江东金矿床黄铁矿矿物学和微量元素特征对成矿过程的指示

江东金矿床位于湘东北地区万古金矿田，赋存于新元古代冷家溪群浅变质岩中，矿体受NW向断裂控制，金资源量约12.9 t，成矿规模大，能有效代表万古金矿田的成矿特征。目前，对于该矿床细致的矿相学、元素地球化学以及金的富集机制研究相对较少，限制了对其成矿过程的理解。本文在野外地质工作的基础上，对江东金矿床的成矿阶段进行了划分，通过背散射图像和LA-ICP-MS微区原位分析，获得江东金矿床不同世代黄铁矿的微量元素特征。研究表明，江东金矿床成矿阶段划分为：石英-白钨矿阶段（I）、石英-黄铁矿阶段（II）、石英-多金属硫化物-金阶段（III）和石英-方解石阶段（IV）。根据黄铁矿的结构和微量元素特征，识别出4种类型的黄铁矿：第II阶段的粗颗粒自形的Py1a（贫Co、Ni、As、Au）和多孔Py1b（富Co、Ni，贫As、Au）；第III阶段的Py2a（蚀变围岩中，富As、Au）以及Py2b（烟灰色石英脉中，富As、Au）。不可见金主要以固溶体金（Au⁺）的形式赋存于黄铁矿晶格中，且其富集和As关系密切。结合前人研究，推断溶解-再沉淀、围岩硫化作用是江东金矿床主要的金沉淀机制。

The mineralogy and trace element characteristics of pyrite， and its indication of the mineralization processs in Jiangdong gold deposit

The Jiangdong gold deposit is located in the Wangu goldfield in northeast Hunan， hosted in the low-grade metamorphic rock of the of the Neoproterozoic Lengjiaxi Group， and the orebody is controlled by the NW-trending fault， with a gold resource of about 12.9 t， which can effectively represent the metallogenic characteristics of the Wangu gold field. At present， there are relatively few studies on the detailed mineralogy， element geochemistry and gold enrichment mechanism of this deposit， which limit the understanding of its mineralization process. In this paper， on the basis of field geological work， the mineralization stages were divided， and the trace element characteristics of pyrite in different generations of Jiangdong gold deposit were obtained by backscattered images and LA-ICP-MS in situ analysis. The study shows that the mineralization stages of Jiangdong gold deposit are divided into： quartz-scheelite stage （I）， quartz-pyrite stage （II）， quartz-polymetallic sulfide-natural gold stage （III） and quartz-calcite stage （IV）. Based on the texture and trace element characteristics of pyrite， four generations of pyrite were identified： coarse-grained euhedral Py1a （Co， Ni， As， Au-poor） and porous Py1b （Co， Ni-rich As， Au-poor） in stage II； In stage III， euhedral Py2b （in altered wallrocks， As- and Au-rich） and subhedral-anhedral and Py2b （in smoky gray quartz veins， As- and Au-rich）. The Au-As relationship of pyrite shows that the invisible gold is mainly lattice gold （Au⁺） in pyrite and it is closely related to As. Combined with previous studies， it is concluded that dissolution-reprecipitation and wall rock alteration are the main gold precipitation mechanisms in Jiangdong gold deposit.