121 21-123 21-125 21-127 Norduna Mine Northeast of Falconbridge 89-462132-145(scan) Rhealt (Brodil Lake road) 89-4614 20-155(scan) Capreol 89-4624 24-35(scan) 4614-166 TIF Red Deer Lake shear pod. 4617-190 Dill Lake SE corner, Raft Lake (NW corner). 4617-191 Dill lake SW corner, Highway 69 NS (east side). 4618-94 Richard Lake (north side), Highway 69. 4618-95 Richard Lake (NW corner) Highway 69. 4618-96 Highway 69 (SW corner). 4618-97 Gravel pit (east central). 4618-98 Wanapitei River NS (centre). 4619-231 not done Richard Lake (south centre). 4619_232 $$not done Richard Lake Daisy Lake (along SW - NE diagonal); check Mississagi Quartzite along the NW shore of the lakes, seems to change character from layered in NW corner to white massive to the SE. 4619_233 TIF$$ Daisy Lake and railroad; complement of 4619-232. 4619_234 TIF NW end of Daisy Lake, Baby lake, Alice Lake, the Wanapitei River, and the railroad. 4619_235 TIF Alice Lake (NW corner), Wanapitei River (centre). 4619_236 TIF Wanapitei River, (NW and SW corners). 4619-237 not done Highway 532 (east side). 4619-238 not done Highway 532 (centre). 4619-239 not done Highway 532 (west side). 4619-240 Dryden road to Elbow Creek (centre). 4619-241 Dryden road to Elbow Creek, intersection with NS Dryden road (centre). 4619-242 TIF $$Northeastern most end of Red Deer Lake; Dryden anorthosite and Sudbury meta-diabase. 4619-242 not done$$ Northeastern most end of Red Deer Lake and Elbow Creek Lakes; Dryden anorthosite and Sudbury meta-diabase. 4620_118 not done Ramsay Lake (west to centre). 4620_119 not done eastern Ramsay Lake (west) and Highway 17 4620_120 TIF Ramsay Lake (western edge); Baby Lake (SE corner).(scan) 4620_121 TIF Coniston (NE corner) Baby Lake (centre south edge). 4620_122 TIF Coniston (North edge); Wanapitei River (SE corner); Baby Lake and northern part of Alice Lake (SW corner).(scan) 4620_123 TIF Coniston (NW corner); Wanapitei River (Diagonal centre east to SW).(scan) 4620_124 TIF Wanapitei village (NE corner); Wanapitei River (diagonal). 4620_125 not done Wanapitei village (center North); Wanapitei River (diagonal North sector). 4620_126 not done Wanapitei village (NE corner); Wanapitei River (diagonal). 4620_127 not done Dryden Road (South sector). 4620_128 not done Dryden Road (south edge); gravel pits (east centre). 4620_129 not done Dryden Road cul-de-sac (SW corner). 4620_130 not done anorthosite body (NE-SW diagonal in east centre). 4621_8 not done Rest Haven/Highway 17 (south centre); Falconbridge - Airport Road (NW). 4621_9 not done Rest Haven (SW corner) /Highway 17; Garson Railroad (North edge). 4621_10 not done Coniston (SE corner); E W Highway 17 (Southern sector); E-W Garson Railroad (North edge). 4621_11 not done Coniston (south sector); N-S Coniston - Garson Mine road (east sector).(scan) 4621_12 TIF Coniston (SW corner); N-S Coniston - Garson Mine road (west centre). 4621_13 TIF N-S Falconbridge railroad (centre); Highway 17 (southern edge); Wanapitei (SE corner). 4621_14 TIF Wanapitei (south-east sector); N-S Falconbridge railroad (west edge); E - W Highway 17 (southern sector). 4621_15 TIF Wanapitei (SW corner) Wanapitei River (NE to SW diagonal). 4621_16 TIF Wanapitei River (NE - SW diagonal); Highway 17 (NE centre to SW corner diagonal). 4621_17 TIF Wanapiti Riverighway 17 (NW sector). 4621_18 not done Wanapitei River (NW corner); Highway 17 (North sector). 4621_19 not done Highway 17 (NW sector). 4622_62 not done Garson Junction - Lebel (NW sector) 4622_63 Garson Junction (north edge). 4622_64 Garson Junction railroad (Southern section). 4622_65 Garson Junction railroad (south section); N-S Coniston-Falconbridge Road (east sector) (scan) 4622_66 Garson Junction railroad (SW corner); N-S Coniston-Falconbridge Road (west sector) 4622_67 N-S Falconbridge railroad (centre); north of 4621-13.(scan) 4622_68 N-S Falconbridge railroad (western edge). 4622_69 Falconbridge refinery road (NE sector); large fold structure evident. 4622_70 Falconbridge refinery road (central sector); large fold structure evident. 4622_71 Falconbridge refinery road (southern sector). 4622_72 Wanapitei River (diagonal, SE sector); Highway 17 (SW corner). 4622_73 Wanapitei River (diagonal, central sector). ************************************************ The following photos are of regions in the Northern Grenville; stored in 350Y Grenville box ? should be north of Sudbury because Coniston photos are 4621 50-4630 18-18 West Tanner Lake 70-4609 9-3 Wanapitei diabase locality 70-4608 8-60 Tyson Lake area 73-4607 65-206 to 212 73-4606 10-78 to 84 73-4605 10-148 to 152 Highway 69 - Highway 64 Jamo area 70-4605 10-235 to 245 59-4604 59-61to 67 and 8-111 to 113 59-4603 8-146 French River 59-4601 35-47 The following photos have been converted to jpg images 12tiff600c.jpg 4614-155rheault2.jpg 4613-152linton.jpg 4613-154brodil.jpg 4614-157raft.jpg 4615-25mikkola.jpg 4616-24meatbird.jpg 4616-26coppersw.jpg 4617-22snider.jpg 4617-24clara.jpg 4617-26copperne.jpg 4618-194murray1700.jpg 4618-194murray.jpg 4618-196frood.jpg 4621-145norduna.jpg 4624-35capreol.jpg 4614-155rheault.jpg 4622_65.jpg 4622_67.jpg 4621_11tc.jpg 4621_11.jpg 4620_123.jpg 4620_122.jpg 4620_120.jpg 21:20:52 06 MAY 00 key[ 350Y 2000b ] 350Y-2000 Return to 350y Field Trips Joe Riddel James Masters Zoran Pejic Jaroslaw Kuczynski Simon Toogood Sun April 30 Travel to Sudbury Mon May 1 The Sudbury Basin and Southern Province to the Grenville Front (instructional day; all students) Tue May 2 Geophysics (all students); checked out the Copper Cliff rhyolite and the Murray Granite; Wed May 3 The northern Grenville (instruction) Thu May 4 Group mapping exercise (instructional day in 13) Fri May 5 The Espanola/Whitefish Falls region (instructional day) visited Raven Lake and Whitefish Falls (norm& had to return to Sudbury by 3 pm); visited Laurentian. Sat May 6 Geophysics (geology students); morning - folded area 13 north of the Water Treatment; afternoon contact of the gabbro and quartzite in the Garson Road quarry (GPS reading on the road), and the fold in the quartzite sliver in the hill north of the quarry. Sun May 7 Mapping further instruction in 13 Mon May 8 Mapping 13 Tue May 9 Mapping 13 Wed May 10 Mapping; morning rain; afternoon area 118 Thu May 11 check area around the Sudbury dump; afternoon map test area until 6 pm. Fri May 12 Visited OGS until 10.15; picked up map by Steve Jackson May 1, Monday 1 Highway 17 and the road to Coniston power generation station, 5 14 166,51 48 276 PDOP 2.7 Walked out a section from behind the Sudbury Water Treatment Plant to the north. 2 garnet bearing felsic dike striking 212, behind the Sudbury Water Treatment Plant, 5 13 917, 51 48 530 PDOP 3.4 3 a second felsic dike striking 192, 5 13 868, 51 48 616, 227m. 4 a vertical 10 metres wide Sudbury diabase trending 82 5 tight isoclinal fold closing to the north and plunging north at 50; cross bedding younging directions indicate the fold is an anticline; hinge exposed at one outcrop. Can be traced northwards through Sudbury breccas to the north but eventually may be cut out by a fault such that rocks on both sides of the fault young eastwards. 6 a third felsic dike strike 178, 5 13 746, 51 48 819 PDOP 2.7. 7 east younging quartzites cut by diabase trending 318; western end of the dike is located at 5 13 849, 51 48 716; the diabase has the same trend as the NW trending Bass Lake Syncline dikes; at western end of the dibase the diabase is transected by a foot scale, orange weathering, ragged dike of Sudbury diabase. The Coniston - Garson road (Quarry) 8 quartzites at the side of the road south of the quarry display folds indicating the existence of an syncline to the east; the gabbro is fine grained near the contact and shows deformation only in the form of very minor non-penetrative shear zones. 9 quarry at 5 12 851, 51 50 113 displays quartzites in the form of a vertical syncline, cut to the east by diabase; the diabase at the contact is possibly finely foliated; Norm has sample of the contact; vague possibility ?? of an isoclinal fold refolded by the vertical fold in the face of the quarry. 10 rocks in the steep slope of the metasedimentary unit north of the quarry show strike variations indicating the existence of a steeply plunging syncline closing to the south. Younging include cross bedding and ball and pillow structures. The amplitude of the fold is not discernable and it seems to be cut off by a NE trending fault marked by a prominent gully, east of which the quartzites again young eastwards (These features need to be mapped on the photos.) 11 samples of metamorphosed quartzite numbered con001, 2a-e, 3a-c. key[ 350y - 2001] Return to 350y c:\fieldlog\Espanola wedge has Whitefish fall and Cutler data: espwedgebasenad83 and espwedgegeolnad83 .dwg files. The geology file has had the layers from the Ontario topographic (roads, rail) basemap as well as road and rail, etc, layers from the Garson, Coniston, etc, 1:100000 maps. It also has a layer for the Fieldcamp area photo localities/descriptions. c:\fieldlog\sudbury region has OGS based sudburybasenad83.dwg and sudburygeolnad83.dwg files. The geology file has road, lake, etc layers attached from the 1:10000 basemaps, and will eventually the master project map for layers attached from the Brodil, Creighton, Drury and Map 1 projects. c:\fieldlog\brodil has Grenville Front Sudbury to Brodil Lake data c:\fieldlog\Map1 has field camp data c:\fieldlog\drury has data being entered by Krista Blears c:\fieldlog\creighton has data being entered by Ronnie Theriault c:\aacrse\350\sudburywherewhat\sudburynad83.dwg has data concerning locations of airphotos, township boundaries, etc. c:\aacrse\350\ogs_esp-sud has a subset of the data from the OGS lambert projection basemap and geology map for the Espanola wedge (SS Marie to Sudbury). The geology map Espgeonad83.dwg has the roads, shorelines, rivers added from the 1:10000 digital basemaps. c:\aacrse\350\ogs has the original Ontario topographic basemap, township, tectonic, and geology files. **************************************** Chiarello, Maria001705359 Duncan, Emily S.000417394 Facey, Grant Richard 001807478 Theresa Griffin (code=03) Krista Blears (code=02) WRC (code = 20) Right-hand rule - dip direction is right hand from the azimuth direction Previously mapped stations in c:\fieldlog\map1 were numbered 1001 to 7158 Station number values e.g 105200501 is coded 1=year, 05=month, 02=student, 06=day (traverse), , 001=station #; all orientation measurments are relative to grid north. (The coding in the relevant Excel file 01map1.xls and 01photosB.xls has been change to wrc = 20, krista 2). Copy the data to Word and sort according to fields in the Fieldlog table into which the data is to be imported. C:\fieldlog\map1\00map1_01.xls and G:\fieldlog\map1\00map1_01.xls contains data including photos for 350y in 2001 (mine and Krista Blears); same data as in asksam 350y-2001 Day 1 May 1st Tue 10501 (Tue) 10501 Tues - Travel to Sudbury 1050201001 Parry Sound section 1050201002, 570000, 5030366, "Nobel eclogite? body" 1050201003, 557185, 5043199, "Shawanaga shear pod" 1050201-04, 51???,, "Sudbury diabase with plag xenoliths, converted to amphibolite" 1050201005, 515315, 5120706, "Sudbury diabase in 'fat' migmatites, Burwash locality" ********************************* Day2 May 2nd Wed 73-12.dwg 10502 (Wed, eastern edge of the map area) Location points of all students have been added to 4621-12maparea.dwg 10502 Wed - Eastern section of the mapping area 1050102001, 514165, 5148287, , , , ," Hydro road junction with 17 east of water works" 1050102002, 514521, 5148297, , , , ,"X-bedded sandstone 209/52, younging west, paleocurrentSW" 1050102003, 514575, 5148476, "sandstone", subed, 224, 80, " (north of the rail tracks)" 1050102004, 514486, 5148869, "sandstone", subed, 224, 80, "slump balls" 1050102005, 514739, 5149192, "sandstone", subed, 256, 50, "felsic dike with acicular amphibole 256/80", " (Photos - 335studs1.JPG - view looking west of Norman and the gang looking at the western end of the felsic dike locality, 336 felsiccontact1.JPG - contact of Felsic dike with quartzites)" 1050102006, 514862, 5149220, "sandstone", subed, 266, 90, "irregular felsic dike app. strike 244", "Photo - 337 felsiccontact2.JPG - irregular contact of felsic dike with quartzite, 338norm.jpg - view to the southwest of quartzites and felsic dike outcrops; mafic dike strike 200; cleaved Sudbury Breccia with matrix cleavage striking 265 (Photo - 339sudbreccfelsdikelocality.JPG, 340sudbreccapoph.JPG, 341felsicdykesudbreccontact.JPG; 342sudbrecfoliation.JPG)" 1050102007 Lunch stop 1050102008, 514604, 5149943, "Quartzite", subed, 312, 90 1050102009, 514858, 5150433, "gabbro", "Nipissing" 1050102010, 514685, 5150357, "sandstone", subed, 310, , "Contact, strike 303, of Nipissing and sandstone; abundant cleaved Sudbury Breccia" . 1050102011, 514052, 5150745, , , , , "E-W mafic trap dike strike 284" 1050102012, 513866, 5150732, "Photo - 346parasitic1.JPG; parasitic fold in a zone of macro folding" 1050102013, 513306, 5150407, "Hill on the pipe line track on way out to the Garson Road" Photos 335-346 335studs1.JPG -Norman and the gang at the felsic dike locality, 514739, 5149192 336felsiccontact1.JPG - Felsic dike with quartzites 514739, 5149192; 337felsiccontact2.JPG - irregular contact of felsic dike with quartzite 514862, 5149220 338norm.JPG - Norman at lunch spot north of felsic dike locality 514862, 5149220 339sudbreccfelsdikelocality.JPG 514862, 5149220 340sudbreccapoph.JPG 514862, 5149220 341felsicdykesudbreccontact.JPG 514862, 5149220 342sudbrecfoliation.JPG 514862, 5149220 343anticline1.JPG 344anticline2.JPG 345anticline3.JPG 346parasitic1.JPG 513866, 5150732 ***************************** Day 3 May 3 Thur 10503 (Thur, southern and western margin of the mapping area) Location points of all students have been added to 4621-12maparea.dwg No photos; no's in brackets are Krista's numbers 1050203001 (21), 513904, 5148530, "dike 010/64 of plag, amph-needles, garnet + Sud Breccia, shatter cones; bedding 184/74" 1050203002, (22), 513810, 5148637, "Sud Breccia; 513670,5148622 bedding turns from 190 to 220" 1050203003, (23), 513617,5148575, "x-bedded sandstone; vein of pegmatite" 1050203004, (24), 513718, 5148717, "diabase either intruding or a clast in breccia; strike 120; dikelets cross cut Nipissing at 513642, 5148727" 1050203005, (25), 513560, 5148717, "sandstone", subed, 165, , 1050203006, (26), 513688, 5148891, "(west end of a small black outcrop); 15m wide cross cutting dike of Sudbury diabase striking 268" 1050203007 (27), 513708, 5148950,"" 1050203008 (28), 513717, 5149283, "sandstone", subed, 188, , 10520203009 (29), 513913, 5149335, "sandstone", subed, 220, 50, "some breccia" 1050203010 (30), 514037, 5149459, "sandstone", subed, 198, 50" 1050203011 (31), 514101, 5149733, "sandstone", subed, 208, ,"Sudbury breccia; E-W foliation in brecciaparticularly when breccia is E-W trending; rocks potentially rotated by faulting or as part of a larger fold" 1050203012 (32), 514196, 5149698, "sandstone", subed, 202, , 1050203013 (33), 514317, 5149677, "(near railway), fine grained, rounded biotite-qtz-feldspar boulders, imbricated towards the west (Current?); E-W strike with relatively shallow dip" ***************************** Day 4 May 4 Fri 10504 (Fri, northern part of map exercise area) 10504 Fri Northern margin of the mapping area Location points of all students have been added to 4621-12maparea.dwg Data collected by Krista Blears (02): 1050204001 (41), 512652, 5150729, "gabbro", "Nipissing trending E-W" 1050204002 (42), 512769, 5150942, "contact strike 164 of Nipissing and Sudbury breccia" 1050204003 (43), 512803, 5150863, "contact strike 164 of Nipissing and Sudbury breccia" 10502041004 (44), 512846, 5150832, "contact 343/50 between Sud breccia and sandstone" 1050204005 (45), 512903, 5150722, "sandstone way up east (Flame structure)" 1050204006 (46), 513209, 5150690, "gabbro" 1050204007 (47), 513398, 5151028, "gabbro", "drill site 267" 1050204008 (48), 513444, 5151239, "contact striking 110 between Nipissing gabbro and sandstone" 1050204009 (49), 513533, 5151242, "sandstone", subed, 100, 66, "Sud breccia" 1050204010 (50), 513628, 5151288, "Sud breccia" 1050204011 (51), 513667, 5151237, "contact between Nipissing gabbro and 5 metre intermediate dike with amph. needles and garnet" 1050204-12 (52), 513807,5150998, "Nipissing gabbro" 1050204013 (53), 513785, 5151228, "cliff of Nipissing Gabbro" 1050204014 (54), 513016, 5150623, "sandstone" 1050204015 (55), 512480, 5150638, "sandstone", subed, 30, 68, E 1050204016 (56), 512461, 5150565, "Nipissing gabbro" 1050204017 (57), 512491, 5150444, "20 degree contact between sandstone (west) and Nipissing gabbro (east)" 1050204018 (58), 512907, 5150464, "contact of sandstone (with pyrrhotite) and Nipissing gabbro" 1050204019 (59), 513012, 5150460, "sandstone", subed, 170, 80 1050204020 (60), 513052, 5150457, "Nipissing gabbro - sandstone to the west" Photos 348 - 359 105010401 349felsicnippcontact2.JPG 105010402 352ripups2.JPG 105010403 353folds.JPG 105010404 354vieweast1.JPG 105010405 355viewnorth1.JPG 105010406 356viewne1.JPG 105010407 357viewfalconbridge.JPG 105010408 358parasite1am.JPG (same as 346) 105010409 359parasitic1b.JPG ***************************** Day 5 May 5 Sat Photos 360 - 372 10505 (Sat, Grenville down to Red Deer Lake) 1052005001, 522995, 5143789, "Sudbury diabase crossing the Dryden anorthosite" 1052005002, 518717, 5140214, " Junction of the Red Deer Lake road and highway 537 Wahnapitae to St Cloud (ophiolite dikes???)" 1052005003, 520058, 5139091, "Junction of Landing road and the Deer Lake Road" 1052005004, 520585, 5139025, "Sudbury diabase outcrop, north side of road" 360anorthosite.JPG 361normemilygrenville1.JPG 362normemilygrenville2.JPG 363dikesreddeer1.JPG 364dikesreddeer2.JPG 365dikesreddeer3.JPG 366dikesreddeer4.JPG 367dikesreddeer5.JPG 368agmatitegrenv1.JPG 369agmatitegrenv2.JPG 370clasts&pebblessuddiabreddeer1.JPG 371clasts&pebbessuddiabreddeer2.JPG 372anorthclast in suddiab.JPG **************************** Day 6 May 6 Sun 10506 (Sun Creighton granite (Clara Belle) to Brodil Lake) 1052006001, 494696, 5148117, "Augen granite of the Creighton pluton" 1052006002, 494700, 5147596, subed, 268, 80, "trap dike cutting granite; foliation in the chilled margin material of the dike 1052006003, 415395, 5146167,subed, 80, 50, S, "Balsam St intersection with highway 17; staurolite bearing meta-greywackes (turbidites); small shatter cones pointing 352 upwards" 1052006004, 501573, 5146130, subed, 90, 60, N, "Shatter cones point downwards to North; Laurentian University road side outcrops" 1052006005, 499187, 5140740, "deformed Sudbury breccia; granite sill in Mississagi Sandstones; highway to Long Lake" 1052006006, 499191, 5141069, subed, 90,90,S,"buff to pink weathering intermediate dike with small amphiolite needles; intrusion post-dates the regional shear deformation (foliation) seen in Sudbury breccia; sandstones dissected by anastomising shears" 1052006007, 500027, 5139680, "amphibolitized gabbro with patches of epidosite, cut by pink granite that has suffered subsequent brittle deformation; 1052006008, 499430, 5138198, subed, 60, 56, "crenulation (148/90) wraps the staurolite in schists at the side of the road 1052006009, 499491, 5138340, "total retrogression of flattened aluminsilicate porphyroblasts in the stream" 1052006010, 502390, 5137358, , , ,"isoclinally folded metasediments intruded by foliated granite; near small lake" 1052006011, 502721, 5134795, 58, 35 , , "western limit of completely recrystallized 'Grenville' gneisses; folded amphibolites; linear fabric oriented 140/490; Davidson's mylonite zone is located slightly north of the road junction" Photos 376-395 373groupphoto01_1.JPG 374groupphoto01_2.JPG 375groupphoto01_3.JPG 376creightongran1.JPG 377foliateddikeincreighton2.JPG 378foliateddikeincreighton1.JPG 379sudbreccincreighton.JPG 380trapdikecontactcreighton1.JPG 381trapdikecontactcreighton2.JPG 382tapdikeincreighton.JPG 383gradedbedbalsam.JPG 384seddefbalsam.JPG 385crencleavbalsam.JPG 386shattconesbalsam1.JPG 387shattconesbalsam2.JPG 388shattconeslaurentian.JPG 389-397 photos of Long Lake section between Silver Lake and Brodil are missing ****************************** Day 7 May 7 Mon 10507 (Mon Cutler granite and Whitefish Falls photos) 1052007001, 415690, 5118000, subed, 36,32, ,"contact with folded amphibolitic metagabbro" 1052007002, 414830, 5117751, subed, 84, 82, , "trap dike trending 276, intruded post foliation; foliation also represented by pseudobedding; Sudbury breccia on top of the outcrop is pre-early foliation; F2 folds plunging 100/36 are the dominant structure" 1052007003, 387196, 5117273, "foliated amphibolite likely Nipissing gabbro cutting distal greywackes, now crenulated garnet-mica schist; foliated rocks and D2 folds are cut by trap dikes, which nevertheless display a foliation in their contact margins; trap dikes are cut by Cutler granite which is also foliated" 1052007004, 387294, 5117266, "trap dike locality" 1052007005, 440010, 5124494, "McKim turbidites; chloritoids wrapped in S2 foliation, predate the main foliation" 1052007006, 443212, 5120043, "Sudbury breccia cut by F2 foliation; Plane Table lake" 1052007007, 433294, 5118940, "downward pointing shatter cone locality near Anderson Lake 1052007008, 444000, 5117317, "highly (rutiliferous), 50 m wide, altered Loon Lake fault zone (87,86) separating the North and South deformation domains" Photos 396-409 398masseycrencleav.JPG 399crencleavageculter1.JPG 400.crencleavagecutler2.JPG 401foldedfoldcutler.JPG 402curveddikecutler.JPG 403foldedcleavage in nipp.JPG 404diabcuttingfolnipp.JPG 405shatconeesp.JPG 406shattconesespanola.JPG 407foldedcleavinsudbreccclast.JPG 408deformeddiabcontactwhitefish.JPG 409diabboudinwhitefish.JPG *************************** Day 8 May 8 Tue 10508 (Tues Morning - Copper Cliff Offset dike, afternoon - Murray granite) Cobalt_805 Scanned text from Fedorowich, J., and Morrison, G., 1999 Maps from the F and M paper are in C:\aaGE\Southern_Province\Sudbury_KMZ\North_Range and C:\aaGE\Southern_Province\Sudbury_KMZ\805_Guide 1052008001, 494263,5146413, , , ,"Sud breccia, McKim Sediments; E-W Trap dikes cross-cut breccia and quartz diorite; see INCO guidebook for this locality which is just west of a track accessed from Cobalt street (From INCO offices turn right onto Power St, cross highway 17, turn left onto Cobalt street and continue to end of the WNW leg of the street onto a rough track running parallel to but west of the NNE leg of Cobalt street.) 1052008002, 496009, 5151959, "Murray Mine plaque; south along the rail track one encounters aphyric and plag-phyric mafic units, pink granite,grey monzodiorite/granodiorite; Murray granite is magnetite bearing; extremely weak fabric if any fabric at all" 1052008003, 496241, 5151463, 292, 90, , "high strain zone in granite" 1052008004, 496241, 5151428, "agmatites with some bands of spotted (cordierite?) hornfels" 1052008005, 496246, 5151050, "strained agmatites" 1052008006, 496230, 5150361, "outcrops with large staurolite xls; on east side of the road are beautifully preserved soft sedimentary structures (sheath-like folds); these rocks display no penetrative deformation." Photos 410 - 424 taken in 2001 are in C:\fieldlog\Southern_Province\Photographs\Sudbury_Coniston\Miscellaneous and photos 410 to 417 have also been transferred to: http://instruct.uwo.ca/earth-sci/fieldlog/Sudbury/Cobalt_St_850_CoppC_Offset/ 410irregcontdiabblcoinsb - irregular indented contact of diabase block in Sudbury Breccia, near stop 1. 411irregcontdiabblcoinsb2 - irregular indented contact of diabase block in Sudbury Breccia, near stop 1. 412rheomorphrhyoloffset - highly irregular felsic blebs in the margin of the offset dike; could originate as rheomorphic melts of the adjacent Copper Cliff rhyolite. 413cucliffoffsetterm - termination of the Copper Cliff offset dike in Sudbury Breccia, stop 5 414cucliffmin1 - sulphide mineralization, stop 7 415cucliffmin1 - sulphide mineralization, stop 7 416dikecuttinsb1 -irregular contact of dike with Sudbury breccia in McKim sediments, with injections of Sudbury breccia material into the diabase. 417dikecuttingsb2 - irregular contact of dike with Sudbury breccia in McKim sediments, with injections of Sudbury breccia material into the diabase. 418agmatite1 - agmatite mafic skialiths of Elsie Mountain mafic rocks in Murray granite 419cordierite1 - cordierite? in sedimentary layer in the Elsie Mountain basalts 420cordierite2 -cordierite? in sedimentary layer in the Elsie Mountain basalts 421agmatite2 - undeformed agmatites with skialiths of mafic Elsie Mountain 422defagmatite - deformed agmatite metres from 421agmatite2 423stobiestaur - coarse staurolite crystals in Stobie sediments; second outcrop north of the junction of the Clara Belle road with Highway 144 424stobiesed - slump balls in Stobie sediments east side of road opposite first outcrop north of the junction of the Clara Belle road with Highway 144; sediments young south. Fedorowich, J., and Morrison, G., 1999, Sudbury Ni-Cu-PGE deposits, South Range (A1) and North Range (B1), Geol. Assoc. Canada -Mineralogical Association of Canada, Joint Annual Meeting, Sudbury. map A1-4, p. Copper Cliff Offset, 850 Orebody area, 20. ************************** Day 9 May 9 Wed 10509 (Wed - Spider Peak area (Norm& went to Laurentian)) Photos 425-427 425vertshattcones1.JPG 426horizshattcones1.JPG 427horizshattcones2.JPG All of Grant's location points (red), and four of Krista's known location points (marked in bold below; Magenta on the .dwg photo) have been plotted on 4620-120spider.dwg Data collected by Krista (02): 1050209001, ?, "sandstone", subed, 270, 45, "two sets of shatter cones point both west and downwards, 425vertshattcones1.JPG; 426horizshattcones1.JPG; 427horizshattcones2.JPG" 1050209002, 509193, 5147922, "junction of road and side road on south side of the railway tracks" 1050209003, 509233, 5147934, "centre of bridge of highway" 1050209004, 508824, 5145966, "?" 1050209005, 508754, 5146052, "sandstone", subed, 130, 42 ,SW, "rotated by folding to 76 to 120; fold axis 204, plunge 42; Sud breccia is foliated" 1050209006, 508613, 5146189, "Nipissing gabbro" 1050209007, 508822, 5146565, "foliated Sudbury breccia" 1050209008, 508911, 5146617, "sandstone 150/74" 1050209009,508854, 5146675, "sandstone 130/58" 1050209010, 508734, 5146688, "strike change 162/64 to 070; folds plunge 45; cross cut by Sud breccia" 1050209011, 508888, 5146446, "sandstone 146/84" 1050209012, 508901, 5146311, "Sud Breccia" 1050209013, 508794, 5146235, "contact, 030 between sandstone and Sud breccia" 1050209014, 508571, 5146070, "sandstone 70/50" 1050209015, 508406, 5145959, "sandstone 40/32, younging east; shatter cones point up" 1050209016, 508247, 5146070, "sandstone 214/50, younging SE" 1050209017, 508089, 5145963, "sandstone 70/78; Sudbury breccia" 1050209018, 507941, 5146090, "sandstone 260/70" 1050209019, 507696, 5146010, "Sud breccia in cross-bedded sandstone; sandstone 65/55, younging east" 1050209021, 508042, 5146240, "Sud breccia" 1050209022, 508128, 5146456, "Sud breccia" 1050209023, 508179, 5146625, "Sud breccia" 1050209024, 508122, 5146774, "sandstone 100/54" 1050209025, 508156, 5146840, "sandstone, 120/50, younging SW" 1050209026, 508002, 5146865, "Sud breccia" 1050209027, 507933, 5146981, "Sud breccia" 1050209028, 507310, 5147465, "road junction with train tracks" 1050209029, 507512, 5147919, "road junction" ************************** Day 10 May 10 Thur 10510 (Thur, the Coniston Fold) 10510 Thur morning - Coniston fold; Thur afternoon - Impact Meeting at the OGS Folds are outlined on paper blowup in platic case. All location points collected by Krista, Grant, Therese, and Maria have been plotted in 4620-122coniston.dwg Data collected by Krista Blears (02): 1050210001, 511464, 5147054, "Road intersection at parking location in Coniston near the gate to the dump road" 1050210002, 511373, 5146873, "fold structure, beds varying in orientation from 30/82 to 111/78; plunge 341" 1050210003, 511371, 5146882, "sandstone 220/67" 1050210004, 511320, 5146882, "" 1050210005, 511331, 5146973, "sandstone 214/72, younging west ?" 1050210006, 511292, 5146966. "folding, Sud breccia" 1050210007, 511261, 5146934, "sandstone, 212/83 younging west; folded to 085/72" 1050210008, 511286, 5146939, "folding from 217/85 (north limb) to 93/68 and back to 34/80" 1050210009, 511327, 5146771, "sandstone 208/74" 1050210010, 511190, 5146835, "sandstone 80/60 folded to 186/72 (plunging 098) returning to 87/76" 1050210011, 511207, 5146892, "sandstone 46/82" 1050210012, 511261, 5147028, "folding from 102/67 to 210/84, plunge east" 1050210013, 511212, 5147041, "fold plunge 54/52, varying from 188/58 to 275/60" 1050210014, 511331, 5147169, "sandstone 120/58, younging west" 1050210015, 511317, 5147243, "sandstone 206/58" 1050210016, 511371, 5147325, "sandstone 204/78" 1050210017, 511479, 5147404, "sandstone 120/74" ************************** Day 11 May 11 Fri 4621-11.dwg 10511 (Fri morning - rain; afternoon - 'bleb' locality, south of rail tracks) 1052011001 X-bedded sandstone with blebs, strike 24/45, tops to east; 510491, 5151420 1052011002 photograph of metasandstone with a shatter cone and blebs, 510449, 5151328 Photos 428-430 428globules1.JPG 429globules2.JPG 430normjump.JPG ************************** Day 12 May 12 Sat 4622-65.dwg 10512 (Sat, test day) 10512 Sat - exam day 1052012001, 512112, 5153620, "gabbro", , , "pegmatite spiral in Nipissing; photos 431-433" 1052012002 "S-fold in quartzite, strike 95/steep, younging south; photo 434 (looking south), 435, 436; views 437-440; no GPS, get value from registered photo" 1052012003, " Outcrops of X-bedded sandstone at the western margin of the Nipissing diabase east of the Garson road to the south of the gravel quarry; Z-folds plunging 205; at south end of the outcrops the sandstone has a strike of 164, dipping ENE; no GPS (battery run out)" 1052012004, 512023, 5149578, subed , 280, ,"outcrop west of rail track before the bend approaching Coniston; Sudbury breccia but some beds possibly striking 280" 1052012005, 511725, 5150711, "sandstone", subed, 246, 90, S, "contact of fine grained Nipissing diabase and x-bedded sandstone" 1052012006, , ,"sandstone", subed, 286, 60, N, " last outcrop in this sector before the rail tracks, just northwest (300) of the gas pumping station north of the bridge" 1052012007, 512399, 5150778, "location of bridge south of the pumping station" 1052012008, 511236, 5151718, " (this value is off by 1 km due to influence of the power line??)", "outcrop east side of the road at the power line" Data collected by Krista BLears (02): 1050212001, 512012, 5153218, "Point zero at road side " 1050212002, 511921, 5153302 , "gabbro", "Nipissing" 1050212003, 511747, 5153100, "sandstone", subed, 95,72, S 1050212004, 511747, 5153100, "sandstone", subed, 100, 87, "foliated" 1050212005, 511442, 5153214, "sandstone", subed, 100, 80, "foliated" 1050212006, 511355, 5153074, "sandstone", subed, 102, 80, "foliated" 1050212007, 511333, 5152915, "sandstone", subed, 95, 87, "foliated" 1050212008, 511411, 5152815, "sandstone", subed, 98, 85, "foliation", 310, 76 1050212009, 511130, 5152952, "sandstone", subed, 78, 82, "foliation", 108, 75, "Sud breccia" 1050212010, 511059, 5153100, "sandstone", subed, 272, 86 1050212011, 510960, 5153045, "sandstone", subed, 75, 73, "foliated" 1050212012, 511133, 5152759, "sandstone", subed, 56, 67, "foliation", 274, 80 1050212013, 511330, 5152849, "sandstone", subed, 91, 70, "foliation" 1050212014, (no data) 1050212015, 511508, 5152790, "sandstone", subed, 92, 70, "foliation", 321, 68 1050212016, 511955, 5152831, "sandstone", subed, 107, 82, "foliation", 298, 60 1050212017, 512186, 5153005, "sandstone", subed, 102, 80, "foliation", 300, 42 1050212018, 512287, 5152702, "sandstone", subed, 96, 68, "foliation", 310, 52 1050212019, 512146, 5152650, "sandstone", subed, 96, 68, "foliation", 302, 60 1050212020, 512379, 5152186, "sandstone", subed, 92, 70, "foliation", 300, 80 Photos 431-447 431spiralpeg3.JPG 432spiralpeg1.JPG 433spiralpeg2.JPG 434sfold1.JPG 435synsedfault.JPG 436sedflame2.JPG 437viewsudbury.JPG 438vieweast.JPG 439viewconiston.JPG 440viewfalconbridge2.JPG 441zfold1garsonroad.JPG 442zfold2garsonroad.JPG 443zfold3garsonroad.JPG 444synsedfoldingnwofbridge1.JPG 445synsedfoldingnwofbridge2.JPG 446xbedsyoungnorthnwofbridge.JPG 447xbedsastsideofroadatpowerline.JPG *************************** Day 13 May 13th return to London Photos 448-453 10513 (Sun) 448giblakemarble1.JPG - marbles on highway 69 at Gibson Lake, UTMNAD83 596426, 4978235 (13105) 449giblakemarble2.JPG 450giblakemarble3.JPG 451giblakemarble4.JPG 452flattire1.JPG 453flattire2.JPG ******************************************************************************* Photographs 10502 (Wed) 335studs1.JPG -Norman and the gang at the felsic dike locality, 4621-12,13 336felsiccontact1.JPG - contact of felsic dike with quartzites, east side of railroad, 4621-12,13 337felsiccontact2.JPG - irregular contact of felsic dike with quartzite 338norm.JPG - Norman at lunch spot north of felsic dike locality, looking south, Highway 17 in far distance 339sudbreccfelsdikelocality.JPG 340sudbreccapoph.JPG 341felsicdukesudbreccontact.JPG 342sudbrecfoliation.JPG 343anticline1.JPG 344anticline2.JPG 345anticline3.JPG 346parasitic1.JPG 10503 (Thur, southwest part of map exercise area) no photos 10504 (Fri, northern part of map exercise area) 348felsicnippcontact1.JPG 349felsicnippcontact2.JPG 350felsicnippcontact3.JPG 351ripups1.JPG 352ripups2.JPG 353folds.JPG 354vieweast1.JPG 355viewnorth1.JPG 356viewne1.JPG 357viewfalconbridge.JPG 358parasite1.JPG 359parasitic1b.JPG 10505 (Sat) 360anorthosite.JPG 361normemilygrenville1.JPG 362normemilygrenville2.JPG 363dikesreddeer1.JPG 364dikesreddeer2.JPG 365dikesreddeer3.JPG 366dikesreddeer4.JPG 367dikesreddeer5.JPG 368agmatitegrenv1.JPG 369agmatitegrenv2.JPG 370clasts&pebblessuddiabreddeer1.JPG 371clasts&pebbessuddiabreddeer2.JPG 372anorthclast in suddiab.JPG 10506 (Sun) 373groupphoto01_1.JPG 374groupphoto01_2.JPG 375groupphoto01_3.JPG 376creightongran1.JPG 377foliateddikeincreighton2.JPG 378foliateddikeincreighton1.JPG 379sudbreccincreighton.JPG 380trapdikecontactcreighton1.JPG 381trapdikecontactcreighton2.JPG 382tapdikeincreighton.JPG 383gradedbedbalsam.JPG 384seddefbalsam.JPG 385crencleavbalsam.JPG 386ahattconesbalsam1.JPG 387shattconesbalsam2.JPG 388shattconeslaurentian.JPG 389-397 photos of Long Lake section between Silver Lake and Brodil are missing 10507 (Mon) 398masseycrencleav.JPG 399crencleavageculter1.JPG 400.crencleavagecutler2.JPG 401foldedfoldcutler.JPG 402curveddikecutler.JPG 403foldedcleavage in nipp.JPG 404diabcuttingfolnipp.JPG 405shatconeesp.JPG 406shattconesespanola.JPG 407foldedcleavinsudbreccclast.JPG 408deformeddiabcontactwhitefish.JPG 409diabboudinwhitefish.JPG 10508 (Wed - Murray granite) 410irregcontdiabblcoinsb - irregular indented contact of diabase block in Sudbury Breccia, near stop 1. 411irregcontdiabblcoinsb2 - irregular indented contact of diabase block in Sudbury Breccia, near stop 1. 412rheomorphrhyoloffset - highly irregular felsic blebs in the margin of the offset dike; could originate as rheomorphic melts of the adjacent Copper Cliff rhyolite. 413cucliffoffsetterm - termination of the Copper Cliff offset dike in Sudbury Breccia, stop 5 414cucliffmin1 - sulphide mineralization, stop 7 415cucliffmin1 - sulphide mineralization, stop 7 416dikecuttinsb1 -irregular contact of dike with Sudbury breccia in McKim sediments, with injections of Sudbury breccia material into the diabase. 