Bedrock geology of Yukon-Tanana terrane in southern Stewart River map area, Yukon Territory

Polydeformed and metamorphosed Paleozoic rocks of the Yukon-Tanana terrane underlie a large part of the Stewart River area, Yukon Territory. Quartz-rich metaclastic rocks (quartzite, quartz-mica schist, psammite) are regionally widespread, and are locally interstratified with, as well structurally interdigitated with, metavolcanic rock (mafic and intermediate garnet-amphibolite). Mafic to felsic ortho-gneiss is almost exclusively associated with the amphibolite, and rarely with metasiliciclastic rock. Complexes of mafic-ultramafic rock and associated orthogneiss are exposed at structurally high levels, and are thought to be part of an erosionally dismembered, originally continuous tectonic sheet, emplaced on top of the metasiliciclastic rock. Emplacement occurred prior to regional transposition deformation and metamor-phism. Post-tectonic Early Jurassic and (?)mid-Cretaceous plutons crosscut the older fabrics. Sporadically preserved, fault-disrupted felsic to mafic volcanic rocks of the late Cretaceous Carmacks Group unconformably overlie all older units. Local felsic porphyritic intrusions (? mostly dykes) are probably Eocene.