滇西北雪鸡坪铜矿床流体包裹体特征研究及矿床成因讨论

雪鸡坪铜矿床产于印支晚期石英二长闪长玢岩-石英闪长玢岩-石英二长斑岩复式侵入体内,为一斑岩型铜矿床。矿床形成经历了多阶段热液成矿作用,主要有微细脉浸染状黄铁矿±黄铜矿-石英、细脉状辉钼矿±黄铁矿±黄铜矿-石英及微细脉状贫硫化物-石英-方解石等。流体包裹体岩相学、显微测温、激光拉曼及碳、氢、氧同位素综合研究表明,微细脉浸染状黄铁矿±黄铜矿-石英阶段石英中主要发育含Na Cl子矿物三相及气液两相包裹体,与含矿的石英二长斑岩石英中发育的流体包裹体特征相似,表明成矿流体主要为中高温、高盐度Na Cl-H2O体系热液,可能主要来源于印支期石英二长斑岩侵入体;辉钼矿±黄铁矿±黄铜矿-石英中主要发育含CO2三相及气液两相包裹体,成矿流体为中温、低盐度Na Cl-CO2-H2O体系热液,与前者来源明显不同;贫硫化物-石英-方解石石英中主要发育气液两相包裹体,成矿流体为中低温、低盐度Na Cl-H2O体系热液,推测其可能较多来自于大气降水。因此,雪鸡坪铜矿床为不同来源、不同地球化学性质热液叠加成矿作用的结果。

Characteristics of fluid inclusions and genesis of Xuejiping copper deposit in northwestern Yunnan Province

Xuejiping copper deposit is a porphyry type deposit that occurred in quartz monzonite diorite porphyry-quartz diorite porphyry-quartz monzonite porphyry intrusive complex. The formation of it experienced multi-stage hydrothermal mineralization, mainly including micro-fine vein disseminated pyrite±chalcopyrite-quartz, fine veinlet molybdenite ± (pyrite) ± (chalcopyrite)-quartz, micro-fine veinlet sulfide-poor quartz-calcite. The comprehensive study on petrography, microthermometry, laser Raman and carbon-hydrogen-oxygen isotopes of fluid inclusions showed that there are mainly halite-bearing three-phase and aqueous two-phase two types of fluid inclusions developed in micro-fine vein disseminated pyrite±chalcopyrite-quartz, which is similar to the fluid inclusions in quartz of ore-bearing quartz monzonite intrusion, so the ore-forming fluids are of medium to high temperature, high salinity NaCl-H₂O type solutions and mainly came from the ore-bearing late Indo-Chinese intrusions. There are mainly CO₂-bearing three-phase and aqueous two-phase fluid inclusions developed in molybdenite ± (pyrite) ± (chalcopyrite)-quartz, and the ore-forming fluids are of medium temperature, low salinity NaCl-CO₂-H₂O type solutions, a different origin is conferred. Only aqueous two-phase fluid inclusions were observed in sulfide-poor-quartz-calcite, the ore-forming fluids are of low to medium temperature, low salinity NaCl-H₂O type solutions and might mainly come from meteoric water. So Xuejiping copper deposit was the product of metallogenic superimposition of different-sourced with different geochemical characteristics magmatic solutions.