Ore genesis of the Tianbaoshan carbonate-hosted Pb–Zn deposit, Southwest China: geologic and isotopic (C–H–O–S–Pb) evidence
Ore genesis of the Tianbaoshan carbonate-hosted Pb–Zn deposit, Southwest China: geologic and isotopic (C–H–O–S–Pb) evidence
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DOI：
10.1080/00206814.2013.782973
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发表时间：
2013-06
影响因子：
2.6
通讯作者：
Jiaxi Zhou;JianGuo Gao;Da Chen;Xinkai Liu
中科院分区：
文献类型：
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作者：
Jiaxi Zhou;JianGuo Gao;Da Chen;Xinkai Liu
天宝山铅锌存款，四川-云南-贵州（SYG）铅锌成矿省的一部分，位于扬子地块西部，含有260万吨10-15重量% Pb + Zn金属。矿体呈脉状、管状产出，产于晚元古代震旦系碳酸盐岩中，构造受南北向安宁河构造带和北西向隐伏断裂控制。矿床矿物学简单，矿石矿物为闪锌矿、方铅矿、黄铁矿、黄铜矿、毒砂、黄铜矿、毒砂、黄铜矿、硫银矿，脉石矿物为白云石、方解石、石英。这些物相以块状、角砾状、细脉状和浸染状等形式出现在上震旦统灯影组白云岩中。热液流体的氢、氧同位素组成分别为-47.6 ‰ ~-51.2‰和-1.7 ‰ ~+3.7‰。这些数据表明，热液中的H2O具有变质水和大气沃茨的混合来源。碳、氧同位素组成范围分别为-6.5 ‰ ~-4.9‰和+19.3 ‰ ~+20.2‰。成矿流体中的CO2具有多源性，包括二叠纪峨眉山溢流玄武岩、震旦-二叠纪海相碳酸盐岩和寒武-二叠纪沉积岩中的有机质。硫同位素组成范围为-0.4 ~+9.6‰，明显低于寒武-二叠纪海水硫酸盐（+15 ~+35‰）和寒武-二叠纪地层蒸发物硫酸盐（+15 ~+28‰），表明硫是由寄主地层蒸发物通过热化学硫酸盐还原作用生成的。206 Pb/204 Pb、207 Pb/204 Pb和208 Pb/204 Pb比值分别为18.110 ~ 18.596、15.514 ~ 15.878和38.032 ~ 39.221，它们与元古宙基底岩石、震旦系白云岩、泥盆-二叠纪碳酸盐岩、二叠纪峨眉山溢流玄武岩的成矿作用，反映了成矿流体中Pb的复杂来源。天宝山铅锌存款矿床地质和同位素研究表明，热液组分具有多源性，流体混合是可能的成矿机制。研究的存款不是远源岩浆热液型、沉积喷流型（SEDEX）或密西西比河谷型（MVT）矿床，而是一种独特的存款类型，本文将其命名为SYG型。
The Tianbaoshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province, is located in the western Yangtze Block and contains 2.6 million tonnes of 10–15 wt.% Pb + Zn metals. Ore bodies occur as vein or tubular types and are hosted in Sinian (late Proterozoic) carbonate rocks and are structurally controlled by the SN-trending Anninghe tectonic belt and NW-trending concealed fractures. The deposits are simple in mineralogy, with sphalerite, galena, pyrite, chalcopyrite, arsenopyrite, freibergite, and pyrargyrite as ore minerals and dolomite, calcite, and quartz as gangue minerals. These phases occur as massive, brecciated, veinlet, and dissemination in dolostone of the upper Sinian Dengying Formation. Hydrogen and oxygen isotope compositions of hydrothermal fluids range from –47.6 to –51.2‰ and –1.7 to +3.7‰, respectively. These data suggest that H2O in hydrothermal fluids had a mixed origin of metamorphic and meteoric waters. Carbon and oxygen isotope compositions range from –6.5 to –4.9‰ and +19.3 to +20.2‰, respectively. These compositions plot in the field between mantle and marine carbonate rocks with a negative correlation, suggesting that CO2 in the ore-forming fluids had multiple sources, including the Permian Emeishan flood basalts, Sinian-to-Permian marine carbonate rocks, and organic matters in Cambrian-to-Permian sedimentary rocks. Sulphur isotope compositions range from –0.4 to +9.6‰, significantly lower than Cambrian-to-Permian seawater sulphate (+15 to +35‰) and sulphate (+15 to +28‰) from evaporates in Cambrian-to-Permian strata, implicating that the S was derived from host-strata evaporates by thermal–chemical sulphate reduction. 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios range from 18.110 to 18.596, 15.514 to 15.878, and 38.032 to 39.221, respectively, which plot in field of the upper crust Pb evolution curve, unlike those of Proterozoic basement rocks, Sinian dolostone, Devonian-to-Permian carbonate rocks, and the Permian Emeishan flood basalts, implying complex derivation of Pb metal in the ore-forming fluids. Geological and isotopic studies of the Tianbaoshan Pb–Zn deposit reveal that constituents in the hydrothermal fluids were derived from multiple sources and that fluid mixing was a possible metallogenic mechanism. The studied deposit is not distal magmatic–hydrothermal, sedimentary exhalative (SEDEX), or Mississippi Valley (MVT) types, rather, it represents a unique ore deposit type, named in this article the SYG type.