Detrital zircon U-Pb geochronological and Hf isotopic constraints on the geological evolution of North Yukon
Published:June 14, 2019
Maurice Colpron*, William C. McClelland*, Justin V. Strauss*, 2019. "Detrital zircon U-Pb geochronological and Hf isotopic constraints on the geological evolution of North Yukon", Circum-Arctic Structural Events: Tectonic Evolution of the Arctic Margins and Trans-Arctic Links with Adjacent Orogens, Karsten Piepjohn, Justin V. Strauss, Lutz Reinhardt, William C. McClelland
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North Yukon lies at the intersection of two major tectonic domains that define the western and northern edges of the North American continent—the northern Cordilleran mountain belt and the Arctic Ocean. The pre-Carboniferous geology in North Yukon includes the Neoproterozoic−lower Paleozoic North Slope subterrane of the Arctic Alaska terrane and, south of the Porcupine shear zone, Mesoproterozoic−Paleozoic rocks of the Yukon stable block. The North Slope subterrane was deformed prior to deposition of Carboniferous and younger strata, and its paleogeographic origins are debated. North Yukon was deformed again during Cretaceous−Cenozoic development of the northern Cordilleran−Brookian orogen.
To help refine understanding of the geological evolution of the region, we present detrital zircon U-Pb and Hf isotopic data for 21 sandstone and conglomerate samples from Neoproterozoic to Cenozoic strata collected across North Yukon, between ~69°15′N and 67°11′N. Neoproterozoic−Cambrian strata in the British Mountains are characterized by a dominance of Paleoproterozoic zircons (peak at 1.7–1.8 Ga), whereas samples from the Barn Mountains to the south have abundant Mesoproterozoic grains (1.0–1.5 Ga), suggesting these rocks may have been deposited along different segments of the northern Laurentian margin. Regional geophysics suggest these domains could be separated by a fault. Northeastern Laurentian origins are indicated by distinct early Neoproterozoic and Ordovician−Silurian zircons in Upper Silurian−Lower Devonian immature sandstone and conglomerate of the Clarence River Group and provide the most compelling evidence for large-scale translation along northern Laurentia.
Precambrian detrital zircons in Carboniferous and younger strata reflect mostly recycling of local older strata. Carboniferous conglomerates all show Late Devonian peaks (365–378 Ma) consistent with erosion of nearby granitoid plutons. Triassic to Paleocene samples yielded a range of Neoproterozoic−Paleozoic zircons recycled from nearby Devonian flysch. Most significantly, these samples also yielded juvenile zircons that are close to depositional age, but for which arc sources are only known in southern Yukon and Alaska, more than 700 km away. These source regions are distinct from NE Russian sources inferred for early Brookian (Early Cretaceous) foreland deposits in Alaska.
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Circum-Arctic Structural Events: Tectonic Evolution of the Arctic Margins and Trans-Arctic Links with Adjacent Orogens
The circum-Arctic region has received considerable attention over the past several decades with vigorous debate focused on topics such as mechanisms for opening the Eurasian and Amerasian basins, the importance of plume-related magmatism in the development of the Arctic Ocean, and mechanisms for ancient terrane translation along the Arctic margins. In recognition of the 25th anniversary of the Circum-Arctic Structural Events (CASE) program, an international polar research effort organized and led by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) of Germany, this volume presents results from 18 major field expeditions involving over 100 international geoscientists from a broad spectrum of disciplines. The resulting publication focuses on the Proterozoic to Cenozoic tectonic evolution of the circum-Arctic region with correlations to adjacent orogens.