Transported slices of the coastal complex, Bay of Islands - Western Newfoundland

Comeau, Reg L. (1972) Transported slices of the coastal complex, Bay of Islands - Western Newfoundland. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (7MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The thesis area, the southern portion of the Coastal Ranges, is underlain by six igneous structural slices. They have been defined as the Coastal Complex. They tectonically overlie an undifferentiated series of transported sedimentary rocks forming part of the Humber Arm Group. All igneous structural slices of the Coastal Complex, except one, are separated from the underlying sediments and each other by melange zones of varying thicknesses and lithologies. The rock types and geological relationships can be correlated between structural slices. -- Foliated amphibolitic gabbros are intruded by soda-rich granodiorites and quartz diorites. These are affected by a second tectonic foliation and are intruded and bordered by tectonically undeformed diabase dykes and dyke breccias, which are presumed to be the feeders for nearby' similarly undeformed extrusive volcanics. -- Contacts between deformed and undeformed rocks are always high angle. Zones of diabase dyke breccias and/or fluidized host rock invariably occur at contact areas and mar original relationships. The fresher volcanics and their associated feeder dykes are similar to and equated with volcanics and sheeted dykes and dyke breccias underlying part of the nearby ophiolitic complexes to the east. -- The recognition that the Coastal Complex is geologically different and separate from the ophiolite complexes to the east requires a new interpretation for the Bay of Islands area. -- The definition of the Coastal Complex to include the foliated gabbros, granodiorites and associated fresh volcanics, along with the redefinition of the Bay of Islands Complex to include only the four large igneous massifs has rendered it possible to regard the Bay of Islands Complex (newly defined) as representing oceanic lithosphere (ophiolites). -- The Coastal Complex is interpreted as "captured" older crustal material incorporated within or above an evolving oceanic ophiolite domain during late Pre-Cambrian or early Paleozoic times.

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