New geological mapping in Yukon-Tanana terrane near Thistle Creek, Stewart River map area, Yukon Territory

Abstract

The Thistle Creek map area (NTS 115-O/3), in the Stewart River area, Yukon Territory, is underlain by poly- deformed and metamorphosed Paleozoic rocks of the Yukon-Tanana terrane, and younger plutonic rocks. Two fault-bounded tectonostratigraphic associations dominate the map: 1) polyphase grey orthogneiss in garnet- amphibolite schist-gneiss, interpreted herein as a metavolcano-plutonic complex; 2) interstratified garnet- amphibolite schist-gneiss and metasedimentary schist and paragneiss derived from psammite, semipelite and quartz-arenite, collectively interpreted as a metavolcano-sedimentary succession. Grey and white banded quartzite beds are generally in fault contact with the gneiss and schist units, and their stratigraphic relationships are equivo- cal. Recognition of this area as an extensive metavolcanic terrane has significant implications for the economic potential of this area. Primary stratigraphy is obscured by an intense transposition deformation, and later, open folds and faults. Regional correlations of plutonic suites indicate that the transposition event was post-Carboniferous and pre-Jurassic.