The Tianqiao Pb-Zn deposit in the western Yangtze Block, southwest China, is part of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province. Ore bodies are hosted in Devonian and Carboniferous carbonate rocks, structurally controlled by a thrust fault and anticline, and carried about 0.38 million tons Pb and Zn metals grading >15% Pb + Zn. Both massive and disseminated Pb-Zn ores occur either as veinlets or disseminations in dolomitic rocks. They are composed of ore minerals, pyrite, sphalerite and galena, and gangue minerals, calcite and dolomite. delta S-34 values of sulfide minerals range from +8.4 to +14.4 parts per thousand and display a decreasing trend from pyrite, sphalerite to galena (delta S-34(pyrite)>delta S-34(sphalerite)>delta S-34(galena)). We interpret that reduced sulfur derived from sedimentary sulfate (gypsum and barite) of the host Devonian to Carboniferous carbonate rocks by thermal-chemical sulfate reduction (TSR). delta C-13(PDB) and delta O-18(SMOW) values of hydrothermal calcite range from -5.3 to -3.4 parts per thousand. and +14.9 to +19.6 parts per thousand, respectively, and fall in the field between mantle and marine carbonate rocks. They display a negative correlation, suggesting that CO2 in the hydrothermal fluid was a mixture origin of mantle, marine carbonate rocks and sedimentary organic matter. Sulfide minerals have homogeneous and low radiogenic Pb isotope compositions (Pb-206/Pb-204 = 18.378 to 18.601, Pb-207/Pb-204 = 15.519 to 15.811 and Pb-208/Pb-204 = 38.666 to 39.571) that are plotted in the upper crust Pb evolution curve and overlap with that of Devonian to Carboniferous carbonate rocks and Proterozoic basement rocks in the SYG province. Pb isotope compositions suggest derivation of Pb metal from mixed sources. Sulfide minerals have Sr-87/Sr-86 ratios ranging from 0.7125 to 0.7167, higher than Sinian to Permian sedimentary rocks and Permian Emeishan flood basalts, but lower than basement rocks. Again, Sr isotope compositions are supportive of a mixture origin of Sr. They have an Rb-Sr isotopic age of 191.9 +/- 6.9Ma, possibly reflecting the timing of Pb-Zn mineralization. C-O-S-Pb-Sr isotope compositions of the Tianqiao Pb-Zn deposit indicate a mixed origin of ore-forming fluids, which have Pb-Sr isotope homogenized before the mineralization. The Permian flood basalts acted as an impermeable layer for the Pb-Zn mineralization hosted in the Devonian-Carboniferous carbonate rocks. (C) 2013 Elsevier B.V. All rights reserved.

Publication name	ORE GEOLOGY REVIEWS　Volume: 53　 Pages: 77-92　 Published: SEP 2013
Author(s)	Zhou, Jiaxi; Huang, Zhilong; Zhou, Meifu; Li, Xiaobiao; Jin, Zhongguo
Corresponding author	HUANG Zhilong  huangzhilong@vip.gyig.ac.cn  Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550002, Peoples R China.

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