THE PRIMORSKY GRANITOID COMPLEX OF WESTERN CISBAIKALIA: GEOCHRONOLOGY AND GEODYNAMIC TYPIFICATION

Abstract

Based on geological, petrochemical, and geochronological data, the postcollisional nature of granitoids of the Primorsky complex in western Cisbaikalia is substantiated. The age of the Primorsky complex granites determined by U-Pb zircon dating is 1859 ± 16 Ma. These granitoids are similar in petrochemistry to A - granites and, partly, to classical Early Proterozoic rapakivi. We have established that in geologic setting, age, and composition the Primorsky complex granitoids are similar to other Early Proterozoic postcollisional granitoid complexes on the periphery of the Siberian craton - Tarak, Sayan, Shumikha, and Kodar. Some petrochemical differences between these granitoid complexes are due to regional variations in the compositions of the sources of granites and the conditions of magma crystallization rather than to different geodynamic settings of the granite formation. The conclusion is drawn that the Early Proterozoic postcollisional granitoids spread throughout the southern flank of the Siberian craton originated during the completion of accretion of large lithospheric blocks and the formation of the Siberian craton in the period 1.84-1.88 Ga.