Tectonic Setting and Uplift History of Metamorphic Rocks, Kigluaik Mountains and Vicinity, Seward Peninusla, Alaska

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Dome-shaped uplifts of high temperature-low to medium pressure metamorphic rocks with cores of Cretaceous granite are flanked by high pressure-low temperature Jurassic (?) blueschists in the Seward Peninsula of Alaska. The origin and tectonic setting of these complexes is controversial, and their uplift has been attributed to thermal relaxation following crustal thickening. Preliminary new work in the Kigluaik Mts. indicates patterns of deformation, metamorphism and magmatism that are similar to those in Cenozoic metamorphic core complexes of the Basin and Range province. Field mapping, structural analyses, andgeochronologic/ thermochronolgoic studies will elucidate the timing and mechanism of uplift of the blueschists rocks on Seward Peninsula. Areas of concentrated study include: the highest structural levels exposed; low angle faults between feebly metamorphosed Paleozoic rocks and greenschist to blueschist facies rocks beneath; and the high temperature core rocks of the domes. This approach will also establish whether uplift was single or multi-stage. The results will bear on the age, regional tectonic setting, and uplift of blueschist facies rocks in N. Alaska and will address the possible history of extension leading to the offshore shelf region beneath the Bering and Chukchi Seas. The results will also provide insight on the interplay between magmatism, metamorphism and strain in regions of the crust that undergo large vertical uplift.