Detrital zircon geochronology of the Taku terrane, southeast Alaska

Abstract

U–Pb geochronologic studies have been conducted on 60 detrital zircon grains from Permian(?) and Triassic metasandstones of the Taku terrane in central southeast Alaska. The resulting ages are mainly in the range 349–387 Ma, with five additional grains that yield probable ages ranging from ~906 to ~2643 Ma. These ages are similar to the ages of detrital zircons in Carboniferous and older rocks of the Yukon–Tanana terrane, which lies directly east of the Taku terrane. In contrast, these ages are different from the ages of detrital zircon grains in the Alexander terrane to the west. The data are accordingly consistent with models in which the Taku terrane is a western component of the Stikine and Yukon–Tanana terranes, and that this crustal fragment is separated by a fundamental tectonic boundary from rocks of the Alexander and Wrangellia terranes to the west.