Age of the Kodar group of the western part of the Kodar-Udokan trough (Aldan shield): results of the U-Th-Pb (LA-ICP-MS) geochronological studies

The paper presents results of U-Th-Pb (LA-ICP-MS) geochronological studies of detrital zircons from metagreywacke of the Kodar Group of the Udokan Complex of the Aldan Shield. It has been established that the terrigenous deposits of the Kodar Group in the Kodar subzone of the Kodar-Udokan trough have an age of 2.02–1.91 Ga. Deposition of the Kodar Group was separated by a stage of deformation and metamorphism from the deposition of rocks of the Chiney and Kemen groups of the Udokan Complex and the formation of copper mineralization at ca. 1.90–1.87 Ga. The obtained geochronological data make it possible to raise the issue of identifying the Kodar Group, or at least the lower parts of its section, as an independent complex. The rocks of the Kodar Group of the Kodar Subzone were derived from the Archean (about 2.76–2.92 Ga) igneous and metamorphic complexes of the Chara-Olekma Geoblock of the Aldan Shield, as well as complexes of island arcs or active continental margins with an age of ca. 2.02 Ga in the western – northwestern and southern (in modern coordinates) framing of the Chara-Olekma Geoblock.