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首页> 外文期刊>Journal of Asian earth sciences >Mineralogical study of sediment-hosted gold deposits in the Yangshan ore field, Western Qinling Orogen, Central China
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Mineralogical study of sediment-hosted gold deposits in the Yangshan ore field, Western Qinling Orogen, Central China

机译：中西部秦岭造山带洋山矿田含泥金矿床的矿物学研究

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摘要

The Yangshan gold ore field is located in the southern subzone of the Western Qinling Orogen. Mineralization is confined by the east-west-striking Anchanghe thrust fault zone. These subparallel faults constitute a branch of the regional Mianlue structural zone, crosscutting Middle Devonian carbonaceous carbonate and clastic rock sequences, an ore-bearing unit locally named the Sanhekou Formation. The metasedimentary clastic and carbonate rocks containing fine-grained sulfides are the main host rocks of the deposit, with minor mineralization occurring as coarse-grained pyrite-quartz veinlets in black shale and as dissemination in some plagiogranite dykes. Electron microprobe (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-1CP-MS) analyses show that arsenian pyrite and arse-nopyrite are the major hosts for gold with tens of ppm up to weight percent levels of Au, and the Au contents in arsenopyrite are one order of magnitude higher than those in pyrite. A negative correlation of As and S in arsenian pyrite is consistent with the substitution of As for S in the mineral. Both arsenian pyrite and arsenopyrite in the Yangshan ore field show chemical zonations with middle parts (mantle) enriched in As and Au relative to cores and the outermost rims, reflecting the chemical evolution of ore-forming fluids. High resolution transmission electron microscopy (HRTEM) analysis failed to identify any nano-partide of native gold even in the highest Au parts of arsenopyrite. This observation combined with the relatively homogenous distribution of Au, a positive correlation of As and Au, and Au/As ratios below the solubility limit of gold in arsenian pyrite and arsenopyrite, suggests that invisible gold is likely present as structurally bound Au*1 in sulfides, although our work cannot exclude the existence of Au nano-particles in arsenian pyrite as identified in American Carlin-type gold deposits. Submicron native gold may be much more easily found in arsenian pyrite than in arsenopyrite, because the later has larger capacity of enrichment of Au~(+1) than the former due to the substitution of As for S. The mechanism for nanoparticle formation is likely exsolution of native gold from metastable arsenian pyrite caused by later hydrothermal event, which was recorded by the outermost As-, Au-poor overgrowths both in arsenian pyrite and arsenopyrite in the Yangshan gold ore field.
机译：洋山金矿田位于西秦岭造山带的南部分区。成矿作用局限于东西走向的安昌河逆冲断裂带。这些次平行断层构成了绵略地区构造带的一个分支，横穿了中泥盆纪碳质碳酸盐岩和碎屑岩层序，一个含矿单元，当地称为三河口组。含细粒硫化物的准沉积碎屑岩和碳酸盐岩是该矿床的主要宿主岩，次生矿化为黑色页岩中的粗粒黄铁矿-石英脉，并在某些斜长花岗岩岩脉中传播。电子探针（EMPA）和激光烧蚀电感耦合等离子体质谱（LA-1CP-MS）分析表明，砷黄铁矿和砷绿铁矿是金的主要基质，金的含量可达数十ppm，而金的重量百分比含量最高。毒砂中的含量比黄铁矿中的含量高一个数量级。砷黄铁矿中As和S的负相关与矿物中As替代As一致。洋山矿田中的砷黄铁矿和毒砂都显示出化学带，其中部（地幔）相对于岩心和最外缘富集了As和Au，反映了成矿流体的化学演化。高分辨率透射电子显微镜（HRTEM）分析无法识别出任何天然金纳米颗粒，即使在毒砂的最高Au部分中也是如此。该观察结果与相对均匀的Au分布，As和Au的正相关性以及低于砷在金的黄铁矿和毒砂中的金溶解度极限的Au / As比呈正相关，表明不可见的金很可能以结构键合的Au * 1的形式存在。硫化物，尽管我们的工作不能排除美国卡林型金矿床中发现的亚砷黄铁矿中金纳米粒子的存在。亚砷黄铁矿中比亚砷黄铁矿更容易发现亚微米天然金，这是因为后者由于As被S取代而比前者具有更丰富的Au〜（+1）富集能力。洋山金矿田中砷黄铁矿和砷黄铁矿中最外层的砷，金贫化的过度生长记录了后来由热液事件引起的亚稳黄铁矿中天然金的释放。

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  • 来源
    《Journal of Asian earth sciences》 |2014年第5期|40-52|共13页
  • 作者

    Jinlong Liang; Weidong Sun; Sanyuan Zhu; He Li; Yulong Liu; Wei Zhai;

  • 作者单位

    Department of Geochemistry, Chengdu University of Technology, Chengdu 610059, China;

    CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China,Guangzhou Mass Spectrometer Center, National Instrument Center, China;

    CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China;

    CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China;

    CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China;

    Department of Earth Sciences, Sun Yat-Sen University, Guangzhou 510275, China;

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  • 正文语种 eng
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  • 关键词

    The Yangshan sediment-hosted gold ore; field; Arsenian pyrite; Structurally bound Au~(+1); Nanoparticle of native gold; Western Qinling Orogen;

    机译：洋山含泥金矿;领域;亚砷黄铁矿;结构键合的Au〜（+1）;天然金的纳米粒子;西秦岭造山带;

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