Author: W.R. Church
Company: None

CONTRIBUTION OF THE
DEPARTMENT OF GEOLOGY
UNIVERSITY OF WESTERN ONTARIO
LONDON, CANADA       NO. 159-b
PRELIMINARY RPT.
Prog. Abst.G.A.C. Ann. Meet., Winnipeg, 1970 P. 13.

METAMORPHIC ECLOGITES FROM THE BURLINGTON PENINSULA,
NEWFOUNDLAND, CANADA
by
W. R. Church
Eclogites occur as boudinaged mafic masses within garnetiferous psammitic metasediments of the Fleur de Lys Supergroup of the Appalachians of Newfoundland. They are composed of omphacite, garnet, amphibole, zoisite, muscovite, quartz,rutile and ilmenite.  The eclogites are the only known occurrences in the Appalachians, and only the second known example of classic type (within a gneissic terrain) in North America.
The eclogites have quartz basalt-normative compositions with low K20 values (0.01 wt. percent) and 100 Mg/Mg+Fe (mol) of 51 to 56.  One retrograded sample of biotite-bearing eclogite contains 0.73 (wt. percent) of K20 and 6 percent normative quartz (mol. norm).  It has a 100 Mg/Mg+Fe (mol) value of 42.and a Poldervaart and Parker Crystallisation Index of 38 which is an uncommonly low value for eclogite.
The omphacite has the composition:  S102-53.45; T102-0.07; A1203-9.49;Fe203-3.48; FeO-2.25; MgO-10.94; CaO-14.53; Na20-5.61 (microprobe analysis). The iron-magnesium partition coefficient determined by microprobe analysis for the pair gar net-amphibole in the eclogite, compared with determinations for garnet-amphible from various metamorphic terrains of different grade, suggests that the eclogites formed  under moderate metamorphic conditions of the staurolite-kyanite grade of metamorphism.
The metasedimentary sequence in which the eclogites occur is comparable to that of the Moine series of Scotland and Ireland, the More suite of Norway, and the Hecia Hoek succession of Spitsbergen, all of which contain eclogite. The Fleur de Lys and Moine successions, and probably the More suite, represent thick early marginal accumulations of clastic material derived from the craton and deposited in the Appalachian-Caledonide geosyncline during the late Proterozoic and Cambrian, and metamorphosed prior to early Ordovician time.  The eclogites were formed by metamorphism of early mafic igneous rocks intruded into a thick sequence of psammitic rocks which had already been compacted and de-watered prior to the onset of metamorphism.