417dikecuttingsb2 - irregular contact of dike with Sudbury breccia in McKim sediments, with injections of Sudbury breccia material into the diabase. 418agmatite1 - agmatite mafic skialiths of Elsie Mountain mafic rocks in Murray granite 419cordierite1 - cordierite? in sedimentary layer in the Elsie Mountain basalts 420cordierite2 -cordierite? in sedimentary layer in the Elsie Mountain basalts 421agmatite2 - undeformed agmatites with skialiths of mafic Elsie Mountain 422defagmatite - deformed agmatite metres from 421agmatite2 423stobiestaur - coarse staurolite crystals in Stobie sediments; second outcrop north of the junction of the Clara Belle road with Highway 144 424stobiesed - slump balls in Stobie sediments east side of road opposite first outcrop north of the junction of the Clara Belle road with Highway 144; sediments young south. 10509 (Wed - 'Spider Peak' orienteering exercise) 425vertshattcones1.JPG 426horizshattcones1.JPG 427horizshattcones2.JPG 10510 (Thur morning - Coniston Fold; afternoon INCO COnference) no photos 10511 (Fri morning - rain; afternoon - 'bleb' locality, south of rail tracks) 428globules1.JPG 429globules2.JPG 430normjump.JPG 10512 (Sat, test day) 431spiralpeg3.JPG 432spiralpeg1.JPG 433spiralpeg2.JPG 434sfold1.JPG 435synsedfault.JPG 436sedflame2.JPG 437viewsudbury.JPG 438vieweast.JPG 439viewconiston.JPG 440viewfalconbridge2.JPG 441zfold1garsonroad.JPG 442zfold2garsonroad.JPG 443zfold3garsonroad.JPG 444synsedfoldingnwofbridge1.JPG 445synsedfoldingnwofbridge2.JPG 446xbedsyoungnorthnwofbridge.JPG 447xbedsastsideofroadatpowerline.JPG 10513 (Sun) 448giblakemarble1.JPG - marbles on highway 69 at Gibson Lake, UTMNAD83 596426, 4978235 (13105) 449giblakemarble2.JPG 450giblakemarble3.JPG 451giblakemarble4.JPG 452flattire1.JPG 453flattire2.JPG 21:44:22 06 JAN 02 key[ Newfoundland geology] - L.B. Goodwin and P.F. Williams Deformation path partitioning within a transpressive shear zone, Marble Cove, Newfoundland; J. Structural Geol., 18, 975-990. 18:01:26 22 JAN 02 key[ geology huronian penokean Zolnai ] Andrew, Thanks for your note and my apologies for being so late acknowledging its receipt. Teaching and adiministration, and an extended family, take up so much of my time that it is difficult to pause for thought. I rarely get to think about the Huronian as a problem except for one lecture in November ( http://instruct.uwo.ca/earth-sci/200a-001/25sudbur.htm ) and during the two week field camp in May. Perhaps when I retire I will have more time. Our primary third-year field camp area is located between Coniston and Garson with secondary interests in the Grenville Front in the Rheault - Brodil area, the Cutler area at the western end of the Espanola wedge, and the Whitefish Falls area where I taught a second year filed course for many years.. At Coniston we are interested in mapping out the relationship between early large scale tight folds, Nipissing gabbros, the large scale aureoles to the gabbros, Sudbury breccia, the NW-SE foliation present only in the matrix to the Sudbury breccia, the trap dikes, a suite of amphibole-garnet bearing felsic dikes, and rare pegmatites, and the structural relationship of this block to the seemingly more open post-breccia folded rocks west of the east end of Ramsey Lake. With respect to the Murray Fault, my attitude has been that in the Sudbury area apparent horizontal displacements are only a few kilometeres, where between Spanish and Bruce Mines the apparent horizontal offset The following is archived on the zip drive in G:\aareview\forpub2\penokean\huron.rtf and ponty/C:\aarev\pub2\Penokean\huron.rtf The Southern Province of Ontario, the GLIMPCE line, and the A-B-C, MID, and GLTZ structural boundaries. To be modified by adding 'badwater.doc' and something on Hofmann. Current models of the tectonic evolution of the Southern Province are based largely on the structural syntheses of Zolnai et al. (1984) for Ontario and Sims et al. (1989) for Michigan/Wisconsin, the GLIMPCE seismic data for Lake Huron (Green et al. 1988) and Lake Michigan (Cannon et al. 1991), and the Nd-Sm isotopic studies of Barovitch et al. (1989) and Dickin et al. (1990). In Ontario, Zolnai et al. (1984) proposed that the Huronian succession was folded at about 2.33 Ga, and later during a period of intense orogeny at 1.89-1.83 Ga. The latter event was considered to involve collision of the Huronian continental margin with a northerly transported allochthonous mass of Archean gneiss possibly represented by gneissic rock recovered in drill core from Manitoulin Island. As a result of the collision the Huronian was depressed to mid-crustal depth, metamorphosed to greenschist-amphibolite facies, folded about east-west axes, and thrust northward over a crustal ramp along the edge of the Superior craton. The model of Zolnai et al. (1984) was predicated on the assumption that the collision boundary in Michigan is represented by the Great Lakes Tectonic Zone (Sims et al. 1980), and that the colliding masses were the Superior Province and an older Archean gneiss terrane. In following Zolnai et al. (1984), Green et al. (1988) suggested that the A-B-C reflector in the GLIMPCE I seismic transect probably outlines the master decollement separating the Huronian from an overthrust "thick wedge of highly deformed Huronian strata and displaced Archean basement or, more likely, the allochthonous mass" thrust from the south. Green et al. (1988) follow Zolnai et al. (1984) in presuming that the allochthonous material could be represented by samples of gneissic rocks from Manitoulin Island, but allow that the allochthon could be a "magmatic arc complex similar to that south of Lake Superior?" In this case the extrapolated surface expression of the A-B-C reflector would presumably be the Manitoulin Island Discontinuity of Van Schmus et al. (1975; Green et al. 1988, Fig. 1), which has also been tentatively identified as the Penokean Suture by Dickin et al. (1990). Green et al. (1988) also drew an analogy between the A-B-C reflector and the seismic expression found in the Quebec Appalachians where a detachment delineated by strong reflections separates highly reflective continental margin basement from an overlying, less reflective magmatic arc complex and exotic microcontinental mass, the amalgamation of which took place during the final closing stages of the Iapetus ocean. More recently, Barovitch et al. (1989), Sims et al. (1989) and Cannon et al. (1991) have proposed that in Michigan/Wisconsin the main terrane boundary separating a northern continental margin domain (Marquette Range Supergroup) from a southern Pembine-Wasau arc terrane is represented by the Niagara fault rather than by the Great Lakes Tectonic zone, and that the Pembine-Wasau arc is itself separated from another even more southern continental margin domain by the Eau Pleine shear zone. In summary, current models suggest that the Southern Province of Michigan/Wisconsin/Minnesota and the northern Grenville of Ontario is composed of a southerly Penokean arc juxterposed against a northern continental margin terrane, the uppermost units of which were deposited in a foreland basin fed by the arc. The Huronian of the 'Espanola Wedge' represents an early continental clastic wedge juxterposed directly against the arc. In evaluating the above scenario particular consideration should be given to the concept of the Mid line and the A-B-C boundary of the GLIMPCE line as a continuation of the Niagara and Penokean sutures. THE MID LINE Van Schmus et al. (1975) defined the Manitoulin Island discontinuity (MID line) as the southern limit of the Huronian Supergroup. The location and East-West orientation of the MID line was in part based on an analysis of the geomagnetics of Manitoulin Island (Van Schmus et al. 1975, Fig. 2). However, the more recent GSC Magnetic Anomaly Map NL-16/17-M shows that the MID line is not coincident with the anomaly pattern across Manitoulin Island. The orientation of the magnetic boundary better correlates with the contact between the Huronian and Killarney granite/porphyry terrane. In this case the drill holes from which the Manitoulin gneiss samples of the 'allochthonous mass' were obtained clearly occur north of the extrapolated magnetic boundary. Other granitic rocks retrieved from wells 1, 5, and 6 south of the MID line on Manitoulin Island (Van Schmus et al., 1975) represent apparently non-magnetic basement of the supposed allochthonous mass. However, non-magnetic granitoids occur within the Huronian of the Cutler and Killarney regions of the Southern Province. Furthermore, it should be noted that the 1.5 Ga quart-monzonite body which overlies the Manitoulin gneisses considered to represent the allochthonous mass also contains xenoliths of "presumably older Huronian quartzite" (Van Schmus et al., 1975, p. 1186). Consequently, the presence of deformed gneisses and granitoid bodies beneath Manitoulin Island cannot without supplementary Sm/Nd data be considered prima facie evidence for the existence of allochthonous Archean basement or Lower Proterozoic arc material. The Huronian occupies the north limb of a synclinorium with progressively younger Huronian units preserved in the cores of synclines from north to south. If the axis of the synclinorium should coincide with the North Channel negative magnetic anomaly, which lies within the present exposure of Huronian rocks, an important consequence is that the sheet dip of Huronian rocks south of the North Channel anomaly may be to the North. A similar argument was used by Van Schmus et al. (1975) - "assuming normal southward progression downward through the Huronian sequence, the southern boundary would fall at about the position indicated." - in placing the MID line. The volcanic rocks sampled in well 17 on Manitoulin Island (Van Schmus et al. 1975, Table 4) could be early Huronian in age, which would support a northerly sheet dip, or they could be equivalent to the 1.9 ? Ga high-TiO2 volcanics of the Baraga Group of the Marquette Range Supergroup of Michigan, or they could represent oceanic or arc volcanics equivalent to those of the Pembine arc terrane of Wisconsin. There is presently no data supporting any of these options. The GLIMPCE profile Green et al. (1988) reported the existence of a prominent north-dipping reflector underlying the region to the south of Manitoulin Island. The surface location of the reflector coincides approximately with the projected trace of the magnetic boundary between the Huronian and Killarney granite terrane. If this magnetic boundary is related to the formation of the Killarney terrane at about 1.75 Ga, it must be younger than the arc amalgamation event at 1.86 Ga (Sims et al., 1989; Cannon et al. 1991). Green has pointed out (previous letter) that this reflector is unlikely to be the A-B-C reflector of profile I, since at shotpoint 800 where the I reflection profile transects the J profile the north dipping reflector lies at a depth of about 25 km. Furthermore, the A-B-C band of reflections lies to the east of the extrapolated Huronian-Killarney magnetic boundary, and is not known to extend into Manitoulin Island. Since the dip of the reflector is not known, the A-B-C reflector could be older, younger, or coeval with the 1.7 Ga plutonic activity of the Killarney terrane, and its relationship to the structure of the Huronian is ambiguous. It may even be argued, on the basis of the suggestion of Dickin et al. (1990) that the Penokean arc terrain may have underthrust the Killarney region, that the A-B-C reflection boundary may mark a zone of underthrusting. Furthermore, the difference in the seismic character of the crust above and below the A-B-C reflector is similar to that exhibited by the crust beneath the Northern Domain of the Penokean of northern Lake Michigan. The Northern Michigan crust is thicker but the densities of the lower and overlying crust is roughly the same. Since the Northern Domain lies north of the Niagara fault, which does not exhibit a seismic image, the A-B-C reflector may represent the upper - lower crust boundary rather than a terrain thrust boundary. The Huronian is heavily injected by mafic intrusives, and the prominence of the A-B-C boundary could reflect the presence of an important horizon of mafic intrusive material. It is not unequivocally a thrust. Within the Huronian, the surface expression of a major decollement surface may be represented by the Loon Lake fault. Major fold structures to the south of the fault are isoclinal and dips are invariably steep; structures to the north of the fault are more open and dips are commonly gentle. The structures to the south pre-date intrusion of Nipissing diabase and Sudbury breccia and are older than 2.1 Ga (but not necessarily older than 2.33 Ga; Dutch, 1979), whereas both these rock units are implicated in the major folding to the north of the Loon Lake fault. The age of the northern folds is constrained to be between the age of the Nipissing diabase and the Sudbury Irruptive. The fold structures show little tendency to verge northwards as would be expected if they had been overthrust by an allochthonous terrane from the south. In this respect the structure of the Huronian is more similar to the structure of the Connecticut Valley - Gaspe synclinorium - Frontenac anticline (Cheve, 1978; Ebinger, 1985) as shown on Figure 11 of Spencer et al., the Loon Lake fault being equivalent to the Guadeloupe Fault, and the north dipping reflectors equivalent to the Western Boundary fault system. The interpretation of Green et al. (1988) favours a structural analogy with the Appalachian section between Logans Line and the Brompton Line. This is difficult to accept in view of the very dissimilar nature of the units (ophiolites, arcs, melanges, flysch) making up these complexes to the Huronian. The shortening of the Huronian may be a reflection of lower crustal imbrication during A-type subduction within the crust underlying the Huronian rather than overthrusting of an allochthonous mass or arc (e.g. Gray et al. 1991). REFERENCES CITED Barovich, K.M., Patchett, P.J., Peterman, Z.E., and Sims, P.K., 1989, Nd isotopes and the origin of 1.9-1.7 Ga Penokean continental crust of the Lake Superior region: BGSA, v. 101, p. 333-338. Cannon, W.F., Lee, M.W., Hinze, W.J., Schulz, K.J., and Green, A.G., 1991, Deep crustal structure of the Precambrian basement beneath northern Lake Michigan, midcontinent North America: Geology, v. 19, p. 207-210. Dickin, A.P., McNutt, R.H., and Clifford, P.M., 1990, A neodymium isotope study of plutons near the Grenville Front in Ontario, Canada: Chemical Geology, v. 83, p. 315-324. Gray, D.R., Wilson, C.J.L., and Barton, T.J., 1991, Intracrustal detachments and implications for crustal evolution within the Lachlan fold belt, southeastern Australia: Geology, v. 19, p. 574-577. Green A.G., Milkereit, B., Davidson, A., Spencer, C., Hutchinson, D.R., Cannon, W.F., Lee, M.W., Agena, W.F., Behrendt, J.C., and Hinze, W.J., 1988, Crustal structure of the Grenville Front and adjacent terranes. Geology, v. 16, p. 788-792. Sims, P.K., Van Schmus, W.R., Schulz, K.J., and Peterman, Z.E., 1989, Tectono-stratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean orogen: CJES, v. 26, p. 2145-2158. Spencer, C., Green, A., Morel-a-l'Huissier, P., Milkereit, B., Luetgert, J., Stewart, D., Unger, J., and Phillips, J., 1990, Allochthonous units in the Northern Appalachians: results from the Quebec-Maine seismic reflection and refraction surveys: Tectonics, v., p. in press. Van Schmus, W.R., Card, K.D. and Harrower, K.L., 1975, Geology and ages of buried Precambrian rocks, Manitoulin Island, Ontario: CJES, v. 12, p. 1175-1189. Zolnai, A.I., Price, R.A., and Helmstaedt, H., 1984, Regional cross section of the Southern Province adjacent to Lake Huron, Ontario: implications for the tectonic significance of the Murray Fault Zone. Canadian Journal of Earth Sciences, v. 21, p. 447-456. *************************************** *************************************************** Bill I noted with interest your posting on post-Subury events in S Province in the Espanola area, begging to differ on my interpretation. On my thesis @ Queen's I worked mainly with Ken Card and Murray Frarey @ GSC, liaised with John Wood and Pete Fralick @ OMNR, but missed you and Grant Young @ UWO (missed a meetingwhen one of us got the time/place wrong, and I returned to Calgary in 18 mo. before I returned). Tho lithotectonic studies you posted are far more detailed than mine, may I suggest you look up John Dixon @ Queen's, who I copied, and ask for my rock samples and thin sections in the area that may interest you - perhaps also a copy of my thesis for more detailed data than published? While mine is all it is, an interpretation, I will stand by three points: a) the 15 or so km relief across Murray Fault Zone (a crustal step down-to-the south) b) Murray Fault continues under Lake Huron not onshore, linking to Penokean foldbelt in Michigan c) significant crustal contrast S of present Manitoulin Isl. to make it likely an allochtonous terrane to the S (tho only sporadic deep drill holes reported by Zel Peterman, Isie Zietz's poorly detailed aeromag and Alan Green's seismic studies failed to elucidate this, as did Berndt Milkereit's further studies E of Grenville Front). What encouraged me is Paul Hoffman's insertion of my less interpretive data in the DNAG volume incl. S Provice (can get exact ref. if you wish): both he and I realised the latter point at the same time... Indeed he dropped the idea of an aulacogen @ Wopmay orogen near Yellowknife... just as Grant Young proposed his for S Province! Coauthors Herb Helmstaedt and Ray Price retired I think, I moved onto petrol. GIS which I now manage @ ESRI's in Redlands CA, and Paul Hoffman's @ Harvard now. Happy retirement in 2002! Cheers Andrew Zolnai www.esri.com/petroleum azolnai.home.att.net **************************************************************************************************************************** 08:23:51 25 MAR 02 key[ geology jgs website] Up to five times more water may be stored in deep rocks than in the global ocean. Laboratory tests by Japanese researchers indicate a large amount of water may be trapped in mineral lattices in the lower mantle (406 to 1800 miles beneath the Earth's surface). Motohiko Murakami and team (Tokyo Institute of Technology) report the synthesis of hydrated lower mantle minerals such as perovskite and magnesiowustite under high temperatures and pressure. The results of their subsequent analysis of the amount of water by weight carried in these minerals (published this week in the US journal Science) suggest that a lower mantle consisting of 79% magnesium-perovskite, 16% magnesiowustite, and 5% calcium-perovskite could hold up to five times more water than the global ocean Lithosphere takes on the mantle March 7, 2002 Super deep rock formations and the upper mantle seem to move in concert In a finding that contradicts conventional wisdom, results (reported in the current issue of Geophysical Research Letters) from a new technique to survey the super-deep upper mantle of southern Africa show that very deep volcanic rock formations have shifted with the lithospheric plates in the area. Previously, geologists had believed that the motion of two such regions would be decoupled. Vinnik and Farra analysed seismic recordings down to 360 kilometers and were able to create images of two areas exposed to similar basalt emplacement more than 200 million years ago. They then compared the known motions of the upper mantles plates to the location of the two rock formations and found that the formation seemed to have migrated along with the plates. Their novel technique uses shear waves converted to compression mode to examine the low-velocity layer of the craton; waves that are often distorted or too weak for accurate signal detection. The observation indicates that the mantle in these regions is quite viscous relative to the convecting upper mantle. Reference: Subcratonic low-velocity layer and flood basalts. Geophysical Research Letters Lev Vinnik, Institute of Physics of the Earth, Moscow, Russia; Veronique Farra, Institut de Pysique du Globe de Paris. Species differences get the drift March 1, 2002 Researchers at Sussex University think they have identified a ratio of 45:55 for the effects of natural selection vs. genetic drift in creating species differences The question of what proportion of the differences between similar species came about as a result of natural selection versus "random genetic drift has vexed evolutionary biology for a century and a half. In a paper in this weeks issue of Nature, University of Sussex biologists put the ratio at 45:55. The DNA sequences of humans and chimpanzees differ by less than 2% but this adds up to about 350,000 amino acid differences. A central problem for evolutionary biologists has been to determine what proportion of this very large number of amino acid differences came about as a result of natural selection and how many are the result of random genetic drift. In the example of humans and chimpanzees, how many of the differences actually helped humans or chimpanzees to adapt to their environment? Nick Smith and Dr. Adam Eyre-Walker from the Centre for the Study of Evolution at the University of Sussex in the UK tackled the problem by looking at the divergence between two species of fruit-fly: Drosophila melanogaster and D. yakuba, a close relative. These two species are thought to have separated about 6 million years ago (about when human and chimpanzee ancestors separated) and to have a roughly similar number of differences to those that divide humans and chimpanzees. Using DNA sequence databases, Smith and Eyre-Walker calculated that about 270,000, or 45%, of all the amino acid differences between these species are adaptive, helping the flies to do better in their own particular environments. Presumably, these differences have been maintained in the two genomes as a result of natural selection, which would favour individuals with beneficial mutations and "punish" those with harmful ones. They calculate that, on average, one such adaptive substitution must have occurred every 45 years during the past six million. The other 55% of differences seem to be relatively neutral in their effect and are probably due to random genetic drift. If the proportion is the same in the case of humans, say the Sussex researchers, we would have about 160,000 adaptive differences from chimpanzees: a small part of the total genome, but nevertheless a very large number of differences. (Reference: Nick G.C. Smith and Adam Eyre-Walker: Adaptive Protein Evolution in Drosophila, Nature, 415, 1022-1024 28 Feb 2002) Core values March 5, 2002 New analysis of anomalous seismic waves passing through the Earths core supports layered model New evidence from short-period earthquake waves may solve a long-standing mystery of Earth's inner core and offers additional support for a layered inner core model, say seismologists at the University of Illinois (UI). For about a decade, the cause for anomalous waves passing through the innermost portion of the planet has been a mystery. Seismic waves that traverse the solid inner core along north-south paths have a much smaller amplitude and a more complex waveform than those that travel along east-west paths. As reported in the February 19 online edition of Geophysical Research Letters (and in the February 15 issue to be distributed in early March), UI professor of geology Xiaodong Song and graduate student Xiaoxia Xu have analysed new data that may help solve the mystery. "Seismic waves travelling through the inner core along a north-south direction are faster than those travelling along an east-west direction, a feature known as the anisotropy of the inner core" Song said. "Understanding the source of anisotropy in the inner core could be crucial to explaining other phenomena, such as how Earth's magnetic field arises and how the core formed and evolved. Using seismic waves generated by earthquakes, we found the structure of the inner core to be much more complicated than we originally thought." Earth's core consists of a solid inner core about 2400 kilometres in diameter and a liquid outer core about 7000 kilometres in diameter. In addition, the solid inner core also appears to be layered into a lower inner core and an upper inner core. The upper inner core creates a transition zone about 250 to 400 kilometres thick, Song said. The layered inner core model was first proposed in 1998 by Song and Donald Helmberger, director of the Seismological Laboratory at the California Institute of Technology. "At that time, we relied heavily upon long-period, broadband data collected from several earthquakes but recorded at very few seismic stations" Song said. "To enhance the model, we needed more short-period data -- which is where most of the anomalies occur." Song and Xu filled the void by studying seismic waves from an earthquake that occurred on Oct. 5, 1997, in the South Sandwich Islands off the coast of South America. After travelling through Earth's inner core, the short-period waves were recorded by more than 100 stations of the Alaska Seismic Network. The new evidence from the short-period waves offers additional support for a layered model of Earth's inner core, Song said. "But, to our surprise, we found that such a model could explain the anomalous short-period waves." The upper part of the inner core is isotropic, but the lower part of the inner core is anisotropic, Song said. "That means seismic waves travelling through the lower inner core will travel at different velocities in different directions." Because the anisotropy in the lower inner core is aligned in the north-south direction, seismic waves traveling along north-south paths will speed up and spread out, producing complicated waveforms with varying arrival times. The smaller amplitudes are a result of the energy being split into multiple branches of waves, Song said. Seismic waves travelling along east-west paths are unaffected. Based on the new earthquake data, the scientists conclude that the anisotropy in the lower inner core is much higher than they previously believed. "Our waveform modelling indicates that the speed of seismic waves in the north-south direction is about 8 percent faster than in the east-west direction," Song said. This result raises new questions on the source of the inner core anisotropy, which many scientists believe is caused by a preferential alignment of iron crystals, Song said. "To explain the amplitude of the anisotropy would require nearly perfect alignment of the iron crystals, according to most recent measurements and predictions of the elasticity of inner-core iron." Late Heavy Bombardment was asteroidal, not cometary March 4, 2002 The bombardment that resurfaced the Earth 3.9 billion years ago was produced by asteroids, not comets, according to David Kring (University of Arizona Lunar & Planetary Laboratory) and Barbara Cohen (University of Hawaii). Their findings appear in the February 28 edition of the Journal of Geophysical Research published by the American Geophysical Union. The significance of this conclusion is that the bombardment was so severe that it destroyed older rocks on Earth. Which, Kring says, is the reason why the oldest rocks found are less than 3.9 billion years (Ga) old. Additionally, they argue, impact-generated hydrothermal systems would have been excellent incubators for pre-biotic chemistry and the early evolution of life, consistent withprevious work that shows life originated in hot water systems around or slightly before 3.85 Ga ago. This same bombardment affected the entire inner solar system, producing thousands of impact craters on Mercury, Venus, the Moon and Mars. Most of the craters in the southern hemisphere of Mars were produced during this event. On Earth, at least 22,000 impact craters with diameters greater than 20 kilometres were produced, including about 40 impact basins with diameters of about 1000 kilometres in diameter. Several impact craters of about 5,000 kilometres were created as well - each one exceeding the dimensions of Australia, Europe, Antarctica or South America. The thousands of impacts occurred in a very short period of time, potentially producing a globally-significant environmental change at an average rate of once per 100 years. Also, the event is recorded in the asteroid belt, as witnessed by the meteoritic fragments that have survived to fall to Earth today. Kring has been involved in the research and measurements of the Chicxulub impact crater located near Merida, Yucatan, Mexico. He has collaborated on and led various international research teams which have drilled to unearth evidence of the Cretaceous-Tertiary (K/T) impact which is thought to have led to mass extinctions on Earth, including dinosaur extinction. Earlier this month, Kring returned from a drilling operation at the impact site where crews worked around the clock to recover core samples to determine what the impactor was and details of the catastrophic event that wiped out more than 75% of all plant and animal species on Earth. Earths core chemistry is silicon enhanced January 16, 2002 Chemistry at the centre of the Earth is surprisingly complicated, according to high-temperature, high-pressure experiments. A team of scientists led by Jung-Fu Lin, a doctoral student in geophysical sciences at the University of Chicago, has found experimental evidence suggesting that the Earth's inner core largely consists of two exotic forms of iron instead of only one. These exotic forms of iron now appear to be alloyed with silicon. A previous study had once practically eliminated silicon as a candidate lighter element of the inner core. "Earth may not be quite as simple as we think in its very deepest parts" says Dion Heinz, Associate Professor in Geophysical Sciences. Lin, Heinz, (and fellow University of Chicago co-authors Andrew Campbell, James Devine and Guoyin Shen) report their findings in the 11 January issue of the journal Science. "Meteorites tell us that iron is a very abundant element in the solar system" Heinz says. The Earth's magnetic field further indicates that the core must be made of a conducting substance. Iron is the only element that is abundant enough and which also conducts at the high pressures and temperatures characteristic of Earth's core. Seismologists have made further deductions about the characteristics of Earth's core from the way that seismic waves travel through Earth from earthquakes and explosives. "They noticed that there has to be about 10 weight percent of a lighter element in the outer core and anywhere from zero to 4 weight percent of a lighter element in the inner core" Heinz explained. The lighter element in the core could be oxygen, sulphur, silicon, hydrogen or carbon. "Oxygen, sulphur and silicon are the three most-studied light elements" Lin says. "Hydrogen and carbon aren't well-studied, yet some studies have shown that these two elements can be ruled out because of their high-pressure properties." A 1995 study by researchers at the University of California, Santa Cruz, seemed to rule out silicon, as well. That study was based on a compound containing an equal amount of iron and silicon. Picture - And we thought it was complicated on the outside... But it now appears that a lesser proportion of silicon is more appropriate for understanding the possible effect of silicon on the properties of iron under conditions at Earth's core. The Chicago study now makes silicon the leading candidate, Lin says, because of its high abundance in the solar system, because it alloys with iron readily, and because it lowers the density of iron under high pressure. The Chicago research team simulated searing subsurface temperatures of approximately 4,200 degrees Fahrenheit and crushing pressures of 840,000 atmospheres with a laser-heated diamond anvil cell. The diamond anvil cell was developed in the late 1950s by the late John Jamieson of the University of Chicago and others at the National Bureau of Standards. A diamond anvil cell is designed to apply a large force to a very small sample squeezed between two diamonds. "One can reach to ultrahigh pressure with a small force" Lin says. "The force is applied mechanically by tightening the screws." The diamonds themselves sometimes break under the high pressures. The atomic structure of iron changes under intense temperatures and pressures. The Chicago team found that iron may take on two different atomic structures together in one tiny sample under conditions that would be found at a depth of more than 1,800 miles beneath the Earth's surface. The existence of two exotic forms of iron at the Earth's core could influence the interpretation of seismic data from there, according to the Chicago team. "The only direct evidence about the core comes from seismic studies" Heinz says. "Our experiments try to reproduce conditions in Earth's deep interior. We compare the in situ measurements of the materials that we study with the seismic observations." Primodial air may have been 'breathable' January 10, 2002 The Earth may have had an oxygen-rich atmosphere as long ago as three billion years and possibly even earlier, three leading geologists have claimed. Their theory challenges long-held ideas about when the Earth's atmosphere became enriched with oxygen, and pushes the likely date for formation of an atmosphere resembling today's far back into the early history of the planet. It may also revolutionise the worldwide search for gold and other minerals, and raises new questions about when and how life could have arisen. Evidence for the presence of oxygen in the primitive atmosphere was put forward by the Chief of CSIRO Exploration and Mining Professor Neil Phillips, Australian-based South African geologist (picture) Mr Jonathan Law and US gold mining consultant Dr Russell Myers in a publication by the Society for Economic Geology. "These findings may have enormous economic implications in that we may simply have been looking in the wrong places for massive gold deposits like South Africa's Witwatersrand," says Professor Phillips. "Or we may actually have found them - and not recognised them for what they are, because we did not understand the processes involved in their formation." The scientists base their case on the presence of iron-rich nodules in the deep strata of the Witwatersrand - nodules they believe are pisoliths, small balls containing ferric iron produced by exposure to an oxygen-rich air. Pisoliths still form nowadays and provide important clues in the search for minerals, including gold. Those found in the Rand come from levels 3-4 kilometres down, which are securely dated at 2.7 to 2.8 billion years old. The researchers' theory has been lent additional weight by evidence from the Western Australian Pilbara region for the presence of sulphates in rocks up to 3.5 billion years old. These, too, could not have formed without an oxygen-rich atmosphere. Pisoliths have been a vital tool in the discovery of A5 billion worth of new gold deposits in WA in recent years,  using techniques developed by CSIRO's Dr Ray Smith, Dr Charles Butt and Dr Ravi Anand. The small iron-rich balls form from iron in groundwater and 'scavenge' traces of other minerals in the local environment. They provide clues, like fingerprints, which point to deposits lying hidden beneath metres of inscrutable surface rubble.

