Rare-Metal Li–F Granites in the Late Paleozoic, Early Mesozoic, and Late Mesozoic Magmatic Areas of Central Asia

Abstract —In the Central Asian Orogenic Belt, Li–F granites formed in magmatic areas of different ages within a wide time interval, 321–134 Ma. The Li–F granites compose large multiphase plutons (Janchivlan and Baga-Gazriin Chuluu) and small intrusions, have specific mineralogic and geochemical characteristics, and show enrichment in Sn, W, Li, Rb, Ta, and Nb, thus forming concentrated mineralization at the late magmatic and postmagmatic stages. The late Paleozoic and Mesozoic small intrusions (Kharagul, Urugudei, Bezymyanka, Henteyn, and Turga) are high-alkali Li–F granites enriched in Zr, Nb, Hf, Th, U, and REE, which differ from ore-bearing Li–F granites in mineral assemblages and geochemical features. Such granites can be classified as an individual subtype of rare-metal granites. Irrespective of geochemical characteristics, the Li–F granites of the studied provinces in Central Asia are geochemically different from typical collision-related granites resulting from the melting of the upper continental crust. It is shown that the formation of rare-metal magmas with different geochemical characteristics is related to the mantle–crust interaction. The geochemical evolution of Li–F granites is significantly contributed to by the activity of mantle fluids containing trace elements and by the differentiation of granitic magma in the crustal intermediate chambers, which is favorable for the formation of associated rare-metal mineralization.