Detrital zircon geochronology of sequence 'C' grits, Dorsey Terrane (Thirtymile Range, southern Yukon): provenance and stratigraphic correlation

Abstract

Detrital zircons analyzed from coarse grits within the eastern Dorsey Terrane of the Thirtymile Range, southern Yukon Territory, yield Proterozoic and Archean 207Pb/206Pb ages that range from ca. 1777 Ma to 2600 Ma, similar to the range of crystallization ages of basement in the Peace River Arch area of northern Alberta and northeastern British Columbia. This suggests that the source of these grits was crystalline basement of western Canada, thus confirming a North American affinity for these sedimentary rocks and their correlation with the Cassiar Terrane of northern British Columbia. The western Canadian provenance documented in the detrital zircons is consistent with models that suggest approximately 450 km of right-lateral displacement along the Tintina-Northern Rocky Mountain Trench fault, rather than recent suggestions of a western Montana provenance for the Cassiar Terrane that require greater than 2000 km displacement.