"Alpine-type" ultramafic rocks of the Kluane metamorphic
assemblage, southwest Yukon: Oceanic crust fragments of a late Mesozoic
back arc basin along the northern Coast Belt
Mezger, J. E. (2000)
Yukon Exploration and Geology 1999: 127-138.
Mica-quartz schist and olivine serpentinites form the Kluane metamorphic assemblage (KMA), a 150-km-long belt that is wedged
between the Yukon Tanana Terrane and the Insular Superterrane in the northern Coast Belt. The olivine serpentinites are
serpentinized dunites that occur as lens-shaped bodies along strike, interlayered with the mica-quartz schist. The larger
ultramafic bodies developed a foliation and shear sense that is similarly oriented to those in the adjacent schist,
suggesting “Alpine-type” emplacement. Tectonic juxtaposition of schist and ultramafic rocks occurred during
collapse and subduction of a back-arc basin underneath the North American continental margin in the Late Cretaceous. Oxygen
isotope analyses point to values similar to known ophiolitic serpentinites. The ultramafic rocks are interpreted to be part
of an oceanic crust that formed topographical highs during subduction and were subsequently sheared off and tectonically
interleaved with metasedimentary rocks during the accretionary process.