XIANG Da-fu1, WANG Lin-jun2, QIAN Zhi-kuan2
(1. NO.106 Geological Team, Bureau of Geology and Mineral Exploration and Development of Guizhou province, Zunyi 563000, China;
2. Architectural Engineering College, Guizhou Minzu University, Guiyang 550025, China)
Abstract: Mangdong deposit, a small scale Pb-Zn deposit near the medium scale Shaojiwan Pb-Zn deposit, is located in the southeast of Yadu-Mangdong tectonic-metallogenic belt, northwestern Guizhou Pb-Zn metallogenic district, China. The S and Pb isotopes of the main ore-forming stage sulfide separates from the main ore body in this deposit were analyzed in this paper. Results show that S isotopic compositions of sulfide separates range from +10.7‰ to +13.7‰ (average +12.2‰, n=12), which is similar to those of sulfide separates from Shaojiwan deposit (+8.4‰～+11.6‰, average 10.5‰, n=11), but is different from those of mantle-derived S (0±3‰). All the δ34S CDT values of sulfide separates from Mangdong and Shaojiwan deposits are similar to those of gypsum (+15‰) and barite-bearing (+22‰～+28‰) evaporites and Devonian to Triassic seawater (+20‰～+35‰). Therefore, the reduced S in the ore-forming fluids was the produce of marine sulfate by thermal chemical sulfate reduction. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values range from 18.582 to 18.668 (average 18.635, n=6), 15.706 to 15.811 (average 15.739, n=6) and 39.075 to 39.341 (average 39.176, n=6), respectively. All the Pb isotopic data plot in the field above the upper crust Pb average evolution line, overlap with that of the Upper Devonian to Lower Permian sedimentary rocks and Proterozoic basement rocks, but are different from that of Emeishan basalts. Therefore, we propose that the ore-forming metals were mainly derived from the carbonate host rocks, but we can’t rule out the contribution of the basement rocks. Geology and isotope geochemistry information suggest that the ore-forming fluids and metals were mainly sourced from the carbonate host rocks, parts originated from the basements, but Emeishan basalts don’t have obvious contribution, and the ore genesis of Mangdong deposit belongs to epigenetic hydrothermal deposit related to basin brines.
Keywords: S-Pb isotope; ore-forming fluid; Mangdong Pb-Zn deposit; Guizhou; Pb-Zn metallogenic district
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ACTA MINERALOGICA SINICA Vol. 35, No. 4, 2015, Page 447-452
