论川西地区金矿中黝铜矿的成分标型特征

On Typomorphic Composition Features of Tetrahedrite in Gold Deposits of Western Sichuan

四川西部金矿床中有 3类金矿含有较多的黝铜矿族矿物,它们与黄铁矿、黄铜矿、方铅矿、闪锌矿和Au -Ag系列矿物共同组成矿石的矿物组合。电子探针分析表明,黝铜矿族矿物的变种有黝铜矿和砷黝铜矿等。在黝铜矿中,As-Sb之间呈完全类质同象。在不同类型金矿中,黝铜矿具有不同的特征参数。产于碳酸盐岩系内的地下水热液型金矿中的黝铜矿成分自上而下由富锌锑向富铁砷演变,而且含银量也有降低的趋势。黝铜矿的产出及分带特征对于区内及相似地区同类金矿的勘查具有重要意义。

In the nine types of gold deposits so far discovered in western part of Sichuan Province, there are relatively abundant tetrahedrite_group minerals in three types of hydrothermal golddeposits: Ⅰ—carbonate rock series_hosted type; Ⅱ—ophiolitic melange rock series_hosted type; and Ⅲ—slightly metamorphosed fine_grained clastic rock series_hosted type. Being products of main ore_forming stages, the tetrahedrite_group minerals occur in irregular grained, veined or stockwork forms, which are combined with pyrite, chalcopyrite, galena, sphalerite, and gold_silver series minerals to constitute the gold ore. The electron microprobe analyses indicate that the tetrahedrite_group minerals include antimony_tetrahedrite and tennatite. The data show that Sb-As is of complete isomorphous replacement in the tetrahedrite_group mineral series. Tetrahedrite minerals in different types of gold deposits have different characteristic parameters. Tetrahedrite_group minerals in Type Ⅰ gold deposits are characterized by lower arsenic, higher silver and antimony, and intermediate iron and zinc, those in Type Ⅱ deposits have higher antimony and iron content and lower silver, arsenic and zinc, and those in Type Ⅲ deposits are enriched in zinc and arsenic, and depleted in silver, iron and antimony. Relatively enriched silver, iron, antimony are typical feature of tetrahedrite_group minerals in Type Ⅳ deposits. The characteristics of gold mineralization may be reflected by the major and particular components of tetrahedrite_group minerals. There exists vertical change in chemical composition of minerals downward from zinc and antimony_rich tetrahedrite to iron and arsenic_rich tetrahedrite, accompanied with the decreasing trend of silver content in the Type Ⅰ deposits. Their occurrence and zonal features are very important for the exploration of gold deposits in western Sichuan and similar regions.