Testing channel flow: Architecture of the Northern Monashee Mountains, SE Canadian Cordillera

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This research project, a collaboration between Earth scientists from McGill University, the University of Calgary and Commerce Resources Corporation, is designed to produce a detailed understanding of the structural and tectonic evolution of the crust in the Monashee Mountains of the SE Canadian Cordillera. The rocks in these mountains form part of a late-Precambrian rifted continental margin that was thickened by folding and thrusting during collisional events in the Mesozoic and Tertiary. They were in the middle crust at the time, and the structures within them formed at temperatures close to melting. Recent modelling studies have indicated that under these conditions such rocks may flow in channels into regions of lower pressure. This has been advocated for the Monashees and is supported by variations in metamorphic ages across the region, but it appears to conflict with existing structural interpretations. We propose a detailed structural study in two well-exposed valleys recently vacated by glaciers, with follow-up metamorphic and geochronological studies, aimed at resolving this apparent conflict. The Monashees contain abundant carbonatite sills, which are prospective for tantalum and niobium. The sills vary significantly in thickness along their lengths, probably due to the deformation. Our planned research will provide a better understanding of the causes of thickness variation and will aid the exploration for economically viable deposits. This study has implications for our understanding of the evolution of the deeper crust in orogens worldwide, and direct bearing on mineral exploration in the region of study and elsewhere.