Abstract: Paleozoic platformal and basinal strata of Cassiar Terrane are separated from rocks of Yukon-Tanana Terrane to the west by an unexposed fault in southeast Glenlyon map area. Quartzite, marble, phyllite, and amphibolite are grouped in Cassiar Terrane, and no rocks of Slide Mountain Terrane are recognized. The mid-Cretaceous Glenlyon batholith contains pendants of Cassiar Terrane and is intruded by at least five andesite dykes. West of the fault, the Yukon-Tanana Terrane includes: (1) mafic volcaniclastic rocks with preserved primary textures; (2) coarse-grained quartz-feldspar grit; and (3) metasiltstone and semi-pelitic schist. The grit is intruded by foliated hornblende granodiorite, likely of early Mississippian age. Small outcrops of tectonized serpentinite were tectonically emplaced into Yukon-Tanana Terrane, and a positive magnetic anomaly parallel to the fault suggests an unexposed extension to the southwest. Two mylonite localities and evidence of brittle cataclasis up to 1 km on either side of the presumed buried fault suggest a complex structural history along this terrane boundary.

Authors: Gladwin, K., Colpron, M., Johnston, S.T., and Black, R.

Keywords: Geological Mapping, Structural Geology

NTS Mapsheet(s): 105L01

Citation: Gladwin, K., Colpron, M., Johnston, S.T., and Black, R., 2002. Geology at the contact between Yukon-Tanana and Cassiar terranes, southeast of Little Salmon Lake (105L/1), south-central Yukon. In: Yukon Exploration and Geology 2001, Emond, D.S., Weston, L.W., and Lewis, L.L. (eds.), Exploration and Geological Sciences Division, Yukon Region, Indian and Northern Affairs Canada, p. 103-110

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