By analysing pisoliths over a wide area for gold content, geologists can construct a pattern of steadily enriching traces, with the hidden deposit lying like a bullseye at the heart of it, usually a bit uphill.

Some geologists believe living organisms may play a part in the formation of pisoliths, raising tantalising questions about the nature and role of life in shaping the Earth's early surface and mineralisation.

The presence of pisoliths in the deep strata of the Rand suggests that the conditions for mineral formation 3 billion years or so ago were different to what many geologists have believed for the past half-century, the team  say. These ideas have already been integrated into a new exploration model for the formation of the Rand deposits by the same researchers.

The Rand is unique on Earth - a vast body of rock very rich in gold. The mightiest gold deposit ever found. Nothing like it has been discovered elsewhere.

Professor Phillips says that this may be because we didn't know what to look for, because we made wrong assumptions about the conditions in which it formed.

In other words, fresh Rands may still await discovery. Some geologists speculate one of them, at least, lies in central Western Australia .

18:40:40  04 DEC 02 key[ geology Huronian discussion ]

Dutch, S.I., 1979, The Creighton Pluton, Ontario: an unusual example of a forcefully emplaced intrusion, CJES v. 16, p. 333-349.

Card, K. discussion, Dutch, S.I. reply, 1979, The Creighton Pluton, Canadian Journal of Earth Sciences, v. 16 p. 2181.

Fueten, F. and Redmond, D.J., 1997, D.J.Documentation of a 1450 Ma contractional orogeny presrved between the 1850 Ma Sudbury impact structure and the 1 Ga Grenville orogenic front, Ontario,  BGSA v109 no3, p. 268-279.

Riller, U., and Schwerdtner, W.M., 1997, Mid-crustal deformation at the southern flank of the Sudbury basin, central Ontario, Canada, BGSA, v. 109, no. 7, p. 841-854.

Davidson. A. 2001.The Chief Lake complex revisited, and the problem of correlation across the Grenville Front south of Sudbury, Ontario. Precambrian Research. v. 107, 5-29

Discussion in preparation.

Riller and Schwerdtner (1997) suggest that the 2.3 Ga-old Creighton and Murray plutons intrusive into Huronian rocks of the south rim of the Sudbury Basin were syn-tectonically emplaced during a 'Blezzardian' tectonic pulse at 2.4-2.22 Ga.

Main points of disagreement.

1) The deformation of the Creighton granite and its envelope is a local non-penetrative event that may be

related to extension early in the depositional history of the Huronian, rather than a penetrative

compressional or gravity-driven event as represented by the major folds in the Huronian of the 'Espanola

triangle.'

2) The use of the term 'Blezzardian' is inappropriate to designate either deformation in the Creighton

granite or the major deformation of the Huronian. It might be useful to designate the non-penetrative

deformation associated with the South Range shear zone.

3) The authors have underestimated the complexity of the sequence of deformation events that have affected

the Huronian regionally, and locally within the Sudbury area.

07:32:19  21 JAN 03 key[ promotion King Saud University Al-Saleh Pan-African Nubian Saudi Arabia age dates]

Al Amar - Idsas

Evaluation Summary

Dr A. M.A. Al-Saleh

Brief Justification for Recommendation

I am impressed that Dr Al-Saleh publications are mostly single authored, and that one of the papers - not withstanding that it is now  5 years out of date - is an attempt to comprehend the overall geology of the eastern Saudi Shield.  I am also satisfied that Dr Al-Saleh's research endeavours include his participation in instrumental analysis.  I am less impressed by the actual value of the data generated by Dr Al-Saleh, and the use of this data to fit the evolution of the eastern Saudi Shield into a simple two phase tectonic model.

I would also note that in Dr Al-Saleh's most recent papers (2001-2003) the only papers referenced more recently than 1997 are all authored by Dr Al-Saleh. Dr Al-Saleh seems to have entered a large vaccuum in Saudi geology!!  There are also notable reference omissions bordering on the scandalous in some of his other papers. Overall I feel therefore that I am being generous in giving Dr Al-Saleh a score of 75%.  Nevertheless, I wish him all the best in the continuation of his research, and recommend his promotion to Associate Professor.

Of the  6 publications Dr Al-Saleh has submitted for evaluation, four papers are single authored by Dr. Saleh and two are joint papers with Dr Saleh as senior author. Five of the papers deal with aspects of the geology of the eastern Arabian Shield,  and one jointly written paper is a literature review of PGE potential in the Arabian Shield.

Two of the papers are reports in University Research Centre Journals, three papers are published as reports in the regional publications 'Annals of the Geological Survey of Egypt' and 'Arabian Gulf Journal of Scientific Research', and only one paper represents publication in an international journal (Journal of African Earth Sciences).

1998 The PGE potential of the Arabian Shield........

Dr Al-Saleh  was the first author of this jointly written paper which is essentially a 1998 5-page resume on the pre-1995 literature concerning PGE exploration in the Arabian Shield. It contains no data contributed directly by the authors or any new ideas concerning PGE mineralization, and reads more like a research proposal. It is therefore of minor importance in the authors publication record.

1998 Terrane Amalgamation and the Later Proterozoic Growth...

TERRANE AMALGAMATION AND THE LATE PROTEROZOIC GROWTH OF THE EASTERN ARABIAN SHIELD AL-SALEH A. M. ; Arab gulf journal of scientific research (Arab gulf j. scient. res.) ISSN 1015-4442  1998, vol. 16, no2, pp. 283-295 [13 page(s) (article)]

......

This paper is a review of regional tectonic relationships in the Eastern Arabian Shield.

Dr Al-Saleh  emphasises his opinion that the "Ar Rayn block is merely a rifted fragment of the Afif microcontinent, etc".  Given that this was exactly the model proposed by Nawab (1979) for the Ar Rayn it is unfortunate that no reference is made to Nawab in the paper. In fact, in none of Dr Al-Saleh's papers is reference made to Nawab, and this notwithstanding that Nawab's model is prominently displayed in the comparison made by Pallister et al (1988, p. 27) of plate tectonic models proposed for the eastern Arabian shield.  The failure to cite Nawab may be an oversight on Al-Saleh's part, but it does seem to border on plagiarism!

It is also difficult to understand the point made by Dr Al-Saleh concerning the Hail. Dr Al-Saleh says that the Hail terrane in comparison to the 'Nabitah Suture' possesses a much longer history of almost continuous volcanomagmatic activity from 740-565 Ma. However, the map of Pallister et al. (1988, Fig. 17) shows three bodies in the 'Nabitah Suture' terrane with ages of 729, 732, 782 Ma.

Al-Saleh also describes the boundary between the Hail and the Afif as the Afif crust thrust over the southern rim of the Hail terrane whereas Pallister et al (1988) clearly show the boundary as the Hail thrust over the Afif - there is no discussion of this point.

Al-Saleh says that late successions such as the Zarghat  and Hadn formations do not exist with the Nabitah suture.  Given the existence of the Jabilah basin with the Afif terrane it is not obvious why this is a relevant point of difference.

2001 Tectonic Setting of the Hummah Gabbro........

In an attempt to determine whether the Hummah Gabbro formed in an oceanic or an island arc environment Al-Saleh presents in graphic form (no tables of the data!) the variation in abundance of Cr, Ti, Ni, and Y in non-layered augite and hornbende gabbros of the sampled suite. Although the paper provides no petrographic descriptions, Dr Al-Saleh assumes that the isotropic gabbros of the suite represent liquids rather than cumulates.  However, the fact that the Y and TiO2 abundances of four of the gabbros lie outside the IAB liquid field suggests that these rocks are cumulates, perhaps adcumulate - intercumulate mixtures, in which case the use of Cr, Ni, Y, and Ti as elemental discriminants for these rocks is of doubtful validity.  Furthermore, where TiO2 and Y abundances  fail to discriminate Hummah and Jifarah gabbros, Dr Al-Saleh allows that the latter may be cumulates.  The best indication that these gabbros formed in a relatively mature island arc is the apparent presence in the gabbros of primary amphibole, a simple fact not elaborated by Al-Saleh. A better test for the environment of formation would have been to analyse the clinopyroxenes for  Ti v FeO/MgO.

Although it is possible if not likely that the Hummah Gabbro formed within a mature component of the Ar Rayn arc,  Al-Saleh's data is not very persuasive in drawing this conclusion.

2001 Structural rejuvenation of the Eastern Arabian Shield....

Structural rejuvenation of the eastern Arabian Shield during continental collision: 40Ar/39Ar evidence from the Ar Ridayniyah ophiolitic melange Al-Saleh A.M. and Boyle A.P.

