TECTONITES - CHECK SHEET
- concentric? similar?
- open? tight? chevron?
- F1?, F2?, F3?
- cleavage?; schistosity? Penetrative? non-penetrative?
- S1?, S2?, S3?
- mylonitic?; axial planar?
- bedding/cleavage relationship? parallel? Oblique? normal?
- crenulation? pinstrip? pseudobedding?
WHAT IS THE PROTOLITH OF THE TECTONITE?
5-0; dark green chloritic phyllite with a single foliation, perhaps a mafic igneous protolith.
dark green chloritic phyllite; note hint of
banding in specimens 5-1a and 5-1b, and
crenulation of the folation
in sample 5-1c; sample 5-1-d is a lineated amphibolite with acicular crystals of actinolite.
2,3,4: 4 samples of dull green and grey, laminated
S1 cleavage, is discordant to bedding, S0, in mudstone samples; note the
prominent L1 bedding-cleavage intersection lineation in some of the samples.
5-2a; 5-2ap1; 5-2ap2; gneiss sample in which there is a faint bedding defined by thick colour bands, S0, which is discordant to the more obvious biotite mineral foliation, S1.
5-2b; silvery sericite schist with an obvious crenulation of the foliation.
5-3a; 4 samples showing a single phase of first generation minor folding F1: 1) orthogneiss, 2) banded iron formation, 3) grey laminated lime mudstone; 4) marble.
5-3b; fine-grained orthogneiss; single phase of deformation characterized by F1 minor fold- note the asymetric nature of the fold with one limb roughly parallel to the axial plane.
5-4p1, 5-4p2; 2 specimens of dark grey, chloritic mudstone to phyllite; folds are F2 because they fold a primary cleavage S1; the more obvious cleavage is actually
a pin-strip crenulation cleavage; the folds have curvilinear axial traces, and are therefore non-cylindrical.
5-5-1; coarse K-feldspar-rich gneiss exhibiting boudinage of the granite layers.
5-5-2p1, 5-5-2p2, 5-5-2p3, 5-5-2p4 : a shape-lineated (stretched) hornblende-plagioclase gneiss.
polyphase deformation clastic metasediments showing compositional banding
and S1 mineral foliation, both folded into closed to isoclinal F2 folds.
Note the prominent S2 foliation developed in the mica rich (pelitic) parts of the fold cores but not in the more quartzofeldspathic (psammitic) layers.
5-6-a is a re-folded amphibolite with an L1 linear fabric of acicular amphibole.
5-6-b is a crenulated graphite-schist.
5-7ap1, 5-7ap2; polydeformed meta-rhyolite; exhibiting F2 crenulation folds and foliation superimposed on a penetrative S1 foliation.
5-7b; pale green sericite/chlorite schist; exhibiting an S1 mineral foliation crenulated by F2 micro-folds, and folded by F3 kink-bands.
5-8ap1; 5-8ap2; pale green phyllites; polyphase deformation: S1 mineral foliation in open, rounded F2 folds in turn crenulated by F3.
5-8b-1; greenish chlorite schist with F1 foliation folded by F2 folds, which are folded in turn by an open F3 fold.
5-8b-2; Grenville gneiss, F1 folds refolded by open F2 folds.
silvery black phyllite exhibiting polyphase deformation; indistinct S1
cleavage folded by a small, rounded open F2 fold with associated S2 cleavage
which forms the predominant planar fabric in the rock; also folded bya third event defined by the spaced crenulation (kinks) of the F2 cleavage.
5-8d; chlorite schist refolded by F2 crenulation folding, producing a rodded surface (lineation).
5-8e; similar fold in Mn-garnet rock; protolith possibly oceanic manganiferous chert (ophiolite, Baie Verte, Newfoundland).
5-8f; folded graphitic metasediment; folds are perhaps sedimentary.
5-9b; refolded linear fabric; S1 mineral foliation is refolded by an open F2 fold; the lineation is discordant to and folded by the F2 fold axis, and is therefore an L1 structure.
5-10-1; this sample
is a sheared gabbro exhibiting a C-S foliation
fabric; the margins of the shear zones define the "C-fabric",
which is at 45 degrees to the maximum stress direction,
whereas the "S- fabric" is the planar fabric within the shear zone discordant to the shear zone boundaries; it is perpendicular to the maximum stress direction.
5-10-2; quartzo-feldspathic mica schist showing a crude C-S fabric.
5-11a; 5-11b; 5-11c; samples: fault fracture slickensided surfaces; Originally, a polished fault surface formed by frictional shear during sliding. Slickensides commonly have
groove lineations on them, and these lineations may indicate the direction of slip on the fault.
initial stage of mylonitization of Grenville
Front granite exhibiting a ‘down dip’ linear fabric; porphyroclasts
of feldspar and quartz in a fine grained matrix of polygonized feldspar.
5-12b1p1; 5-12b1p2; 5-12b2; fine grained, compositionally layered mylonite derived from 5-12a.
5-12cp1; 5-12cp2; 5-12cp3 ; mylonitized felsic rock; protolith unknown.
5-12d; mylonitized Grenville diabase.
5-13a; S1 biotite and/or hornblende mineral foliation in annealed diorite-quartz diorite; some compositional segregation into melanocratic and leucocratic bands.
mylonite; note porphyroclasts of olivine.