安徽安庆铁铜矿床物质来源与演化——地质和硫、碳、氧同位素制约  

Sources and Evolution of the Ore-forming Materials in the Anqing Cu-Fe Deposit in Anhui Province——Geological and S, C, O Isotopic Constraints

作　　者：杨光树[1] 温汉捷[2] 胡瑞忠[2] 范良伍 燕永锋[1] 毛致博 王凯[1] YANG Guangshu;WEN Hanjie;HU Ruizhong;FAN Liangwu;YAN Yongfeng;MAO Zhibo;WANG Kai(Faculty of Land Resource Engineering,Kunming University of Science and Technology,Kunming 650093,Yunnan,China;Institute of Geochemistry,Chinese Academy of Science,Guiyang 550081,Guizhou,China;Beijing Sinoking Resource Company,Beijing 100012,China)

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650093 [2]中国科学院地球化学研究所,贵州贵阳550081 [3]北京华盛金泰资源科技有限公司,北京100012

出　　处：《大地构造与成矿学》2018年第4期651-663,共13页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(41103026; 41373050);国家重点研发计划(2017YFC0602500)联合资助

摘　　要：安庆铁铜矿床是安徽沿江地区具代表性的大型铁铜矿床之一,其形成机制一直存在较大争议。本文在分析成矿地质特征的基础上,研究了矿石和围岩的硫、碳、氧同位素组成特征,探讨了该矿床的成矿物质来源与成矿过程。研究结果表明,矿床具有显著的水平分带特征。矿石硫化物δ^(34)S值范围为-6.5‰～10.6‰,变化大,闪长岩浆为成矿提供了大部分硫,前三叠纪碎屑地层和三叠纪围岩提供了部分硫;从闪长岩体到围岩,δ^(34)S值呈V字型变化,是不同来源硫混合的结果。碳酸盐矿物δ^(13)C范围为-5.5‰～2.0‰,从外带到内带呈下降趋势,表明碳主要源自岩浆热液,混入了部分地层碳。近矿围岩中δ^(13)C和δ^(18)O值相对地层偏低,是流体改造作用的结果。外接触带致密块状磁铁矿体具有最低的δ^(18)O值和部分贯入成因地质特征,可能为高温流体沿接触带和断层贯入充填的产物。综合研究认为,该矿床可能存在流体贯入充填与热液交代两种成矿形式。高温富铁流体贯入接触带形成了外带块状磁铁矿体,其分异热液与闪长岩体的交代作用、地层流体混入等综合作用形成了矽卡岩型铜矿体和含铜蚀变闪长岩,二者在空间上的叠加构成了矽卡岩型铁铜矿床,不同成矿方式的叠加导致了矿床分带及元素迁移特征有别于典型矽卡岩矿床。The Anqing Cu-Fe deposit is one of the representative large Cu-Fe deposits along the Yangtze River in Anhui province,with controversial metallogenic mechanism.Based on the ore-forming geological characteristics,this paper focus on the sulfur,carbon and oxygen isotopic compositions of the ores and surrounding rocks,and discuss the sources and evolution processes of the ore-forming materials.The Cu-Fe deposit occurs in the contact zone between the early Yanshanian Yueshan diorite and Triassic marble,with clear horizontal zonings in the skarns and ore bodies.The garnet skarn and thick massive magnetite ore body commonly occur within the external contact zone,which have clear boundaries with the surrounding rocks;whereas the diopside skarns with disseminated copper sulfide commonly occur within the internal contact zone and show gradual and transitional relations with the diorite.Theδ34S values of the ores range from-6.5‰to 10.6‰,and show a V-shaped trend from the diorite to the outer marble.This compositional variation indicates that most of the sulfur may come from magma,with involvement of some pre-Triassic clastic strata sulfur and Triassic marine sulfates in the later stage.Theδ13C values of the gangue minerals range from-5.5‰to 2.0‰,which decrease from the external contact zone to internal contact zone,indicating that the carbons of the ore-forming fluids may be mainly derived from magma,with some Triassic carbonate stratigraphic carbon involved.The marbles nearby the orebody showδ18O values lower than those of the Triassic strata,indicating that they have been remolded by the lowδ18O magmatic hydrothermal fluids.The magnetite have some magma filling geological features and extremely lowδ18O value,may be the result from the filling of the high temperature iron-rich fluids along the contact zone and fault.This study shows that the ore-magma filling type and hydrothermal-metasomatic type ore bodies coexist in the Anqing Fe-Cu deposit.The immiscibility between iron oxide and silicate melt occurred in

关 键 词：安庆铁铜矿床 矽卡岩 硫、碳、氧同位素 成矿过程 成矿物质来源 

分 类 号：P611[天文地球—矿床学]