The northern Cache Creek terrane: record of Middle Triassic arc activity and Jurassic-Cretaceous terrane imbrication

Abstract

The northern termination of the Cache Creek terrane in the Cordillera contains oceanic crustal lithologies including subalkaline mafic intrusive rocks with an arc geochemical signature, mafic volcanics with arc to back-arc signatures, and an arc-flanking volcaniclastic succession informally termed the Michie formation. This formation contains unimodal zircon populations with U-Pb dates of 245.85 ± 0.07 and 244.64 ± 0.08 Ma. These dates differ from the dominant detrital zircon age population of ca. 190 Ma found in the adjacent Whitehorse trough, but are similar to igneous crystallization ages of the Kutcho arc of northern British Columbia. Two main faults record oppositely verging deformational events: 1) The Judas Mountain thrust, a west-verging structure that emplaced Cache Creek terrane rocks above Stikinia and the Whitehorse trough, and 2) the Mount Michie thrust, an east-verging second phase structure that imbricated Stikinia and Whitehorse trough rocks onto and replaced them over the Cache Creek terrane