Kooyak Island is small, kilometer-sized island located about 75 km off the northeastern coast of the Boothia Mainland, Nunavut. The Boothia Mainland lies within the Rae Domain of the Western Churchill Province; a polymetamorphic, multiply-deformed Archean terrane flanked by Palaeoproterozoic orogenic belts. Kooyak Island is dominated by granulite facies gneissic rocks of pelitic origin. Peak metamorphism reached the second sillimanite zone with conditions of 750-850°C, 7-9 kbars. Retrogression is characterized by a chlorite-sericite assemblage with conditions of 525-575°C, 3-5 kbars. Within the granulites are numerous northeast-trending mylonite zones characterized by sinistral ductile shearing. Shearing began during retrograde metamorphism and finished before the chlorite-sericite assemblage formed. Two deformational events shaped the island's structure. The first, shown by NNW-SSE-trending crenulating folds, is overprinted by the second, shown by northeast-trending large-scale folds which dominate the structural grain of the island.
The structure and metamorphic events of Kooyak Island correlate with that of the Boothia Mainland and Rae Domain described in literature. Prograde metamorphism and the first deformational event correspond to the crustal thickening compressional event that affected the Rae Domain at 2.43-2.35 Ga. This reflects thermal reworking during the Arrowsmith orogeny. The second deformational event on Kooyak Island corresponds with the Rae Domain's compressional event related to the Trans-Hudson orogen at 1.82-1.80 Ga. The mylonites also occur regionally with syn- to late-shear pegmatites of assumed Palaeoproterozoic age and are thought to represent the last stages of crustal stabilization.
Dan is currently working for Pacific Northwest Capital Corp. (PFN) as a project geologist
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