LE3 .A278 2020

2020

Barr, Sandra
Archibald, Donnelly B.

Acadia University

Master of Science

Masters

Geology

Earth & Environmental Sciences

Geological mapping, petrological studies and U-Pb (zircon) dating were done to better characterize metasedimentary and metaigneous rock units in the northeastern Aspy terrane, Cape Breton Highlands, Nova Scotia. Foliated biotite monzogranite of the newly recognized South Aspy River pluton has a Silurian age (440.3± 2.1Maor 421.6 ± 4.0 Ma). An early Devonian age for the Glasgow Brook granodiorite pluton was confirmed at 415.7± 2.7Ma, consistent with a previously reported age of 416.0±1.9 Ma. U-Pb (zircon) ages from the Cheticamp Lake Gneiss of 416.9± 1.3 Ma and 415.9± 1.9 Ma, combined with mineralogical and textural similarities, suggests that the Cheticamp Lake orthogneiss and Glasgow Brook pluton may be related. Both the South Aspy River pluton and Glasgow Brook pluton were emplaced in a volcanic-arc tectonic setting and combined with ages of volcanic and plutonic rocks from other parts of the Aspy terrane indicate an extended history of arc magmatism from the early Silurian through the early Devonian. The plutonic units intruded metasedimentary rocks previously assigned to the Money Point Group but now named the Little Southwest Brook formation. The youngest detrital zircon population in a semi-pelitic schist sample provides a maximum depositional age of 441.2 ± 2.5 Ma. Mineral assemblages, lack of evidence for melting, and thermobarometry constrain peak prograde metamorphic conditions to <650 °Cat 5.5 –7kbar. Based on similar lithologies, includingcharac teristic pelitic rocks interlayered with amphibolite and marble as well as similar detrital zircon signatures, the Little Southwest Brook formation is interpreted to be part of the Cape North Group and correlative with high-grade metamorphic rocks elsewhere in the northern, western, and central Aspy terrane. The igneous, metamorphic and deformational history of the area records the Salinic and Acadian orogenies and the Silurian-Devonian collision between the Aspy and Bras d'Or terranes.

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https://scholar.acadiau.ca/islandora/object/theses:3531