【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(²⁰⁷Pb/²⁰⁴Pb)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⁸⁷Sr/⁸⁶Sr比值较高（0.70874～0.71232）,而白龙厂矿床的⁸⁷Sr/⁸⁶Sr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δ³⁴S值变化最大,为-20.5‰～+7.0‰。水泄矿床中硫化物的δ³⁴S值变化最小,为-0.1‰～+4.2‰。而白龙厂矿床中硫化物的δ³⁴S值为-14.3‰～-3.6‰。水泄和白龙厂矿床中重晶石的δ³⁴S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δ³⁴S值(+10.8‰?更多还原

【Abstract】 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 207Pb/204Pb 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 Jinman deposit in the north the ore-forming fluids have higher 87Sr/86Sr ratios of 0. 70874 ~ 0. 71232 than that of the Bailongchang deposit in the south (0. 70829 ~ 0. 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. 5‰ to + 7. 0‰, whereas the Shuixie deposit has the smallest variation from -0. 1‰ to +4. 2‰. The sulfur isotope compositions of sulfides in Bailongchang deposit vary from - 14. 3‰ to -3. 6‰. Barites from Shuixie and Bailongchang deposits have δ34S values of + 12. 3‰ to + 19. 0‰and + 13. 1‰, respectively, similar to that of the evaporitic gypsum from the basin sedimentary rocks ( + 10. 8‰ ~ + 15. 7‰). It is suggested that the sulfur sources of these vein-type copper deposits are mainly derived from local evaporites in the host rocks. The variation of sulfur isotopic compositions in each individual deposit reflects variations of their physical-chemical conditions of the ore-forming fluids. In conclusion, we suggest that the basin brines evolved from local meteoric water leached the lead and other metals and sulfur from the Mesozoic-Cenozoic country rocks, and they precipitated the vein-type copper ores in suitable fracture systems in the basin.更多还原