LE3 .A278 2022

2022

Barr, Sandra

Acadia University

Bachelor of Science

Honours

Earth and Environmental Science

Earth & Environmental Sciences

The late Devonian Park Spur pluton (PSP) is located in the central Cape Breton Highlands, near the eastern margin of the Aspy terrane and its tectonic contact with the adjacent Bras d'Or terrane. This study was undertaken to determine the field relations and petrological characteristics of the PSP, including its potential for critical element mineralization, and to compare it to nearby plutons of similar age, the Black Brook Granitic Suite (BBGS) to the northeast and the Bothan Brook-West Branch North River pluton (BB-WBNRP) to the south. As a result of field mapping and petrological studies of about 40 samples, the shape of the PSP has been modified compared to published maps, and it has been divided into three units: medium-grained muscovite-biotite monzogranite which forms most of the pluton, finer-grained garnet-bearing muscovite monzogranite which occurs primarily in the northwestern tip, and protomylonitic monzogranite along the southern margin. Pegmatite and aplite dykes occur throughout the PSP, and pegmatite-aplite and monzogranite dykes occur in the adjacent Ordovician–Silurian Calumruadh Brook Formation. Most samples from the PSP contain 71–74% SiO2 but the fine-grained muscovite monzogranite is more evolved, with 74–75% SiO2. Chemical variations in the PSP can be explained by fractional crystallization involving K-feldspar, plagioclase, biotite, and accessory minerals. The PSP and BBGS are similar in texture, mineralogy, and chemistry and are likely comagmatic mesozonal plutons. The BB-WBNRP lacks muscovite and appears to represent a related but more evolved magma emplaced at a shallower depth. The plutons have chemical characteristics consistent with emplacement during subducted slab failure during the waning stages of the Acadian orogeny. They appear to lack direct evidence of critical element mineralization but display characteristics of fertile granites which have potential to have produced such mineralization.

The author retains copyright in this thesis. Any substantial copying or any other actions that exceed fair dealing or other exceptions in the Copyright Act require the permission of the author.

https://scholar.acadiau.ca/islandora/object/theses:3753