Ore Genesis of Caixiashan Pb-Zn Deposit in Middle Tianshan, NW China

Caixiashan Pb-Zn deposit is the largest Pb-Zn deposit discovered in the middle Tianshan area. Examples of Carboniferous magmatic and tectonic activity are widely distributed. The ore bodies are controlled by EW trend faults, based on field observations. The main ore minerals are galena, sphalerite, pyrrhotite, pyrite and chalcopyrite, while quartz, sericite and calcite are the main alteration minerals. The ore also exhibits minerals zoning. In addition, the wide range of S isotopic composition, high temperature and moderate salinity of fluid inclusions, and good correlation of ore and wall rock Pb isotopes together with H, O, C isotopic compositions indicate mixing of magmatic origin and upper sedimentary rocks. Combined with high concentration of pyrite and pyrrhotite and some argentite, the Pb-Zn deposit may be controlled by the Hercynian orogeny, which controlled the EW-NEE faults and Carboniferous igneous rocks. The faults provided the channel for fluid transport and the igneous rocks provided heat and main source of the metals. When the fluid passed through metal-bearing rocks, it extracted Pb, Zn, Ag etc.. Interaction of the metal-bearing fluid with the brecciated and fractured marble caused the metals to be deposited. Thus the Caixiashan Pb-Zn deposit is a fault-controlled hydrothermal deposit.