LE3 .A278 2022

2022

Barr, Sandra
van Rooyen, Deanne

Acadia University

Master of Science

Masters

Earth & Environmental Science

Earth & Environmental Sciences

The Aspy and Bras d’Or terranes of northern Cape Breton Island are both part of Ganderia but contrast in rock types, ages, and magmatic, metamorphic, and tectonic history. The two terranes were juxtaposed along the Eastern Highlands shear zone (EHSZ). The purpose of this study is to determine the extent and timing of deformation and metamorphism in the rocks within and adjacent to the EHSZ in the central Cape Breton Highlands where its location and history are poorly constrained. The main units in the study area are the Ordovician to Silurian Calumruadh Brook Formation (CBF) and Middle River metamorphic suite (MRMS) in the Aspy terrane, and the Neoproterozoic McMillan Flowage Formation (MFF) and Kathy Road dioritic suite (KRDS) in the Bras d’Or terrane. Evidence was observed in the study area for three deformational events, two of which are interpreted to have been related to the EHSZ. D1 of the EHSZ is sinistral transpressional, and D2 is dextral transpressional with an oblique component. Contrasting pressure and temperature conditions of the MRMS (543-617 ̊C at 3.4-4.9 kbar) and the CBF (517-569 ̊C at 3.1-3.4 kbar) indicate that the boundary between the two units is a faulted contact within the Coinneach Brook shear zone which merges with the EHSZ in the south of the study area. A new age indicates that metamorphism occurred at ca. 395 Ma in the MRMS. The metamorphic minerals in the rocks affected by the movement on the EHSZ are limited to chlorite, overprinting pre-existing amphibolite-facies metamorphism in the western margin of the MFF and upper greenschist facies metamorphism in the CBF. Data from this study indicate that the EHSZ affected rocks up to 3 km away on either side of the Aspy-Bras d'Or terrane boundary and comprises a ca. 1 km wide mylonite zone. Activity on the shear zone in this area occurred between ca. 424-374 Ma.

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https://scholar.acadiau.ca/islandora/object/theses:3736