First Find of Ordovician Granitoids in Senyavin Granite-Metamorphic Dome, East Chukotka: Age Substantiation and Composition Affinities

The granitoids, intruding complexes of crystalline basement, represented by Penkigney metamorphic formation, have been dated in the western part of Senyavin granite-metamorphic dome of East Chukotka for the first time. U–Th–Pb (SIMS) geochronological study of leucogranites is carried out and their age estimate 467 ± 6 Ma, corresponding to Middle Ordovician is obtained, which suggests the existence of the Early Paleozoic (Ordovician) stage of granitoid magmatism in this region. Composition affinities of granitoids indicate their similarity to I–S granites or differentiated I-type granites. The intrusion of granitoids might have been caused by Caledonian tectono-magmatic events, indicating possible connections with the Caledonides of East Greenland, Svalbard, and the Peary terrane.