GEOCHEMISTRY AND AGE OF MAFIC DYKES OF THE Be-DEPOSIT SNEZNOE: LATE PALEOZOIC MANTLE PLUME MAGMATISM EVIDENCE IN EASTERN SAYAN

Abstract

Within the East Sayan rift zone of the Late Paleozoic Barguzin salic large igneous province (SLIP), along with alkaline-peralkaline granitoids with ore mineralization, mafic subvolcanic bodies (gabbroids, mafic dykes) are common. One of the typomorphic mafic – peralkaline granitoid association is the Snezhnoye beryllium deposit. Using the U–Pb LA–ICP–MS method, mafic dykes of the Snezhnoye beryllium deposit were dated. The age of zircons from the diabase (dolerite) dyke was 301 ± 6 Ma, and from the microgabbro one, 297 ± 2 Ma. The obtained dates are close to the age of fluorite-beryl mineralization (306 Ma) and peralkaline granites with Ta-Nb mineralization attributed to the Ognite complex (311–295 Ma). The geochemical features of mafic dykes suggest the generation of mafic magmas from an asthenospheric mantle source, which, taking into account the intracontinental setting, testifies in favor of the plume-mantle nature of mafic – alkaline-peralkaline granitoid magmatism of the East Sayan rift (rare-metal) zone.