云南兰坪-思茅盆地脉状铜矿床铅、硫同位素地球化学与成矿物质来源研究  

Lead and sulfur isotope geochemistry and the ore sources of the vein-type copper deposits in Lanping-Simao Basin, Yunnan province.

作　　者：吴南平[1] 蒋少涌[1] 廖启林[2] 潘家永[1] 戴宝章[1] 

机构地区：[1]南京大学地球科学系成矿作用国家重点实验室,南京210093 [2]江苏省地质调查研究院,南京210018

出　　处：《岩石学报》2003年第4期799-807,共9页Acta Petrologica Sinica

基　　金：973项目(G1999043208);国家杰出青年基金(49925306)

摘　　要：云南兰坪-思茅盆地中-新生代砂页岩中赋存有许多脉状铜矿床。本文对盆地内从北至南三个典型脉状铜矿床(金满、水泄和白龙厂)进行了详细的铅、硫同位素研究,探讨了该类型矿床的成矿物质来源。分析表明,该类型矿床的铅同位素组成总体变化较小,且均位于上地壳铅演化线附近,说明成矿流体中铅具有稳定的上地壳来源。各矿床由于赋矿层位不同.矿石铅同位素组成表现出一定差异,如由兰坪盆地侏罗纪地层中的金满矿床到思茅盆地二叠纪地层中的白龙厂矿床,铅同位素比值(^(207)Pb/^(204)Pb)呈增高趋势,这表明这类矿床的铅主要来源于围岩地层,且地层越老,提供的铅就相对富含放射成因铅。 矿床中脉石矿物重晶石、铁白云石等的锶同位素组成也表明,金满矿床成矿流体的^(87)Sr/^(86)Sr比值较高(0.70874～0.71232),而白龙厂矿床的^(87)Sr/^(86)Sr比值较低(0.70829～0.70938),接近于围岩灰岩的值(0.70755)。硫同位素研究表明,金满矿床中硫化物的δ^(34)S值变化最大,为-20.5‰～+7.0‰。水泄矿床中硫化物的δ^(34)S值变化最小,为-0.1‰～+4.2‰。而白龙厂矿床中硫化物的δ^(34)S值为-14.3‰～-3.6‰。水泄和白龙厂矿床中重晶石的δ^(34)S值分别为+12.3％0～+19.0‰和+13.1‰,它们与盆地中蒸发岩层中石膏的δ^(34)S值(+10.8‰?The copper deposits occurring in Lanping-Simao Basin of Yunnan province is a new type of copper deposit with many unique features. In this study we report a detailed Pb and S isotopic investigation on three representative vein-type copper deposits in the basin, namely, Jinman, Shuixie and Bailongchang deposits from north to south. The Pb-isotopic compositions of the sulfides from the three deposits show very narrow variations and plot near the upper crust evolution curve in Zartman's Pb diagram, suggesting a unique upper crust Pb source for these deposits. However, each deposit shows a slightly different variation in Pb-isotopic compositions. For example, the Bailongchang deposit in the south displays higher Pb-207/Pb-204 ratios than that of the Jinman deposit in the north. We suggest that this spatial variation of Pb isotopes is likely corresponding to the different ages of the host rock strata, i.e., the older strata of Permian in the south may have provided more radiogenic Pb than the younger strata of Jurassic in the north. The gangue minerals of barite and dolomite in these deposits also show different Sr isotopic compositions. At the human deposit in the north the ore-forming fluids have higher Sr-87/(86) Sr ratios of 0.70874similar to0.71232 than that of the Bailongchang deposit in the south (0.70829similar to0.70938). The Sr isotopic ratios of the Bailongchang barites are quite close to those of the host rocks of limestone (0.70755). The Jinman deposit shows the largest sulfur isotope variation of sulfides from -20.5parts per thousand to +7.0parts per thousand, whereas the Shuixie deposit has the smallest variation from -0.1parts per thousand to +4.2parts per thousand. The sulfur isotope compositions of sulfides in Bailongchang deposit vary from -14.3parts per thousand to -3.6parts per thousand. Barites from Shuixie and Bailongchang deposits have delta(34)S values of +12.3parts per thousand to +19.0parts per thousand and +13.1parts per thousand, respectively, similar to that of the evaporitic gypsum from

关 键 词：脉状铜矿床 铅、硫同位素 物质来源 兰坪-思茅盆地 

分 类 号：P618.41[天文地球—矿床学] P597.2[天文地球—地质学]