Pb-Zn Mineralization in Kuergasheng Pb-Zn Deposit, Xinjiang: Constraints from In-situ Micro Composition of Quartz and Sphalerite

The Kuergasheng Pb-Zn deposit, located in the Serimu area of the western Tianshan of Xinjiang, is a hydrothermal vein-type Pb-Zn deposit formed in the extensional environment of the plate. The ore body is veined, reticulated and lenticular in the upper subgroup of the Upper Devonian Toskurtau Formation, and is controlled by three north-west fault zones that are spread in parallel with each other. The mineralization process can be divided into three stages: the pre-ore quartz stage (I), the quartz-polymetallic sulphides stage (II) (main mineralization stage) and the calcite stage (III). In this study, the LA-ICP-MS method was used to analyze quartz and sphalerite at different stages of mineralization. The results showed that: (1) The Quartz in the I and II stages of the Kuergasheng Pb-Zn ore area contained more trace elements. Among them, Al, K, Na and Li are mainly enriched. The mass fractions of Al, K, Na and Li varied from 547.56×10⁻⁶～4355.49×10⁻⁶, 9.41×10⁻⁶～626.66×10⁻⁶, 23.78×10⁻⁶～994.40×10⁻⁶, and 43.37×10⁻⁶～265.52×10⁻⁶, respectively, showing a significant linear positive correlation between Al and Li+Na+K. The contents of Ti and Ge were low, and the contents of Ti and Ge varied from 3.17×10⁻⁶～14.05×10⁻⁶, and 1.77×10⁻⁶～6.50×10⁻⁶, respectively, reflecting the low mineralization temperature. Compared with the world's typical porphyry-type and epithermal Pb-Zn deposits, the quartz trace elements characteristics of the Kuergasheng Pb-Zn deposit are more similar to the epithermal Pb-Zn deposits. (2) The content and ratio of trace elements such as Mn, In, Fe, Ga, Ge in sphalerite indicate that the deposit was formed in a medium to low temperature environment, and the mineralization temperature was further limited to be 122～178 ℃ by using sphalerite GGIMFis thermometer. The Ga/In ratio and lnw(Ga)-lnw(In) characteristics indicate that the formation of sphalerite is related to sedimentation. Combining the trace element characteristics of host rock with the previous Pb isotopic data, it is speculated that the ore-forming materials of the Kuergasheng Pb-Zn deposit were mainly derived from the host rock.