THE PRIMORSKY GRANITOID COMPLEX OF WESTERN CISBAIKALIA: GEOCHRONOLOGY AND GEODYNAMIC TYPIFICATION
T.V. Donskaya, E.V. Bibikova*, A.M. Mazukabzov, I.K. Kozakov**, D.P. Gladkochub, T.I. Kirnozova*, Yu.V. Plotkina**, and L.Z. Reznitsky
Institute of the Earth's Crust, Siberian Branch of the RAS, 128 ul. Lermontova, Irkutsk, 664033, Russia
* Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences,
19 ul. Kosygina, Moscow, 117975, Russia
** Institute of Geology and Geochronology of the Precambrian, Russian Academy of Sciences,
2 nab. Makarova, St. Petersburg, 199034, Russia
Keywords: Granitoids, geochemistry, geochronology, postcollisional magmatism, Early Proterozoic, Siberian craton
Pages: 968-979
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 the U-Pb zircon method is 1859  16 Ma. These granitoids are similar in petrochemistry to A-type 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. |
