陕西勉略宁地块车渡磁铁石英岩型金矿床多期成矿作用

Multistage Mineralization of Chedu Magnetite Quartzite Gold Deposit in Mianluening Block of Shaanxi, China

基于野外地质调查和矿相学综合研究,对陕西勉略宁地块车渡金矿床成矿期次进行了详细划分。根据岩(矿)石变质程度、矿物穿插包裹关系,将成矿作用划分为3期:①沉积-变质期,伴随磁铁石英岩沉积-变质作用,形成了高品位层状金矿体;②热液成矿期,分为烟灰色石英硫化物脉和含硫化物碳酸盐脉两个成矿阶段,两类脉体均可见自然金;③表生作用期,在磁铁矿被氧化为褐铁矿的过程中,Au进一步富集形成大量自然金。车渡金矿床中可见金主要赋存状态为粒间金、包裹金和裂隙金。基于石英硫化物脉和磁铁石英岩沉积条带中Au品位及分布规模,将车渡金矿床成因类型归为磁铁石英岩型金矿床,这对于该区域下一步地质找矿工作具有重要意义。

Based on the field investigation and mineragraphy, the mineralization stages were identified for Chedu gold deposit in Mianluening block of Shaanxi. According to the metamorphic degree of rock(ore) and crosscutting relationship of minerals, the mineralization can be divided into three stages: ① sedimentary-metamorphic stage, high-grade layered gold ore body formed is accompanied by the sedimentation-metamorphism of magnetite quartzite;② hydrothermal mineralization stage, is divided into two substages, including smoky gray quartz sulfide vein and sulphide-bearing carbonate vein, in which native golds are observed;③ supergenesis stage, gold is further enriched to form large native gold grains accompanied by oxidization of magnetite. The native gold in Chedu gold deposit occurs as magnetite fractures, along the grain boundaries of magnetite and quartz, and within magnetite, pyrite, and calcite. The main occurrence states of gold in Chedu gold deposit are intergranular gold, inclusion gold and fissure gold. Based on high-grade gold and distribution scale in quartz sulfide veins and sedimentary bands of magnetite quartzite, the genesis of Chedu gold deposit is classified as magnetite quartzite type, which is of great significance for the next geological prospecting in the area.