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首页> 外文期刊>Journal of Asian earth sciences >Geology, isotope geochemistry and geochronology of the Jinshachang carbonate-hosted Pb-Zn deposit, southwest China
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Geology, isotope geochemistry and geochronology of the Jinshachang carbonate-hosted Pb-Zn deposit, southwest China

机译：中国西南地区金沙场碳酸盐岩铅锌矿床的地质，同位素地球化学和年代学

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摘要

The Jinshachang Pb-Zn deposit, an exceptionally radiogenic Pb-enriched sulfide deposit, hosted by dolo-stone of the Upper Sinian (Neoproterozoic) Dengying Formation and the Lower Cambrian Meishucun Formation, is located in the western Yangtze Block, about 300 km northeast of Kunming city in southwest China. Ore bodies in this deposit are dominated by strata-bound type and steeply dipping vein type. Primary ores in these two types are composed of sphalerite, galena, fluorite, barite and quartz with massive, banded, veined and disseminated structures. Twenty-seven ore bodies in the Jinshachang deposit host 4.6 million tons of sulfide ores at average grades of 4.07 wt.% Pb and 5.03 wt.% Zn. Quartz separates from the sulfide ores have δD_(H2O) values ranging from -137‰ to -86.2‰ with an average of -114‰ (n = 7), lower than those of magmatic, metamorphic and meteoric water, suggesting a contribution of organic water. δ~(34)S_(CDT) values of ninety-one sulfide separates range from +l.l‰ to +13.4‰ with an average of +5.7‰, lower than those of evaporites (δ~(34)S_(CDT) = +15‰ to +35‰) in the Cambrian to Triassic sedimentary strata in NE Yunnan province. δ~(34)S_(CDT) values of eight barite separates range from +32‰ to +35‰ (average +34‰), within the range of evaporites. These data suggest that S~(2-) in the hydrothermal fluids derived from evaporites by thermo-chemical sulfate reduction (TSR), whereas SO_4~(2-) directly originated from the evaporites. Six sulfide separates have highly radiogenic ~(206)Pb/~(204)Pb ratios ranging from 20.74 to 21.18 (average 20.92), ~(207)Pb/~(204)Pb ratios ranging from 15.85 to 15.89 (average 15.87), and ~(208)Pb/~(204)Pb ratios ranging from 40.89 to 41.42 (average 41.16). The Pb isotopes of the sulfides plot above the upper crust Pb average evolution curve and overlap the Cambrian sedimentary rocks, but are different from the Sinian dolostone. This indicates a crustal source of Pb most likely derived from the Cambrian sedimentary rocks. The initial ~(87)Sr/~(86)Sr ratio of seven main stage sphalerite separates from the Jinshachang deposit is 0.713, which is higher than those of the Upper Sinian Dengying Formation dolostone (0.708-0.710), Lower Cambrian carbonates (0.708-0.710), Devonian to Lower Permian sedimentary rocks (0.707-0.711) and Middle Permian Emeishan flood basalts (0.704-0.708), and lower than those of the Proterozoic folded basement rocks (0.724-0.729), but similar to those of Lower Cambrian black shale (0.712-0.714). Therefore, the Sr isotope data of the sphalerite support the view that the Lower Cambrian sedimentary rocks, in particular the black shale, were important source of metals. The main stage sphalerite separates have an Rb-Sr isotopic age of 206.8 ± 3.7 Ma, reflecting the timing of Pb-Zn mineralization. This study suggests that the Jinshachang Pb-Zn deposit is an epigenetic, thrust fold-controlled and strata-bound deposit with fluids and metals derived from the Cambrian sedimentary strata.
机译：金沙场铅锌矿床是一种异常放射性的富含铅的硫化物矿床，由上震旦统（新元古代）灯影组和下寒武统梅村村组的白云岩所蕴藏，位于扬子地块的西部，距东北约300公里。中国西南地区的昆明市。该矿床的矿体以地层约束型和陡倾脉型为主。这两种类型的原矿由闪锌矿，方铅矿，萤石，重晶石和石英组成，具有块状，带状，脉状和散布的结构。金沙场矿床中有27个矿体，含460万吨硫化矿石，平均品位为4.07 wt。％Pb和5.03 wt。％Zn。硫化矿中分离出的石英的δD_（H2O）值在-137‰至-86.2‰之间，平均为-114‰（n = 7），低于岩浆，变质和陨石水，表明有机物的贡献水。 91个硫化物的δ〜（34）S_（CDT）值范围为+ 11‰至+ 13.4‰，平均为+ 5.7‰，低于蒸发岩的δ〜（34）S_（CDT）= +云南东北部寒武纪至三叠纪沉积地层的15‰至+ 35‰）。八个重晶石分离区的δ〜（34）S_（CDT）值在蒸发岩范围内，从+ 32‰到+ 35‰（平均+ 34‰）。这些数据表明，通过热化学硫酸盐还原法（TSR）从蒸发岩获得的热液中的S〜（2-），而SO_4〜（2-）直接来源于蒸发岩。六个硫化物分离物具有高放射源性〜（206）Pb /〜（204）Pb比，范围从20.74至21.18（平均20.92），〜（207）Pb /〜（204）Pb比，范围从15.85至15.89（平均15.87）， 〜（208）Pb /〜（204）Pb的比率范围为40.89至41.42（平均值41.16）。硫化物的Pb同位素在上地壳Pb平均演化曲线上方并与寒武纪沉积岩重叠，但与震旦系白云岩不同。这表明铅的地壳来源很可能来自寒武纪沉积岩。金沙场矿床中七个主要阶段闪锌矿的初始〜（87）Sr /〜（86）Sr比为0.713，高于上震旦统灯影组白云岩（0.708-0.710），下寒武统碳酸盐岩（0.708） -0.710），泥盆纪至下二叠统沉积岩（0.707-0.711）和中二叠纪峨眉山洪水玄武岩（0.704-0.708），并低于元古代折叠基底岩（0.724-0.729），但与下寒武统相似黑色页岩（0.712-0.714）。因此，闪锌矿的Sr同位素数据支持这样的观点，即下寒武统沉积岩，尤其是黑色页岩是重要的金属来源。主要阶段的闪锌矿分离物的Rb-Sr同位素年龄为206.8±3.7 Ma，反映了Pb-Zn矿化的时间。这项研究表明，金沙场铅锌矿床是一种表生成因，逆冲褶皱控制和地层约束的矿床，其流体和金属来自寒武纪沉积地层。

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  • 来源
    《Journal of Asian earth sciences》 |2015年第2期|272-284|共13页
  • 作者

    Jia-Xi Zhou; Jun-Hao Bai; Zhi-Long Huang; Dan Zhu; Zai-Fei Yan; Zhi-Cheng Lv;

  • 作者单位

    State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China,Development and Research Center, China Geological Survey, Beijing 100037, China;

    Henan Academy of Land and Resources, Zhengzhou 450053, China;

    State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;

    State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;

    State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;

    Development and Research Center, China Geological Survey, Beijing 100037, China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    H-O-S and Pb isotopes; Sphalerite Rb-Sr dating; Geodynamic setting; The Jinshachang Pb-Zn deposit; Yangtze Block; Southwest China;

    机译：H-O-S和Pb同位素;闪锌矿Rb-Sr测年;地球动力学设置;金沙场铅锌矿床;扬子街区;中国西南;

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