Age, geochemistry, and significance of Devonian felsic magmatism in the North Slope subterrane, Yukon, Canadian Arctic
William P. Ward, Justin V. Strauss, Benjamin G. Johnson, William C. McClelland, Maurice Colpron, Werner von Gosen, Karsten Piepjohn, Matthew A. Coble, Peter W. Crockford, Joshua Landis, "Age, geochemistry, and significance of Devonian felsic magmatism in the North Slope subterrane, Yukon, Canadian Arctic", 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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New zircon U-Pb dates from the Mount Fitton, Mount Sedgwick, Mount Schaeffer, Old Crow, and Dave Lord plutons indicate that granitoids of the Old Crow plutonic suite in northern Yukon were emplaced in the North Slope subterrane of the Arctic Alaska composite terrane between 375 ± 2 Ma and 368 ± 3 Ma. Whole-rock major and trace element and Nd-Sr isotope geochemistry, combined with zircon trace element and Hf isotope geochemistry, indicate magma genesis involved significant contribution from older continental crust. Samples from the five plutons yield whole-rock εNd(t) values from −3.9 to −11.6 and 87Sr/86Sr(i) ratios of 0.7085–0.7444 and 0.8055. Zircon εHf(t) values range from −6.2 to − 13.3. These North Slope subterrane granitoids are generally younger and isotopically more evolved than felsic rocks in the Coldfoot and Hammond subterranes of the southern Brooks Range (Arctic Alaska terrane), but in part are coeval with felsic rocks on the Seward and Chukotka peninsulas. The North Slope granitoids are also coeval and geochemically similar to arc magmatism in the Yukon-Tanana terrane in Yukon and on Axel Heiberg and northern Ellesmere islands, Nunavut. The Old Crow plutonic suite is interpreted as part of a Late Devonian arc system developed along the Arctic and Cordilleran margins. Late Devonian plutons were most likely emplaced after initial translation of the North Slope subterrane along the northern Laurentian margin. The plutons lie within or north of the Porcupine shear zone and thus do not limit post-Late Devonian displacement on the boundary between the North Slope subterrane and northwestern Laurentia.