Age of the Kodar Group of the Western Part of the Kodar–Udokan Trough, Aldan Shield: Results of U–Th–Pb (LA-ICP-MS) Geochronological Studies

The results of U‒Th‒Pb (LA-ICP-MS) geochronological studies of detrital zircon from metagraywackes of the Kodar Group of the Udokan complex of the Aldan Shield are presented. It is established that the age of terrigenous rocks of the Kodar Group of the Kodar Subzone of the Kodar–Udokan Trough is 2.02−1.91 Ga. The accumulation of rocks of the Kodar Group was separated from the accumulation of rocks of the Chinei and Kemen groups of the Udokan complex and the formation of Cu mineralization of ~1.90–1.87 Ga ago by a deformation and metamorphism stage. Our geochronological data allow us to raise a question on the recognition of the Kodar Group or, at least, its lower part as an individual complex. The rocks of the Kodar Group of the Kodar Subzone were sourced from the Archean (~2.76–2.92 Ga) igneous and metamorphic complexes of the Chara–Olekma Geoblock of the Aldan Shield, as well as unidentified (at the present level of erosion) island arc or active continental margin complexes with an age of ~2.02 Ga in the western–northwestern and southern (in the present-day coordinates) framework of the Chara–Olekma Geoblock.