Age, Composition, and Sources of Rocks and Ores of the Okunevskoe Fluorite–Leucophanite Deposit, Western Sayan: Assessment of the Contribution of Magmatism to Ore Mineralization

Resumo

The paper presents data on the structure of the Okunevskoe fluorite–leucophanite deposit, located within the Early Paleozoic East Sayan rare metal metallogenic zone. The deposit is controlled by alkali granitoids, with ore mineralization concentrated at the contact between granitoids and host carbonates. Mineralization is represented by leucophanite–fluorite and pyroxene–fluorite ore types. The Ar–Ar age of granitoids is established at ~485 Ma. Geochemical characteristics of igneous rocks, ores, and host carbonates are determined. It is shown that, in geochemical parameters, leucophanite–fluorite ores are close to alkali granites, while pyroxene–fluorite ores are close to alkali syenites. The characteristics of the Nd isotope composition in rocks and ores of the deposits are given. Igneous rocks (granitoids and dike basites) are characterized by ɛ_Nd(t) values from +4 to +5.5. The ɛ_Nd (t) values in ores range from +1.2 to +4.2; in skarns +4.8. The host carbonates have abruptly contrasting values, ɛ_Nd (t) = –4.2. Based on these data, which demonstrate a high compositional similarity between granitoids and ores, a conclusion is drawn about the leading contribution from magmatic processes to the ore mineralization of the Okunevskoe deposit.