Journal of African Earth Sciences, Volume 33, Number 1, July 2001, pp. 135-141(7)

The Ar Ridayniyah ophiolitic melange is one of a number of such complexes found within or at the peripheries of the Neoproterozoic Al-Amar Suture of the eastern Arabian Shield. This suture is sandwiched between the Ar Rayn island-arc terrane on the east and the much larger Afif continental block to the west, and is thought to represent the site of a 695-680 Ma back-arc basin that separated the two terranes. A thick and monotonous unit of metagraywacke (Abt Schist) underlies most of the suture along with scattered outcrops of metavolcanics and ophiolitic melange. One of these bodies is the Ar Ridayniyah melange, which occurs as a longitudinal belt of sheared ultramafic schists enclosing abundant blocks of oceanic serpentinites, as well as subordinate gabbros and basalts. The western boundary of this melange is defined by the Ar Ridayniyah thrust fault. The 610-600 Ma ages obtained from the metagabbros of this complex are considered to record the reactivation of the Ar Ridayniyah Fault during continental collision, 60 Ma after ophiolite emplacement.

This paper presents the results of Ar-Ar dating of amphibole in gabbro blocks within the Ar Ridayniyah ophiolitic melange. The time range of 610-600 Ma of the amphiboles records the last time the gabbros were cooled below the blocking temperature of hornblende, and this age marks the exhumation of the melange along the Ar Ridayniyah fault, itself  a manifestation of regional strike-slip faulting of the Najd system during collision of the Arabian Craton with a large continental mass east of the Ar Rayn arc.

The author argues that collision of the Afif and Ar Rayn terranes along the Al-Amar suture delineated by the outcrop of the Abt formation was coeval with the emplacement of the Urd ophiolite onto the eastern border of the Afif 690-680 Ma ago, and that the period between 680 Ma and 620 Ma was a period of tectonic quiescence.  Tectonic activity then resumed at c. 620-610 as the result of collision of the accreted Arabian Craton and a large continental mass east of the Ar Rayn arc, leading to thrust stacking and folding in the Al-Amar zone, high grade metamorphism of the Hillit (and Anjal Groups?), and extensive granite magmatism between 620 and 575 Ma.

However, to the contrary it would seem that development of major transpressional fault systems and associated magmatism in the Saudi Shield (Junayah and Nabitah shear zones) had already begun been initiated by 654 Ma following the formation of the Murdama (including volcanics) and Bani Ghayy basins marginal to the thrust front demarcated by the Urd ophiolite belt, and that the magmatism (Musayrah, Abss, Junayah, Tathlith, etc, etc) continued through to 580 Ma and later. The formation of the Jurdhawiyaj and Hibshi basins between 640 Ma and 620 Ma, and the Jibalah basin at 580-570 Ma mark the surface manifestation of the faulting.  It would seem therefore that the data presented in this paper is of only local significance, and unfortunately provides no basis for any major reorganisation of thought concerning the development of the Arabian Shield.

NOT EVALUATED

Metamorphism and 40Ar/39Ar dating of the Halaban Ophiolite and associated units: evidence for two-stage orogenesis in the eastern Arabian Shield AL-SALEH A.M.; BOYLE A.P.; MUSSETT A.E2

Journal of the Geological Society, Volume 155, Number 1, 1998, pp. 165-175(11)

The Arabian Shield has long been recognized as a region where plate-tectonic processes have been in action during most of the Late Proterozoic resulting in the amalgamation of the shields five constituent terranes along four major suture zones. Studies thus far carried out on these collisional belts have concentrated on the origin and dating of intermediate to acidic igneous rocks, and very little emphasis has been placed on the understanding of metamorphic processes operative during plate convergence. The Al-Amar Suture separates the Afif microplate from the Ar Rayn Block in the easternmost section of the Shield. Among several ophiolite occurrences in this suture, the Halaban Belt is by far the largest and preserves within and around it a record of a number of thermal/structural events related to the opening and eventual closure of a supra-subduction zone back-arc basin that existed in the period 695680 Ma. The bimodal nature of 40Ar/39Ar dates from the Halaban Ophiolite and associated units is indicative of a two-stage orogenesis climaxing at 680 and 600 Ma, instead of the previously proposed model of a single orogenic episode between 670 and 630 Ma. The first stage (680 Ma) is believed to be related to basin closure and ophiolite emplacement as the Ar Rayn island arc collided with the Afif microcontinent. The second episode (600 Ma) was the outcome of a major collisional event between the Arabian craton and a large continental mass east of the Ar Rayn Block.

2002 Origin of manganese and base metal anomalies.......

This is an interesting and well reasoned paper.  It does contain original data and with some embellishment could well have been published in an international journal.

2003 Metamorphic History of Gabbroic Blocks within the Ar Ridayniyah.......

This paper is the most recent of Dr Al-Saleh's contributions concerning the Ar Ridayniyah fault zone, and reports the observation that gabbros of the Ar Ridayniyah serpentinite melange have suffered both an early retrograde metamorphism and a late-stage epidote-amphibolite metamorphism. Based on this single observation, Dr.  Al-Saleh proposes that the serpentinites and gabbros, depicted as isolated oceanic diapirs injected into back-arc basin sediments (Abt Schist), were buried to a depth of more than 10 km during westward thrusting c. 610 Ma ago, and then rapidly exhumed by faulting, represented by the Ridayniyah Fault, during "the final collisional orogeny between the Ar Rayn and Afif  terranes" (p. 77).  In this respect Dr Al-Saleh seems to have change his mind concerning his earlier proposition that the Ar Ridayniyah fault was formed during collision "between the Arabian Craton and a large continental mass east of the Ar Rayn arc" (Al-Saleh and Boyle, 2001).

The main problem in drawing these conclusions concerns Dr Al-Saleh's supposition that the Abt sediments were layed down on the Urd - Al-Amar ocean floor. Given the presence of both continental (including garnet) and ultramafic (chromite) detritus in the Abt turbidites and associated debris flows of the Al-Amar - Idsas region, the Abt sediments are unlikely to be 'primary' oceanic abyssal deposits. The Abt sediments must be entirely younger than any ophiolite obduction event, but older than the culminating Afif/Ar Rayn collisional event, and they could have been laid down in a successor basin developed above the obducted ophiolite foreland sequence following the initial phase of accretion of the Ar Rayn to the Afif.  In this case the Abt would be located stratigraphically above the ophiolitic sequences, and the Ridayniyah Fault would be located along the western margin of the melange. Dr Al-Saleh should provide good reason as to why the Abt is not coeval (670-650) with the sediments and volcanic rocks of the Murdama basin west of the 'Urd line'.

Alternatively, the Abt turbidites may have been deposited in a foreland basin during the obduction process, in which case the eastern Abt Formation would initially be structurally located beneath the obducted oceanic material.  As in the case of the complex structure of the ophiolite and the Abt and Abu Sawarir sedimentary formations along the line of the Idsas - J. Rugain (Selib) structural front, one can envisage that the Ar Ridayniyah ophiolitic melange may be bounded to the west by a primary obduction thrust, and to the east by a relatively young collisional, out-of-sequence thrust represented by the Ridayniyah fault.

`One other difficulty concerning this paper concerns that fact that the Abt Schist is invaded by numerous granite bodies, some which are thought to be derived from the melting of the Abt sediments.  The author gives no major consideration to the possibility that this thermal event may be responsible for the localized growth of prograde amphibolite assemblages in the melange gabbros.

It should also be noted that amphibole may also overgrow low grade actinolite in ophiolitic metagabbros during the development of inverted thermal aureoles related to the subduction/obduction process, and the Ar-Ar age of 610 Ma may therefore not represent the actual crystallization age of the amphiboles, but rather the age of exhumation of the melange along the fault.

Profesor W.R. Church

Department of Earth Sciences

University of Western Ontario

London, Ontario

******************************************************************************************************************

Saudi Chronology Jan 2003

523 Um Aud diorite (unpublished)

557 +/-15 Ar/Ar on biotite Jabal Kirsch (Al Saleh, in press, 2010)

575 Rb-Sr, 579 zircon - Gebel Qattar granite (Stern and Hedge, 1985)

578 +/-15 - Nakhil Granite (Sultan et al. 1990)

580-570 - the Jibalah group deposited in small, isolated, pull-apart basins caused by strike- and dip-slip movements on faults of the Najd fault system.

583? Gattarian granites

583  Salah El Belih granodiorite (571 Rb-Sr) cuts the Hammamat (Stern and Hedge 1985)

585 +/- 13 Hammamat; youngest detrital ziron; U-Pb age peaks at 640and 680 Ma;

also 750 to 2630

585 +/-15 R-Sr Hammamat (Willis et al. 1988)

589 +/-9 - Rb-Sr dikes cutting the G Qattar granite

590 +/-11 Um Had granite (Ries and Darbyshire, unpub) cuts the Hammamat

592 +/-26 Rb-Sr Dokhan Gebel Dokhan (Stern & Hedge 1985)

593 +/-13 - youngest Dokhan volcanics (Wilde and Youssef, 2000);

602 +/-9 - oldest Dokhan volcanics (Wilde and Youssef, 2000);

606 - Hadabah pluton 606 2 Ma Shearing on the Ibran shear zone in the central part of the terrane, constrained by the age of the Hadabah pluton, may have occurred as late as 605 Ma.

610 - Ar/Ar amphibole Ar Ridaniyah shear zone

610 - movement on the Umm Farwah shear zone, which cuts the eastern margin of the Ablah group, occurred about 610 Ma or later.

613 - Ablah group rhyolite. 613 7 Ma (but see 641 below);

*616 +/-9 Dokhan? at Wadi Sodmein (Ries and Darbyshire, unpub)

*********634 zircon maxima in Hammamat H2

639 - Tathlith gneiss.  Crops out on either side of the Nabitah fault zone, represent magmatic events approximately 100 million years later than the Tabalah shearing. Zircons from these plutons range in age from 710-361 Ma and 711-451 Ma, respectively, suggesting complex evolutionary and isotopic histories, including inheritance and lead loss. ****************************************************************************************************************

641 - age of rhyolite in the Ablah molasse basin;

620-640 - the Jurdhawiyah group and Hibshi formations were deposited in fault controlled basin (isolated fault-controlled lake). East-west convergence conceivably accounts for the creation of the Jurdhawiyah and Hibshi basins as a result of concomitant northward extension or tectonic escape. Basins closed and inverted during subsequent north-south shortening and north- and south-vergent reverse faulting.

****************************************************************************************************************

640 - Ash Shawhatah pluton 640 3 Ma The Ash Shawhatah pluton (ID# 7) intrudes the Nabitah fault zone, indicating cessation of Nabitah orogeny ductile deformation in the eastern part of the terrane by 640 Ma, although brittle deformation occurred after 640 Ma, as evidenced by faulting at the contact of the granite.

645 - Ar Rayn Trondhjemite

646 - Junaynah granite 646 10 Ma The Junaynah granite (ID# 4) has undergone brittle deformation by the Junaynah fault zone, and is considered as an evidence for brittle deformation in the central part of the terrane after about 645 Ma, comparable to the brittle faulting on the Nabitah fault zone.

*********646 zircon maxima in Hammamat

650 - The basins were closed and inverted by folding. Northerly trend of Murdama and Bani Ghayy folds implies bulk east-west shortening.

650 - Ar Rayn tonalite

651 -Abss granodiorite 651 4 Ma  The Abss granodiorite and Tathlith gneiss which crop out on either side of the Nabitah fault zone, represent magmatic events approximately 100 million years later than the Tabalah shearing (>755 ma).  Zircons from these plutons range in age from 710-361 Ma and 711-451 Ma, respectively, suggesting complex evolutionary and isotopic histories, including inheritance and lead loss. The Abss and Tathlith results in Table 1 are preferred formation ages, implying that the plutons belong to the suite of syn-Nabitah orogeny intrusions well known in the eastern part of the terrane (Stoeser and Stacey, 1988).

654 - Musayrah pluton 654 3 Ma The Musayrah pluton has the same age, within error, as the Abss granodiorite. It intrudes the Abss granodiorite, but is evidently part of the same Nabitah -654orogeny magmatic event as the granodiorite.

******************************************************************************************************************

650-670 - 8000 m sandstone, conglomerate, bimodal volcanic rocks, and limestone(Murdama basin) and in narrow grabens (Bani Ghayy basins). Possibly >10 km uplift and erosion in parts of the region prior to deposition. Much of the region was at a low elevation soon after terraneamalgamation and orogeny. The two basins are foreland basins at subsided and extended parts of a newly amalgamated crust in the center of the study area that was downflexed by the overthrusting of an ophiolite complex and other terranes from the east.

******************************************************************************************************************

667 - Ar Rayn trondhjemite

******** *671, 693 zircon maxima in Hammamat H1 and H2, respectively (Wilde & Youssef 2002)

686 +/- 56 Rb-Sr Dokhan? volcanics at Gebel Nuqrah (Stern & Hedge 1985)

685 +/- 16 (Wilde & Youssef, 2000) upper Dokhan  weighted mean inherited zircon cores

690 single grain zircon with inheritance of 1.9-2.1; Uweinat, Gebel El Asr  (Sultan et al. 1994)

694 - Urdd ophiolite

******************************************************************************************************************

710-725 Midyan diorite; tonalite

711 - tonalite, Dixon 1981, Um Samiuki area

712 - Shadli (Um Samiuki) volcanics of southern Egypt (Stern et al. 1991)

720 - lower intercept (down to 663 Ma) of 2650-1065 Sabaloka granulite gneiss & migmatite

(Kroner et al 1987)

720 - lower intercept Duweishat 2.6 -1.23 gneisses (Wadi Halfa) (Stern et al. 1994)

728-782 Al Qarah tonalite

731 - Murat tonalite

743 (Ledru) - 696 (Pallister) - Jar and Salajah tonilites

750 age of Nubian Wadi Gerf ophiolite

*********750  zircon maxima in Hammamat , both H1 and H2

750 - Siham arc (Khida region) (Whitehouse et al. 2001) old ages of 2.6-2.4, 1.9-1.65, 950-800

755 - Al Khalij pluton 755 7 Ma, intrudes the Tabalah shear zone. Its age indicates that shearing occurred prior to 755 Ma and defines, in the west-central part of the terrane, the earliest deformation event documented. 760-780 Ma. The shear zone dates the onset of arc-arc convergence in what eventually became the Arabian-Nubian shield. Marks the beginning of the complex, heterogeneous process of terrane amalgamation and continental accretion that led to the eventual convergence of East and West Gondwana.

760 - lead loss Al-Mahfid 2550 granite gneiss with older components at 2938-2730;

coeval granite sheets (Whitehouse et al. 1998)

768 +/-61 - Abu Swayel (S&H, 1985), rhyodacite

780 - J. Ess ophiolite

779 +/-4 Um Ba'anib granite gneiss (Meatiq; has 1149 Ma orthoamphibolite xenolith)

(Loizenbauer et al 2001)788 +/-13 sediments overlying Meatiq gneiss

**********804 , 823 zircon maxima in Hammamat H1 and H2 respectively

821 Iqwaq tonalite

816-847 Asir Terrane arc.

820-870 Ma - the Bir Umq-Nakasib suture zone, 5-65 km wide and over 600 km long.

900 - Abas terrane (Yemen)  zircons w. weighted average age of 939+/-47; inherited core 2605+/-15

also met at 760 (Whitehouse et al 1998)

945 - Rabigh (Asir)

*********962 zircon maxima in Hammamat

Neumayr, P.; Hoinkes, G.; Puhl, J. The Migif-Hafafit gneissic complex of the Egyptian Eastern Desert; fold interference patterns involving multiply deformed sheath folds. Tectonophysics 346, no. 3-4 (2002 03 15): 247-275

Genna, A.; Nehlig, P.; Le Goff, E., and others Proterozoic tectonism of the Arabian Shield. Precambrian Research 117, no. 1-2 (2002 07 31): 21-40

Loizenbauer, Juergen; Wallbrecher, E.; Fritz, H., and others Structural geology, single zircon ages and fluid inclusion studies of the Meatiq metamorphic core complex; implications for Neoproterozoic tectonics in the Eastern Desert of Egypt. Assembly and breakup of Rodinia Precambrian Research 110, no. 1-4 (200108): 357-383

Fowler, T. J.; Osman, A. F.Gneiss-cored interference dome associated with two phases of late Pan-African thrusting in the central Eastern Desert, Egypt. Precambrian Research 108, no. 1-2 (2001 0501): 17-43

Whitehouse, M.J., Stoeser, D.B., and Stacey, J.S. 2001. The Khida terrane - geochronological and isotopic for Paleoproterozoic and ARchean crust in the eastern Arabian Shield of Saudi Arabia. In Diva, R.s. and Yoshida, M., Tectonics and Mineralization in the Arabian Shield and its Extensions. IGCP 368 International Conference Abstracts, Jeddah, Saudi Arabia. Gondwana research, 4, 200-202. ..

El-Sayed, M. M.; Furnes, H.; Hassanen, M. A., and others Crustal evolution of the Egyptian Shield; a proposed new geotectonic model. Geological Society of America, 1999 annual meeting Abstracts with Programs - Geological Society of America 31, no. 7 (1999): 179

Stern, R. J.; Abdelsalam, M. G. Univ. Texas at Dallas, Center Lithospheric Studies, Richardson, TX, United States  Formation of juvenile continental crust in the Arabian-Nubian Shield; evidence from granitic rocks of the Nakasib Suture, NE Sudan.  Geologische Rundschau 87, no. 1 (1998): 150-160

Stern and Kroener.  University of Texas at Dallas, Programs in Geosciences, Richardson, TX, United States;  Johannes Gutenberg-Universitaet, Federal Republic of Germany. Late Precambrian crustal evolution in NE Sudan; isotopic and geochronologic constraints.  Journal of Geology 101, no. 5 (1993 09): 555-574

Kroener, A.; Todt, W.; Hussein, I. M., and others Universitaet Mainz, Institut fuer Geowissenschaften, Mainz, Federal Republic of Germany; Max-Planck-Institut fuer Chemie, Federal Republic of Germany; Geological Research Authority, Sudan; Egyptian Geological Survey and Mining Authority, Egypt. Dating of late Proterozoic ophiolites in Egypt and the Sudan using the single grain zircon evaporation technique. Precambrian Research 59, no. 1-2 (1992 11): 15-32

Stern and Dawoud;   Univ. Tex. at Dallas, Programs Geosci., Dallas, TX, United States; Univ. Khartoum, Sudan.  Late Precambrian (740 Ma) charnockite, enderbite, and granite from Jebel Moya, Sudan; a link between the Mozambique Belt and the Arabian-Nubian Shield? Journal of Geology 99, no. 5 (1991 09): 649-659

Sultan, M., Chamberlain, K.R., Bowring, S.A., and Arvidson, R.E. 1990. Geochronologic and isotopic evidence for involvement of pre-Pan-African crust in the Nubian Shield, Egypt. Geology, 18, 764-761.

Kroner, A., Stern, R.B., et al. 1987. The Pan-African continental margin of northern Africa: evidence from a geochronological study of granulites at Sabaloka, Sudan. EPSL, 85, 91-104.

SW_USA15:29 13 Feb 2004 key[ SW_USA geology faults Whipple Buckskin detachment ]

Dec 14 2016   SWUSA_Kompozer_winSCP

TO CREATE, MAKE LINK TO, AND RUN A KMZ FILE IN GOOGLE EARTH DIRECTLY FROM THE UNIVERSITY WEB SITE  of Professor W.R. Church

--------------------------------------------------------------------------------------------------------------

Dec 3 12  Special Paper 489

Grand Canyon Geology: Two Billion Years of Earth's History

Edited by J. Michael Timmons and Karl E. Karlstrom

http://www.azgs.az.gov/services_azgeomap.shtml - Arizona Geological Survey map of Arizona

and paper C:\fieldlog\cargo\Arizona\Mineral Resources in Buckskin and Rawhide Mtns in 1989.pdf

Google Earth kml heirarchy-SWUSA  -  SW-USA kml and jpg files referenced by the Kmls

http://www.gsajournals.org/gsaonline/?request=get-document&doi=10.1130%2FGES00016.1#i1553-040x-1-3-147-f1001 - SW USA extensional animation; click animation link at the bottom of the article dx.doi.org/10.1130/GES00016.1.s1

ES_Geography Field Trip   Picacho Mine   Arizona_06  Arizona_09   Arizona_11

\fieldlog\cargo    orocopia   Franciscan  Whipple_Mntns

I have created a website detailing a recent student camping trip to examine crustal extension in relationship to gold mineralization within extensional fault zones in the SW USA.  The website - which will continue to be developed as more photographic material becomes available - contains topomaps, airphotos, UTM grids, Aster satellite images, geologic maps, details of camp sites, as well as waypoints recorded as UTM coordinates, that might be of use to others contemplating a similar trip to the extensional/gold belts of Arizona, Nevada, and SE California.

Bill Church

UWO

I was recently in Arizona on a camping trip with a party of a dozen geology students from Canada. We arrived improptu at Cattail Cove park (Buckskin park was closed) very late and in the rain, and set our tents up in the beach area. In spite of this being somewhat against the park regulations, the next morning the park rangers were very obliging and treated us in a very pleasant way - even allowing us to stay another night on the same spot. I want you to know that our welcome under these circumstances was very much appreciated, and we look forward to coming down again. FYI, our trip is recorded at: http://instruct.uwo.ca/earth-sci/fieldlog/cargo/indexcargo.htm  It is perhaps the most comprehensive existing web site for the 'extensional tectonic/gold' geology of the Whipple/Buckskin/Oatman region. Thanks again to the park staff!!

Picacho Mine

Richard, Stephen M. and Spencer, Jon E. Geologic map of the Picacho mine area, southeastern California. Scale 1:10,000. Arizona Geological Survey open file report 96-30, pub. 1996. OCLC #37324717

Steven Losh1 ( , Dan Purvance (Glamis Gold Inc, Yuma), Ross Sherlock (SRK Consulting, Suite 800, 580 Hornby Street, Vancouver, BC, Canada, V6C 3B6)  and E. Craig Jowett (Waterloo Centre for Groundwater Research, University of Waterloo, Waterloo, ON, Canada, N2L 3G1) 2005. Geologic and geochemical study of the Picacho gold mine, California: gold in a low-angle normal fault environment Journal Mineralium Deposita Publisher Springer Berlin / Heidelberg ISSN 0026-4598 (Print) 1432-1866 (Online) Subject

Earth and Environmental Science  Issue Volume 40, Number 2 / August, 2005

Abstract The Picacho gold deposit, located in southeasternmost California, is a low-grade gold deposit in a nearly flat-lying denudational fault of regional extent and probable Oligocene age. The deposit is hosted by intensely fractured and faulted Mesozoic leucogranite and by chloritic augen gneiss and schist, and is overlain unconformably and in fault contact by unmineralized late Oligocene Quechan volcanic rocks. The deposit is structurally characterized by normal and normal-oblique faults of low to high dip at shallow depths in the mine, merging downward with a synchronous, low-dipping ore-stage extensional fault system (the Chocolate Mountains/Gatuna Fault) of probable Oligocene age in deeper portions of the deposit. The fault system was infiltrated during much of its active life by hot, dilute, highly exchanged meteoric water having temperatures of 170210 C, salinity <2 wt% NaCl equivalent and calculated d18Ofluid between -2.6 and 5.2. This main-stage fluid precipitated quartz, pyrite, and specular hematite, accompanied by silicification and sericitization. Auriferous ore-stage pyrite was precipitated late in the fault evolution probably by mixing of reducing ore fluid with relatively oxidized main-stage fluid during regional Oligocene extension on the Chocolate Mountains/Gatuna Fault. The Picacho deposit is characterized by a goldarsenicantimony geochemical signature consistent with bisulfide complexing of gold in reducing fluid, in contrast with typical denudation fault-hosted base-metal-rich deposits associated with high-salinity fluids elsewhere in the southwestern United States. The deposit is overprinted by Miocene normal faults having a wide range of dips. These postore faults are associated with red earthy hematite precipitation, pyrite oxidation, and supergene enrichment of gold.

Richard, Stephen M. and Spencer, Jon E. Geologic map of the Picacho mine area, southeastern California. Scale 1:10,000. Arizona Geological Survey open file report 96-30, pub. 1996. OCLC #37324717

Haxel, G.B., Jacobson, C.E., Richard, S.M., Tosdal, R.M., and

Grubensky, M.J., 2002, The Orocopia Schist in southwest

Arizona: Early Tertiary oceanic rocks trapped or transported

far inland: Geological Society of America, Special Paper

365, p. 99, scale 1:45000.

Morton, P.K., 1977, Geology and mineral resources of Imperial

County, California: California Division of Mines and Geology,

County Report 7, scale 1:125000.

http://www.access.gpo.gov/cgi-bin/modalldep.cgi?cmd+CA

USGS California depository libraries

Federal and state government publications also are made available to the public at "depository libraries" across the country. A complete list of depository libraries is available. Many of these libraries are "selected" depositories and may not contain earth science listings. Libraries listed as "Regional" (see map below) received all federal publications distributed by the Superintendent of Documents and will have received USGS publications.

http://ngmsvr.wr.usgs.gov/ngmdb/ngm_SMsearch.html

USGS map index

http://ngmdb.usgs.gov/ngmdb/ngmdb_home.html

National Geologic Map Database

http://ngmdb.usgs.gov/

USGS map database

http://geology.wr.usgs.gov/docs/stateinfo/CA.html

http://rockyweb.cr.usgs.gov/acis-bin/choosebylocation.pl?statechoice=California

Map retailers california

usgs maps

http://www.lib.utexas.edu/geo/onlineguides.html

Listing of virtual field trips US and Canada

http://geology.wr.usgs.gov/docs/usgsnps/deva/devaft.html

USGS Virtual Field trip to Death Valley

http://wrgis.wr.usgs.gov/open-file/of99-34/hpk_map.pdf

Example of an internet accessible map of th e Hart Peak 7.5 minute quadrangle, California/Nevada border area:

West_Bounding_Coordinate: -115.13

East_Bounding_Coordinate: -115.00

North_Bounding_Coordinate: 35.38

South_Bounding_Coordinate: 35.25

URL: http://instruct.uwo.ca/earth-sci/fieldlog/cargo/indexcargo.htm

University of Nevada, Las Vegas, Dept of Geoscience

4505 Maryland Parkway Box 454010 Las Vegas, NV 89154-4010

Telephone: (702) 895-3262

E-Mail:

http://www.unlv.edu/Campus_Map/

Campus Map - Lily Fong Geoscience Building # 38

North of Airport, on east end of Harmon St, west of the Rotunda; parking off west side of Maryland Parkway (N-S st); access to parking at Harmon St (E-W street)

Peggy Thompson, Technical Manager Building Construction, BMI Complex, P.O. Box 127, Henderson, Nevada 89015; 800 374 -2907; 702 565- 3833; fax 702 565-7473

Go to Cargo Muchachos

http://www.pr.state.az.us/Parks/parkhtml/buckskin.html

Buckskin Mountain State Park is located on Arizona Highway 95, about 12 miles north of Parker. The River Island unit is one mile north of Buckskin Mountain State Park.

