胶东金矿硫同位素组成特征及其来源

    Sulfur isotopic composition and its source of Jiaodong gold deposit

    • 摘要: 胶东是全球第三大金矿集中区,矿床主要分布于胶西北、栖蓬福、牟乳等成矿区,矿化类型以蚀变岩型和石英脉型为主。由于金主要赋存于黄铁矿等硫化物中,这些硫化物的硫同位素组成对反映成矿物质来源具有重要指示意义。按照成矿区域、赋矿深度、矿化类型和含硫矿物对有关硫同位素数据进行了分类统计对比。分析表明,金矿床的δ34S值为-14.0‰~15.1‰,各典型金矿床的δ34S平均值在5.5‰~13.0‰之间,主要集中在6.0‰~10.0‰。δ34S值呈现如下规律性变化:牟乳成矿区>胶莱盆地东北缘>胶西北成矿区>栖蓬福成矿区,硫化物石英脉型>蚀变岩型>石英脉型,浅部矿>深部矿,黄铁矿>闪锌矿>黄铜矿>方铅矿。研究认为,金矿床中的硫为混合来源,由早前寒武纪变质岩系、晚中生代花岗岩类和地幔端元的多源同位素混合而成。硫同位素组成的变化主要与上述端元的混合比例有关,被较多晚中生代花岗岩物质混染的金矿床δ34S值较高,成矿深度较大、地壳物质混染较少的金矿床δ34S值较低。金矿形成于一次集中爆发的成矿事件,成矿过程中硫同位素体系已基本达到均一。

       

      Abstract: Jiaodong is the third largest gold deposit concentration area in the world, with gold reserves of more than 5000 tons.The gold deposits are mainly distributed in the Northwest Jiaodong, Qi-Peng-Fu, Mu-Ru and other metallogenic regions.The metallogenic types are mainly fracture zone altered rock-type(Jiaojia-type), quartz vein-type(Linglong-type), and their transition types.Since gold mainly occurs in pyrite and other sulfides, the sulfur isotopic composition of these sulfides can reflect the source of ore-forming materials.In this paper, the sulfur isotopic compositions are classified and statistically compared according to the metallogenic regions, ore bearing depth, metallogenic types and sulfur-containing minerals.The δ34S value of gold deposits ranges from -14.0‰ to 15.1‰, with an average value of 5.5‰ to 13.0‰, and mainly concentrated in 6.0‰~10.0‰.The δ34S value shows the following rules: Mu-Ru metallogenic region > Northeast margin of Jiaolai Basin metallogenic region > Northwest Jiaodong metallogenic region > Qi-Peng-Fu metallogenic region, sulfide quartz vein-type > altered rock-type > quartz vein-type, shallow deposit > deep deposit, pyrite > sphalerite > chalcopyrite > galena.The study shows that the sulfur of the gold deposit is a mixed source, which is composed of multi-source isotopes of Early Precambrian metamorphic rock series, Late Mesozoic granitoids and Mantle material.The change of sulfur isotopic composition is mainly related to the type of country rock and sulfur source.The δ34S value of the gold deposit mixed with much late Mesozoic granite materials is relatively high, but the gold deposit in depth mixed with less crustal materials is relatively low.The sulfur isotope system in the metallogenic process is uniformity and controlled by one centralized explosion metallogenic event.

       

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