| Summary: | Subduction of an oceanic plate beneath the Bering Strait region resulted in the formation of an extensive magmatic belt along the margin of the region during the Cretaceous. Plutons and gneiss domes of this age are broadly distributed throughout parts of the region, in Chukotka, Russia and in Alaska. Variably deformed biotite granite and related diorite through tonalite dikes intrude all levels of the Koolen gneiss dome in NE Chukotka. Granodiorite and granite plutons and associated mafic hypabyssals form a cauldera assemblage at the eastern tip of the Okhotsk-Chukotsk volcanic belt in SE Chukotka. Mafic rocks from both localities show trace element characteristics indicative of subduction-related magmatism, including LILE enrichement and Nb and Ti depletion. All rocks from both localities classify as high-K calc-alkaline rocks and have comparably enriched REE concentrations. These characteristics, along with enriched isotope ratios, suggest derivation of the mafic rocks from enriched subcontinental mantle. At both field areas, mantle-derived magma, produced during subduction processes, intruded lower crustal levels and differentiated. (Abstract shortened by UMI.)
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