云南东川铜矿床流体演化与成矿机制研究

Fluid Evolution and Mineralization Mechanism of Dongchuan Copper Deposit in Yunnan Province

东川铜矿床是我国重要的沉积岩容矿的层状铜矿床(SSC),具有显著的多层位成矿特征和典型的铜硫化物分带。本研究以不同层位铜矿体的流体包裹体为研究对象,通过岩相学观察、显微测温和激光拉曼成分分析,发现东川群多层位铜矿体存在浅色和深色包裹体2种类型:浅色包裹体成分以H2O为主,含丰富的石盐子晶和少量钾盐、硬石膏子晶,代表了氧化型含矿卤水,具中低温(140~300℃)、中高盐度(12%~44%)的特征,属于Na^(+)、K^(+)、Ca^(2+)-Cl^(-)(SO_(4)^(2-))型盆地卤水,主要来源于海相蒸发岩的溶解和层间建造水;深色的含有机质包裹体代表了还原型流体,来源于黑山组碳质板岩和落雪组中的藻类生物分解。东川铜矿床以落雪组的含叠层石砂质白云岩作为主要沉淀系统,黑山组碳质板岩为隔挡层,形成一个流体封闭的物理化学圈闭,氧化含矿卤水通过供给系统运移到具还原性质的沉淀系统中,与还原型富硫流体和含有机质的地层发生混合反应,形成多层位的层状铜矿体和层控脉状铜矿体。

Dongchuan copper deposit is important sediment-hosted stratiform copper deposits(SSC)in China,which has remarkable multilayered metallogenic characteristics and typical copper sulfide zoning.In this study,the fluid inclusions of copper ore from different layers were analyzed by microthermometry and laser Raman spectrum.The results show that:two types of inclusions are distinguished in the copper ores of Dongchuan Group,which are the light-colored and the dark-colored inclusions.The composition of light-colored inclusions is dominated by H2O,riching in halite,a small amount of sylvite,and anhydrite crystals,which represents oxidized ore-bearing brine,coming from dissolution of marine evaporate and formation water between strata.Microthermometry analysis shows that the ore-forming brine has the characteristics of low-medium temperature(140-300℃),middle-high salinity(12%-44%),and belongs to Na^(+)-K^(+)-Ca^(2-)-Cl^(-)(SO_(4)^(2-))basin brine.The dark-colored organic inclusion represents reduced fluid,which comes from the carbonaceous slate of Heishan Formation and the algal organism decomposed Luoxue Formation.Dongchuan copper deposit took the stromatolite-rich sandstone dolomite of Luoxue Formation as the precipitation system,and the carbonaceous slate of Heishan Formation as the barrier layer,forming a fluid closed physicochemical trap.The oxidized ore-bearing brine was transported to the reductive precipitation system through the supply system,and mixed with the reduced fluid and the organic-bearing stratum,and formed the sediment-hosted stratiform and veined copper orebodies.