吉林省大横路铜钴矿复杂的沉积-变质变形-热液作用演化过程及其对钴的赋存状态和富集成矿的制约  

Complex evolution of the sedimentation,metamorphismdeformation and hydrothermal processes and their constraints on the occurrence,enrichment and mineralization of Co in the Dahenglu Cu-Co deposit,Jilin Province

作　　者：王慧宁 刘福来[1] 朱志勇 王舫[1] 田忠华[1] WANG HuiNing;LIU FuLai;ZHU ZhiYong;WANG Fang;TIAN ZhongHua(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2023年第4期998-1018,共21页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(92062214);国家重点研发计划项目(2022YFC2903502);中国地质科学院地质研究所基本科研业务费项目(J2009)联合资助。

摘　　要：吉林省白山市大横路铜钴矿为国内少有的沉积-变质变形-热液等多种成因叠加改造的大型钴矿床,是综合研究古元古代造山带钴复杂成矿作用过程的理想地区。目前,有关该矿床中钴的赋存状态、富集迁移规律及复杂的成矿过程等方面的研究十分薄弱。本文采集矿床内典型钻孔样品,通过精细的矿相结构观察、扫描电镜物相分析、X射线元素面扫描和矿物成分定量分析等综合研究,发现大横路铜钴矿床经历了多期多阶段复杂的沉积-变质变形-热液作用,钴主要以Co的独立矿物(硫镍钴矿和辉砷钴矿),类质同象进入富Co黄铁矿和在磁黄铁矿中发育钴镍黄铁矿出溶体等形式存在。该矿床成矿作用分为以下5个阶段:沉积阶段以黄铁矿-磁黄铁矿-黄铜矿呈极细粒包体零星分布为特点;变质变形阶段以硫镍钴矿-磁黄铁矿-黄铜矿组合沿绢云母-黑云母-石英变质千枚理定向分布为特点,变质程度达高绿片岩相;早期热液作用主要沉淀粗大脉状磁黄铁矿及其钴镍黄铁矿出溶体;中期热液作用以条带状自形富Co黄铁矿和硫镍钴矿为标志,该阶段为Co富集成矿的主成矿期;网脉状黄铜矿沉淀对应于最晚期热液作用,同时发育极少量细粒辉砷钴矿。矿体的蚀变类型以硅化、碳酸盐化、钠长石化和绿泥石化为主,次为钾长石化和绢云母化。其中,硅化、铁白云石化和钠长石化蚀变稍早于金属硫化物形成,为金属硫化物的沉淀与富集提供了有利条件;辉砷钴矿的沉淀与钠长石的绿泥石化、钾长石化和绢云母化等蚀变作用关系密切。由此可见,多期多阶段沉积-变质变形-热液事件对Co的迁移-富集起着关键的控制作用,不同的变质变形-热液演化阶段均存在富Co硫化物的沉淀,Co的赋存形式也存在明显差异。富Co黄铁矿和硫镍钴矿为大横路铜钴矿Co最主要的赋存形式。综上所述,在辽-吉古元古造山带The Dahenglu Cu-Co deposit in Baishan City,Jilin Province,is a large cobalt deposit in Northeast China.It is an ideal research area in investigating the multi-metallogenic processes within the Paleoproterozoic orogenic belt,whose genesis is controlled by multi-factors such as sedimentation,metamorphism and hydrotherm.At present,the occurrence,enrichment and migration of cobalt and the complex mineralizing processes of this deposit were poorly studied.In this study,representative drilling samples from the Dahenglu Cu-Co deposit were investigated in terms of detailed mineral texture observations,scanning electron microscope analysis,X-ray element mapping,and quantitative analysis of mineral compositions.It is revealed that the Dahenglu Cu-Co deposit underwent multiple stages of sedimentation,metamorphism and hydrothermal alterations.The cobalt in this deposit mainly exists in the form of independent minerals(i.e.,siegenite,cobaltite and cobalt pentlandite),isomorphism in Co-enriched pyrite and exsolution of cobalt pentlandite in pyrrhotite.The pristine sedimentary stage is marked by the formation of very fine mineral inclusions of pyrite-pyrrhotite-chalcopyrite.The metamorphic stage is represented by the oriented siegenite-pyrrhotite-chalcopyrite aggregates that are distributed along the phyllitic foliation defined by high-greenschist-facies sericite-biotite-quartz assemblage.The precipitation of coarse-veined pyrrhotite and cobalt pentlandite exsolution within it defines the early-stage hydrothermal metasomatism.The subsequent hydrothermal stage is marked by the formation of banded euhedral Co-enriched pyrite and siegenite,which represents the main metallogenic epoch.The precipitation of chalcopyrite occurs during the late hydrothermal metasomatism,which is accompanied by the growth of fine-grained cobaltite.The alteration mainly includes silication,carbonatation,albitization,and chloritization,along with potassic feldspathization and sericitization.The silication,ankeritization,and albitization predate the metal

关 键 词：辽-吉古元古造山带 大横路大型铜钴矿 钴赋存状态 沉积-变质变形-热液作用 蚀变类型 关键控制因素 

分 类 号：P618.41[天文地球—矿床学] P618.62[天文地球—地质学]