Geological Position, Age, and Sources of the Tallai Gabbro–Diorite–Plagiogranite Pluton (Middle Vitim Highland).

The results of geochronological study (U–Pb SHRIMP-II) of zircons from granodiorites and plagiogranites of the main phase of the Tallai pluton of the Baikal–Vitim belt are presented. The obtained estimates of the age of the magmatic cores of zircons from granodiorite and plagiogranite coincide with each other within the limits of errors and are interpreted as the age of crystallization of rocks of the main phase of the Tallai pluton, 661 ± 6 Ma. The weighted average value of the age of the metamorphic rims of zircon from these rocks is 637 ± 5 Ma. The high positive values of εNd (660), +7.2 and +7.3, in the rocks of the main phase indicate a juvenile source of the parental melts. Based on new and earlier published geochronological data, a conclusion about the formation of Late Baikalian juvenile gabbro–granite associations of the same type within the Baikal–Vitim belt 660 million years ago (Tallai complex) and in the interval of 603–615 Ma (Padora complex) was made. [ABSTRACT FROM AUTHOR]