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位于河南洛宁境内的沙沟热液脉型Ag-Pb-Zn矿床是熊耳山地区近年来新发现的大型矿床.野外观察和矿相学研究表明成矿过程包含4个阶段,分别为石英-菱铁矿阶段(Ⅰ)、石英-闪锌矿阶段(Ⅱ)、石英-银矿物-方铅矿阶段(Ⅲ)和石英-碳酸盐阶段(Ⅳ),其中Ⅱ、Ⅲ阶段为主成矿阶段.扫描电子显微镜-能谱分析(SEM-EDS)和电子显微探针微区成分分析(EMP)结果显示,沙沟矿床中的银以不可见银和可见银两种形式存在,但以可见银为主.不可见银主要以次显微包体(<1μm)的形式被包裹在黄铜矿和闪锌矿等硫化物中,而可见银通常以各种银的独立矿物形式交代方铅矿和黄铜矿等硫化物或充填在硫化物和石英的显微裂隙内.结合本文研究和前人对沙沟矿床流体包裹体的研究认为,银和铅、锌等金属离子在成矿早期高温阶段以氯络合物的形式搬运,随着成矿热液温度和氧逸度的降低以及pH值的升高,氯络合物因稳定性降低而解体,硫氢络合物成为银、铅、锌的主要迁移形式.随着成矿热液温度的继续降低,铅、锌等金属硫氢络合物开始分解,方铅矿、黄铜矿和闪锌矿等硫化物得以沉淀,此时部分银以显微和次显微包体银的形式被包裹于这些硫化物中.铅锌硫化物的大量沉淀引起成矿热液组成和性质的显著变化,最终导致银从硫氢络合物中彻底解体,并与Cu+、Sb3+等离子结合形成大量独立银矿物(如含银黝铜矿、硫锑铜银矿和辉铜银矿等),而溶液中过饱和的银则以自然银的形式沉淀.
The Shagou hydrothermal vein-type Ag-Pb-Zn deposit located in Luoning, Henan Province is a newly discovered large deposit in Xiong’ershan area.Field observations and mineralogical studies show that the mineralization process consists of four stages, namely quartz- Siderite (Ⅰ), quartz-zinc blende (Ⅱ), quartz-silver mineral-galena (Ⅲ) and quartz-carbonate Stage.The results of SEM-EDS and EMP showed that the silver in the Shagou deposit existed in the form of invisible silver and visible silver, but in the visible Silver is dominant, and invisible silver is mainly encapsulated in chalcogenides such as chalcopyrite and sphalerite in the form of sub-microscopic inclusions (<1 μm), whereas silver is often accounted for in the form of a separate mineral of various silver Ore and chalcopyrite sulfide or fill in the fissures of sulfide and quartz.Combining with this paper and previous studies on the fluid inclusions in the Shagou deposit, it is concluded that the metal ions such as silver, High-temperature phase of chlorine complexes in the form of handling, with the hydrothermal fluid temperature and oxygen fugacity decreased and pH , The complex of chlorine and sulfur disintegrated due to the decrease of stability, and the sulfur and hydrogen complexes became the main migration forms of silver, lead and zinc.With the further decrease of the temperature of the hydrothermal fluid, The material begins to decompose, and sulfide such as galena, chalcopyrite and sphalerite are precipitated, at which time part of the silver is encapsulated in these sulfides in the form of microscopic and sub-microscopic silver inclusions. A large amount of precipitation caused a significant change in the composition and properties of the hydrothermal fluid, eventually leading to the complete dissolution of silver from the sulfhydryl complex and the formation of a large number of independent silver minerals (such as silver-containing tetrahedrite and antimony thiosulfate) combined with Cu + and Sb3 + Silver and silver gibbsite, etc.), while supersaturated silver in solution precipitates in the form of natural silver.