陕西煎茶岭镍矿床亲铜元素地球化学特征及其地质意义  

Geochemical Characteristics of Chalcophile Elements in Jianchaling Nickel Deposit of Shaanxi,China and Their Geological Significance

作　　者：栾燕[1,2,3] 王瑞廷 白世恒 刘民武 焦建刚[1,2,3] LUAN Yan;WANG Rui-ting;BAI Shi-heng;LIU Min-wu;JIAO Jian-gang(School of Earth Science and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;Laboratory of Mineralization and Dynamics,Chang'an University,Xi'an 710054,Shaanxi,China;Xi'an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Chang'an University,Xi'an 710054,Shaanxi,China;Northwest Nonferrous Geological and Mining Group Co.,Ltd.,Xi'an 710054,Shaanxi,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学成矿作用及其动力学实验室,陕西西安710054 [3]长安大学西安市关键金属成矿与高效利用重点实验室,陕西西安710054 [4]西北有色地质矿业集团有限公司,陕西西安710054

出　　处：《地球科学与环境学报》2023年第5期1132-1148,共17页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41603040,41503035);陕西省自然科学基础研究计划项目(2023-JC-YB-239,2022JM-152);中央高校基本科研业务费专项资金项目(300102271201)。

摘　　要：煎茶岭镍矿床是陕西省勉略宁矿集区最具代表性的矿床之一,其形成与热液蚀变密切相关,形成了滑镁岩型、蛇纹岩型、透闪岩型和菱镁岩型等4种镍矿石。对煎茶岭镍矿床矿石全岩主量、微量和亲铜元素开展系统研究,并结合自动矿物识别系统,查明煎茶岭镍矿床亲铜元素的分布特征和赋存状态,并进一步探讨矿床成因。结果表明:煎茶岭镍矿床中的Ni和Cu主要以镍黄铁矿和黄铜矿的形式存在,而Co主要以类质同象赋存于镍黄铁矿和磁黄铁矿等硫化物中;Ir和Ru主要赋存于镍黄铁矿中,Pt和Pd主要赋存于黄铜矿中;Rh与其他铂族元素(PGE)明显不同的地球化学特征表明母岩浆侵位前可能发生了含铑矿物的结晶分异。同时,较高的Cu/Pd值((2.82~10.9)×10^(4))也表明其母岩浆在深部经历了早期硫化物熔离作用,随之带走大量Cu、Ni、PGE等,这是煎茶岭镍矿床矿石铂族元素亏损的主要原因。综合分析推断,煎茶岭镍矿床的形成经历了两个阶段:(1)煎茶岭镍矿床母岩浆侵位到浅部岩浆房之后,发生硫化物二次熔离形成Co、Ni含量较低的贫硫化物矿石;(2)橄榄石等硅酸盐矿物和原生硫化物在热液蚀变过程中释放出Co、Ni、S等成矿元素,并随热液迁移到花岗斑岩外接触带发生再沉淀和富集,从而形成富钴镍矿体。Jianchaling nickel deposit is one of the most representative deposits in Mian-Lue-Ning ore-concentrated area of Shaanxi,and its genesis is closely related to the alteration hydrothermal fluid.Four types of nickel ores have been identified in Jianchaling nickel deposit,including talc-magnesite type,serpentinite type,tremolite type and magnesite type.According to the systematic studies on the major,trace and chalcophile elements compositions,combined with the TESCAN integrated mineral analyzer,the distribution characteristics and occurrence states of chalcophile elements in Jianchaling nickel deposit have been determined for the further investigation of the deposit genesis.The results show that the Ni and Cu in Jianchaling nickel deposit are mainly displayed as independent minerals of pentlandite and chalcopyrite,respectively;however,Co is mainly associated with pentlandite and pyrrhotite due to the isomorphism.Meanwhile,Ir and Ru are mainly associated with pentlandite,while Pt and Pd are mainly associated with chalcopyrite.The geochemical characteristics of Rh are obviously different from the other PGEs,indicating the crystallization and differentiation of Rh-bearing minerals before the emplacement of the parental magma.Meanwhile,the higher Cu/Pd ratio((2.82-10.9)×10^(4)) also indicates the early sulfide segregation in the deep,which subsequently carried away a large amount of Cu,Ni and PGE,leading to PGE depletions of Jianchaling nickel ore.Based on comprehensive analysis,it is inferred that the formation of Jianchaling nickel deposit can be divided into two stages:(1) when Jianchaling parental magma intrudes into the shallow magma chamber,second-stage sulfide S saturation occurs to form the primary sulfide-poor ores with low contents of Co and Ni;(2) during the hydrothermal alteration process,olivine and primary sulfides release ore-forming elements such as Co,Ni,S and so on,which migrate with the hydrothermal fluid to the outer contact zone of the granite porphyry for re-precipitation and enrichment,resulting

关 键 词：镍矿床 亲铜元素 元素分布 硫化物熔离 热液蚀变 矿床成因 勉略宁矿集区 

分 类 号：P578[天文地球—矿物学] P599[天文地球—地质学]