Nature of the basement to Quesnel Terrane near Christina Lake, southeastern British Columbia

Abstract

The character of the Paleozoic basement of Quesnel Terrane and the position of the terrane accretion surface that separates Quesnel and Kootenay terranes from rocks of the ancient North American margin are subjects of debate. To address these problems, detailed mapping and U–Pb geochronologic studies were carried out in the Christina Lake area to define the relationship of the Mollie Creek assemblage, Josh Creek diorite, and Fife diorite to similar lithologies in the Greenwood – Grand Forks and Rossland regions, and to place limits on the ages of regional deformation and local position of the terrane accretion surface. Deformed metasedimentary rocks of the Mollie Creek assemblage may correlate with sedimentary rocks of the Pennsylvanian to Early Triassic Mount Roberts Formation in the Rossland area. The Mollie Creek assemblage is intruded by the foliated Late Triassic Josh Creek diorite. The Josh Creek diorite and Mollie Creek assemblage have been deformed together as a result of phase two deformation, following the intrusion of the Josh Creek diorite in the Late Triassic and prior to the intrusion of the Fife diorite and deposition of the overlying Rossland Group in the Early Jurassic. Based on relative age, structural position, and lithological similarities to other units within Quesnel Terrane, the Mollie Creek assemblage, Josh Creek diorite, and Fife diorite are a part of Quesnel Terrane and lie above the terrane accretion surface in the Christina Lake area. Therefore, Quesnel Terrane does not unconformably overlie basement rocks of known North American affinity in this region.