Geology, Geochemistry And Genesis Of The Bogutu Gold Deposit, Western Tien Shan, Xinjiang

The Bogutu larger gold deposit, western Tien Shan, has be discovered recently. It was located in the eastern Yishijilike metallogenic belt, XinJiang. Gold mineralization is hosted by volcanic rocks of the Lower Carboniferous Dahalajunshan Formation. The ore bodies are bedded and lenticular and controlled by EW and NW trending faults. The main wall-rock alteration are silicification, beresitization, propylitization from the orebody to the wallrock. Ore minerals mainly consist of pyrite, arsenopyrite, Galena, sphalerite, electrum, argentite, whereas gangue minerals mainly consist of quartz, chalcedony, calcite, sericite. By electron probe scanning of the main minerals, the gold was often wrapped in pyrite or embodied as intergranular.Homogenization temperatures of the main stage ore-forming fluid are 129℃~260℃, while the mean is 165℃; the salinities are 0~8.4% NaCleqv, and the mean is 3.9% NaCleqv. The δ18OH2O-SMOW of vein quartz is from-4.2‰ to 1.4‰, δDV-SMOW from-94.1‰ to-111.2‰, showing that ore-forming fluids were low temperature and low salinity circulating atmospheric water. The ore δ34S V-CDT(from-7.5‰ to 5.8‰, the mean value 0.45‰) is close to the mantle value of 0‰. The ore Pb isotope composition is similar to the volcanic rock, 206Pb/204 Pb ranges from 18.243 to 18.535, 207Pb/204 Pb from 15.565 to 15.753, 208Pb/204 Pb from 38.021 to 38.647. The radiogenic initial 187Os/188Os(i) of gold-bearing pyrite is 0.774±0.076, the γOs(t) mean value is 520, indicating that the metal was sourced from hosted volcanic rocks. Andesitic tuff are the main host rocks, with a 353.4±2.0Ma zircon U-Pb concordia age. The zircon U-Pb dating of K-feldspar granite is 344.0±3.7Ma. The ages of regional volcanic rocks range from 344±6Ma to 368.3±1.7Ma. Re-Os dating of gold-bearing pyrite yielded an isochron age of the 356.1±9.3Ma(MSWD=16), the mineralization was formed almost simultaneously with volcanic.Based on the above studies, the Bogutu gold deposit was associated with the paleo Tien Shan ocean subducting beneath the Yili plate, should be a epithermal gold deposit. The research will help the prospecting breakthrough in Yishijilike metallogenic belt, western Tien Shan.