The timing and provenance record of the Late Permian Klondike orogeny in northwestern Canada and arc-continent collision along western North America

Abstract

The northern Canadian Cordillera exhibits coeval accreted arc, subduction zone, ocean basin, and continental margin assemblages that make the region an exceptional place to understand tectonic processes involved in arc-continent collision. In this study, we use U-Pb zircon and monazite geochronology to define the timing and provenance record of Late Permian collisional orogeny related to the accretion of the Yukon-Tanana terrane onto the ancestral North American continental margin of northwestern Canada. New U-Pb crystallization ages of Permian intrusive rocks in the Klondike District of western Yukon bracket the timing of collision-related ductile deformation and greenschist- to amphibolite-facies metamorphism on the Yukon-Tanana terrane between 260 and 252.5 Ma. This tectonothermal event is herein named the Klondike orogeny. Detrital zircon U-Pb geochronology of Triassic strata provides the sedimentary record of arc-continent collision and crustal reworking along the Cordilleran margin. Arc-derived detrital zircons in Early to Middle Triassic (251-235 Ma) strata overlying the ancestral North American continental margin in Yukon suggest that a foreland-style basin developed adjacent to the Klondike orogen. Regionally extensive Late Triassic (235-200 Ma) strata containing primarily North American detrital zircons form an overlap assemblage that covered the accreted terranes and western North America. The timing of the Klondike orogeny is roughly synchronous with other contractional events along the ∼5000 km strike length of the Cordillera, including the Late Permian-Early Triassic Sonoman orogeny in Nevada. Global plate reorganization linked to assembly of Pangaea may have been the tectonic engine for late Paleozoic-early Mesozoic development of the North American Cordillera. Copyright © 2011 by the American Geophysical Union.