Maps of Arizona

Arizona Geological Survey publications

http://www-glg.la.asu.edu/%7Esreynolds/azgeomap/azgeomap_home.htm

Geological Map of Arizona, Steve Reynolds

http://darkwing.uoregon.edu/~rdorsey/Detach.html

Map of Whipple Mountains, archived as Whipplemap.jpg in C:\fieldlog\cargo\geol\Whipple

Geology3120 - Metamorphic Core Complexes

Site has maps and photos of the Whipple Mountain and Buckskin-Rawhide detachments.

Whipple Mountains geologic map copied as whipplemap2.jpg in C:\fieldlog\cargo\geol\Whipple

Map of California

Largest scale general map of California

Smaller scale generalized map of California

http://scamp.wr.usgs.gov/scamp/html/gm.html

Southern California Areal Mapping Project (SCAMP)

1980. Dickey, D.D., Carr, W.J., and Bull, W.B. 1980 Geologic map of the Parker NW, Parker, and parts of the Whipple Mountains SW and Whipple Wash quadrangles, California and Arizona USGS I-1124 24

1986. Structural evolution of the Whipple and South Mountains shear zones, southwestern United States: Geology, v. 14, p. 7-10 (G. A. Davis, G. S. Lister, and S. J. Reynolds).

1987. Field trip guide to parts of the Harquahala, Granite Wash, Whipple and Buckskin Mountains, west-central Arizona and southeastern California, p. 351-364 in Geological diversity of Arizona and its margins: excursions to choice areas (Davis, G. H., and VandenDolde, E. M., Eds.): Ariz. Bur. Geology and Min. Technology Special Paper 5, 422 p. (J. E. Spencer, S. J. Reynolds, J. L. Anderson, G. A. Davis, S. E. Laubach, S. M. Richard, and Stephen Marshak).

1988.  Rapid upward transport of mid-crustal mylonitic gneisses in the footwall of a Miocene detachment fault, Whipple Mountains, southeastern California: Geologische Rundschau, v. 77, no. 1, p. 191-209

1989. The origin of metamorphic core complexes and detachment faults formed during Tertiary continental extension in the northern Colorado River region, U.S.A.: Jour. Struct. Geol., v. 11, p. 65-95. (G. S. Lister and G. A. Davis).

1989. Seismic reflectivity of the Whipple Mountain shear zone in southern California, Jour. Geophys. Research, v. 94, p. 2985-3005. (Chi-Yuen Wang, D. A. Okaya, Charles Ruppert, G. A. Davis, Tie-Shuan Guo, Zengqiu Zhong, and Hans-Rufolf Wenk).

1989. Terry Shackelford: a retrospective view, p. 11-14 in Geology and mineral resources of the Buckskin and Rawhide Mountains, west-central Arizona (Spencer, J. E., and Reynolds, S. J., eds.): Arizona Geological Survey Bulletin 198 (Shackelford Volume), 279 p.

1991. Low-angle normal faulting and rapid uplift of mid-crustal rocks in the Whipple Mountains metamorphic core complex, southeastern California: discussion and field guide, p. 417-446 in Geological excursions in southern California and Mexico (Walawender, M. J., and Hanan, B. B., eds.), Dept. of Geological Sciences, San Diego State University, 515 p. (G. A. Davis, and J. L. Anderson)

http://www.lowell.edu/users/tweedr/thes_ch5.html  no maps

Spencer, J.E., and Reynolds, S.J., 1987, Geologic map of the Swansea-Copper Penny area, central Buckskin Mountains, west-central Arizona: Arizona Bureau of Geology and Mineral Technology Open-file Report 87-2, 10 p., scale 1:12,000.

http://geology.csupomona.edu/drjessey/fieldtrips/calico/calico.htm

The Calico Mining district - silver barite

http://gateway.library.uiuc.edu/gex/bibs/geol315-415ariz.html

UIUC Geology course 315/415 Field Trip Arizona and Southern California

http://www.nbmg.unr.edu/staff/pdfs/NCREC.pdf

CENOZOIC EVOLUTION OF THE NORTHERN COLORADO RIVER EXTENSIONAL CORRIDOR, SOUTHERN NEVADA AND NORTHWEST ARIZONA JAMES E. FAULDS, DANIEL L. FEUERBACH, CALVIN F. MILLER,

AND EUGENE I. SMITH Department of Geoscience, University of Nevada, Las Vegas, NV 89154

ABSTRACT

The northern Colorado River extensional corridor is a 70- to 100-km-wide region of moderately to highly extended crust along the eastern margin of the Basin and Range province in southern Nevada and northwestern Arizona. It has occupied a critical structural position in the western Cordillera since Mesozoic time. In the Cretaceous through early Tertiary, it stood just east and north of major fold and thrust belts and also marked the northern end of a broad, gently (~15o) north-plunging uplift (Kingman arch) that extended southeastward through much of central Arizona. Mesozoic and Paleozoic strata were stripped from the arch by northeast-flowing streams. Peraluminous 65 to 73 Ma granites were emplaced at depths of at least 10 km and exposed in the core of the arch by earliest Miocene time.

Calc-alkaline magmatism swept northward through the northern Colorado River extensional corridor during early to middle Miocene time, beginning at ~22 Ma in the south and ~12 Ma in the north. Major east-west extension followed the initiation of magmatism by 1 to 4 m.y., progressing northward at a rate of ~3 cm/yr. The style of volcanism changed during the course of east-west extension. Eruptions of calc-alkaline to mildly alkaline mafic to intermediate magmas predated extension. Calcalkaline to mildly alkaline mafic, intermediate, and felsic magmas were prevalent during major extension. Tholeiitic and alkalic basalts were then erupted after significant block tilting. The most voluminous volcanism occurred in early Miocene time and was accompanied by mild north-south extension. Belts of east-west extension bordered the region to both the north and south in early Miocene time. Large-magnitude east-west extension engulfed nearly the entire region in middle Miocene time, beginning in most areas ~16 Ma and ending by ~9 Ma. Tilt rates commonly exceeded 80o/m.y. during the early stages of east-west extension.

Although less voluminous than that in the early Miocene, volcanism generally spanned the entire episode of extension south of Lake Mead. Thus, thick volcanic sections, as opposed to sedimentary rock, accumulated in many growth-fault basins. The northward advancing magmatic front stalled, however, in the Lake Mead area along the southern margin of the southern Nevada amagmatic gap. Thus, Tertiary sections in the Lake Mead area are dominated by sedimentary units, including alluvial fan, continental playa, and lacustrine deposits. During middle Miocene extension, strain was partitioned into a west-dipping normal-fault system in the north and an east-dipping system in the south. The two fault systems and attendant opposing tilt-block domains overlap and terminate within the generally east-northeast-trending Black Mountains accommodation zone. Major east-west extension was contemporaneous on either side of the accommodation zone. The west-dipping normal fault system in the north is kinematically linked to major strike-slip faults along the northern margin of the corridor, where a complex three-dimensional

strain field, involving both east-west extension and north-south shortening, characterized the middle to late Miocene.

The transition between the Colorado Plateau and the Basin and Range is unusually sharp along the eastern margin of the northern Colorado River extensional corridor and is marked by a single west-dipping fault zone, the Grand Wash fault zone.

Subhorizontal, relatively unfaulted strata on the Colorado Plateau give way to moderately to steeply east-tilted fault blocks across the Grand Wash fault zone. Topographic and structural relief across this boundary developed during middle Miocene extension and was established by 9 Ma. The location and abruptness of the Colorado Plateau-Basin and Range transition in this region may have been controlled by an ancient north-trending crustal flaw, inasmuch as it follows a diffuse boundary between Early Proterozoic

crustal provinces.

Bassett, A.M., and Kupfer, D.H. 1964 A geologic reconnaissance in the southeastern Mojave Desert, California DMG SR 83, pl. 1 1:125000 (1cm = 1.25 km)

Calzia, J.P., and others 1983 Mineral resource potential of the Coxcomb Mountains Wilderness Study Area (CDCA-328), San Bernardino and Riverside counties, California USGS MF-1603-A 1:62000 (1cm = 0.62 km)

Carr, W.J. 1991 A contribution to the structural history of the Vidal-Parker region, California and Arizona USGS P 1430, pl. 1 1:125000 (1cm = 1.25 km)

Crowe, B.M. 1978 Cenozoic volcanic geology and probable age of inception of basin-range faulting in the southeasternmost Chocolate Mountains, California GSA Bull. v. 89, no .2, p. 251-264, 1:81000 (1cm = 0.81km)

Hamilton, W.B. 1984 Generalized geologic map of the Big Maria Mountains, northeastern Riverside County, California USGS OF 84-407 1:48000 (1cm = 0..48km)

Haxel, G.B., and others 1988 Mineral resources of the Orocopia Mountains Wilderness Study Area, Riverside County, California USGS B 1710-E 1:100000 (1cm = 1 km)

Kahle, J.E., and others 1984 Preliminary geologic map of the California-Baja border region, Imperial and San Diego counties, California DMG OFR 84-59 1:250000 (1cm = 1.25 km)

Kupfer, D.H., and Bassett, A.M. 1962 Geologic reconnaissance map of part of the southeastern Mojave Desert, California USGS MF-205 1:125000 (1cm = 1.25 km)

Metzger, D.G., Loeltz, O.J. , Irelan, B. 1973 Geohydrology of the Parker-Blyth-Cibola area, Arizona and California USGS PP 486-G 1:125000 (1cm = 1.25 km)

Powell, R.E. 2001 Geologic Map and Digital Database of the Conejo Well 7.5 minute Quadrangle, Riverside County, Southern CA USGS OF 01-031 1:24000 (1cm = 0.24km)

Powell, R.E. 2001 Geologic Map and Digital Database of the Porcupine Wash 7.5-minute quadrangle, Riverside County, Southern CA USGS OF 01-030 1:24000 (1cm = 0.24km)

Smith, D.B., and others 1987 Mineral resources of the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California USGS B 1711-A, pl. 1 1:24000 (1cm = 0.24km)

Stone, P. 1990 Preliminary geologic map of the Blythe 30-min. x 60-min. quadrangle, California and Arizona USGS OF 90-497 1:100000 (1cm = 1 km)

Stone, P., and Kelly, M.M. 1989 Geologic map of the Palen Pass quadrangle, Riverside County, California USGS MF-2070 1:24000 (1cm = 0.24km)

http://www.gis.usu.edu/docs/data/nasa_arc/nasa_arc97/SDSU/LaCuesta.pdf

Integrated Use of Remote Sensing and GIS for Mineral Exploration:

A Project of the NASA Affiliated Research Center at San Diego State University

http://ngmsvr.wr.usgs.gov/MapProgress/MapProgress_home.html

The "Geologic Mapping in Progress" database lists areas that are now being mapped, and describes who to contact for more information.

http://ngmsvr.wr.usgs.gov/MapProgress/24k_01/24k_01.htm

Geologic Mapping in Progress - select a state

http://ngmsvr.wr.usgs.gov/MapProgress/100k_01/100k_01.htm

Select a state -- areas being mapped are in blue

http://ncgmp.usgs.gov/statemap/CA03.pdf

Digital

Saucedo, G.J., Bedford, D.R., Raines, G.L., Miller, R.J.,

Wentworth, C.M., Jennings, C.W., Strand, R.G., and Rogers,

T.H., 2000, GIS data for the geologic map of California:

California Division of Mines and Geology, CD 2000-007, scale

1:750000.

Vigil, J.F., Pike, R.J., and Howell, D.G., 2000,

time and terrain: U.S. Geological Survey, Geologic Investigations

Series Map I-2720, scale 1:1350000.

Rea, Alan and Cederstrand, J.R., 1994, GCIP reference data set

(GREDS): U.S. Geological Survey, Open-File Report OF-94-388,

scale 1:2500000.

Schruben, Paul G., Arndt, Raymond E., and Bawiec, Walter J.,

1994, Geology of the Conterminous United States at 1:2,500,000

Scale -- A Digital Representation of the 1974 P.B. King and

H.M. Beikman Map: U.S. Geological Survey, Digital Data Series

DDS-11, scale 1:2500000.

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http://www.johnmartin.com/earthquakes/eqsafs/safs_361.htm

TRANSVERSE RANGES AND THE SALTON TROUGH

http://earthview.sdsu.edu/trees/oroword.html

Orocopia Mountains Detachment System

http://earthview.sdsu.edu/trees/OROTOUR.html

TM image of the Orocopia Mountains east of the Salton Sea

http://seis.natsci.csulb.edu/deptweb/SkinnyCalSites/TrnsverseRng/SanGabriels/SanGablOview2.html

Geological overviews of the SAN GABRIEL MOUNTAINS

12:16 2004/04/14 key[ geology faults shear Jiang ]

Hi everybody,

- I'm workin on the Southern Iberian shear zone (SISZ), a ductile shear zone which has been traditionally considered as a transpressional one, mostly because it has developed under a oblique continental collision setting. The SISZ is not vertical and, considering that it constitutes a former subducted oceanic slab, it is realistic to believe that was never vertical. Within this shear zone, mylonitic foliation (S) and stretching lineation (L) are oriented in such a way that nicely fits foliation and lineation orientations predicted theoretically by different models (see Lin et al., 1998 or Jones and Holdsworth, 1998) for vertical transpressional shear zones, once they are rotated towards the current position of the SISZ. In these models, a vertical shear zones is defined and the pure shear is divided into two components: thinning accros the shear zone (X2) and stretching along the dip direction (X3). Furthermore, the simple shear obliquity (fi) is defined as the angle between simple shear direction and the shear plane azimuth (X1). If a vertical transpressional shear zone is passively rotated by late folding, the main deformation directions are rotated in the same sense, so if we rotate X1, X2 and X3 in the same sense as foliations and lineations, X1 and X3 are no longer the azimuth and the dip direction of the shear plane. Some questions arise:

- Should I assume that the stretching due to pure shear is parallel to the new position of X3 or the stretching of the pure shear is always parallel to the dip direction of the shear zone, regardless of the shear zone orientation?

Jiang: No, the maximum stretching direction of the pure shear component does not have to be parallel to the current dipline of the shear zone. It might have been parallel to the dipline of the zone initially, but since the shear zone has been reoriented, the initial dipline and the current dipline are in general not the same material line any more, and the X1 direction need not be the strike line of the current zone either.

- The angle fi between the simple shear direction and X1, once that this is rotated is the same, but now is meaningless. A new angle, between the simple shear direction (which has been rotated as well) and the real current shear plane azimuth should be measured, or , alternatively, a new simple shear direction with the same original obliquity (fi) with respect to the shear zone azimuth must be defined (the original obliquity of the model needs to be maintained even after rotation)?

Jiang: I don't know how to define the coordinate axes (X1X2X3) precisely for a shear zone, but if you wish to apply the modeling results of Lin et al (1998) and Jiang and Williams (1998, JSG), you can make use of the modeling observation that in simple-shear concentrated domains and/or high finite strain domains, the strain geometry approximates monoclinic. This allows you to constrain the orientation of the vorticity, vorticity-normal section etc. You can then use the overall strain geometry, such as lineation pattern across the zone etc. to place a limit on the possible orientation range of the pure-shear component.

- In any case, what do you think about a more general transpressional model in which the shear plane is not vertical?

Jiang: If a zone is not vertical and the shear direction is not parallel to the dip direction or the strike direction, then the kinematics within the zone has to be triclinic. To compare predicted strain pattern with observed pattern requires that the coordinate axes for a natural zone be defined as you have realized.

A more general model of transpression will need to, in my opinion, include investigating how boundary non-steadiness affect the strain geometry, and how migration of boundaries through material (widening zone of W. Means 1995 Tectonophysics) affect the strain geometries etc.

Manuel

Manuel Daz Azpiroz

Dpto. Ciencias Ambientales

Crtra. Utrera, km 1

41013 Sevilla

-----------------------------------------------------------------

Comments by Dazhi Jiang, Assistant Professor

Department of Geology

University of Maryland

College Park, MD 20742

Phone:(301) 405-6979, Fax:(301)314-7970

e-mail:

Manuel's message (see below) raises some interesting questions about the

triclinic transpression model of Lin et al. (1998) and its application to natural shear zones. His specific questions have been addressed by  Dazhi Jiang and Richard Jones in their replies to the message. I will  add a few points here. A manuscript version of the paper Lin et al.

(1998) in .pdf format is available on , for those who dont have access to it.

In the model of Lin et al. (1998), as well as that of Jiang and Williams (1998), the shear zones dont need to be vertical. Although the zones are shown as vertical for convenience of presentation in the papers, geometry predicted for non-vertical shear zones can be obtained by rotating the diagrams like Fig. 9 of Lin et al. (1998), as is explicitly pointed out in the figure caption to this diagram. This was what Lin et al. did when they applied the modeling results to the Roper Lake shear zone (their Fig. 11). The Alpine fault in New Zealand is interpreted by Jiang et al. (2001) as another example of triclinic non-vertical transpression zone. In these models, the reference frame x1x2x3 are fixed to the shear zone boundary (and therefore should be rotated with the boundary), and x1, x2 and x3 are parallel to the three principal stretchings defined therein. They dont have to be horizontal or

vertical (i.e. can be oblique). This is especially true for the unified model of Jiang and Williams (1998). What really matters is the angle (phi) between the boundary-parallel simple shear (gamma) and x1, as well as the values of the simple shear and the three principal stretchings.

Lin et al.s theoretical model is based on a homogeneous domain (not a homogenous shear zone). A domain can be infinitesimal in size.  Parameters such as strain magnitude, the angle phi and the simple shear/pure shear ratio can vary from domain to domain (or from point to point) in a shear zone (Lin et al., p. 53). Lin et al. (1998) especially emphasize the variation of simple shear/pure shear ratio across a shear zone, a phenomenon referred to as deformation path partitioning by Lin

et al. (1999). Czeck and Hudlestone (2003) suggest that the orientation of principal stretchings can also vary in a shear zone. Such variations lead to variation in lineation orientation in a shear zone, and lineations orientations can potentially vary continuously from subhorizontal to downdip (see, e.g., Fig. 9 of Lin et al. 1998, and natural examples described in Lin et al. 1998, Lin and Jiang 2001). (It should be noted that the statement in a recent paper on transpression that the triclinic model of Lin et al. (1998) predicts an obliquely plunging lineation orientation that is fixed across the boundary is NOT correct.)

Because there is more than one variable that can contribute to the variation in lineation orientation in a shear zone, the modelling results should be applied to natural shear zones with care.

Shoufa Lin

Jiang, D., and Williams, P.F., 1998, High-strain zones: A unified model: Journal of Structural Geology, v. 20, p. 1105-1120.

Jiang, D., Lin, S. & Williams, P.F. 2001. Deformation path in high-strain zones, with reference to slip partitioning in transpressional plate-boundary regions. Journal of Structural Geology,

v. 23, p. 991-1005.

Lin, S., Jiang, D., & Williams, P.F. 1998. Transpression (or transtension) zones of triclinic symmetry: natural example and theoretical modelling. In: Holdsworth, R.E., Strachan, R.A. & Dewey, J.F. (eds) 1998. Continental transpressional and transtensional tectonics. Geological Society, London, Special Publications, No. 135, p. 41-57.

Lin, S., Jiang, D. & Williams, P.F. 1999. Discussion on transpression and transtension zones. Journal of the Geological Society, London, v. 156, p. 1045-1048.

Lin, S. & Jiang, D. 2001. Using along-strike variation in strain and kinematics to define the movement direction of curved transpressional shear zones: an example from northwestern Superior Province, Manitoba. Geology, v. 29, p. 767-770.

Czeck, D. & Hudleston, P.J. 2003. Testing models for obliquely plunging lineations in transpression: a natural example and theoretical discussion. Journal of Structural Geology, 25, 959-982.

*********************************************************

Dr. Shoufa Lin, Associate Professor

Department of Earth Sciences

University of Waterloo

200 University Avenue West

Tel: +1 (519) 888-4567, ext. 6557

Fax: +1 (519) 746-7484

E-mail:

**********************************************************

Azpiroz

Hi Shoufa Lin and others. With respect to inclined (i.e., non-vertical) transpressional shear zones, Shoufa Lin pointed out that "In the model of Lin et al. (1998), as well as that of Jiang and Williams (1998), the shear zones dont need to be vertical. Although the zones are shown as vertical for convenience of presentation in the papers, geometry predicted for non-vertical shear zones can be obtained by rotating the diagrams like Fig. 9 of Lin et al. (1998), as is explicitly pointed out in the figure caption to this diagram. This was what Lin et al. did when they applied the modeling results to the Roper Lake shear zone (their Fig. 11). The Alpine fault in New Zealand is interpreted by Jiang et al. (2001) as another example of triclinic non-vertical transpression zone." This is true. Nevertheless, some questions about obliquity remain uncertain.Comparison between strain geometry of natural shear zones and strain geometry predicted for theoretical models, by rotating the latter from a vertical position to a new orientation that fits the geometry of the former seems reasonable. The reference frame X1, X2, X3 of these models is fixed in such a way that X1 is parallel to the shear zone strike. As we rotate the entire structure (shear zone, shear direction and

reference frame, as Shoufa Lin proposes), the angle phi between the boundary-parallel simple shear (gamma) and x1 remains constant, but the new direction x1 has no meaning in the new situation. It is only an axis included in the shear plane but with no significance in the strain

geometry. On the other hand, the angle between the rotated gamma (which is, actually, the "real" shear direction) and the actual observed shear plane direction should be considered as the real obliquity of the shear zone (it is important to keep in mind that shear zone didn' t developed

in a vertical position and zone was later passively rotated to the current orientation, but deformation took place in the observed inclined position), as it is monstrated in figure 10 of Jiang et al (2001). In a general case, this angle is not equal to phi in the predicted vertical shear zone before rotation. This doesn't mean that obliquity of the shear zone has changed due to passive rotation, and gives place to a paradox: the obliquity of the natural shear zone, which has been deduced from a theoretical model, differs from the obliquity of the theoretical model that I've used to deduce the obliquity of the natural shear zone. Moreover, we must suppose that the "new" real obliquity of the inclined shear zone would lead to a different strain geometry than the strain geometry of the natural shear zone, and then, do you think it would possible to calculate this strain geometry directly from the inclined position of the shear zone if the shear direction is unknown?

Jiang

You are right in stating that it is impossible from strain geometry alone to determine the "paleo-" X1-direction of a transpressional zone. But, fortunately, you do not need to know the initial phi to test theoretical predictions with observations. From the variation of strain geometry across the zone, you may constrain the VNS (vorticity-normal section) and that combined with the shear plane will serve as an internal reference frame for you to perform the rotation (either of field data or theoretical results) required to do the comparison.

In essence, choosing a coordinate system for strain modeling can be arbitrary, for the strain and kinematics of a model is INDEPENDENT of the coordinate system one happens to adopt (otherwise the results are fortuitous). To answer your paradox, if you do wish to apply Lin et al. (1998) and Jiang and Williams (1998) type of modeling but with the current strike of the shear zone as the X1-direction (thus your "new" real obliquity), you certainly will arrive at identical strain geometries AS LONG AS you accordingly adjust the pure shear component orientations in this coordinate system! It is the obliquity between the pure shear component and the simple shear component (a coordinate system independent property of the flow) that leads to the triclinic strain geometry. This point is missed in some transpression papers.

Lin

> The reference frame X1, X2, X3 of these models is fixed in such a way that X1 is parallel to the shear zone strike. As we rotate the entire structure (shear zone, shear direction and reference frame, as Shoufa Lin proposes), the angle phi between the boundary-parallel simple shear (gamma) and x1 remains constant, but the new direction x1 has no meaning in the new situation. It is only an axis included in the shear plane but with no significance in the strain geometry. On the other hand, the angle between the rotated gamma (which  is, actually, the "real" shear direction) and the actual observed shear plane direction should be considered as the real obliquity of the shear zone

I think the key here is to fully understand what the angle phi really is in our papers (Lin et al. 1998, Jiang and Williams 1998). It is really the angle between the boundary-parallel simple shear direction and one of the principal stretching axes of the pure shear component. For convenience in presentation, this axis is shown as horizontal in the papers, and in this case only, the angle phi is equal to the angle between the strike of the shear zone and the shear direction. This may not be explicit in Lin et al., but is clear is Jiang and Williams (1998, p. 1106, paragraph 3). With this original definition of angle phi (as the angle between the boundary-parallel simple shear direction and one of the principal stretching axes of the pure shear component), the angle does not change in value with rotation of the shear zone in the way you mentioned. It should be emphasized that, it is the obliquity between the boundary-parallel simple shear direction and the principal stretching

axes of the pure shear component that leads to triclinic kinematics and geometry. Because this obliquity is generally present, we believe that the kinematics of shear zones are general triclinic. Even if the direction of simple shear is horizontal, the kinematics can still be triclinic if the principal stretching axes are oblique to the shear direction. A potential example is that of Czeck, & Hudleston (2003).

> In a general case, this angle is not equal to phi in the predicted vertical shear zone before rotation. This doesn't mean that obliquity of the shear zone has changed due to passive rotation, and gives place to a paradox: the obliquity of the natural shear zone, which has been deduced from a theoretical model, differs from the obliquity of the theoretical model that I've used to deduce the obliquity of the natural shear zone.

With the above understanding of the angle Phi, there is no real paradox, as far as I can see.

Shoufa Lin

Jiang, D., and Williams, P.F., 1998, High-strain zones: A unified model: Journal of Structural Geology, v. 20, p. 1105-1120.

Lin, S., Jiang, D., & Williams, P.F. 1998. Transpression (or transtension) zones of triclinic symmetry: natural example and theoretical modelling. In: Holdsworth, R.E., Strachan, R.A. & Dewey, J.F. (eds) 1998. Continental transpressional and transtensional tectonics. Geological Society, London, Special Publications, No. 135, p. 41-57. see

http://www.science.uwaterloo.ca/earth/faculty/lin/lin%20paper.pdf for a copy of the paper.

