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 con-trolled 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 min-eralization 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× 10-6～4 355.49× 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 lin-ear 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 mineral-ization 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 de-posits.(2)The content and ratio of trace elements such as Mn,In,Fe,Ga,Ge in sphalerite indicate that the de-posit 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.
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