Abstract: Granodiorite of the Coast Plutonic Complex intruded metasedimentary rocks in the Dezadeash Range of the northern Coast Belt in the late Mesozoic. Graphitic staurolite-biotite schist, associated with the Kluane Metamorphic Assemblage, underlies the western Dezadeash Range, whereas cordierite-biotite gneiss, previously correlated with the Late Proterozoic - Paleozoic Nisling Assemblage, is exposed in the eastern and southern regions. A terrane boundary was placed in the central Dezadeash Range.

Recent petrographic studies reveal a southeastward increase in metamorphic grade. Prograde appearance of cordierite partly obliterated an older schistosity and caused a fabric change near the postulated terrane boundary. Furthermore, typical continental margin rocks, such as marble and quartzite, are not observed. This suggests that all metamorphic rocks in the Dezadeash Range can be correlated with the Kluane Metamorphic Assemblage, whereas Nisling Assemblage rocks occur in the Coast Mountains to the east. Therefore, the terrane boundary is located in the Dezadeash River valley, further southeast than previously thought.

Authors: Mezger, J.E.

Keywords: bedrock mapping, Petrology

NTS Mapsheet(s): 115A

Citation: Mezger, J.E., 2003. Geology of the Dezadeash Range and adjacent northern Coast Mountains (115A), southwestern Yukon: Re-examination of a terrane boundary. In: Yukon Exploration and Geology 2002, Emond, D.S. and Lewis, L.L. (eds.), Indian & Northern Affairs Canada/Department of Indian & Northern Development: Exploration & Geological Services Division, p. 149-163.

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