Age of the Basement of the Arctic Alaska–Chukotka Microplate from the Example of the Velitkenai Granite–Metamorphic Dome (Northeastern Russia)

Аbstract The basement of Arctic Alaska–Chukotka microcontinent (AAChM) is exposed in the Velitkenai granite–metamorphic dome of Chukotka. U–Th–Pb (SIMS) geochronological study of the orthogneisses of the basement, paragneisses after Paleozoic rocks, and leucogranites of the Velitkenai massif in the central and southwestern parts of this structure was carried out. The Neoproterozoic age of basement orthogneisses (Velitkenai complex) and the Albian age of granitoids of the last stage of the Velitkenai massif were confirmed. The latter coincides with the age of migmatization of orthogneisses. The youngest zircon populations from paragneisses within the Velitkenai complex are from the Cambrian and the Silurian; single zircon crystals contain inherited cores with ages of 1.7 and 1.9 Ga. The correlation of the Neoproterozoic orthogneisses of the Velitkenai granite–metamorphic dome with similar complexes of the other AAChM regions indicates the unity of its basement. It is suggested to enter the Velitkenai metamorphic complex into the legend of the Chukotka series of the third-generation geological map sheets.