Sources of the ore metals of the Huize ore field in Yunnan province: constraints from Pb, S, C, H, O and Sr isotope geochemistry

云南会泽铅锌矿田是我国著名的超大型特富铅锌矿田之一,由相距3公里的矿山厂和麒麟厂两个独立的矿床组成,Zn+Pb 金属量超过五百万吨,矿石品位在25%至35%之间。为确定矿床成矿流体和成矿金属来源,本文系统研究了矿床的 Pb、S、C、O、H 和 Sr 同位素组成特征。矿石硫化物的铅同位素组成均一,~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb 和~(208)Pb/~(104)Pb 的变化范围分别为18.251～18.530,15.663～15.855和38.487～39.433,与围岩碳酸盐岩中浸染状黄铁矿一致,与碳酸盐地层相近,在~(208)Pb/~(204)Pb-~(...The Huize ore field is one of the most famous high-grade Zn-Pb ore field in China. In this ore belt, the Kuangshanchang and Qilinchang deposits are the two largest Zn-Pb deposits with a Zn + Ph reserve of > 5Mt and ore grades of 25% to 35%. Ph, S, C, O, H and Sr isotope geochemistry is discussed in this paper in an effect to understand the sources of the ore metals and ore-fluids. The Pb-206/Ph-204, Pb-207/Ph-204 and Pb-208/Ph-204 values for the ores range from 18.251-18.530, 15.663-15.855 and 38.487-39.433, respectively, which are similar to those of the host carbonate rocks. The pyrites disseminated in the wall rocks have indistinguishable Ph isotope compositions with the ores, indicating that these rocks may have provided metals to the ore fluid. The delta S-14 values of the ores show a total range from 10.9 parts per thousand to 17.4 parts per thousand, but most of them are between 13 parts per thousand and 17 parts per thousand, which indicating that the sulfur should be derived from the in situ thermochemical reduction of sulfates from the sedimentary strata. There are three types of gangue calcite in the ores, and all of them share similar isotope compositions, whth delta C-13-PDB values of -2.1 parts per thousand to 3.5 parts per thousand and delta O-18-SMOW values of 16.8 parts per thousand to 18.6 parts per thousand. The delta D-F1 values of fluid inclusions in these calcites display a narrow range of -50 parts per thousand to -60 parts per thousand and the delta(OH2O)-O-18 values calculated from delta O-18 values of calcite range from 7.0 parts per thousand to 8.8 parts per thousand if their formation temperature is 200 degrees C. These data indicate that the ore fluid was likely metamorphic water and had water-rock interaction and isotope exchange with shale, clastic rocks and mudstone underlain the ore-bearing strata during their ascending from the depth. Initial Sr-87/Sr-86 values of the pyrite, sphalerite and calcite from the ores range from 0.714 to 0.717. The initial Sr-87/Sr-86 values of unaltered host dolomite rock (0.7083-0.7093) are lower than that of the altered dolomite (0.7106). The high initial Sr-87/Sr-86 values for the ore-forming fluids also suggest water-rock reaction and isotope exchange between the ore fluid and the shale, clastic rocks and mudstones or the fluid might have originated from these rocks.SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)6102567-25802