Sources of metallogenic materials and metallogenic mechanism of Tianbaoshan Pb-Zn deposit in Sichuan Province: Constraints from fluid inclusions and isotopic evidences

As one of the famous high-grade Pb-Zn ore fields in the Sichuan-Yunnan-Guizhou ore concentration area, the Tianbaoshan Pb-Zn deposit which is located on the southwestern margin of Yangtze Craton, has a total Pb + Zn reserve of 2.6Mt with grades of 10% similar to 15%. Geochemistry of C-H-O-S-Pb-Sr isotopes and fluid inclusions are discussed in this paper to understand the sources of the ore metals and ore-fluids. The H-O isotopes and fluid inclusions show that the ore-forming fluid of the deposit is characterized by medium-low temperature (140 similar to 200 degrees C) and medium-low salinity (6% similar to 12% NaCleqv). The delta C-13(V-PDB) and delta O-18(SMOW) values of the Dengying Formation dolostones are similar to that of the coeval marine carbonate, suggesting that the dolostones belong to marine carbonate. The delta(13) CV-PDB and delta(18) O-SMOW values of hydrothermal calcites and ore-bearing dolomites are lower than that of the Dengying Formation dolostone, indicating that the CO2 in the ore-forming fluid was derived from dissolution of the Dengying Formation dolostone. The delta S-34 values of ore minerals range from 1.1 parts per thousand to 7.5 parts per thousand, indicating the sulfurs were derived from a mixed source of Dengying Formation marine sulfate modified by thermochemical sulfate reduction and magmatic sulfate. The Pb-207/Pb-204 versus Pb-206/Pb-204 discrimination diagrams show a crustal Pb origin, indicating that the ore-forming metals were derived from a mixed source of sedimentary rocks and basement rocks. The Sr-87/Sr-86 values of sphalerites (0.71099 similar to 0.71856) and hydrothermal calcites (0.71014 similar to 0.71169) are higher than that of the Dengying Formation dolostones (0.70773 similar to 0.71026), suggesting that the ore-forming fluid must flow through a high Sr-87/Sr-86 basement stratum which results in a water-rock reaction and isotope exchange of its ore-forming mineral sources.