Czeck, D. & Hudleston, P.J. 2003. Testing models for obliquely plunging lineations in transpression: a natural example and theoretical discussion. Journal of Structural Geology, 25, 959-982.

http://www.geology.sdsu.edu/visualstructure/vss/htm_hlp/index.htm

Incremental strains are the increments of distortion that affect a body during deformation. Finite strain represents the total strain experienced by a rock body. It is the summation of all of the incremental components. If the increments of strain are a constant volume process, the overall mechanism of distortion is termed plane strain. Pure shear and simple shear are two end members of plane strain (Davis and Reynolds, 1996).

The components of deformation of a rock body are rotation, translation, distortion, and dilation

Strain is only synonymous with deformation if there has been distortion without any volume change, translation, or rotation. In short, strain represents only one of four possible components involved in the overall deformation of a rock body where it has been transformed from its original position, size, and shape to some new location and configuration

Stretch = S = ratio of the new dimension to the original dimension = e + 1 where e is the fractional extension

ie  e = (L1 - L)/L and e+ 1 = (L1 - L)/L = L1/L - 1 + 1 = L1/L = the stretch

The quadratic elongation lamba is the square of the stretch = (L1/L)2

Flinn diagram represents K = ln(lamba1/lambda2) / ln(Lambda2/lambda3)

Lambda1/Lambda2 = L1/L2 = the ratio of the length of the major axis to the intermediate axis; and Lambda2/Lambda3 = L2/L3 = the ratio of intermediate axis to the short axis

where K = 1 then LI/L2 = L2/L3 and L2 - L, ie it does not change, and the increase in L1 iscompensated only by a commensurate decrease in L3; e.g. if L1 = 2 then L3 = .5. Note that in this case ln 2 (= .69) = - ln .5 (= -.69).  Where L2=L3 the result is a prolate ellipsoid if L1 > L3, and an oblate elllipsoid if L1 < L3.

Pure shear (gamma) - flattening

Simple shear (epsilon) - shearing

Large gamma/epsilon values = preponderance of flattening

http://www.science.uwaterloo.ca/earth/faculty/lin/lin%20paper.pdf

Interpretation and discussion

Application of theoretical modelling results

The results of the theoretical modelling should be applied to natural shear zones with care and the

following points should be kept in mind.

(1) The present model assumes both isochoric (A line upon a thermodynamic diagram so drawn as to represent the pressures corresponding to changes of temperature when the volume of the gas operated on is constant) deformation and constant strike length of the shear zone. A more general model that includes triclinic flow, volume change and strike-length change is given in Jiang & Williams (in press).

(2) The theoretical model is for a homogeneous domain and a steady period, and the more closely these conditions are approximated by a natural shear zone the better the comparison will be. Heterogeneously deformed shear zones are best treated by dividing them into domains that better approximate the homogeneous condition, as is generally done in structural analysis, and the results of the present modelling can be readily applied to such shear zones. The heterogeneity arises in a number of ways. Not only strain magnitude, but also phi and gammaprime/epsilonprime, may vary from point to point. Thus different parts of a shear zone may have different phi value paths, different gammaprime/epsilonprime paths, and/or have been at different positions along any one of these paths. Structural data from natural shear zones do not necessarily, and generally do not, define complete paths as shown in Fig. 9.

(3) We have assumed here that lineation and foliation are approximately parallel to the finite strain axes (lambda1 and lambda1 lambda2, respectively). This is not always true and the theoretical models should only be applied where there is good reason to believe that the assumption is valid. Taking the Roper Lake shear zone as an example (Fig. 4a), finite strain-related stretching lineations (Ls) were carefully differentiated from the "ridge-in-groove"-type striations (Lc). Only Ls and poles to S-foliations are compared with the theoretical results. But C-surfaces give an approximation of the shear zone boundary and plots of Lc indicate the shear direction (Figs. 4a and 11). The scatter of Ls plots reflects the heterogeneity of the shear zone. The most significant point of this data is that the statistically defined mean for the stretching lineation of the marginal domain deviates from the great circle girdle defined by the data of the central domain.

Interpretation of the Roper Lake shear zone

The structural geometry of the Roper Lake shear zone is characterized by variable orientations of the lineations and relatively constant orientations of foliations. Comparison with the results of the theoretical modelling indicates that the shear zone can be interpreted as a transpression zone with oblique boundary-parallel motion (i.e. oblique transpression) and a higher gammaprime/epsilonprime ratio (flattening)  in the central domain than in the marginal domain (Figs. 11 and 12). The latter explains why the stretching lineation is shallower in the former domain and steeper in the latter domain. As described earlier, C-surfaces, asymmetrical mica fish and an oblique shape fabric in recrystallized quartz grains are much more intensely developed or only observed, and quartz c-axis fabrics are stronger, in the central domain. These all indicate localization of the simple shear component ( gammaprime) there. Thus, we suggest that variation in the gammaprime/epsilonprime ratio is due more to the localization

of the simple shear ( gammaprime) than variation in the pure shear (epsilonprime) across the shear zone (Fig. 12). As discussed below,  ratio in the central domain than in the marginal domain (Figs. 11 and 12). The latter explains why the stretching lineation is shallower in the former domain and steeper in the latter domain. As described earlier, C-surfaces, asymmetrical mica fish and an oblique shape fabric in recrystallized quartz grains are much more intensely developed or only observed, and quartz c-axis fabrics are stronger, in the central domain. These all indicate localization of the simple shear component ( gammaprime) there. Thus, we suggest that variation in the gammaprime/epsilonprime ratio is due more to the localization

of the simple shear ( gammaprime) than variation in the pure shear (epsilonprime) across the shear zone (Fig. 12). As discussed below, oblique transpression (0 < phi < 90) (and thus a triclinic movement picture) and variation in the gammaprime/epsilonprime ratio due to localization of gammaprime are probably common features.

Oblique transpression and triclinic movement picture

Observations of present plate motions suggest that most convergent plate boundaries have an oblique displacement vector (e.g. Liu et al. 1995). Such an oblique convergence is often heterogeneously accommodated as a result of slip partitioning; i.e., the net oblique displacement is partitioned into a more dipslip component accommodated at the subduction zone and a component accommodated in the overriding and underriding plates via intraplate deformation (e.g. Fitch

1972; Demets 1992; McCaffrey 1992; Shen-Tu et al. 1995). The intraplate deformation shows evidence of further slip partitioning (e.g. Gao & Wallace 1995). However, a complete partitioning where the net oblique slip is partitioned into two end members: pure dip-slip and pure strike-slip components, as argued in e.g., Tikoff & Teyssier (1994 and references therein), may be

rare. Liu et al. (1995) defined a parameter  to measure the degree of slip partitioning for a subduction zone. K = 0 (e.g. in northeastern Japan) and K = 1 (e.g. in New Hebrides) represent zero and complete partitioning respectively (Liu et al. 1995, fig. 6). It is probable that K generally lies between 0 and 1, as for example in the Aleutians where K = 0.34 (Liu et al. 1995, fig. 6). The

general incompleteness of slip partitioning implies that the imposed boundary displacements for many deformation zones are oblique; the boundary displacement vector may lie anywhere in the spectrum from dip-slip (phi = 90 degrees) to strike-slip (phi = 0 degrees). This gives rise to triclinic movement pictures for the internal deformation. Shear zones with triclinic movement

pictures are probably far more common than reported in the literature. The observed monoclinic symmetry in natural deformation zones could well be reflecting a high gammaprime/epsilonprime ratio rather than a true monoclinic movement picture. As demonstrated above, when the ratio of gammaprime/epsilonprime  is high, the structures and fabrics in an oblique transpressional zone (having a triclinic movement picture) will exhibit monoclinic symmetry within the resolution of observation. It is likely that many natural shear zones described in the literature are only the

equivalents of the central domain of the Roper Lake shear zone described above, in the sense that they only represent more intensely deformed portions (with higher ratios of gammaprime/epsilonprime) of much wider shear zones. Without the less intensely deformed portions (or the equivalents of the marginal domain of the Roper Lake shear zone) being considered together with the more deformed portions, the potential triclinicity of these shear zones cannot be easily recognized, as exemplified by the Roper Lake shear zone.

Strain rate

Localization of simple shear

Studies of ancient shear zones (including the Roper Lake shear zone described above) and observations of current plate-boundary deformation indicate that in shear zones and orogens alike the component of boundary-parallel motion (simple shear component   ) tends to be localized whereas the component of boundary-normal motion (pure shear component   ) tends to be widely distributed (see Gordon 1995 and references therein). Shear zones are localized features of much wider orogenic belts (Fig. 13). Theoretical models lead to the same conclusion. For example, for power law rheology with stress exponents n =3 and n =10, the length/width ratio for a pure compression or extension zone is 1 and 2 respectively whereas it is 5 and 10 respectively for a simple shear zone (England et al. 1985; Sonder & England 1986; England & Jackson 1986). This means that boundary parallel motions are approximately 5 times more localized than boundary-normal motions. frictional) an increasingly effective deformation mechanism. Pure shear on the other hand aligns grain boundaries progressively more perpendicular to the shortening direction. Thus grain boundary sliding becomes increasingly difficult and further deformation requires stronger intragranular mechanisms to operate. We therefore conclude that localization of boundaryparallel motion within a wider zone of compression or extension perpendicular to the zone boundary is a general phenomenon. Localization does not require pre-existing surfaces of weakness (e.g. faults, shear zones, lithological boundaries, weak layers and/or rheological anisotropy) (c.f. Jones & Tanner 1995), although the presence of such surfaces or zones will facilitate the process.

There are other factors that may contribute to this phenomenon. (1) Boundary-normal motion results in thickening or thinning of the crust leading to buoyancy forces that make further thickening or thinning more difficult (see also England et al. 1985; England & Jackson 1989). (2) Simple shear is believed to be a fabric weakening process whereas pure shear is believed to be a fabric hardening process (Williams & Price 1990; Williams & Vernon submitted). Much of deformation at the granular scale tends to take place along weak grain boundaries. Simple shear aligns elongate minerals and therefore makes grain boundaries ever closer to the shear plane orientation thus making grain boundary sliding (diffusion dependant or frictional) an increasingly effective deformation mechanism. Pure shear on the other hand aligns grain boundaries progressively more perpendicular to the shortening direction. Thus grain boundary sliding becomes increasingly difficult and further deformation requires stronger intragranular mechanisms to operate.  We therefore conclude that localization of boundaryparallel motion within a wider zone of compression or extension perpendicular to the zone boundary is a general phenomenon. Localization does not require pre-existing surfaces of weakness (e.g. faults, shear zones, lithological boundaries, weak layers and/or rheological anisotropy) (c.f. Jones & Tanner 1995), although the presence of such surfaces or zones will facilitate the process.

09:52 2004/06/24 key[ travel Aster St Cast St_Cast Brittany Bretagne  France 2004 ]

Thur July 8th 04 Travel to France

Fri July 9th 04   Arrrive France - met by Jannik

Sat July 10th     Paris - Notre Dame; Sorbonne;

Sun July 10th    Brocants de Pontault

Mon July 11th   Conciergerie; St Chapelle; Louvre

Tues July 12th   rest day (rain)

Wed July 13th   Versailles

Thur July 14th    Brocantes de Guerard; Voulangis

Fri  July 15th 04 Jeannine

Sat July 16th 04 Paris - Les Invalides; Tour Eiffel; Regine (missed train to Guerard)

Sun July 17th 04 Washing and packing

Mon July 18th 04 Paris - Monmartre; overnight at Francine's

Tue July 20th 04  Travel to St Cast

Wed July 21th 04 Cap Frehel

Thur July 22nd 04 Forte la Latte

Fri July 23rd 04    St Malo

Sun July 25th 04  Yvette Joinville le Pont; Tour de France

Air Transat    SNCF St Cast

Mme Jannik Coutant, 119 Av de la Republique, Pontault Combault, Seine et Marne 77340, France  tel:  from Canada 011-33-1-60.28.16.36; portable 011-33-1-64.63.72.54 (Lisette -friend of Jannik, portable -

011-33-6-14.42.32.72

M. Nelly Levesque, Bouleurs, Crecy La Chapelle, Seine et Marne; tel[011 33 1 64 63 72 43]

Mme Regine Lebouvier, Montherand, Seine et Marne; tel[64.04.78.09; portable 06.82.00.69.09]

Mme Jeannine Alary, 9 bis Rue J. Dore, Chennevieres sur Marne, 94 430; tel[011-33-1-45.94.98.78

Departure

Leave from Pearson International, toronto, Terminal 3,Thursday, July 8, 2004at  7:10 PM. air transatflight  TS 410.arrive at  paris, Charles De Gaulle, Terminal T3at  10:10 AM, Friday, July 9, 2004 .

Return

Leave from Paris, Charles De Gaulle, Terminal T3, Monday, July 26, 2004at  2:55 PM. Air Transatflight  TS 713.arrive at  Toronto, Pearson International, Terminal 3at  5:25 PM, Monday, July 26, 2004 .

Train to Brittany:

PARIS MONTPARNASSE 1 ET 2

Aller : le 20/07 9h05 arr Lamballe 11.57

TGV 08693 voiture 8 places 21, 25, 26

Retour : le 24/07 9h39 arr Rennes 10.45 lv Rennes 11.05 arr Paris13.25

TER 55624 -> TGV  08232 voiture 5 places 35, 36, 37

Nicole et Andre Brignon

Le Cdre Bleu, 52 Boulevard DUPONCHEL

22380 St Cast Le Guildo, Cots-d'Amor

Tel: 0296418693

http://www.meteo.fr/meteonet/#

http://www.lachainemeteo.com/MeteoJ0.asp?CodeVille=ST_BRIEUC&Commune=SAINT-CAST-LE-GUILDO&CP=22380&Pop=3291&Alt=49&Partner=LCM

http://oiswww.eumetsat.org/IDDS-cgi/listImages?a=1,m=8,f=1,c=9,o=1,s=2,n=12,d=0,v=400,p=0

http://www.ot-st-cast-le-guildo.fr/

http://www.saint-cast.com/plan.htm?langue=french

Archeology

Les premiers bretons d'armorique. 246p., Coll. Archologie et Culture, PUR d

A l'initiative de P.-R. Giot qui lgue dans cet ouvrage posthume la synthse d'un demi-sicle de recherches sur la Bretagne, les auteurs y prsentent les modalits du peuplement de la Bretagne, ses diffrentes causes, son importance numrique et ethnique, ses effets linguistiques, culturels, conomiques, technologiques et religieux, ceci en prenant en compte les nouvelles donnes archologiques, bio-anthropologiques et environnementales acquises ces dernires annes. Les milieux naturels ayant particip des choix, des succs et des insuccs des manires de vivre des habitants d'une rgion la gologie aussi diversifie, celle-ci est prsente en dbut d'ouvrage par quelqu'un qui fut l'origine gologue.

Aster Satellite Imagery

Registered on June 24 2004; user - password porthaster; user name Church8750 (8750 = phone#)

http://asterweb.jpl.nasa.gov/

http://asterweb.jpl.nasa.gov/application/geology/default.HTM

http://asterweb.jpl.nasa.gov/documents/aster_user_guide_v2.pdf

Simple browser window is at: http://glovis.usgs.gov/

Lat Long for St Cast is: 48.63, -2.25

Lat Long for Erquy is: 48.635, -2.4665

For St Cast the VNIR scene is:

ASTER L1B REGISTERED RADIANCE AT THE SENSOR V003

VNIR; WRS-2 Path/Row 202/26 Lat/Long 48.6/-2.3

ID: AST_L1B.003:2015416589; Cloud Cover: 0%; Date: 2003/7/14

Landsat WRS-2 Path/Row 202/26 Lat/Long 48.9/-2.3

ID: 7202026000310650 Cloud Cover: 0% Date: 2003/4/16

The following is taken from:  http://asterweb.jpl.nasa.gov/APAA/ASTER.htm

ASTER itself takes about 600 pictures ("scenes") a day, each covering an area of 60 x 60 km.  A separate image is created for each color (or more precisely, each wavelength range, or "band").  ASTER has a total of 14 bands.  When an image is "processed", each band can be treated separately, leading to some very powerful (and sometimes very complicated) analysis techniques. To keep things simple, and to save space, the images on this disk are "composite" images derived from bands 1, 2, and 3. A website is planned that will provide the full multi-band images along with some simple tools to help analyze them.

.

The Images

All digital images, whether from personal digital cameras or from those in space, are composed of pixels (picture elements). Each ASTER image on this disk has about 16 million pixels (4200 x 4200), and is a "composite" color image derived from bands 1, 2, and 3, which are sensitive to green, red, and near-infrared, respectively. Each pixel in these images corresponds to about a 15 x 15 m patch on the ground. The jpg format was chosen to decrease the size of the images so a sufficient number of them could be placed on a single CD. Because a substantial amount of compression is required to sufficiently reduce the file size there is some loss of image quality.

In these images live vegetation appears red--the brighter and redder the more healthy the vegetation. Man-made materials like concrete and buildings tend to be a light blue or gray. Bare soil can vary in color and brightness depending on what materials it is made of. Water is very dark.

Many people wonder why the scenes are not displayed in their natural colors, and there are several reasons for this. The first is due to historical reasons. Much early remote sensing work used infrared-sensitive film because healthy vegetation strongly reflects those wavelengths (a plant cannot use them for photosynthesis). The human eye can not see infrared, yet some visible color has to be used to represent it if the images are going to be useful. For infrared-sensitive film, that color was red, and so red has been used to represent the infrared ever since, even for digital images that use no film, such as ASTER.

The second is that ASTER does not have a band that detects blue light (this is because blue light tends to be scattered much by the atmosphere), so a real "natural color" image is not possible. Although natural color can be simulated using some image processing tricks, it is rather difficult to automate those tricks and create consistently good images. Because automated image processing was necessary to create the 50+ images on this disk, we decided to use these "vegetation is red" representations (though you may find a couple exceptions).

The third answer is that this is the way the "color assignments" have been made. The color red is assigned to band 3 (sensitive to part of the infrared spectrum), green is assigned to band 2 (sensitive to red) and blue is assigned to band 1 (sensitive to green). So, a piece of ground that reflects highly in band 3 will appear bright red in the processed image, one that reflects highly in band 2 will appear bright green, and one that reflects highly in band 1 will appear bright blue. Of course, most things are actually a combination of these, though often one band predominates.

The Full ASTER Data Archive

All ASTER scenes (currently numbering roughly one million) are archived at a data center in South Dakota, USA (as well as at the equivalent data center in Tokyo). Access to the data in the US archive is by one or both of the following tools (the first provides both search and order capability, the second only search--but a much friendlier search-- and an easy path to ordering):

Tourism

http://www.tourismebretagne.com/document/telechargement/pat_nat/P24a37.pdf

Geology of the Armorican Massif -

http://www.sgmb.univ-rennes1.fr/DOSSIERS/bibliographie/BIBLIOGRAPHIEfeuille.htm

Socit gologique et minralogique de Bretagne,

Gosciences Rennes, Universit de Rennes 1, Campus de Beaulieu, 263, av. du gnral Leclerc - CS 74205, 35042 Rennes Cedex

Le Prsident

Tlphone 02 23 23 65 12

Saint-Cast, 206  COGNE (J.) Orlans : 1980, 1 feuille

Erquy

map        section

608 7 Millions d'annes la srie spilitique d'Erquy (domaine cadomien breton, Massif armoricain, France).

COCHERIE A., CHANTRAINE J., FANNING C. M., DABARD M. P., PARIS F., LE HERISSE A. & EGAL E., 2001 - U/Pb dating: Brioverian age of the Erquy series (Armorican massif, France) C. R. Acad. Sci. Paris, 333 (8), 427-434

http://www.brgm.fr/geofrance3d/presentation/colloque_21_11_95/armorc.html

CARTOGRAPHIE 3D DE CIBLES REGIONALES

LE MASSIF ARMORICAIN :

DE L'ACCRETION CADOMIENNE, D'UN ARC VOLCANIQUE

A LA COLLISION CONTINENTALE HERCYNIENNE

J.P. Brun et P. Guennoc

Composition du groupe thmatique :

M. Ballvre, J.P. Brun, J. Chantraine, A. Galdeano, D. Gapais, P. Guennoc, B. Le Gall, E. Le Goff, C. Truffert, J. Van Den Driessche.

1. Zonation gologique et gophysique

Le Massif Armoricain, en premire approche, est un segment troit de la collision continentale hercynienne, intermdiaire entre une syntaxe au NW de la Pninsule Ibrique et un segment trs large, le Massif central. Il est dcoup en trois domaines troits (Fig. 1) d'orientation moyenne EW par deux zones de dcrochement hercyniens majeures (dcrochements Nord et Sud Armoricain).

Ces trois domaines sont du Nord au Sud :

1) Le domaine Nord Armoricain qui vers l'Est est majoritairement occup par les formations Cadomiennes, Socle prcambrien tardif (Panafricain de la Chane hercynienne). C'est cette zone qui fait l'objet du projet ARMOR/GEOFRANCE 3D, actuellement en cours.

Ce domaine prcambrien est caractris par une tectonique d'accrtion d'arc volcanique, processus gologique particulirement original et probablement unique dans tout l'Ouest Europen.

2) Le domaine Centre Armoricain qui est bord, au Nord comme au Sud, par les deux zones de dcrochement voques plus haut contient des formations sdimentaires palozoques reposant en discordance sur les sdiments du Briovrien dont l'ge partiellement Cambrien pourrait descendre dans le Prcambrien terminal. L'ensemble, trs mtamorphique, est affect par des plis droits en chelon associs aux dcrochements hercyniens d'ge Carbonifre moyen suprieur.

Tant l'origine des sdiments dit "Briovriens" que l'absence globale d'information sur les formations sur lesquelles elles reposent (Socle Cadomien?) font du domaine Centre Bretagne une des nigmes majeures du domaine hercynien franais.

3) Le domaine Sud Armoricain, (Fig. 2) , situ au Sud du cisaillement Sud Armoricain, est majoritairement caractris par des sries mtamorphiques de haute trs haute (20 Kb) pression d'ge Silurien Dvonien infrieur et de basse moyenne pression partielle d'ge Dvonien Carbonifre. Ce domaine contient peu de traces structurales des pisodes compressifs prcoces, trs fortement repris par une extension Carbonifre suprieur Permien.

D'un point de vue gophysique, on note que le compartimentage en trois domaines, distingu ci-dessus par leurs caractres gologiques, est clairement soulign par les cartes gravimtriques et magntiques (Fig. 3) Ceci atteste d'une structure moyenne de la crote, diffrente d'un compartiment l'autre. Le domaine Nord est marqu par de fortes anomalies magntiques de faible longueur d'onde corrles une forte anomalie gravimtrique, l'ensemble tant li aux formations de l'arc volcanique Cadomien de la Baie de St.-Brieuc. Le Domaine Centre est marqu par des anomalies magntiques intenses le plus souvent l'aplomb des plis des formations palozoques (ferrifres) et par un fort gradient gravimtrique parallle au dcrochement Sud Armoricain, et aux granites associs. Le Domaine Sud est marqu par de fortes anomalies magntiques d'orientation NW-SE associes le plus souvent aux roches basiques et ultrabasiques et par une anomalie faible l'aplomb des nappes de Champtoceaux.

Les donnes de sismique rflexion grand-angle (profil complmentaire ECORS Nord de la France) acquises dans l'Est du Massif Armoricain montrent que la crote infrieure est partout trs rflective avec un moho situ entre 30 et 35 km. Le Domaine Centre est caractris par une crote moyenne trs rflective (Fig. 4), correspondant trs probablement aux structures du Socle Cadomien non affleurant du Domaine Nord Armoricain et soulignent l'intrt d'une exploration gophysique approfondie de ce domaine.

2. Cibles pour un projet d'imagerie 3D dans la crote

Sur la base des lments qui prcdent, il ne fait aucun doute que l'Est du Massif Armoricain prsente, dans la connaissance actuelle que nous en avons, quelques traits caractristiques de la premire importance pour justifier un projet GoFrance 3D (Fig. 5).

1) Du point de vue de la "connaissance rgionale" de la Chane Hercynienne, le Massif Armoricain prsente l'affleurement la zone de suture de la Chane. Il contient les roches mtamorphiques de plus haute pression connue dans la Chane Hercynienne, et c'est la seule zone de la Chane Hercynienne o est observable le socle antcambrien, peu perturb par les dformations et les mtamorphismes hercyniens.

Enfin du Nord de la Bretagne, dj couvert par le projet ARMOR, la Vende, il offre la coupe quasi-complte la plus courte de la zone de collision hercynienne.

2) Du point de vue des processus gologiques reprsents, et outre les intrts purement rgionaux voqus au paragraphe prcdent, un projet GoFrance 3D concernant l'Est du Massif Armoricain permettrait de traiter quelques-uns des problmes les plus actuels de la godynamique continentale :

- Nature et signification des dcrochements d'chelle continentale l'chelle crustale

NB : le cisaillement Sud-Armoricain est mondialement connu pour avoir t le site pilote o furent dcouvertes les fameuses structures C/S des granites mylonitiques et o furent labors les concepts modernes de la base de la cinmatique et de la mcanique de mise en place des plutons dans les grandes zones de dcrochements.

Approfondir l'aide de l'imagerie gophysique 3D ce site exemplaire est un objectif en soi.

- Mcanismes de l'exhumation des roches mtamorphiques de trs haute pression pendant l'extension synconvergence.

Les donnes actuellement disponibles montrent que le mtamorphisme de trs haute pression (20 Kb) de Champtoceaux est synchrone du dpt, dans le mme domaine de la chane, de sries marines.

Illustrer par la gophysique la gomtrie d'chelle crustale des structures qui ont permis l'exhumation de roches trs profondes pendant la convergence est aussi un objectif majeur qui dpasse largement son intrt purement rgional.

- Mcanismes d'amincissement par extension, dans une direction parallle la chane, de toutes les sries mtamorphiques du domaine pralablement paissi de la zone de suture.

Cette extension se fait la faveur d'une combinaison de dcollements, d'ampleur rgionale dans certains niveaux lithologiques favorables (ex. : porphyrodes), et de dtachements, permettant la remonte des noyaux migmatitiques.

Ici encore l'illustration gophysique l'chelle crustale de ce phnomne est de la premire importance tant sur le plan de la comprhension du mcanisme que de ses retombes gophysiques (il s'agit trs probablement, comme l'ont suggr plusieurs auteurs, du mcanisme principal qui est l'origine du litage de la crote infrieure observ sur les profils sismiques en coute longue).

