鄂东南铁山铁铜矿床成矿流体特征及铁的迁移与沉淀富集机制  

Thermodynamic conditions of ore-forming fluid and migration and enrichment mechanism of iron in the Tieshan Fe-Cu deposit, southeastern Hubei Province

作　　者：王伟[1,2] 王敏芳[1,3] 刘坤[1] 魏克涛[4] 柯于富 WANG Wei;WANG Minfang;LIU Kun;WEI Ketao;KE Yufu(Faculty of Earth Resources,China University of Geosciences,Wuhan 430074,Hubei,China;Guangxi Science Technology Normal University,Laibin 546100,Guangxi,China;State Key Laboratory of Geological Processes and Mineral Resources,China Uni/versity of Geosciences,Wuhan 430074,Hubei,China;No.1 Geological Party,Hubei Bureau of Geology,Daye 435100,Hubei,China)

机构地区：[1]中国地质大学(武汉)资源学院,湖北武汉430074 [2]广西科技师范学院,广西来宾546100 [3]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074 [4]湖北省地质局第一地质大队,湖北大冶435100

出　　处：《地质通报》2018年第6期1125-1141,共17页Geological Bulletin of China

基　　金：国家自然科学基金项目<鄂东南矿集区铁/铜矿床中铂族元素的赋存状态及富集机制研究>(批准号:41272097);国家重点研发计划项目<深部矿产三维预测模型与虚拟现实>(编号:2016YFC0600508);中国地质大学(武汉)教学实验室开发基金项目<鄂东南矿集区鸡冠咀矿床成矿流体特征研究><中甸普朗铜矿kt1矿体数字模型的建立>(编号:SKJ2016013;SKJ2018026)

摘　　要：对铁山铁铜矿床的流体包裹体研究发现,在石榴子石和透闪石中主要发育气液两相富液相、富气相和含石盐子晶三相包裹体。显微测温结果表明,进矽卡岩阶段热液流体均一温度为499.2~594.8℃,盐度多集中分布在17.3%_(Na Cl)~19.5%_(Na Cl)之间,密度为0.45~0.62g/cm^3,形成压力为58.0~90.6MPa;退化蚀变阶段成矿流体均一温度为356.2~428.6℃,盐度多集中分布在7.2%_(Na Cl)~15.5%_(Na Cl)之间,密度为0.52~0.83g/cm^3,成矿压力为23.8~29.7MPa,成矿深度为0.90~1.12km,主成矿阶段成矿流体具有高温、中-低盐度、低密度、较低成矿压力的特征,属于浅成矽卡岩型铁铜矿床。同时,群体包裹体气液相成分结果显示,气相成分以H_2O和CO_2为主,并含有少量CH_4、C_2H_6、N_2和H_2S气体;液相成分阳离子以Na^+、Ca^(2+)、K^+为主,阴离子以SO_4^(2-)、Cl^-为主。研究表明,Cl^-、SO_4^(2-)和碳酸络合物在铁质搬运与富集过程中发挥了重要作用,流体混合和成矿热液p H值的系统演变可能是导致铁山铁铜矿床铁质超常富集沉淀的重要机制。Based on petrographic observations of garnet and tremolite collected from the Tieshan Fe-Cu deposit, the authors found that the primary fluid inclusions are generally of three types： gaseous inclusions, liquid inclusions and halite daughter mineral-bearing three-phase inclusion. According to temperature measurement results, the homogenization temperatures at the prograde skarn stage range from 499.2℃ to 594.8℃, the fluid salinity peak values range from 17.3 %naci to 19.5 %naci, the densities range from 0.45g/cm3 to 0.62g/cm3 , and the pressure ranges from 58.0x106 Pa to 90.6×10^6 Pa; the homogenization temperatures at the retrograde alterationstage range from 356.2℃ to 428.6℃, the fluid salinity peak values range from 7.2%NJd to 15.5%naci, the densities range from 0.52g/ cm3 to 0.83g/cm3, the metallogenic pressure ranges from 23.8×10^6 Pa to 29.7 × 10^6 Pa, and the metallogenic depth ranges from0.90km to 1.12km with an average of 0.95km. These data indicate that the ore-forming fluid of the Tieshan Fe-Cu deposit has the characteristics of high temperature, moderate-low salinity, and low density. Therefore, the Tieshan Fe-Cu deposit is an epithermal skari deposit. Composition analysis of grouped fluid inclusions indicates that gaseous composition is dominated by H 2O and CO2, fo l-lowed by small amounts of CH 4, C2 H6, N2 and H2S, the cations of liquid composition are dominated by Na＋, Ca2＋ and K＋, and the an-ions are dominated by SO42 and Cl. The results show that Cl , SO42 and carbonate complexes played an important role in migration and enrichment of iron. The mixing of fluids of different origins and the evolution of pH might have been the dominant enrichment and precipitation mechanism of the Tieshan Fe-Cu deposit.

关 键 词：成矿流体 铁的迁移形式 富集沉淀机制 铁山铁铜矿床 

分 类 号：P618.2[天文地球—矿床学]