Rare-metal lithium-fluorine granites, ongonites, and topazites of the southern Baikal region

Geochemical data were obtained on the rare-metal granites and ongonites of the Utulik intrusive-dike complex and the Kharagul Massif, which is located to the west of the complex. Both structures are confined to the peripheral zone of the Early Mesozoic magmatic area of the Mongolia-Okhotsk belt. The subtypes of fluorite-bearing granites, with a mica composition ranging fro m biotite to protolinite, and topaz-bearing granites, with a mica compositi on ranging from Li-biotite to zinnwaldite and lepidolite (associated with L i-phengite-muscovite), were distinguished among the studied rocks of the Li -F geochemical type. The defined subtypes of Li-F granites differ in their distribution of the rare-earth elements and K/Rb, La/Yb, Zr/Hf, and Nb/Ta r atios. The fluorite-bearing biotite granites and granosyenites enriched in the light rare earths and zirconium are genetically related to subalkaline monzonitoid magma and the abyssal fluid associated with it. The topaz-beari ng Li-F granites and ongonites resulted from the profound differentiation o f crustal granitic magmas, a process responsible for the concentration of S n, Ta, Li, and W and the rare-metal mineralization.