Metallogenic regularity and prospecting direction of pegmatitic rare -mental deposits in western Yunnan.

Western Yunnan is located in the southwestern margin of the "Sanjiang" Tethyan tectonic domain, with developed rare mental pegmatite which occurred as groups along the tectonic belt. The pegmatitic rare -metal mineralization in western Yunnan is mainly Be, with Li, Nb, Ta, Sn, etc. The metallogenic regionalization of pegmatitic rare -metals in western Yunnan can be divided into four metallogenic belts: Gaoligong Mountain metallogenic belt, Tengchong-Lianghe metallogenic belt, Ximeng metallogenic belt and Fengqing-Lincang metallogenic belt. Pegmatitic rare -metal orebodies mainly occur as veins in the metamorphic rock series, contact zone of granite rocks, or tectonic belt far from the rock but related to the rock. The mineralization of pegmatitic rare -metal in the Gaoligong Mountain metallogenic belt resulted from deep melting, and orebodies mainly occurred in the tectonic fissures of medium -deep metamorphic rocks. In the other three metallogenic belts, the rare metal pegmatites are closely related to the granites, and the ore bodies mainly occur in the granite, contact zones and fissures. The mineralization mainly occurred in the Himalayan Period from 62Ma to 15 Ma, including Paleocene, Eocene, Oligocene and Miocene. The continental collision of the Indian plate and Eurasian plate caused strong compression, strike -slip and thrust nappe in the "Sanjiang" Tethyan tectonic zone, which resulted in crustal thickening and deep melting, leading to the pegmatitic rare -metal mineralization in western Yunnan. The distribution area with rare metal ( Li, Be, Nb, Ta, Sn) geochemical anomaly is the primary exploration target. The pegmatite with albitization and greisenization or related to leucogranite should be focused in these areas.