大横路钴铜矿电气石及方解石稀土元素、同位素组成及其对成矿过程的指示  

Tracing the ore forming process of Dahenglu copper-cobalt deposit with the rare earth elements and isotopic compositions of tourmaline and calcite

作　　者：朱志勇 佘宇伟 马健雄 潘辰旭 姜杭云 冀磊 ZHU ZhiYong;SHE YuWei;MA JianXiong;PAN ChenXu;JIANG HangYun;JI Lei(MNR Key Laboratory of Isotope Geology,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;SinoProbe Lab,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]自然资源部同位素地质重点实验室,中国地质科学院地质研究所,北京100037 [2]自然资源部深地科学与探测技术实验室,中国地质科学院地质研究所,北京100037 [3]中国地质科学院,北京100037

出　　处：《岩石学报》2024年第10期3010-3027,共18页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2022YFC2903502);国家自然科学基金项目(92062214);中国地质科学院基本科研业务费重点攻关项目(JKYZD202311)联合资助.

摘　　要：大横路钴铜矿钴的储量为2.7万t,它是我国大型的钴矿床,其经历了复杂的沉积-变质作用,长期以来被认为是典型的沉积-变质型矿床。其热液期成矿作用可能被低估,本研究通过详细的岩相-矿相学观察,证实了除变质流体外,确实有岩浆热液作用参与了成矿过程。本研究对方解石锶同位素,电气石硼同位素进行了激光微区分析。电气石硼同位素在空间上有显著变化,自热液脉至基质由-4‰降低至-14‰左右;电气石与方解石锶同位素(^(87)Sr/^(86)Sr)并无显著差异,其平均值分别为1.0896和1.0948,略低于全岩的平均值1.1063。尽管目前还无法定量估算岩浆热液对成矿物质的贡献,但是本研究表明岩浆热源所驱动的热液促进了成矿元素的氧化、活化和迁移;然后热液在赋矿层位的碳质千枚岩中还原沉淀,这是岩浆热液期最主要的成矿方式。但是岩浆热液在成矿物质上并无显著贡献,且本次研究暂未发现海相蒸发岩参与成矿的证据。因而,方解石与电气石单矿物微量元素和同位素组成是重建热液成矿作用过程的重要指示矿物。The Dahenglu copper-cobalt mine is classified as a large cobalt deposit in China,which has experienced complex sedimentary-metamorphic effects and has long been considered a typical sedimentary-metamorphic deposit.However,the late-stage hydrothermal mineralization may have been underestimated.In this study,we proved that the magmatic-hydrothermal fluid was involved in the mineralization process through detailed petrographic-mineralogical observations,in addition to metamorphic fluids mineralization.In-situ calcite strontium isotope,tourmaline boron isotope was analyzed.Boron isotope varies from the vein(ca.-4‰)to the matrix(ca.-14‰).Strontium isotope does not show differences between tourmaline and calcite,with the average of 1.0896 and 1.0948,respectively.Both of which are slightly lower than that of whole rock.Although it is impossible to quantitatively estimate the contribution of magmatic-hydrothermal fluids to mineralization currently,this study shows that the hydrothermal fluid driven by the magmatic heat promotes the oxidation,activation,and migration of cobalt by in-situ calcite strontium isotope,tourmaline boron isotope,and trace elements techniques.Then the fluid was reduced and precipitated in the calcite-quartz veins,which was the most important way of mineralization during the magmatic hydrothermal ore-forming stage.However,the magmatic-hydrothermal fluid did not contribute significantly to mineralization in the aspect of cobalt source,and no evidence of marine evaporites participating in mineralization was found in this study.Therefore,the trace element and isotopic compositions of calcite and tourmaline are important indicator minerals for the reconstruction of hydrothermal mineralization.

关 键 词：成矿过程 硼同位素 锶同位素 电气石 方解石 稀土元素 

分 类 号：P578.61[天文地球—矿物学] P578.953[天文地球—地质学] P618.62