桂西北明山卡林型金矿床多源流体成矿作用研究

Carlin-type gold deposit is one of the most important gold deposit types worldwide which has great economic significance and huge resource potential. The origin of these deposits in China, however, is still an enigma. The sources and evolution of the ore-fluids in such deposits has been one of the key problems debated around the world. This application focuses on the Mingshan gold deposit, which is a typical Carlin-type gold deposit, and is the object of this study. Based on careful field work, hand specimen descriptions, petrography, BSE, CL, and EMPA etc., a detailed paragenesis and understanding of the ore-forming stages will be determined. Using fluid inclusion microthermometry and laser Raman spectroscopy, the physical and chemical nature of the ore-forming fluids will be determined. In situ laser ablation quadrupole and multi-collector ICPMS analysis of trace elements and Pb and Sr isotope in hydrothermal minerals, in combination with hydrogen and oxygen isotopic analysis of fluid inclusions, will be used to deduce the sources of fluids and ore-forming components. The comprehensive analytical results described above, along with accurate geochronological data, mining and exploration data for the Mingshan gold deposit, and geological and geochemical data for the Mingshan deposit and Dian-Qian-Gui ore district, will be used to determine the fluid evolution and throw light on the mineralizing mechanisms for the Mingshan gold deposit. These new data will be of great scientific significance in the field of metallogenetic theory. It could also guide evaluation of the resource potential and exploration models.

卡林型金矿是经济意义和资源潜力十分巨大的一种金矿类型，然而该类矿床的成因一直悬而未决，其中成矿流体来源与演化是国内外长期争论的焦点问题之一。本申请拟选择明山金矿这一代表性卡林型金矿床为研究对象，在详细的野外地质调查基础上，通过岩（矿）相学观察、背散射电子影像、阴极发光、电子探针分析等，划分成矿期次、成矿阶段、矿物生成顺序；利用流体包裹体显微测温和激光拉曼光谱分析，获取成矿流体的物理化学性质；利用激光剥蚀多接收等离子体质谱（LA-MC-ICP-MS）微区原位分析热液矿物的微量元素和Pb、Sr同位素组成，结合流体包裹体氢氧同位素分析，判断成矿流体来源；并根据精确的成岩成矿年代学数据，综合矿山探采资料和前人积累的本矿床和矿集区地质地球化学资料，揭示流体演化过程，阐明矿床形成机制。研究成果对于丰富矿床成矿理论具有重要科学价值，对于指导卡林型金矿资源潜力评价和找矿勘探也具有重要的现实意义。

卡林型金矿是经济意义和资源潜力十分巨大的一种金矿类型，然而该类矿床的成因一直悬而未决，其中成矿流体来源与演化是国内外长期争论的焦点问题之一。本项目在野外调查的基础上，主要针对明山金矿成矿流体特征、成矿物质来源进行了流体包裹体显微测温、激光拉曼光谱分析、电子探针分析、氢氧硫氩铅同位素分析、主微量元素和稀土元素分析等。取得了以下认识：明山金矿成矿主阶段和成矿晚阶段流体均属于中低温低盐度低密度流体，δD分别为-55.0‰~-43.0‰和-105.0‰~-54.0‰，δ18O水分别为7.92‰~11.82‰和6.12‰~7.02‰，在δD-δ18O水图中投入岩浆水和变质水范围。成矿主阶段和晚阶段石英流体包裹体中的氩同位素数据在40Ar/36Ar –大气氩36Ar同位素演化图中明显显示出岩浆水与大气水混合的特征。沉积地层、蚀变围岩和矿石中共识别出6期黄铁矿，区域沉积地层中的沉积期和早成岩期黄铁矿中Au和As的含量很低；矿区蚀变围岩中晚成岩/早变质成因黄铁矿中Au和As的含量都高，最高可达0.44%和4.6%，说明晚成岩/早变质使得Au发生富集，且含量从中心向边缘逐渐减少，说明Au在后期热液事件中发生了活化迁移；矿石中晚成岩/早变质黄铁矿中Au和As的含量明显较低，而围绕它的三个热液环带黄铁矿中Au和As的含量都较高，说明环带黄铁矿中的Au和As来自核心黄铁矿的蚀变活化。这些线索证明明山金矿Au主要来源于围岩地层，而黄铁矿则是金的主要载体。以明山金矿多源流体成矿特征为依据，结合区域地质和金矿成矿规律，初步建立了右江盆地卡林型金矿三阶段综合成矿模式：海西期-印支早期同沉积成矿、印支褶皱造山期变质成矿、燕山期岩浆活动与大气降水渗滤成矿。项目研究成果为揭示卡林型金矿成矿流体演化过程和阐明矿床形成机制，提供了重要科学资料，对于指导卡林型金矿资源潜力评价和找矿勘探也具有重要的现实意义。