贵州铜仁塘边铅锌矿床成因的流体包裹体和同位素证据

Ore genesis of Tangbian Pb-Zn deposit in Tongren, Guizhou:Evidence from ore-forming fluids and isotopes

文章阐述了塘边铅锌矿床地质特征,首次对闪锌矿和成矿期方解石进行了流体包裹体测温和流体成分分析,测定了方解石碳氢氧同位素。结果显示,成矿流体温度范围较低,为92~193℃,盐度w(Na Cleq)相对较高,为8.9%~21.2%,流体包裹体阳离子主要为Ca2+、Mg2+、Na+、K+等,阴离子主要为Cl-、NO-3、F-、Br-等;气相成分主要为N2、H2O、CO2、O2及少量的还原性气体。方解石的δ13CV-PDB介于-0.5‰~1.5‰,δ18OV-SMOW值介于21.2‰~25.1‰,δDV-SMOW值为-93‰^-57‰,成矿流体的中的δ18O流体值为8.8‰~12.7‰,提出成矿流体具多来源特点,碳来源于围岩。结合前人研究成果认为,矿床成因属MVT型铅锌矿床,矿床形成与湘黔断裂带演化密切相关。

：The Tangbian Pb-Zn deposit is located in the southeast of Yangtze landmass. It is adjacent to the famous Huayuan Pb-Zn orefield. The orebody, occurs in algal limestone of Lower Cambrian Qingxudong Formation, showing layered and bedded forms. Sphalerite and galena are the main ore minerals. Systematical study of fluid inclusions in sphalerite and calcite associated with mineralization was conducted through the analysis of homogenization temperatures, salinity, gas compositions, liquid compositions by heating/freezing system, and C, H, O isotopes of calcite were also analyzed in this paper. The results show that the ore-forming fluid is characterized by low temperature of 92-193℃, relatively high salinity of 8.9%-21.2% and relatively high density of 0.98-1.1 g/cm^3. The cations in the fluid inclusions are mainly Ca^2＋, Mg^2＋, Na^＋ and K^＋, while the anions are mainly Cl^-, NO3^-, F^- and Br^-. The gas compositions of fluid inclusions are N2, H2O, CO2, O2 and a small amount of reducing gas such as CH4. The δ^13CV-PDB, δ^18OV-SMOW and δDV-SMOW of calcites are respectively from -0.5‰ to 1.5‰, from 21.2‰ to 25.1‰ and from -93‰--57‰, with δ^18Ofluid values of ore-forming fluid being from 8.8‰ to 12.7‰. According to the above result, the authors believe that the ore-forming fluid had the feature of multi-source, and there were ancient seawater, formation water, metamorphic water, organic water and a little rainwater. Based on a comparison of the Tangbian Pb-Zn deposit with the sediment-hosted base metal sulfide deposits in the world, the authors classified the Tangbian Pb-Zn deposit as the MVT Pb-Zn deposit. On such a basis and according to previous studies, the relationship between Pb-Zn mineralization and evolution of the Hunan-Guizhou fault zone was discussed.