中央级公益性基本业务费专项基金(J1314);"973"项目 (2011CB403104); 国家自然科学基金(41403043, 41320104004, 41273050, 41302067); 中国地质调查局项目(1212011220908); 国际地质对比计划(IGCP/SIDA-600)
Two kinds of carbonate hosted Pb-Zn deposits, namely carbonate-rich Pb-Zn deposits and fluorite-rich Pb-Zn deposits, extensively exist in the same Pb-Zn metallogenic belt in the world according to the classification based on gangue mineral assemblages. The relationship between the two kinds of deposits remains unclear. In the middle part of the 'Sanjiang' metallogenic belt in the Tibetan Plateau, the Dongmozhazhua carbonate-rich Pb-Zn deposit and the Mohailaheng fluorite-rich Pb-Zn deposit occur in the same carbonate-hosted Pb-Zn ore concentration area. In the two deposits, the carbonate strata are host rocks, the thrust faults are the main ore-controlling structures, the main orebody attitudes are of stratabound type, and sphalerite and galena are the main ore minerals. However, calcite and dolomite are the main gangue minerals in the Dongmozhazhua deposit while calcite and fluorite are the main gangue minerals in the Mohailaheng deposit. The geochemical features of rare earth elements (REE) in calcium-bearing minerals are different in the two deposits. The REE values of calcite in the Dongmozhazhua deposit are mainly characterized by obvious fractionation of LREE and HREE, enrichment of LREE, negative Eu anomalies and 'V'_shaped curves of chondrite-normalized REE patterns with right deviation. In contrast, the REE values of calcite and fluorite in the Mohailaheng deposit are chiefly characterized by no obvious fractionation between LREE and HREE, negative Eu anomalies and 'M'_shaped curves of chondrite-normalized REE patterns with right deviation. The total concentrations of REE (∑REE) of calcite (0.46×10-6～10.79×10-6) in the Dongmozhazhua deposit are higher than those in the Mohailaheng deposit (0.25×10-6～5.88×10-6). The geochemistry of the REE indicates that calcium-bearing minerals in the two deposits were all precipitated from a kind of hydrothermal fluids which had nothing to do with igneous activities. The salinity and reducibility of the fluids decreased with the sulfide precipitation. The two kinds of deposits had similar hydrothermal fluids; nevertheless, there existed another kind of fluid for the Mohailaheng deposit, which was a kind of fluorine-rich fluid from deep metamorphic basement. This fluorine-rich fluid controlled the location of the fluorite-rich carbonate hosted Pb-Zn deposits and could be used to explain the phenomenon why this kind of Pb-Zn deposits were more easily precipitated near the main thrust faults and the lowest carbonate strata in the region. The result achieved by the authors could answer the question why the carbonate-rich Pb-Zn deposit and the fluorite-rich Pb-Zn deposit can occur in the same region and same time in the world.