Fluid Inclusions of Calcite and Sources of Ore-forming Fluids in the Huize Zn-Pb-(Ag-Ge) District, Yunnan, China

摘要

The Huize Zn-Pb- (Ag-Ge) district is a typical representative of the well-known medium-to large-sized carbonate-hosted Zn-Pb- (Ag-Ge) deposits, occurring in the Sichuan-Yunnan-Guizhou Pb-Zn Ore-forming Zone.Generally, fluid inclusions within calcite, one of the major gangue minerals, are dominated by two kinds of small (1-10μm) inclusions including pure-liquid and liquid. The inclusions exist in concentrated groups along the crystal planes of the calcite. The ore-forming fluids containing Pb and Zn, which belong to the Na+-K+-Ca2+-C1--F--SO42- type, are characterized by temperatures of 164-221 ℃, medium salinity in 5-10.8 wt% NaCl, and medium pressure at 410xl0s to 661 x 10s Pa. The contents of Na+-K+ and Cl--F-, and ratios of Na+/K+-Cl-/F- in fluid inclusions present good linearity. The ratios of Na+/K+ (4.66-6.71) and C1-/F- (1 8.21-31.04) in the fluid inclusions of calcite are relatively high, while those of Na+/K+ (0.29-5.69) and Cl-/F- (5.00-26.0) in the inclusions of sphalerite and pyrite are relatively low. The ratio of Na+/K+increases in accord with those of C1-/F, which indicates that ore-forming fluid of deep source participates in the mineralization. The waters of fluid inclusions have δD values from -43.5‰ to -55.4‰ of calcite. The δ18Ov-sMow values of the ore-forming fluids, calculated values, range from 17.09‰ to 18.56‰ of calcite and 17.80‰ to 23.14‰ for dolomite.δ13 Cv-PDB values range from -1.94‰ to -3.31‰ for calcite and -3.35‰ to 0.85‰ for the ore-bearing dolomite. These data better demonstrate that the ore-forming fluids were mainly derived from metamorphic water and magmatic hot fluid, in relation to the metamorphism of the Kunyang Group in the basement and magmatic hydrothermalism. The deposit itself might have resulted from ascending cycles of ore-forming fluid, enriched in Pb and Zn. The Huize Zn-Pb- (Ag-Ge)deposits related to carbonate-hosted Zn-Pb sulphides.