The Kluane Metamorphic Assemblage (KMA) forms a NW-SE striking belt of medium to high grade metamorphic rocks underlying 3000 km2 in the northwestern margin of the Coast Belt in the North American Cordillera. It is bound to the west by the Denali fault, separating it from the Insular Superterrane, and to the east by the Eocene Ruby Range Batholith (RRB),obscuring the contact with metamorphic assemblages of North American affinity. The KMA consists of generally NE dipping graphitic mica-quartz schists that show an increase in metamorphic grade from greenschist facies in the SW to upper amphibolite facies (630°C at 6 kbar) near the intrusive contact with the RRB. Kinematic indicators in the lower grade schist close to the Denali fault zone record a predominantly sinistral sense of shear relative to the orientation of the Denali fault, indicating possible sinistral sense of motion along a proto-Denali fault, prior to the development of dextral motion along the fault during early Tertiary.
Neodymium isotope studies of eight samples of the KMA, four samples of mica-quartz schists of the Aishihik Metamorphic Suite (AMS, Nisling terrane), and two samples of sub-greenschist grade shales of the Dezadeash Formation (DF, part of Jurassic-Cretaceous Gambier overlap assemblage) show that the KMA with average epsilon Nd(0) = -3 and depleted mantle model ages (TDM) of 1.24 Ga is less evolved than the AMS (epsilon Nd(0) = -25, TDM = 2.6 Ga), but also less juvenile than source rocks of the DF (epsilon Nd(0) = +1.9, TDM = 0.95 Ga).
Several olivine serpentinite lenses interlayered within the schists of the KMA have delta18 O-values of 6.5, similar to serpentinites in ophiolitic sequences. The protolith of the KMA was likely situated in a backarc basin where the majority of its material was derived from an oceanic island arc, while minor detritus came from a continental source region. Transpressional accretion of slivers of pelitic sediments and oceanic crust during eastward subduction underneath North America in the Cretaceous (?) formed schists with well developed kinematic indicators, that were partially annealed during Eocene intrusional events.
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