Stages of Granitoid Magmatism and Formation of the Continental Crust of Eastern Arctic

Three main stages of granitoid magmatism and continental crust formation of Eastern Arctic are distinguished: Neoproterozoic (750–550 Ma), Devonian–Early Carboniferous (390–350 Ma), and Early Cretaceous (117–105 Ma). The correlation of Neoproterozoic granitoid magmatism of the New Siberian Islands, Wrangel Island, the Chukchi Peninsula, Chukchi Borderland, and Northern Alaska indicates the unity of the basement of Arctic Alaska–Chukotka microplate (AАСM) and its Meso–Neoproterozoic age. The geodynamic setting of the formation of Neoproterozoic granitoids of most of the microplate is supposed as continental margin, less often active rifting (Seward Peninsula, Alaska).The Devonian-Early Carboniferous stage is related to different phases of Ellesmerian orogeny in the Arctic region. The formation of granitoids of this age occurred in an island arc, continental margin, or back-arc settings. The Early Cretaceous stage of continental crust formation is related to the collision between the Siberian continent and AАСM in Hauterivian–Barremian. In Aptian–Albian, the collisional compression regime was followed by postcollisional extension, accompanied by the formation of metamorphic core complexes, granitoid intrusion, and superimposed orogenic basins. Data on the mineralogical, chemical, and geochemical compositions of granitoids of all three stages indicate that the Neoproterozoic granitoids are similar to S- and I-type granites; Devonian–Early Carboniferous, to predominantly I-type granites; Early Cretaceous, to I- and A-type granites. Sr–Nd isotopic data, as well as Lu–Hf zircon data, indicate the participation of both crustal and mantle components in the formation of the source of granitoid melts at all stages.