Geological, fluid inclusion and isotopic studies of the Baiyangping Pb-Zn-Cu-Ag polymetallic deposit, Lanping basin, Yunnan province, China

摘要

Baiyangping Pb-Zn-Cu-Ag deposit is located in Lanping basin, northwestern Yunnan province. The deposit is composed of a few ore veins and can be divided into several ore blocks. The ore bodies are primarily hosted in Mesozoic carbonate, sandstone and siltstone along the north-south-striking, NWW-striking and NE-SW-striking fault zones. There are breccia, massive, vein like and disseminated ores. The main ore minerals are sphalerite, galena, gratonite, jordanite, tetrahedrite series minerals, chalcocite, chalcopyrite, realgar, orpiment, bournonite, cobalt-bearing arsenopyrite, argentite, kongsbergite, cobaltine, siegenite. The sizes of fluid inclusions in Baiyangping deposit are generally less than 10 gm and have the shape of round, oval, irregular, etc. The ore-forming fluid system is Ca2+-Na+-K+-Mg2+-Cl--F--NO3- brine system. The freezing temperature of fluid inclusions in mineral deposits ranges from -26.4 to -0.2 degrees C, average -14.6 degrees C; the homogenization temperature is concentrated in 120-180 degrees C, and the salinity is between 0.35 and 24.73 wt% (NaCleq), average 16.9 wt% (NaCleq). delta C-13(PDB) and delta O-18(SMOW) values of hydrothermal calcite range from -4.16 parts per thousand to 3 parts per thousand and -2.5 parts per thousand to 20.4 parts per thousand, respectively. delta S-34 values of sulfide minerals range from -10.2 parts per thousand to 11.2 parts per thousand, average 5.6 parts per thousand. The sulfide samples yield Pb-206/Pb-204 values of 18.609-18.818, Pb-207/Pb-204 of 15.548-15.842 and Pb-208/Pb-204 = 38.514-39.556. C-O-S-Pb isotope compositions of the Baiyangping deposit indicate a homogeneous carbon source, and the carbon in hydrothermal calcite is derived from the dissolution of carbonate rock strata, the ore-forming fluid belongs to basin brine fluid system, which is mixed with the precipitate water, sulfur in sulfides and sulfosalts is derived from thermal chemical sulfate reduction, and the thermal decomposition of sulfur-bearing organic matter. The metal mineralization material is from sedimentary strata and basement. The late Pb-Zn polymetallic mineralization event superposed within early Cu-Co polymetallic mineralization event resulted in the differences of ore-forming elements for Baiyangping deposit. (C) 2015 Elsevier Ltd. All rights reserved.