NEOPROTEROZOIC AND DEVONIAN GRANITES OF THE KOOLENSKY GRANITE-GNEISS DOME, ARCTIC CHUKOTKA

New U-Pb zircon dating of rock samples from the core of the Koolensky granite-gneiss dome in Chukotka yielded a Neoproterozoic age (650–530 Ma) for the orthogneisses and a Devonian age (390–360 Ma) for the granitoids. Devonian granites and quartz monzonites are assigned to the peraluminum magnesian calc-alkaline varieties of volcanic arc granitoids formed during the Ellesmerian orogeny of the Arctic. All rocks of the complex show evidence of having been subject to the last peak of metamorphism and extensional deformation in the Early Cretaceous, as follows from the age of the syndeformational pegmatites.