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    胶东和辽东金成矿对比研究——来自年代学、流体包裹体和同位素视角

    Comparison of gold mineralization between the Jiaodong and Liaodong Peninsulas: Perspectives from geochronology, fluid inclusions, and isotopic signatures

    • 摘要:
      研究目的 胶东与辽东具有相似的金矿成矿地质背景,两地金矿床也具有很多相似之处,然而目前已知的辽东金矿资源量明显少于胶东金矿资源量。
      研究方法 本研究系统收集了辽东金矿床的成矿年代学、流体包裹体和H–O–S–Pb–He–Ar等同位素数据结果,借用前人已系统整理的胶东金矿床数据集为背景值(阴影部分区域),将辽东金矿床相关数据与之对比。
      研究结果 结果表明胶东金矿床成矿时代主要集中在~120 Ma,辽东金矿床成矿时代主要有古元古代、三叠纪、早侏罗世和早白垩世。但以早白垩世金矿床在辽东地区分布最为广泛。胶东和辽东金矿床均为中温、中低盐度的CO2–H2O–NaCl热液流体成矿体系,流体不混溶作用和流体混合作用是重要的金沉淀机制。其中,辽东蚀变岩型金矿床明显具有中高温中高盐度的岩浆热液流体特征。胶东和辽东金矿床的成矿流体均表现出壳幔混合的特征,但幔源流体对于胶东金矿床的贡献作用明显大于辽东金矿床。此外,太古宇胶东群和古元古界辽河群盖县组地层分别对胶东和辽东金成矿具有重要的贡献,而太古宇鞍山群并未明显参与辽东金成矿作用。
      结论 相比于胶东,辽东地区找矿效果不理想可能是由于成矿作用复杂性和可能的构造控矿差异共同导致的,加强对辽东地区多期叠加成矿和控矿构造研究,尤其聚焦于高角度正断层和低角度顺层伸展滑动破碎带,有望在辽东取得更大找矿突破。

       

      Abstract:
      This paper is the result of mineral exploration engineering.
      Objective The Jiaodong and Liaodong Peninsulas share similar geological backgrounds for gold mineralization, and there are many similarities between the Jiaodong and Liaodong gold deposits. However, the currently known gold endowment of the Liaodong gold deposit is significantly lower than that of the Jiaodong gold deposit.
      Methods In this study, we systematically collected the age of gold mineralization, fluid inclusions, and H-O-S-Pb-He-Ar isotopes data from the Liaodong gold deposits. The consistent dataset of Jiaodong gold deposits, which has been systematically summarized by previous researchers, was used as the background values (shaded area), and then we conducted a comparative study of gold mineralization between the Jiaodong and Liaodong peninsulas.
      Results This comparative study shows that the mineralization age of the Jiaodong gold deposits is mainly clustered at ~120 Ma. The mineralization age of the Liaodong gold deposits mainly includes Paleoproterozoic, Triassic, Early Jurassic, and Early Cretaceous. Among them, the Early Cretaceous gold mineralization is extensively distributed in the Liaodong. The ore-forming fluids of the Jiaodong and Liaodong gold deposits are both medium temperatures, and medium to low salinity CO2-H2O-NaCl hydrothermal fluid systems. Fluid immiscibility and fluid mixing are key mechanisms for gold precipitation. Among them, the Liaodong altered-rock type gold deposits markedly have high to medium temperature, and high to medium salinity magmatic-hydrothermal fluids. The ore-forming fluids of the Jiaodong and Liaodong gold deposits were a mixture of crustal-derived and mantle-derived fluids. However, the contribution of mantle-derived fluids to the Jiaodong gold deposits is prominently greater than that of the Liaodong gold deposits. In addition, the Archean Jiaodong Group and Paleoproterozoic Gaixian Formation of Liaohe Group have made great contributions to the gold mineralization in the Jiaodong and Liaodong, respectively, while the Archean Anshan Group did not play an important role in the Liaodong gold mineralization.
      Conclusions Compared to the Jiaodong, the unsatisfactory prospecting results in the Liaodong Peninsula may be attributed to the complexity of mineralization and potential differences in ore-controlling structures. Strengthening the study on multistage superimposed metallogeny and ore-controlling structures in Liaodong Peninsula, especially focusing on high angle normal faults and low angle bedding extension and sliding fractured zones, which is expected to achieve breakthroughs in gold exploration in Liaodong.

       

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