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    甘肃省阳山金矿床稳定同位素地球化学和成矿年代学及矿床成因

    Isotope geochemistry, chronology and genesis of the Yangshan gold deposit, Gansu

    • 摘要: 提要:阳山金矿位于川陕甘交界地带,为近年发现的一特大型微细浸染型金矿床。对矿石中石英细脉δD、δ18O分析结果表明,该矿成矿流体以岩浆水为主。对各种硫化物δ34S分析结果表明,矿区沉积硫与岩浆硫共存且二者δ34S差别较大,而矿石金属硫化物中主要为岩浆成因硫。而δ13C分析结果表明,矿区既有岩浆岩成因碳又有沉积碳。K-Ar、39Ar-40Ar、Rb-Sr以及U-Pb同位素年代学研究表明,矿区斜长花岗斑岩脉形成于侏罗纪早期,此外,矿区还存在白垩纪早期以及古近纪早期隐伏岩浆岩体,与之相关的热液活动也表现出多期次性。笔者进一步探讨了矿床成因,认为在泥盆纪本区形成了一套炭、硅、泥质热水沉积,在印支期区域浅变质过程中金初步富集,其后本区发生了多期岩浆活动,与之相关的成矿热液及成矿物质沿安昌河—观音坝断裂运移,并在有利的构造部位富集、叠加形成了阳山金矿。

       

      Abstract: Abstract:The Yangshan gold deposit, located in the Sichuan-Shaanxi-Gansu border region, is a superlarge finely disseminated gold deposit recently found in China. δD and δ18OH2O analysis of quartz veinlets in ores shows that the ore fluids of the deposit are dominated by magmatic water, and the δ34S analysis of various sulfides indicates that sedimentary sulfur and magmatic sulfur coexist in the gold district and show significant difference in δ34S, while the sulfur in metal sulfides in the ores is mainly of magmatic origin. δ13C analysis indicates that both magmogenic carbon and sedimentary carbon exist in the gold deposit. K-Ar, 39Ar-40Ar, Rb-Sr and U-Pb isotopic datings show that plagiogranite porphyry dikes originated in the Early Jurassic, and in addition, Early Cretaceous and early Paleogene buried intrusions do also exist in the gold district and their related hydrothermal activities also exhibit the feature of repeated occurrence. Based on the data and other analyses, the authors further discuss the genesis of the deposit and think that:a sequence of hydrothermal carbonaceous, siliceous and argillaceous sediments formed in the area in the Devonian and gold was primarily concentrated in the process of regional low-grade metamorphism in the Indosinian metamorphism; afterwards multiple magmatic activities occurred in the district and their related ore fluids and materials migrated along the Anchanghe-Guayinba fault and were concentrated and stacked in favorable structural sites, thus resulting in the formation of the Yangshan gold deposit.

       

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