The U-Pb Age of Rare-Metal Alkali Granites at the Snezhnoe Deposit: Age Homogeneity Assessment of Ognit Granitoids (Eastern Sayan Region)

The higher alkali granitoids traditionally combined into the Middle Paleozoic (Silurian-Devonian) Ognit complex are widespread in the Oka part of the Eastern Sayan region. The Snezhnoe biotite-phenakite-beryl deposit is located within their outcrops. Its age was earlier determined at 305 Ma. The geochronological U-Pb (ID-TIMS) studies of zircon from alkali granites containing the deposit resulted in an age of 311 +/- 1 Ma. A similar age (307 +/- 1 Ma) was obtained for monzogabbro from the bimodal gabbro-alkali granite assemblage in the Ust'-Sentsa massif in the same area. The obtained age estimates are indicative of the fact that, along with Ognit Middle Paleozoic granitoids, Late Paleozoic alkali granitoids and moderately alkali gabbro assemblages were also formed within the Oka part of the Eastern Sayan region. Their characteristic feature was enrichment in rare metals and the structural connection with the Eastern Sayan riftogenic rare-metal magmatism zone.