Geochemistry and Age of Basic Dikes of the Snezhnoe Be Deposit: Evidence for the Late Paleozoic Plume – Mantle Magmatism of East Sayan

Mafic subvolcanic bodies (gabbroids, mafic dikes) occur within the East Sayan rift zone of the Late Paleozoic Barguzin silicic large igneous province (SLIP) together with ore-bearing alkali granitoids. The Snezhnoe Be deposit is a typical object with a mafic-alkali granitoid association. The mafic dikes intruding the ore structures of the deposit are dated using the LA-ICP-MS U–Pb method. The age of zircons from the diabase (dolerite) and microgabbro dikes is 301 ± 6 and 297 ± 2 Ma, respectively. These ages are similar to that of fluorite–phenakite–beryllium mineralization (306 Ma) and associated alkali granites with Ta–Nb mineralization, which are ascribed to the Ognit complex (311–295 Ma). The geochemical features of mafic dikes suggests the generation of mafic magmas from an asthenospheric mantle source, which, taking into account the intracontinental setting, indicates in favor of a plume–mantle nature of mafic-alkali granitoid magmatism of the East Sayan rift (rare metal) zone, in particular, the entire Barguzin SLIP in general.