Detrital zircon U-Pb geochronology and Hf isotope geochemistry of the Laberge Group: synorogenic siliciclastic record of early Mesozoic crustal thickening and tectonic evolution of the Whitehorse trough in the northern Canadian Cordillera

Abstract

The Laberge Group consists of synorogenic, marginal-marine to deep-marine strata that were deposited in the Whitehorse trough of central Yukon during the collision of the northern Intermontane terranes along the western Laurentian margin. New detrital zircon U-Pb-Hf data from Laberge Group rock units constrain the Early to Middle Jurassic depositional ages and provenance of Whitehorse trough strata and determine their relationship to the unroofing history of adjacent basement successions. The Whitehorse trough initiated in the Sinemurian as a long, narrow basin that subsequently grew to the west, east, and south by Aalenian time and was sourced by Paleozoic Yukon- Tanana and Stikinia basement rocks and their synorogenic Late Triassic-Early Jurassic plutonic suites. Late Triassic-Middle Jurassic detrital zircon grains from the northern apex of the Whitehorse trough record an excursion to subchondritic Hf(t) values that coincides with the burial of Intermontane terranes and may record crustal thickening proximal to northern regions of the basin.