LE3 .A278 1981

1981

Colwell, John

Acadia University

Master of Science

Masters

Geology

Earth & Environmental Sciences

The Deer Lake Complex is a narrow band of Ordovician(?) mafic-ultrarnafic rocks in western Newfoundland interpreted as an incomplete ophiolite derived from the ocean crust and upper mantle. The complex consists of the following stratiforrn sequence of·rocks: 1) an ultrarnafic unit of asbestos-bearing serpentinized harzburgite, 2) a layered unit of coarse-grained ultrarnafic rocks ranging from wehrlite to clinopyroxenite and leucocratic gabbro, and 3) a volcanic unit of spilitized basalt. All rocks are metamorphosed to the lower greenschist facies. The complex is chemically similar to other ophiolites and modern day oceanic crust. The mafic volcanic rocks show distinct tholeiitic affinities and an ocean floor tectonic setting. The complex generally strikes in a northeasterly direction (035°) and dips vertically to steeply to the east. The mafic-ultramafic rocks are flanked on the west by polydeformed and metamorphosed siliciclastic rocks of the Fleur de Lys Supergroup and on the east by a chaotic sedimentary breccia. These rocks together with the complex are bounded unconformably by Carboniferous sedimentary rocks of the Deer Lake Basin. The Deer Lake Complex is correlated directly with the Baie Verte-Brompton Line which has been interpreted as the surface trace of an ancient continent-ocean interface along the full length of the Canadian Appalachians.

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