3. En rsum

Un prolongement vers le SE, jusqu'en Vende, de la zone tudie par le projet ARMOR utilisant la mme mthodologie (Aromagntisme, Gravimtrie, Sismique, Gologie) permettrait :

- d'obtenir une coupe complte de la zone de la collision hercynienne, y inclus la structure Cadomienne de son socle,

- de contribuer la comprhension de la dynamique de grands dcrochements continentaux, de l'exhumation synconvergence de la crote profonde, et de l'extension tardi post-orognique des chanes de montagnes.

Bibliographie

BALLEVRE M., PARIS F. et ROABETD M. (1992). Corrlations ibero-armoricaines au Palozoque : une confrontation des donnes palobiogographiques et tectonomtamorphiques. C.R. Acad. Sci., t. 315, Sr. II, pp. 1783-1789.

BALLEVRE M., MARCHAND J., GODARD G., GOUJOU J.C. and WYNS R. (1994). Eo-Hercynian events in the Armorican Massif. In "Pre-Mesozoic Geology in France and related areas", J.D. Keppie edit., p. 183-194.

AUTRAN A., LEFORT J.P., DEBEGLIA N., EDEL J.-B. and VIGNERESSE J.-L. (1994). Gravity and magnetic expression of terrannes in France and their correlations beneath overstep sequences. In "Pre-Mesozoic Geology in France and related areas", J.D. Keppie edit., p. 49-72.

BOIS C., CAZES J., CHOUKROUNE P., GARIEL O., HIRN A., LE GALL B., LEFORT J.-P., MATTE P., and PINET B. (1994). Seismic reflection images of the pre-Mesozoic crust in France and adjacent areas. In "Pre-Mesozoic Geology in France and related areas", J.D. Keppie edit., p. 33-47.

BRUN J.P. and BALE P. (1990). Cadomian tectonics in Northern Brittany. In "The Caledonian Orogeny" D'Lermos RS., Strachan R.A., Topley C.G. Edit., Geol, Soc. Spec. Pub. 51 : 95-114.

GAPAIS D.and LE CORRE C. (1980). Is the Hercynian belt of Brittany a major shear zone ? Nature 288-579 : 574-576.

GAPAIS D., LAGARDE J.-L., LE CORRE C., AUDREN C., JEGOUZO P., CASAS SAINZ A., et VAN DEN DRIESSCHE J. (1993). La zone de cisaillement de Quiberon. Tmoin d'extension de la Chane Varisque en Bretagne mridonale au Carbonifre. C.R. Acad. Sci., t. 316, Ser. II, p. 1123-1129.

JEGOUZO P. (1980). The South Armoricain Shear Zone. Jour. Struct. Geol. 2 : 39-47.

LE CORRE C. (1977). Le Briovrien de Bretagne Centrale : essai de synthse lithologique et structurale. Bull. Bur. Rech. Geol. Min. 1-3 : 299-254.

MATTE P. and HIRN A. (1988). Seismic signature and tectonic cross section of the Variscan Ouest in Western France. Tectonics 7,2 : 141-155.

Fig. 1 - Schmas du Massif Armoricain montrant la zonation en trois bandes d'orientation E-W, dlimites par les dcrochements Nord et Sud Armoricain.

Le domaine Nord (Projet Armor) est subdivis en deux domaines, Domnonen (contenant les formations d'arc volcanique) et Mancellien, qui caractrisent le bloc Cadomien. La tectonique hercynienne y est faible modre.

Le domaine Centre est caractris par l'absence de Socle ant-ordovicien (en blanc). En gris apparaissent les formations sdimentaires du Briovrien dont l'ge est, en majeure partie, trs probablement Cambrien.

Le domaine Sud ne contient que quelques vidences locales gochronologique de formations prcambriennes. Pour la structure de dtail voir figure 2.

Fig. 2 - Carte structurale du Domaine Sud-Armoricain montrant l'existence de grands contacts tectoniques extensifs d'ge Carbonifre entre les units mtamorphiques de bas grade et les units de haut grade clogites et schistes bleus. Seule l'unit de Champtoceaux montre un contact chevauchant incontestable (au Nord de Nantes). D'aprs Gapais et al. (1993).

Fig. 3 - Carte de l'anomalie de Bouguer (a) et du champ magntique total rduit au ple (b).

Fig. 4 - Extrait du profil de sismique grand angle ECORS tir dans l'Est du Massif Armoricain, Matte et Hirn (1988), montrant la forte rflectivit de la crote moyenne dans le Domaine Centre Armoricain. Les structures inclines associes pourraient tre d'ge Cadomien, d'un type comparable celles du Domaine Nord Armoricain.

Fig. 5 - Coupe submridienne du Massif Armoricain avec caractrisation des trois domaines (Nord, Centre et Sud) et des objectifs d'un projet d'imagerie 3D l'chelle crustale.

Seawater-sediment-basalt interactions : Stable isotope (H, O) and elemental fluxes within the Ordovician volcano-sedimentary sequence of Erquy (Brittany, France)

Contribution to Mineralogy and Petrology 1995, 120 (3/4), p. 249-264

The Ordovician volcano-sedimentary succession of Erquy (northern Brittany) is made of immature sediments thermally metamorphosed at the contact of intruding basic sills. Pillow lavas constitute the upper part of the sequence. The trace element geochemistry of sills and pillow lavas suggests that they were derived from a tholeiitic source located beneath a passive margin. This volcanic sequence was metamorphosed under low to moderate greenschist facies conditions. In this study the direction and amplitude of chemical and isotopic fluxes in the basalt-sediment-water system were established and the oxygen and hydrogen isotope compositions of the aqueous fluid that reacted with the volcanic rocks were characterized. Cationic thermometry on chlorites and isotopic thermometry on plagioclase-chlorite pairs indicate closure metamorphic temperatures in the range 200-250C for the basaltic sills. Stable isotope compositions of iron-rich chlorites ('18O = 5.5; 'D from -60 to -50) and plagioclases ('18O from +9 to +10) reveal that the source of the fluid was certainly seawater. The '18O variations within the sills are strongly correlated with the rate of progress of the main metamorphic reaction:clinopyroxene + plagioclase + ilmenite M chlorite + albite + epidote + quartz + sphene that produced major element mobility at the scale of the volcano-sedimentary sequence. Calculation of elemental fluxes by mass balance combined with oxygen isotopic compositions of basalts shows that the highest water-rock ratios (S1) were at sill-sediment boundaries and within pillow lavas at the top of the pile. The volcanosedimentary sequence of Erquy was a net sink for Na and a source for Ca. No Mg uptake could be detected whereas the hydrothermal alteration of the sediments released Fe, Si, and K trapped by the volcanic rocks. The '18O value of the fluid reacting with sills appears to have shifted no more than +4 after percolation at low temperature through immature sediments ('18O , +12). The Erquy volcano-sedimentary sequence represents a marine hydrothermal system dominated by low-temperature exchange which allowed a general 18O-enrichment of the volcanic rocks and a 18O-depletion of sediments.

SuitcaseToilet bagBike bagWear

Pyjamas+TStalc powdermaps

ponchotweezerscamera long pants

pillowscissorsflannel+glassslip

4Xyellow shirts+tieelec. razortoothbrush/pastesocks

4xsocksrazor cablekfsred sweater

4xslipsrazor brushflashlightjacket

shorts/bathingsoap  AA batterieswatch

glasses

thermos+cup+tea

gel seatbeclamethasoneslippers (under)

glovesvisineIce-pack+bottle

floss

tylenol

spare glassesaspirin

2 of AC/AC plugsaltComputerWaist Bag

bungy cord.sunscreenToshiba M30fold bag

flashing lightbacteomyceneexternal batterypassport/money

Gerber toolszoviraxDVD's

lock (key in bike bag and wallet)smart card readerBack_Pack

earphonesfootwear

Things left in France 2000 (bikes and bags are at Olivier's) - Monique's front bag and saddle bags; Dad's 2 side bags.

Monique

-

front bag

:

front pocket = elastoplasts; right side pocket = floss; small type of presun 30; cure dents;

left side pocket = chewing gum;

main pocket = front light; 2 cups; 1 glass; set of 3 electrical adaptors bought in Spain; 2 packs of surgical tape + a pack of bandages; 2 dish clothes; calamine; whistle; Kleenex; cologne; Shampoo; water spray bottle; washing powder; spot remover; white Gilligan hat.

:

top pocket = cycle gloves; 'sensible shoes'; 3 large bungy cords, red, yellow, white;

right small pocket = empty;

right medium pocket = blue espadrilles;

right large pocket = Cannes towel; large orange Cologne bottle; purple overpants; spare small plastic poncho; Logis de France guidebook and Poitou-Vendee -Charente Michelin Guide; Coppertone 25 sun tan lotion; plastic bags

left small pocket = suntan protection; talcum;

left medium sized pocket = green poncho;

left large pocket = whisk; pink bag; multicoloured hooded sweater; large towel;

Dad -     left bag: small blue bag = washing powder; electric water heater; knife; flashlight without batteries; 4 small bungy cords; rear flashing red light; repair bag = rustines; glue; plastic bag of punctured inner tubes; 1 good spare inner tube; spare cable; first aid kit; bike tools; pump + new adaptor for Monique's inner tubes; plastic bag with KNF+ oyster knife + tea bags + black whistle + front and back lights that came with the bicycle; blue 'glass thermos'; Monique's lock + key (Monique has other key); bicycle manuals and invoices; plastic water bottle.

right bag: cycle gloves; Olivier's shirt; old long pants for cycling or repair work (has a patch); swim suite; Cannes Towel; small towel; cycling shorts and cycling underwear (bought at Decathlon in 2000); 1 serviette; red windcheater; blue Gilligan's hat; blue poncho.

Travelling iron with adaptor, bicycle pump and repair kit, are in left side of top draw in guest room at Jannick's.

14:09 2004/09/01 key[ geology deformation coaxial strain ]

>> John Whalley: I'll start it off by drawing your attention to the symposium put together by Rob Butler and Stefano Mazzoli - Styles of continental compression: thin-skinned, thick-skinned, simple shear and pure shear. In some aspects this revisited the pure shear/simple shear debate that we had on Geo-tectonics a couple of years back. I want to offer up a point that Rob himself made during his talk - have we concentrated too much on the patently non-coaxial strain zones of thrust belts and overlooked the part played by broader zones of near coaxial strains, often associated with vertical stretching?

***************************

> Mark Brandon: Now to the science comment by you John on simple shear vs. pure shear. I fully agree with statement below. The focus on shear zones has caused us to overlook the role of penetrative deformation in orogenic settings. With our work on exhumed subduction complexes, we find that the deformation within many subduction wedges is commonly coaxial, including both ductile and brittle deformation. This result suggests that the base of the wedge is very weak (so that little to no vorticity is created there) and that strain softening is uncommon within the wedge. There were two topics that received attention in the exhumation sessions at Florence.

1) There remains a split between those who want to use discrete normal faults to account for all aspects of unroofing HP and UHP metamorphic rocks, and those who envision a combination of ductile thinning, faulting, and surface erosion.

2) There seems to be much disagreement about the timing of exhumation relative to convergence. Does deep exhumation occur during convergence and collision? Or does it represent a late-orogenic or post-orogenic process, as the gravity collapsers would have it? Or does it mainly occur by plate divergence, as documented in the Woodlark Basin east of New Guinea.

***************************

Tim Bell: Our experience in the high metamorphic grade cores of several orogens around the world, where we have quantitatively examined the inclusion trail asymmetry in porphyroblasts both across and along the orogen, suggests that orogenesis is essentially coaxial during horizontal bulk shortening and gravitational collapse events. One dominant asymmetry is rare. This may indicate that significant translational deformation is always very discreetly partitioned.  We have very little information on the uplift path because the start of uplift is accompanied by just the last gasps of porphyroblast growth. Why should gravitational collapse occur only at the end of orogenesis if what we see currently in mountain belts forming in active plate margins around the world is a key to the past?

16:53 2004/10/10 key[ Mantle Plumes  ]

Plates Plumes and Paradigms 2005 Foulger Natland Presnall, Anderson GSA SPE388 ISBN 0-8137-2388-4

http://www.gsajournals.org/gsaonline/?request=get-abstract&doi=10.1130%2FG22135.1 - dating mantle rootsof young continental crust by Lu-Hf systematics - Massif Centrale

http://www.mantleplumes.org/Chapman/GPDFinalReport.pdf

Foulger, G.R., Natland, J.H., and Anderson, D.L. 2004. Penrose conference Report: Plume IV: Beyond the Plume Hypothesis - Tests of the plume paradigm and alternatives. GSA Today, 14, 1, p. 26-28.

Ernst, R.L. and Buchan, K.L., 2004. Mantle Plumes: their identification through time. GSA Special Publication 352, 575 p. ISB 0-8137-2352-3 http://www.geosociety.org

http://www.mantleplumes.org - the anti-plume group

http://www.largeigneousprovinces.org/  - large igneous province subcommission

http://www.geolsoc.org.uk/template.cfm?name=NakedEmperor  - Geol soc webpage 'Wot no plumes'

]

Basalts erupted from the Hawaian volcano Mauna Loa contain minerals whose isotopic ratios prove they originated from recycled ocean crust, scientists say.

The olivines of Mauna Loa basalts contain strontium-enriched melt inclusions whose complete trace-element  patterns strongly resemble those of layered gabbros, similar to those found in ophiolites.  Ophiolites, or fossilized ocean floor crust, are characterized by cumulus plagioclase which is very rich in the element strontium.

The major-element compositions of these melt inclusions indicate that they are not the result of the assimilation of present-day oceanic crust, through which the melts have travelled to the surface. Rather, an original gabbro has  been transformed into a (high-pressure) eclogite by subduction and recycling, and subsequently incorporated into  the Hawaiian mantle plume - the "hot spot" that rises, probably from the mantle/core boundary, and gives rise to the volcanism at the mid-Pacific islands.  Hawaii is thousands of miles from the nearest point of subduction.

The trace-element signature of the original cumulus plagioclase is present as a so-called "ghost" signature, which  allows scientists to identify precisely the recycled rock type. The ghost signature shows that the former gabbro can retain much of its original chemical identity through the convective cycle, without completely mixing with other  portions of the former oceanic crust.

ALEXANDER V. SOBOLEV, ALBRECHT W. HOFMANN & IGOR K. NIKOGOSIAN: Recycled oceanic crust observed in 'ghost plagioclase' within the source of Mauna Loa lavas.  Nature 404, 986 - 990 (2000)

******************

The region worst affected by dust in the State is the Far North, with about 60 dusty days per year, followed by Port Pirie with19, Lincoln, the West Coast and Whyalla with 17, the Riverland and Murray Mallee with 12 and Adelaide, the Barossa and Yorke Peninsula with eight. The last two severe dust storms to occur in SA during the past 20 years were on February 16, 1983 and May 24,1994.

******************

Wobbles within wobbles probe planet's core  January 31, 2001

Millimetre deviations from the expected wobble of the Earth's axis are giving geophysicists clues to what happens at the boundary between the Earth's mantle and its iron core.

A new theory proposes that iron-rich sediments are floating to the top of the Earth's core and sticking like gum to  the bottom of the mantle, creating drag that throws the Earth's wobble off by a millimetre or two over a period of  about 18.6 years.

"The wobble is explained by the presence of metal patches attached to the core-mantle boundary," explained Raymond Jeanloz, professor of geology  and planetary science at the University of California, Berkeley. "As the outer core turns, its magnetic field lines are deflected by the patches and the core fluid gets slowed down, just like mountains rubbing against the atmosphere  slows the Earth down."

Light elements are segregated into the outer core as the inner core grows by   solidification. The increasing concentration of light elements in the outer core causes excess light elements to precipitate as a sediment. The sediment accumulates in depressions at he top of the core, which may    account for the ultra-low-velocity zones (ULVZs) inferred from  seismological observations. The theory, first proposed by Bruce A. Buffett of the Department of Earth  and Ocean Sciences at the University of British Columbia, also explains a peculiar slowing of seismic waves that ripple along the core-mantle boundary.

Buffett laid out the theory at the December meeting of the American Geophysical Union and in an article with Jeanloz and former UC Berkeley post-doctoral fellow Edward J. Garnero, now at Arizona State University's Department of Geological Sciences in Tempe, in the Nov. 17 issue of Science. Much of the work was done while Buffett was on sabbatical at UC Berkeley.

The wobble values explained by the theory have been adopted by the International Astronomical Union as its standard for calculating the position of the Earth's axis into the past as well as the future.   As the Earth spins on its axis the moon and sun tug on its bulging equator and create a large wobble or  precession, producing the precession of the equinoxes with a period of 25,800 years. Other periodic processes  in the solar system nudge the Earth, too, creating small wobbles - called nutations - in the wobble. The principal components of the nutation are caused by the Earth's annual circuit of the sun and the 18.6-year precession of the  moon's orbit.

While these nutations have been known for many years, extremely precise geodetic measurements of the  pointing direction of the Earth's axis have turned up unexplained deviations from the predicted nutation.

An annual deviation that lagged behind the tidal pull of the sun first suggested to Buffett 10 years ago that strange  processes may be going on at the boundary between the mantle, made up of viscous rock that extends 1,800 miles below the crust, and the outer core, which is thought to be liquid iron with the consistency of water. The inner core, made of very pure, solid iron, rotates along with the outer core, dragging the Earth's magnetic field with them.

"The Earth is getting pulled and tugged at regular periods, but we observe a difference in the way the Earth  responds to these tugs and pulls and what we predict," Buffett said. "One of the ways you could explain that is by  having some dissipation in the vicinity of the core-mantle boundary as the fluid moves back and forth relative to  the mantle. But the viscosity of the fluid core is comparable to water, and having water slosh back and forth  relative to a rigid mantle wasn't going to produce the kinds of dissipation we needed to see."

He hit on another way the rotating core could dissipate energy: via electrical drag.

Based on experiments Jeanloz had performed on the chemistry of rocks at the high temperatures and pressures characteristic of the core-mantle boundary, Buffett suggested that silicon-containing minerals would float to the top of the liquid outer core, carrying iron with it. Together they would form iron-rich, porous sediment at the mantle boundary that would stick to the mantle, settling into depressions.

Because the Earth's core rotates about a slightly different axis than the mantle (due to the tug of the Sun and  Moon), the core's magnetic field is dragged through the mantle, passing unhindered because the mantle does not  conduct electricity. The porous, iron-containing sediment stuck to the mantle, however, would resist the rotation of    the magnetic field, creating just enough tug to perturb the Earth's rotation.

"As the core rotates it sweeps the magnetic field with it, which easily slips through the mantle with no resistance,"  said Buffett. "But if the bottom of the mantle has conductivity, then it's not so easy to slip the magnetic field lines  through the mantle. The magnetic field tends to stretch and shear or pull out right across the interface. That generates currents, and those currents damp out the motion and create the kind of dissipation we need to explain  this lag in response."

The sediment layer would have to be less than a kilometre thick (about half a mile) in order to have the observed  effect, and would probably cover only patches of the outer core.

Support for the idea that a thin layer of iron-rich silicates may be plastered to the underside of the mantle came from the work of Arizona State University's Garnero and his colleagues, who use seismic waves to probe the  mantle and core. They had observed very thin layers at the core-mantle boundary in which seismic waves slow to a crawl. Using Buffett's ideas, Garnero modelled what a thin silicate layer would do to seismic waves and found agreement with the data.

The team subsequently predicted where these patches are located, based on where seismic waves slow down  substantially and where they do not.

"Think of it as a fuzzy boundary between the mantle and the core, with patches perhaps 10 to 20 kilometres across and up to a thousand metres thick," Jeanloz said.

The rising sediment eventually would squeeze out the iron, leaving the silicate sediments tucked to the bottom of  the mantle as the iron falls toward the solid iron inner core. The rising of the silicate contaminants and the subsequent fall of metallic iron would create a convection in the outer core consistent with what geologists think to  be the source of the core's magnetic field. Thus, the rising sediments and falling iron could rev up the Earth's dynamo.

"In one of the popular models, created by Gary Glatzmaier and Paul Roberts, the dynamo is powered mainly by the growth of the inner core as light elements get excluded and float up through liquid iron, driving convection that   powers the dynamo," Buffett said. "If this idea about sediments is right, the sediments would add a component to drive flow from the top down. This is going to have a pretty important effect on the style of fluid motions in the core, and even in the way in which the magnetic field gets generated."

The silicates stuck to the mantle also might be caught up in mantle convection and carried to the surface, accounting for reports of core material in lava erupting from hot spot plumes like that under Hawaii.

Though Buffett first proposed his theory 10 years ago in his PhD thesis, the data to prove it were not available. In  particular, long-term measurements were needed to accurately determine an out-of-phase anomaly in the 18.6  period wobble.

"Now, with more than 20 years of data, we can confirm that the discrepancy is there and is explained very nicely by the Earth's magnetic field causing friction at the bottom of the mantle," Jeanloz said.  The work was supported by the National Science Foundation, the University of California Institute of Geophysics and the Natural Sciences and Engineering Research Council of Canada.

*********************

17:06 2004/10/10 key[ structure deformation strain ]

Styles of Continental Contraction  2006 Mazzoli and Butler ISBN-10 0-8237-2414-7

The large wavelength deformation of the lithosphere: materials for a history of the evolution of thought from the earliest times to plate tectonics 2003 Sengor GSA Mem MWR196 ISBN 0-8137-1196-7

http://www.geol.umd.edu/~dzjiang/LSGT/publications/ - Jiang

http://www.sci.uidaho.edu/cyber/documents/cSIS_report-draft.doc - future of structural geology

Debate with Falk Mostly agree with RKoenemann

From Google "What is" vorticity geology -atmosphere

http://www.google.ca/search?q=cache:bghNmZNytZYJ:www.geology.yale.edu/~dberco/papers/2003/EPSL-Frontiers-PlateGen.pdf+%22What+is%22+vorticity+geology+-atmosphere&hl=en - vorticity; generation of plate tectonics from mantle convection

http://www.google.ca/search?q=cache:SwP6Q3cVmmYJ:www.earthsciences.uq.edu.au/~rodh/publications/NZ_Abs_2001.pdf+%22What+is%22+vorticity+geology+-atmosphere&hl=en - MIDDLE CRUSTAL PROCESSES OF OBLIQUE COLLISION IN THE CENTRAL SOUTHERN ALPS, NEW ZEALAND: WHAT RECORD IS PROVIDED BY DUCTILE FABRICS IN THE ALPINE SCHIST?

Co-axial deformation

If during an experiment the principal axes of a series of finite strains are parallel to the principal axes of incremental strain, then the experiment is an example of coaxial progressive strain. On the other hand if the principal axes of a series of finite strains are not parallel to the principal axes of incremental strain, then the experiment exemplifies non-coaxial progressive strain.

Which of the two experiments (progressive simple or progressive pure shear) is an example of coaxial strain and which is an example of non-coaxial strain?

Rotational/Irrotational and Coaxial/Noncoaxial Deformation

rotational deformation is progressive deformation that involves the rotation of finite strain

axes over time (otherwise it is called irrotational deformation)

coaxial deformation is progressive deformation in which the incremental and finite strain

axes are parallel during each time increment of deformation (otherwise it is called

noncoaxial deformation)

http://www.geo.cornell.edu/geology/classes/RWA/GS_326/LecNotes/326-99_lecture_01-20.pdf  - structural geology, Allmendinger, Cornell

Coaxial if the axes of the finite and infinitesimal strain ellipses are parallel. ( Non-rotational - the axes in the restored and final states are parallel - refers just to finite strain.)

Finite StrainInfinitesimal Strain

Non-rotational -> pure shearCoaxial -> progressive pure shear

Rotational -> simple shearNon-coaxial -> progressive simple shear

In practice it is difficult to apply these distinctions. Deformation could however be non-coaxial in terms of infinitesimal strain and non-rotational in terms of finite strain.

see Jiang - discusssion on transpressional shear zones

http://www.earthsciences.uq.edu.au/~rodh/courses/ERTH2004/ - Rod Holcombe, Queensland

http://www.kuleuven.ac.be/geology/hsg/SG&T/SG&T-project13.html - An integrated study of the interaction between deformation and fluids in a tectonic wrench context - Monts d'Arre, Brittany, France

http://ic.ucsc.edu/~casey/eart150/Lectures/Strain/10def&strain.htm - Cowell

http://www.tcd.ie/Geology/shiptonz/Pakistan.html - strain Nanga Parbat, Butler

http://www.geol.vt.edu/research/gssrs/gssrs2003/abstracts/cook.doc - vorticity

To[ GEO-TECTONICS@JISCMAIL.AC.UK ] From[ John Ramsay <Ramsay-Dietrich@WANADOO.FR> ] Date[   Thu, 2 Sep 2004 16:35:09 +0200 ]

Subject[ pure vs. simple shear ] John Ramsay Cratoule, Issirac, F-30760 St. Julien de Peyrolas France Tel.: +33  4 66 82 32 28 E-mail<ramsay-dietrich@wanadoo.fr>

Dear John, Mark and Tim

I am very surprised that the controversy of whether geological processes are of simple shear or of pure shear nature still continues to come up in discussions.  These two types of deformation are singular end members of a great spectrum of possibilities for finite and progressive strain.  Simple

shear, or something close to it, can occur in certain types of shear zones but pure or irrotational strains are most unlikely to be important in tectonic processes.  Most finite strains arising from tectonic processes lie between the two end members and almost all will have significant rotational components

The reason for this conclusion is clear when one studies the types of displacement equations arising in tectonic processes.  If rocks involved in deformation processes form a continuum (which from my field experience is generally the case), if originally planar marker surfaces such as bedding are curved or folded and if the finite strain states one observes are heterogeneous then practically all strains must have rotational components.

This is not to say that these strains have the specific rotations arising in simple shear and, in fact, generally have rotational components less than those of simple shear.  These conclusions arise directly from the nature of the displacement gradient equations.  Irrotational finite strains can only arise when the displacement gradient matrix is symmetric, a situation that is generally not attained with the geometric constraints of all practical tectonic situations.  Discussions of this irrefutable mathematical argument can be found in Ramsay and Graham 1970, (pp. 792,794 and 795) and Ramsay and Lisle 2000 (pp 917 and the following worked examples).

References:-

Ramsay, J.G. and Graham, R.H., 1970.  Strain variation in shear belts. Canad J; Earth Sci. 7, 786-813.

Ramsay, J.G. and Lisle, R.J., 2000.  The Techniques of modern structural geology Vol.3, Applications of continuum mechanics in structural geology.

