陆相砂岩型铜矿床矿物分带模式的pH-Eh相图——以楚雄盆地大姚六苴铜矿床为例  

Application of Thermodynamics pH-Eh to Mineral Zonation Model of Sandstone-hosted Type Copper Deposits in the Chuxiong Basin,Central Yunnan Province,China

作　　者：张艳[1] 韩润生[1] 吴鹏[1] 魏平堂 

机构地区：[1]昆明理工大学有色金属矿产地质调查中心西南地质调查所,云南昆明650093 [2]中国冶金地质总局昆明地质勘查院,云南昆明6500024

出　　处：《矿物学报》2013年第3期363-368,共6页Acta Mineralogica Sinica

基　　金：教育部博导基金项目(编号:20115314110010);国家危机矿山专项(编号:20089943);国家自然科学基金项目(批放研究基金(编号:201109);昆明理工大学成矿动力学与隐伏矿预测创新团队项目(编号:2010)

摘　　要：滇中楚雄盆地砂岩型铜矿床,如大姚六苴铜矿床,赋存于上白垩统马头山组六苴下亚段(K2mml1)紫色砂岩与浅色砂岩过渡带靠近浅色一侧,铜矿化受氧化还原界面控制。从紫色砂岩向浅色砂岩,金属矿物依次呈现赤铁矿→辉铜矿→斑铜矿→黄铜矿→黄铁矿的水平分带规律。以矿物分带中的金属矿物为主要研究对象,结合流体包裹体测试成果,构建和绘制了大姚六苴铜矿床主要成矿温度下的pH-Eh相图,理论计算结果与宏观地质特征吻合。依据pH-Eh相图,阐述了主要金属矿物的沉淀条件及其分带机理,认为楚雄盆地砂岩铜矿床金属矿物分带受pH和Eh双重控制;在373～523 K间温度变化对金属矿物沉淀的pH和Eh影响不大;S2-只能在低于473 K下的热液中稳定存在,辉铜矿(Cu2S)形成温度低于473 K。该研究为该类矿床成矿机制研究提供了重要依据。Sandstone copper deposits in central Yunnan Province,China such as Liuju copper in Dayao deposit are near the light-colored side of the transition zone of purple sandstone and light-colored sandstone from Liuju sub-segment （K2ml1 ） of the upper Cretaceous.Copper mineralization is controlled by the redox interface.From purple sandstone to light-colored sandstone,metallic minerals present a horizontal zoning in order as hematite,chalcocite,bornite,chalcopyrite and pyrite.Metallic minerals in the mineral zoning were studied.Based on test results of fluid inclusion,the pH-Eh phase diagram for Dayao copper deposit at ore-forming temperature was made.Results of theoretic calculation are consistent with macro-geological characteristics.Based on pH-Eh diagram,precipitation conditions and zoning mechanism of major metallic minerals were elaborated.It is believed that metallic mineral zonage of the sandstone copper deposit in Chuxiong Basin is under the dual control of pH and Eh.Between 373 K and 523 K,temperature changes have little effect on pH and Eh of the metallic mineral precipitation.The S2 can only be stable at temperature lower than 473 K,and the formation temperature of chalcocite （Cu2S） is below 473 K.The study has provided an important basis for ore forming mechanism.

关 键 词：pH-Eh相图 砂岩铜矿床 楚雄盆地 大姚六苴铜矿床 

分 类 号：P611[天文地球—矿床学] P618[天文地球—地质学]