Abstract: This report summarizes the results of geological mapping and preliminary petrological studies of an exposure of ultramafic rocks, the Buffalo Pitts Peridotite (BPP), in the eastern Dawson Range, central Yukon. The BPP is characterized by fresh spinel peridotite. Plagioclase mantles on spinel grains are interpreted to have developed during decompressive metamorphism during exhumation from sub-crustal depths to mid- to upper-crustal depths. The peridotite body forms a foliaform lens 580 m by 100 m that is enclosed in and intruded by leucocratic, biotite-garnet-corundum blue orthogneiss.The peridotite and blue corundum orthogneiss are in turn hosted in a north-dipping panel of amphibolite-grade metamorphic rocks that are included in the pericratonic Devono-Mississippian Wolverine Creek metamorphic suite, part of the Yukon-Tanana Terrane. Quartzite, quartz-mica schist and amphibolite with minor marble and calc-silicate units occur largely south of, and structurally beneath the peridotite body. Leucocratic tonalite gneiss, part of the ~357 Ma Selwyn Gneiss, occurs north of, and structurally above the BPP. Tonalite veins intrude the blue corundum orthogneiss and are interpreted as marginal intrusions of the Selwyn orthogneiss. Intrusion of dykes derived from the Selwyn Gneiss requires exhumation and emplacement of the BPP and the enclosing blue corundum orthogneiss in or prior to the earliest Mississippian.

Authors: Evers, K.G., Johnston, S.T., and Canil, D.

Keywords: Geological Mapping, Petrology

NTS Mapsheet(s): 105E, 115I, 115J

Citation: Evers, K.G., Johnston, S.T., and Canil, D., 2001. An alpine peridotite in the Dawson Range, Yukon-Tanana Terrane: Preliminary results and interpretations. In: Yukon Exploration and Geology 2000, Emond, D.S. and Weston, L.W. (eds.), Exploration and Geological Sciences Division, Yukon Region, Indian and Northern Affairs Canada, p. 137-146.

Downloads

Name	Comment
Report	File is .84 MB	Download PDF