Kilometre-scale folding in the Teslin zone, northern Canadian Cordillera, and its tectonic implications for the accretion of the Yukon-Tanana terrane to North Ametica

摘要

The Teslin zone in south-central Yukon haspreviously been described as a discrete zone with a steep foliationunique to the zone. It includes the Anvil assemblage and thenarrowest portion of the Yukon-Tanana terrane (the Nisutlinassemblage), and is defined by post-accretionary faults: the BigSalmon fault to the west and the d'Abbadie fault system to the east.The zone was interpreted as a lithospheric suture or a crustal-scaletranspression zone, and as the root zone of klippen lying on theNorth American craton to the east. We demonstrate thatdeformation and metamorphism are the same inside and outsidethe zone. The steep transposition foliation in the zone, in contrastto adjacent rocks to the east, coincides with the steep limb of aregional F_3 structure. This fold has a shallow limb in theeasternmost part of the zone and immediately east of the zone.Thus we reject earlier interpretations. If a suture exists between theobducted Anvil and Yukon-Tanana Nisutlin assemblages andNorth America, it is a shear zone that occurs at the base of theobducted rocks, which has been folded by the F_3 fold, However,evidence that this thrust boundary is a lithospheric suture islacking. A consequence of our interpretation is that NorthAmerican rocks pass under the eastern Teslin zone and outcrop tothe west of the Nisutlin and Anvil assemblages. This geometryprecludes the possibility of the Teslin zone being the root zone of the klippen.