Fluid inclusion and stable isotope (H-O-S-Pb) constraints on the genesis of the Haxi gold deposit, west Junggar, China

The Haxi gold deposit located in the Hatu-Saertuohai metallogenic belt of the west Junggar region, China, is a newly discovered gold deposit with proven reserves of similar to 10 tons of gold and an average grade of 6.70 g/t. Primarily, the deposit is hosted in the early Carboniferous Tailegula Formation, controlled by the NEE-trending Anqi fault. The gold ore bodies contain gold-bearing quartz veins and altered basalt. The ore mineral is domi-nated by abundant sulfides, such as pyrite, arsenopyrite, chalcopyrite, and a little gersdorffite. To date, three types of fluid inclusion in quartz veins have been identified: liquid-gas (V-type), CO2-H2O (C-type), and liq-uid-rich (L-type). The ore-forming fluids exhibit medium homogenization temperatures (Th) of 226 degrees C-325 degrees C with low salinities of 2.24-9.34 wt% NaCl equivalent and low densities from 0.72 to 0.88 g/cm(3). The Delta D values range from-115.3%o to-100.7%o, with an average value of-109.1%o; the Delta 18O values range from 11.3%o to 12.2%o, with an average value of 11.8%o; and the Delta 34S values in sulfide range from 0.3%o to 1.8%o, with an average of 1.2%o. The average values of Pb-206/Pb-204, Pb-207/Pb-204, and Pb-208/Pb-204 in sulfide are 18.059, 15.547, and 37.996, respectively. To summarize, the metallogenic fluids were derived not from a single source but from late magmatic-hydrothermal fluid mixed with paleo-atmospheric water; furthermore, the ore-forming materials principally originated from a crust-mantle mixed source. The Pb model age calculated using Hautman's formula is 347-365 Ma, leading to the speculation that the metallogenic period may be Devonian-Carboniferous.