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.

Geology, Mantle Tomography, and Inclination Corrected Paleogeographic Trajectories Support Westward Subduction During Cretaceous Orogenesis in the North American Cordillera

“…Note the abundant remnants of 70 Ma Carmacks volcanic rocks, which in multiple studies, yielded paleolatitudes of San Francisco (Johnston et al 1996;Enkin et al 2006a). As rocks of Selwyn basin, Cassiar platform, and Yukon-Tanana terrane were joined together at 260-253 Ma (Beranek and Mortensen 2011) they are all interpreted to have been located within the Great Basin-Sonora segments of the orogen at 70 Ma and migrated to their present northerly latitude mostly during the early Tertiary. Dots adjacent to the Tintina fault are approximate pre-fault piercing points (Gabrielse et al 2006).…”

“…4), which were joined between 260-253 Ma (Beranek and Mortensen 2011). Slab failure magmatism commonly overlaps the terminal stages of deformation and is highly metalliferous (Solomon 1990;McDowell et al 1996;de Boorder et al 1998;Cloos et al 2005;Hildebrand 2009Hildebrand , 2013.…”

“…The western platform was involved in several orogenic events: (1) initially during the latest Devonian-early Mississippian when rocks of the Roberts Mountain allochthon were thrust upon it (Roberts et al 1958;Miller et al 1992); (2) between 260-253 Ma when the Slide Mountain ocean was subducted during the collision of the YukonTanana terrane Beranek and Mortensen 2011);(3) at 250 Ma when the Golconda allochthon was emplaced on the western margin of the Roberts Mountain allochthon (Silberling and Roberts 1962);and (4) at both 187-185 Ma and 173 Ma, when Kootenay terrane, which contains Cassiar platform, or equivalents, in southern Canada, collided with Quesnellia to the west (Nixon et al 1993) and then with rocks of the Belt-Purcell-Windermere block to the east, respectively (Murphy et al 1995;Colpron et al 1996). All of these terranes plus others, such as the complex group of collided Jurassic arcs and intervening mélange terranes of western Nevada, the Sierra Nevada, Klamaths, and British Columbia, plus the Insular composite terrane of coastal British Columbia and Alaska, formed part of the Cordilleran Ribbon Continent (Hildebrand 2009(Hildebrand , 2013.…”

Controlling factors on source rock development: implications from 3D stratigraphic modeling of Triassic deposits in the Western Canada Sedimentary Basin

“…1a). These Formations were deposited during the Early and Middle Triassic (Golding et al, 2015b;Orchard and Zonneveld, 2009) on the western margin of Pangaea and recent studies suggest a fore-arc basin geodynamic setting (Beranek and Mortensen, 2011;Rohais et al, 2016). At the time of the deposition, the basin was located in latitudes inferior to 30°N (Fig.…”

“…1). A reconstruction of the missing parts of these formations was carried out, based on our understanding of the regional stratigraphic architecture and of the paleogeographic and geodynamic (Beranek and Mortensen, 2011;Crombez, 2016;Rohais et al, 2016) evolution of the basin.…”