湖南西部钨锑金矿床成矿规律及找矿应用

Metallogenic model of tungsten-antimony-gold deposits in west Hunan province and the application of the model to the ore exploration

湖南西部钨锑金矿床赋存于雪峰弧形构造带之前寒武系浅变质岩系中,受到韧-脆性剪切构造控制,具有明显的地层层位效应。区域变质和动力变形过程中,大规模深层次的韧性剪切变形促使矿源层中的Au活化迁移,连同SiO2,K等活性组分和岩石中的H2O一起形成含金动力变质热液,当其进入伸展型脆韧性剪切带及其剥离构造带、张扭性断裂带时,形成充填交代型含金石英脉型和破碎带蚀变岩型金矿。研究表明,矿床具有特定的元素共生组合,矿脉(体)沿倾向延伸大且普遍具有侧伏成矿现象,沿控矿构造方向侵入的长英质脉岩带与成矿有一定的联系;载金的硫(砷)化物以富集轻硫同位素为特点,氧化-还原反应是金成矿的主要化学机制等特征性成矿标志。矿床广泛发育中低温热液蚀变,黄铁矿、毒砂矿物和As元素是找金的标型矿物和指示元素。矿床成因主要属于受韧-脆性脆剪切带控制的变质热液型金矿。

Tungsten antimony-gold deposits in west Hunan province occur in the Pre-cambrian low grade amorphic rock sequence and are controlled by ductile-brittle shear zone and horizons. During regional dynamic metamorphism deep ductile shearing deformation in large scale facilitated remobilization of Au in the source bed to form Au bearing metamorphic hydrothermal fluid together with H20 within the rock and active constituents, such as SiO2 ,K etc. When the Au-bearing hydrothermal fluid entered in the extensional ductile shear zone and its detachment tectonic zone, tension shear zone Au-bearing filling replacement quartz vein and altered cataclastic rock type gold deposits were formed. Studies show that such Au deposits are characteristic of specific element combination, more extension along dip and pitch of ore vein （body） and felsic rock belt emplaced along the gold ore-control structure is related to gold metallogeny. The Au metallogeny is characterized by light sulfur isotope enrichment of Au-bearing sulfides and arsenides and oxidation-reduction reaction is the main chemical mechanism. Meso-epithermal alteration is developed with such Au deposits. Pyrite, arsenopyrite and As element are the typomorph mineral and mark element for the ore prospecting. Genetically, such Au deposit is the ductile-brittle shear zone-controlled metamorphic hydrothermal Au deposit.