Study on the geology and ore-fluids of the tin deposits in Laoyaquan alkaline granites in eastern Junggar, Xinjiang.
新疆东准噶尔老鸦泉富碱花岗岩型锡矿床地质及成矿流体

Laoyaquan alkaline granite is located in eastern Junggar area, northern Xinjiang. Identification of the rock and minerals in Laoyaquan alkaline granite body and the Kamusite tin deposit and Ganliangzi tin deposit,and the REE geochemical and fluid inclusions studies indicate that all of the granite porphyry, ore-bearing quartzite, greisen body-type tin ore body, and quartz vein-type ore body were the products derived from the same alkali-rich granitic magma. The ore-forming fluid from the Kamusite sin deposit has characteristics of middle-high temperature, low salinity. Large gas-water hydrothermal which was formed in the later evolution stage of alkaline magma were Sn-Si-alkali-F-Cl- SO24 rich and oxygen fugacity-acidity/alkalinity-temperature high. And the hydrothermal lead to auto-metamorphism of the granite, such as silicification, greisen-type alteration, etc. During auto-metamorphism the reduction-oxidation state of ore forming fluid had changed with the dropping of the temperature and pressure, and the escaping of CH4 and CO2. The fluid transformed into relatively high reduction state and strong alkaline environment. Under the new conditions of reduction-oxidation state and acidity-alkalinity, the tin-complex taken by the fluid was decompounded because of its unstabilizing, which lead the tin element to be deposited and form the ore.