New Evidences of Paleoproterozoic Age of Metasedimentary Rocks of the Kurumkan Group of the Aldan Shield: Results of U–Th–Pb (LA-ICP-MS) Geochronological Studies of Zircon

The results of U–Th–Pb (LA-ICP-MS) geochronological studies of detrital zircon from metasedimentary rocks (high-alumina, garnet-biotite, biotite gneisses and hypersthene-bearing quartzite-gneisses) of the Kurumkan Group of the West-Aldan megablock of the Aldan Shield are presented. It is established that igneous complexes of Paleoproterozoic (2.07, 2.31 and 2.45 Ga), Neoarchean (2.56 and 2.67 Ga), as well as Meso- and Paleoarchean (about 2.80−3.26 Ga) age were the sources of the metaterrigenous rocks in the Kurumkan Group, and the age of superimposed metamorphism is approximately 1.94 Ga. Significant differences in the age of the metasedimentary rocks in the Kurumkan Group (ca. 2.1−2.0 Ga) and the associated metavolcanics (ca. 2.4 Ga) indicate that these rocks belong to different stratigraphic units. The age of the metasedimentary rocks in the Kurumkan Group is close to that of the island-arc rocks of the Fedorov Group. The most likely geodynamic setting for the formation of the protoliths of the metasedimentary rocks in the Kurumkan Group is a back-arc basin, synchronous with the formation of the Fedorov island arc.