Chris Yakymchuk

This study presents the first P-T estimates and 40Ar/39Ar dates from mafic granulite enclaves from Southampton Island, south-central Nunavut, indicating a tectonmetamorphic affinity to the Rae domain of the western Churchill Province. Southampton Island occupies the "Dorset corridor", the enigmatic boundary region between the Trans-Hudson Orogen and the western Churchill Province. The eastern part of the island is underlain largely by granulite and upper amphibolite facies metagranitoid rocks, with local supracrustal plutonic enclaves. Mineral assemblages, textures, and P-T estimates in mafic enclaves from the eastern part of the island shed light on first-order aspects of the regional tectonometamorphic history. Most samples contain the granulite facies assemblage Grt + Opx + Cpx + Plag ± Hbl, with spectacular coronitic textures developed around garnet porphyroblasts. Three suites of texturally heterogeneous granulites each preserve three textural domains, interpreted to represent three points on the P-T path: (1) near-peak metamorphic conditions of 800-850^oC and 9-12 kbar; (2) near-isothermal decompression to 750-850^oC and 7-9 kbar; (3) retrogression to amphibolite-facies conditions. ⁴⁰Ar/³⁹Ar thermochronology on hornblende yields ages of 1750-1720 Ma. The P-T-t evolution documented by these samples is interpreted to represent tectonic thickening, tectonic transport to mid-crustal levels, intrusion of granites, slow cooling and exhumation controlled by thrusting and erosion. Similar P-T-t estimates from the western Churchill Province indicate Southampton Island may be the southeast extent of the Rae Province.

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Pages: 131
Supervisor: Rebecca A. Jamieson