BEDROCK GEOLOGY, INTERNAL STRUCTURE, KINEMATICS, AND CARBONACEOUS FAULT ROCKS OF THE DENALI FAULT ZONE AT TELLURIDE AND KIMBERLEY CREEKS, SOUTHWEST YUKON, CANADA

Exceptional exposure of the Denali fault zone occurs in Kimberley and Telluride creeks, two NW-striking drainages incised into the fault zone. Along Telluride, a single fault strand juxtaposes greenstone, ultramafic and carbonaceous metaclastic rocks of the Bear Creek assemblage (BCA) against rocks of the Insular terranes. To the SE along Kimberley, the single strand splits into three strands such that the fault zone is ~1.5 km-wide and Insular terrane rocks and Paleogene intrusions are juxtaposed against deformed Paleogene conglomerate, fault rocks, and a volcano-sedimentary assemblage of uncertain affinity, all further juxtaposed to the NE against Jura-Cretaceous clastic rocks of the Dezadeash Formation.

Central to each of the Denali fault strands is a complex zone of concentrated, primarily brittle deformation. At Telluride, listwanitic metagabbroic fault rocks of the BCA include rare mylonite, breccia, polished and striated slip surfaces, and pervasive cataclastic veins filled by Fe-rich carbonate and Cr micas. Phyllite of the BCA grades into a 35 m-wide zone of sooty clay-rich and incohesive fault rocks with lenticular quartz pods bearing Cr mica near the juxtaposition with metagabbro. Phyllite and clay-rich fault rocks are foliated with rootless isoclinal folds, pervasive thin zones of cataclasis and cross-cutting planar slip surfaces coated with striated clay. There is a clear strength contrast between the metagabbro and pelite where apparent carbonization, perhaps by frictional heating and fluid-related processes, has progressively localized strain. At Kimberley, the SW strand of the fault zone is marked by 2.5 to >10 m-wide zones of highly foliated, polished and striated, carbon- and clay-rich materials that envelop lens-shaped pods of more competent and internally foliated materials. Radial slickenlines emanate from the apices of the lenses on both sides and indicate strain partitioning with complex interplay between pure and simple shear. Oligocene cobble conglomerates were horizontally deposited on the vertically foliated fault rocks bracketing their age.

Kinematic data mirror the regional fault zone geometry, indicating NW-striking, steeply dipping dextral strike-slip with components of oblique contraction and extension, all compatible with NNE-SSW subhorizontal shortening.