John Ramsay

To[ GEO-TECTONICS@JISCMAIL.AC.UK ] From[ Tim Bell <tim.bell@JCU.EDU.AU> ]

Date[         Fri, 3 Sep 2004 12:04:53 +1000 ] Subject[ Re: pure vs. simple shear ]

Dear John, Mark, John and Falk

I prefer not to be lumped in with the pure and simple shearers (no sheep and sheriff jokes - please!). Surely progressive heterogeneous simple shear is only possible in a ductile environment on a vertical transform fault. In any other environment there will be a component of bulk shortening across the zone of deformation due to plate collision or gravitational collapse.

Furthermore, progressive pure shear is a silly concept for ductilely deforming rocks since they are heterogeneous and always deform inhomogeneously.

Presumably most people using the terms pure and simple shear know their strict definitions and realize this but do it as a broad brush approach to simplify conceptually what I describe below. Using these terms rests uneasily with me though as heterogeneities provide the key to all the

structural and metamorphic processes that I have ever observed in rocks.

What I mean by overall coaxial deformation is that in spite of the heterogeneity of the crust, porphyroblasts record roughly equal numbers of both asymmetries of inclusion trails across the core of an orogen. We know this from quantitative work comparing asymmetries for successive generations of FIAs (foliation inflection/intersection axes preserved within the porphyroblasts). The deformation is always quite heterogeneous, very partitioned, and at some scale non-coaxial, yet, in general, both asymmetries are developed for long periods of geologic time across large tracts of porphyroblast bearing rocks independent of regional folds. This

makes sense at a whole orogen scale because orogen topography and presumably therefore, deformation, is close to symmetrical at that scale,  probably because plates appear to be only partially coupled across the subduction zone. Therefore, both horizontal shortening and gravitational collapse generated structures should be somewhat coaxial at orogen scale. However, gravitational collapse structures must be quite asymmetrical well away from

the orogen core, e.g., thrusts. Perhaps the answer is that porphs generally do not grow very far out from the orogen core. Alternatively, translational deformation may be so discretely partitioned that porphs can never grow, even at the very start of deformation, in that environment. However, in general the bulk of rock in the portion of an orogen where porphs can grow records an over all coaxial history. So it may not be surprising if people are finding evidence for this in environments other than orogen cores. Dramatic translations may be confined to very spatially

restricted fault like zones. This is obviously the case with thrusts on orogen margins. Why not in orogen cores as well.

To[ GEO-TECTONICS@JISCMAIL.AC.UK ] From[ Shoufa Lin <shoufa@SCIBORG.UWATERLOO.CA> ] Date[ Thu, 2 Sep 2004 22:07:08 -0400 ]Subject[ Re: pure shear vs. simple shear, and the role of coaxial deformation ]

Hi all,

Concerning pure shear vs. simple shear and the role of coaxial deformation, I would like to offer the following comments:

1. Simple shear and pure shear are two end members of infinite number of deformation paths, and most natural deformations contain both components, i.e. are of general shear. Pure simple shear and pure pure shear are special cases and are probably rare.

2. Both theoretical considerations and field observations indicate that simple shear is generally more localized than pure shear and the simple shear/pure shear ratio often varies across a high-strain zone (a phenomenon referred to as deformation-path partitioning by Lin et al. 1999). Because shear zones are, by definition, zones of localized strain, many shear zones described in the literature are likely only the higher-strained part (with higher simple shear/pure shear ratio) of a much wider zone, and the lower-strained parts on both sides (with lower simple shear/pure shear ratio) are considered as the wall rocks. It is necessary to consider both the higher-strained and the lower-strained parts for a full kinematic interpretation of a high-strain zone. This is further discussed by Lin et al. (1998) based on theoretical considerations and a natural example (particularly the last two sections under the subheadings of oblique transpression and triclinic movement picture and localization of simple shear, respectively).

3. Pure shear is coaxial and simple shear is non-coaxial. For this reason, strain related to pure shear accumulates more efficiently than that related to simple shear. Therefore, pure shear may contribute significantly to the finite strain even where the simple shear/pure shear ratio is high.

4. Because simple shear and pure shear are independent of one another, for a deformation of general shear (with both simple shear and pure shear components), the simple shear direction is most likely oblique to all of the 3 principal axes of the pure shear component, which means that the resulting kinematics is generally of triclinic symmetry. Deformations with kinematics of monoclinic symmetry (where the simple shear direction is parallel to any of the 3 principal axes of the pure shear component or where the pure shear component is zero) are special cases. In triclinic high-strain zones, variation in simple shear/pure shear ratio, as well as in strain intensity and shear direction, can lead to variation in orientation of stretching lineations across a high-strain zone, and stretching lineations in such zones can vary continuously from subhorizontal to down dip. This is discussed extensively by Lin et al. (1998) and Jiang and Williams (1998), based on theoretical modelling and a natural example (see also Lin and Jiang 2001).

References:

Lin, S., Jiang, D., and Williams, P.F., 1998, Transpression (or transtension) zones of triclinic symmetry: Natural example and theoretical modelling, in Holdsworth, R.E., et al., eds, Continental transpressional and transtensional tectonics: Geological Society [London] Special Publication 135, p. 41-57. (This paper can be down-loaded from http://www.sci.uwaterloo.ca/earth/about/people/facdir/lin/pubresearch.html )

Jiang, D., and Williams, P.F., 1998, High-strain zones: A unified model: Journal of Structural Geology, v. 20, p. 1105-1120.

Lin, S., Jiang, D., and Williams, P.F., 1999, Discussion on transpression and transtension zones: Journal of the Geological Society  [London], v. 156, p. 1045-1048.

Lin, S. & Jiang, D. 2001. Using along-strike variation in strain and kinematics to define the movement direction of curved transpressional shear zones: an example from northwestern Superior Province, Manitoba. Geology, v. 29, p. 767-770.

Shoufa Lin

To[ GEO-TECTONICS@JISCMAIL.AC.UK ]

From[ Mark Brandon <mark.brandon@YALE.EDU> ]

Date[         Thu, 2 Sep 2004 22:34:05 -0400 ]

Subject[ Re: pure vs. simple shear ]

I would like to reply briefly to comments by John and Falk. Please recognize that my comments are offered only for intellectual exchange, and that I have no intent to challenge my good colleagues, who I hold in high respect.

To John: my comments were concerned with deformation at the full scale of an orogen, not at the outcrop scale. You have argued in the past that the Alps were deformed in a simple-shear fashion at the regional scale.

To both John and Falk: In continuum mechanics, it is well known that there is always a unique irrotational velocity field that can account for the distribution of fluxes around an orogen--that is  influxes due to accretion and outfluxes due to erosion.

To state this in another fashion, there is always a coaxial solution for an orogen. Furthermore, vorticity is produced only at boundaries, such as the boundaries at the base of an orogen (e.g., coupling at the basal thrust), or at local scales due  to contrasts in rheology. Those contrasts can be initial (i.e. due to lithology) or evolutionary (i.e. due to strain softening leading to localization). Thus, the degree of coxiality at the regional scale tells about the degree of vorticity generation and/or strain localization at the regional scale.

To Falk: It has often been noted that there is less work needed to create a strain by simple shear than by pure shear (see discussion by Arpad L. Nadai in his book on plasticity). Unfortunately, this question is incomplete. To calculate work, we would need to know both strain and stress, and stress requires that the rheology is known. Second, there are other contributions to work in an orogen, such as the work against gravity. Third, the conditions may not be correct to create a simple-shear deformation (e.g. strong boundaries bounding a weaker material). Finally, it has never been established that a process will always be able to find its minimum work solution. Thus, the minimum work argument for simple shear is, I think, a red herring.

Mark Brandon

To[ GEO-TECTONICS@JISCMAIL.AC.UK ] From[ Stefano Mazzoli <s.mazzoli@GEO.UNIURB.IT> ]

Date[ Sat, 4 Sep 2004 10:14:19 +0200 ] Subject[ Re: pure vs. simple shear ]

Dear all,

that "simple shear and pure shear" in the title of our IGC32 session on   Styles of Continental Compression" was indeed a (over?)simplified concept concerned with orogen-scale deformation. John's argument is  clearly irrefutable (and I'm sure not only to a former John's student  like myself!) when dealing with finite strain states in rocks at the  outcrop scale. The debate we wished to raise with the session was  perhaps more on the role of localised (along narrow, 'weak' zones of  (quasi-) simple shear) vs distributed deformation in orogens. The  examples of broad deformation zones discussed in the session were  apparently dominated by bulk coaxial strain (e.g. Nanga-Parbat), and  this has led the discussion towards an analysis of the relative  importance of non-coaxial (high) strain zones vs broader zones of  (relatively low) near coaxial strains associated with vertical  stretching in orogens. Although near coaxial strain does not need to be  the rule for bulk deformation at the orogen scale (see, e.g.,  orogen-scale simple shear models for the Helvetic Nappes by John and  co-workers), it appears indeed to be important in many instances  (including subduction complexes, as also mentioned by Mark). In any  case, the fundamental question of the role played by distributed and localised deformation in orogens still remains, and so does the possibility that structural geologists have sometimes overlooked the  former to concentrate on the latter. And, as Mark pointed out, this is  probably the case not only for contractional deformation, but also for  syn- to post-convergence extensional deformation - and related tectonic  exhumation - for which a combination of roughly coaxial bulk vertical  shortening and localised deformation along extensional detachments  appears to be common.

As session convener and Italian geologist, let me finally thank all of  you who made it to Florence and contributed to a very good conference  with quite a bit of high-level science, particularly in structural  geology and tectonics.

Stefano Mazzoli

To[ GEO-TECTONICS@JISCMAIL.AC.UK ] From[ Richard Jones <r.r.jones@DURHAM.AC.UK> ]

Date[         Tue, 7 Sep 2004 03:02:40 +0100 ] Subject[ Re: pure vs. simple shear ]

John (and other contributors to the pure vs. simple shear debate),

The recent "pure shear vs simple shear" session at IGC was interesting and thought provoking, and the subsequent discussion here on Geotectonics suggests that there is still some degree of controversy, despite the fact that all of us have been brought up on a healthy diet of Ramsay (1967), Ramsay & Graham, Ramsay & Huber etc.! I guess this means that some of us still cant adequately explain all observed structures entirely in terms of simple shear ( volume change), or

something close to it.

While mathematical arguments based upon the equations of strain compatibility may be irrefutable, in using these equations as a starting point for analyzing crustal deformation we have to assume that the continuum approximation is valid at all scales of analysis, from outcrop scale to whole orogens. I dont think it's been adequately proven that this is necessarily always the case. Sure, in many areas there are structures for which the approximation is valid across the whole outcrop, area, or large-scale nappe, and the standard methods of quantitative structural geology can be applied. But in some areas, it isnt always clear that there really is mechanical continuity throughout the region, at all scales of observation i.e. it always seems possible to find some continuity at some (arbitrary) scales, but not always possible to find continuity at all scales! As long as we choose an area of sufficiently homogeneous continuous strain, then the continuum assumption may be valid at that scale, but that doesn't prove that the assumption holds at larger scales.

I dont think theres any fundamental law of physics which means that rocks have to obey the laws of strain compatibility but with the  limits of our current understanding of rock deformation, it's convenient for us to impose this requirement (strain compatability) upon them in order to be able to analyse them adequately in a quantitative way. A more realistic model for crustal deformation might be based on discontinuum mechanics.

Plate motion on a sphere must inevitably give rise to long lengths of plate margin in which bulk deformation is non-coaxial and non-plane strain - and in these regions the overall deformation cannot be described as simple shear (or anything remotely close to it), even if some individual shear zones within the orogen are zones of localised simple shear. Bulk strains must have significant components of pure shear (not just a slight departure from simple shear), even if that makes them problematical for us to understand in terms of strain compatibility.

Richard Jones e-Science Research Institute University of Durham

P.S. See here for handy hints on how to get started with "cream-cake

tectonics" analogue modelling:

http://www.globalgourmet.com/food/ilc/0499/profit.html

To[ GEO-TECTONICS@JISCMAIL.AC.UK ] From[ Rob Butler <butler@EARTH.LEEDS.AC.UK> ]

Date[ Tue, 7 Sep 2004 09:31:08 +0100 ] Subject[ Pure vs simple shear (is it really  what we're discussing?) ]

Interesting discussions. Id like to re-iterate what my fellow convenor of the "Styles of continental compression" symposium at IGC stated as to its background. Stefano and I were interested (and remain interested!) in examining the different styles of continental deformation. As Stefano points

out the really key issue seems to be about localisation. So heres my tuppence-worth to the debate. Its 2-dimensional (some may say one).

If we buy into a Dewey & Bird (for the old-timers) or Houseman/England view of Tibet for example we dont need very large strains (at an outcrop scale) to thicken the crust and hence accommodate say 75% of the total convergence in the India-Asia collision system because the strain is distributed across (now) 2000+km across-trend crust. In contrast, the Himalayas (say 25% of the convergence) is narrow  and the thrust zones (e.g. MCT) narrow too (with locally very high strains  appropriately consistent sense-of-shear indicators).  Of course we can argue that distributed strain is accommodated through an array of anastamosing simple-shear-dominant shear zones but is that just a convenience? The localisation behaviour is different the controls on partitioning, the timing and evolution of partitioning remain interesting issues. Looking through my slide collect I find Ive lots photos of narrow deformation zones that have the qualitative/semi-quantitative aspects of dominant simple shear. They probably have integrative displacements across the whole lot of <1km!  By way of illustrationon the field trip to the Outer Hebrides that preceded the Mike Coward meeting in May, we visited the North Uist coast home to the classic Ramsay and Graham shear zones. Rod led the visit. Something like 40 man hours were spend scouring the immediate vicinity of Caisteal Odair the two classic examples are still there (ones in a boulder). Theyre very beautiful of course and we all photographed them. But there are only 2. Of the dozens of other, narrow deformation zones, no others seemed to have a simple foliation pattern so perhaps do not approximate closely to simple shear zones. Theyre less elegant (and largely unstudied). Furthermore the area sits in a tract of gneisses many km across with very little asymmetry evident. Mike Coward interpreted this lot (and many other examples, as have others since) as very broad (and therefore crustal-scale, big-displacementso orogenically important) simple shear-dominated deformation zones. But are they? Ive spent lots of time in thrust belts only have had only passing interests in slate belts. Both types of structure exist.and they are different beasts. Even bits of thrust belts are different parts of the Moine Thrust Belt for example show km-wide zones of layer-parallel shortening, others have none at all. For me the issues are not whether various end-member strains exist but the application of mixtures to real settings. 25 years ago there was a bandwagon looking at strain in thrust belts (a few brave souls have continued). Then this became unfashionable. People "realised" that thrust displacements are more important (in thrust belts!) at accumulating the bulk convergence. 20 years on there are still cross-sections drawn on a crustal scale that extrapolate discrete thrusts to the Moho (although everyone recognises that these, if they exist, will actually be shear zones rather than cataclastic, discrete faults at depth). There are advantages in this simplicity, but surely not if they generate simple kink-geometry dip-changes at the surface (an issue the John Ramsay raised way back). How sensitive are these models to subtle changes in the model at depth? What if the thrusts passed back down into distributed strain (check out Adrian Pfiffners papers from the mid 80s on this one) - or even down onto sub-vertical stretching?

When Dave Prior and I worked on the structure of Nanga Parbat in the mid80s we were taken (distracted?) by lots of shear criteria and a dramatic discrete fault. But it only represents the edge of the massif. Theres lots of moderate sub-vertical stretching throughout which, if you speculate/integrate the strains, proves to accommodate more shortening than the attractive "shear zone" on the edge. Doubtless old hands will chuckle at this "road to Damascus" like conversion.

To return to the issue what are the key controls and their sensitivities for influencing the degree of deformation localisation (partitioning) within the continents? Is it the number, orientation and linkage of pre-existing weakness? Is it the influx of fluids (or the hydrated state of minerals

within the crust), is it heat,, are the reasons intracrystalline? Or is it down to erosion or other "external" factors? I suspect that the phenomena we should be discussing are not merely those exhumed deeper crustal materials we photograph at outcrop but also information from geodetic surveys, seismic reflection data, seismology (anisotropy and earthquake distributions). But

surely we must be open to the wide range of approaches particularly in trying to link across scales, not to mention make adequate mechanical descriptions/predictions of structures. A bit of an

apple-pie/grandmother/eggs statement I know. These are some of the issues our session tried to capture. Were putting together a proceedings with provisional acceptance for a Special Paper of

GSA. We can take some extra contributions (subject to approval/review etc) so if youve been aroused by the discussions send a title and abstract to Stefano (Stefano Mazzoli <s.mazzoli@geo.uniurb.it>) who is taking the lead in editing the volume. The article submission deadline will be the end of December 2004.

Cheers, Rob Butler

From: "Tim Bell" < tim.bell@JCU.EDU.AU>  To: < GEO-TECTONICS@JISCMAIL.AC.UK>

Sent: Monday, September 13, 2004 11:03 PM Subject: Re: Pure vs simple shear (is it really what we're discussing?)

I enjoyed reading Robs note. We are all coming to similar realizations about what is taking place during deformation at the larger scale.

The degree of partitioning of multiple successive foliation producing events that we observe using porphyroblasts is extreme within single large outcrops. This generates local highly non-coaxial strains against porphyroblast rims, but not necessarily distributed away from them into the matrix as each foliation developed. That is, away from porphyroblast margins the deformation intensity may be minimal for each event. However, the actual strain accumulated across many such zones could be significant, over many deformations and periods of porph growth. It could even be

different in its non-coaxial large-scale displacive effects to that suggested by the porphyroblast inclusion trail asymmetry. The reason for this is that porphs always grow very early during deformation. They do not track the deformation as it intensifies in one event. The non-coaxial

component of the deformation always increases as the strain increases. Potentially it could go more non-coaxial in the matrix with the opposite shear sense after the porph has formed and as the deformation intensifies.

However, the most important point with regards to Robs comments is that matrix foliations preserve almost none of the very lengthy history that is trapped in the porphyroblasts. Sections perpendicular to lineation or parallel to lineation but perpendicular to foliation commonly show inclusion trails that appear to be continuous with the matrix when they are actually truncated if one looks at other section orientations. This is dealt with to some degree in Cihan (2004) just out in JSG on web. This lengthy history has all been wrapped into the inevitable schistosity parallel to compositional layering in the rocks that we deal with from orogen cores. Such S0//S1 hides

the bulk of the deformation history in our experience. If S0 is //S1 in non-porphyroblastic rocks then there is probably a very lengthy deformation and thus displacive history that cannot be extracted. The displacive history can be extracted, to some degree, by probing garnet cores that formed in successive FIA sets from a confined region, and plotting Mn, Ca and Fe isopleths on  pseudosections constructed using THERMOCALC. The resulting path of PTs is much more extended than available by other means. Where we  have done this it tracked an extended downwards path into the orogen in some detail. Porph growth stopped soon after uplift began.

Regionally, the distribution pattern of all FIA trends on a total rose plot can be remarkably similar (Bell et al, 2004 JSG) with overall relatively uniform distributions of inclusion trail asymmetries between FIA sets. Where we have seen regional variation in partitioning in terms of FIA distribution (same paper as above) is around terrains underlain by thick large feldspar granitic gneisses that apparently behaved more competently at lower temperatures earlier in the metamorphic history.

In summary,

1. Locally the deformation can be very intense, and very non-coaxial particularly at small scales. Yet the distribution of this small-scale non-coaxiality as preserved by porphs is such that the bulk deformation appears to be relatively coaxial.

2. If the same thing happens at a whole range of scales then local mesoscopic shear zones (which only track very late history) may average out relatively coaxial at a bigger scale, or have minimal translational effects compared to the bulk, but much lower strains occurring in intervening zones.

3. Since the bulk of such a prolonged foliation development history undergone by multiply deformed rocks now lies in the foliation parallel to S0, so may too the bulk of displacement history. In that case matrix shear zones would tell us absolutely nothing about the large-scale displacement

history!

11:36 2004/10/24 key[ Fieldlog structural symbols ]

BEDDING

subed

s-bed

sobed

PILLOW

PILLOW

suplw

s-plw

soplw

IGNEOUS LAYERING

IGNEOUS LAYERING

sulay

s-lay

solay

FLOW CONTACT

FLOW CONTACT

suflow

s-flow

soflow

FOLIATION

FOLIATION

sufol

s-fol1

s-fol2

s-fol3

s-fol4

s-fol5

FAULT

FAULT

fu

fd

fs

fn

fr

SHEAR ZONE

SHEAR ZONE

xu

xd

xs

xn

xr

JOINT

JOINT

ju

j

DYKE

DYKE

d

NEXT/PREV

AXIAL PLANE

AXIAL PLANE

buax

b-ax1

b-ax2

b-ax3

b-ax4

b-ax5

LINEAR

LINEAR

L-FABRIC

L-FABRIC

lu

l-1

l-2

l-3

l-4

l-5

BOUDINAGE AXIS

BOUDINAGE AXIS

l-bdn1

l-bdn2

l-bdn3

l-bdn4

l-bdn5

INTERSECTION LINEATION

INTERSECTION LINEATION

luint

l-int1

l-int2

l-int3

l-int4

l-int5

FOLD AXIS

FOLD AXIS

l-fold1

l-fold2

l-fold3

l-fold4

l-fold5

Z FOLD

Z FOLD

buz

b-z1

b-z2

b-z3

b-z4

b-z5

S FOLD

S FOLD

bus

b-s1

b-s2

b-s3

b-s4

b-s5

U FOLD

U FOLD

buu

b-u1

b-u2

b-u3

b-u4

b-u5

VEIN

VEIN

v

SLICKEN STRIAE

SLICKEN STRIAE

l-ss

OTHER

OTHER

outcrop

FRI 12/17/2004 05:06 PM key[ geology Fieldlog Brodaric e-mail ]

11

Dec 17 2004 5:28

At 11:27 AM 2/6/97 EST, you wrote:

>Thanks for the info. The crashing is unacceptable. Can you send me the

>ascii files and I will try to duplicate the problem. You are using the

>snowemp database ?

From: "Prof. W.R.Church" < wrchurch@uwovax.uwo.ca>, on 2/6/97 11:20 PM:

Boyan,

I retried the full installation of the snowemp database (with the addition of longitude, latitude, and elevation fields to STATI, and lithcode and metals fields to LITHO) along with the import of the two attached files, on my computer at home (same hardware as at the University but with 64 Meg RAM); and when it crashed during the Query plotting procedure got the message 'Internal Error: General Protection Exception (at 97:0027F3)'. I could not however replicate the error related to the use of Palette from within the Plot menu. I will have the 12 grad students carry out the same procedure as a test next Wednesday and Friday.

Regards,

Bill

12

Dec 17 2004 5:30

Boyan,

Yesterday I replaced the Fieldlog version I downloaded last May with the current version and had six students redo the import exercise as a midterm test. After importing the stati and litho tables, checking them with STATI and LITHO Query macros, and saving the setup, I had them logoff without trying to plot the data through Query. In all cases, irrespective of the hardware or operating system, Fieldlog crashed at the point of hitting the OK button in logoff!! After recovery (I now have a bat file that allows recovery relatively painlessly, and that doesn't require Autocad reconfigeration) and logging back on, Fieldlog behaves without problem. On the good side the students have had lots of practice recovering from Acad crashes, and I have fourteen students who can now at last flawlessly customize snowemp.exe, carry out the tranformation, import, and plot procedures, and draw a vector map of non overlapping geologic units from the plotted data!

One other point. It would seem that each time one logs on to Fieldlog, it is necessary to run through the Map Setup procedure before plotting data from Query. It doesn't seem to remember the parameters set in the previous session. Is there a reason for this?

Thanks,

Bill c.

At 11:48 AM 2/7/97 EST, you wrote:

>I will try it here also. Sounds like a bug. I've been free of those for

>some time now - just your bad luck. I thought it was actually bug-free by

>now. Have you a recent version ? If you don't have one from late fall,

>

>I won't be able to look at it until next week sometime.

>Boyan

>Boyan Brodaric

>615 Booth St., room 234B

>tel: (613)992-3562

>fax: (613)995-9273

>email: brodaric@gsc.nrcan.gc.ca

13

Dec 17 2004 5:32

Boyan,

Attached are my student instruction notes (imptofl3.rtf) detailing the procedure for the setting up and modifying of 'snowemp' for the importation of two ascii files into the STATI and LITHO tables. I have run it now for about 40 students, and the only problem I have had is that in spite of judiciously saving the setup before carrying out the plotting step via Query, the very final step of actually activating the plot invariably causes Autocad to crash, to the point that it has to be reconfigured (deleting acad.pwd etc.). Also, changing the field parameters via Palette from the plot menu rather than from within Setup, also causes Autocad to crash badly!

Once the system has been rebooted and reloaded, everything seems to work fine.

Thought you might be interested. Regards, Bill c.

At 11:27 AM 2/6/97 EST, you wrote:

Thanks for the info. The crashing is unacceptable. Can you send me the ascii files and I will try to duplicate the problem. You are using the snowemp database ?

From: "Prof. W.R.Church" < wrchurch@uwovax.uwo.ca>, on 2/6/97 11:20 PM:

Boyan,

I retried the full installation of the snowemp database (with the addition of longitude, latitude, and elevation fields to STATI, and lithcode and metals fields to LITHO) along with the import of the two attached files, on my computer at home (same hardware as at the University but with 64 Meg RAM); and when it crashed during the Query plotting procedure got the message 'Internal Error: General Protection Exception (at 97:0027F3)'. I could not however replicate the error related to the use of Palette from within the Plot menu. I will have the 12 grad students carry out the same procedure as a test next Wednesday and Friday.

Regards,

Bill

At 11:48 AM 2/7/97 EST, you wrote:

I will try it here also. Sounds like a bug. I've been free of those for

some time now - just your bad luck. I thought it was actually bug-free by

now. Have you a recent version ? If you don't have one from late fall,

I won't be able to look at it until next week sometime. Boyan

FRI 12/17/2004 09:14 PM key[ geology fieldlog email Brodaric ]

From: "Prof. W.R.Church" < wrchurch@uwovax.uwo.ca>, on 11/4/96 12:03 AM:

Boyan,

Just a short note to let you know that FLOG3 has been successfully

integrated into my current GIS course, and I have been promoting its use in

various field studies around her. I currently have a 2nd year class of 50

students who have taken instruction in Flog v2.83 with CorelDraw, and will