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    甘肃寨上金矿床矿物组成特征与矿质沉淀机理

    Characteristics of mineral association and mechanism of Au precipitation in the Zhaishang gold deposit, southern Gansu

    • 摘要: 提要:位于西秦岭礼(县)—岷(县)成矿带西段的寨上金矿床,是近年发现的一个大型微细浸染型金矿。笔者通过显微镜观察、电子探针和扫描分析等综合分析技术,确认金矿床中矿物组成相当丰富,既有大量硫化物、硫盐、氧化物、硫酸盐、碳酸盐、钨酸盐,又有碲化物、自然金属及多金属互化物。除常见矿物为自然金、黄铁矿、黄铜矿、黝铜矿、方铅矿、闪锌矿、辉锑矿、石英、白钨矿、方解石、菱铁矿、铁白云石和重晶石外,笔者还鉴定出在卡林型金矿床较少见的一些矿物,如硫铜锑矿、车轮矿、辉锑铅矿、辉钼矿、碲汞矿、碲镍矿、Cu-Zn-Ni-Sn-Fe的金属互化物和白钨矿等。矿石中矿物种类较多,组成较复杂以及存在显微自然金,构成寨上金矿床的一大特色。赋矿围岩中含Fe碳酸盐矿物溶解释放Fe以及溶解Fe的大量硫化物化,是寨上金矿床中存在显微可见自然金的最重要因素和金沉淀富集的有利条件。

       

      Abstract: Abstract:Located in the western part of the Minxian County-Lixian County metallogenic belt, West Qinling Mountains, the Zhaishang gold deposit is a recently discovered large-sized Carlin-type disseminated gold deposit. Examination of ores by optical microscope, electron microprobe and X-ray surface scanning has revealed that the ore deposit is quite complex in mineralogy. Up to now more than 40 minerals have been identified. These minerals include not only sulfides and sulfosalt of Cu, Pb, Zn, As, Mo, Ni and Sb -bearing minerals, a variety of oxides, sulfate, carbonate, and tungstate minerals but also visible gold grains, tellurides, native metals, and polymetallic intermetallic compounds. Among the most common minerals there are native gold, pyrite, chalcopyrite, tetrahedrite, galena, sphalerite, stibnite, quartz, calcite, ankerite, siderite, and barite. The identification of some rare minerals in the Carlin-type gold deposits such as chalcostibnite, bournonite, zinkenite, molybdenite, coloradoite, melonite, native metals, Cu-Zn-Ni-Sn-Fe intermetallic compounds and scheelite is of great significance. The diversity of mineral species in the ores and the occurrence of visible native gold minerals constitute outstanding features of the gold deposit. Dissolution of ferruginous limestone in the host rocks and sulfidation of the dissolved iron by H2S introduced by ore fluids were not only the most important depositional mechanism for visible gold grains but also the advantageous conditions for gold enrichment in the Zhaishang gold deposit.

       

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