岩浆-热液成矿系统中铁同位素地球化学研究现状  

Status and progress on geochemical behavior of iron isotope in magmatichydrothermal system

作　　者：王续文 李宇轩 安芳[1] WANG XuWen;LI YuXuan;AN Fang(State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,Shaanxi,China)

机构地区：[1]大陆动力学国家重点实验室西北大学地质学系,陕西西安710069

出　　处：《矿床地质》2023年第6期1214-1228,共15页Mineral Deposits

基　　金：国家自然科学基金项目(编号:42273062、42130102);西北大学地质学系科研基金项目的联合资助。

摘　　要：铁元素是岩浆-热液成矿系统中参与成矿的重要金属元素之一,岩浆-热液矿床中富铁矿物(黄铁矿、磁铁矿、黄铜矿、磁黄铁矿、斑铜矿、毒砂、菱铁矿)的δ^(56)Fe值变化较大(-2.07‰~+1.58‰),指示铁同位素在岩浆演化、流体出溶和热液演化过程中均存在明显的分馏,因此,在约束岩浆-热液成矿系统中成矿金属的迁移-富集-沉淀过程和示踪成矿物质来源方面具有巨大的应用潜力。通过整理和分析前人研究资料,文章总结了岩浆-热液成矿系统岩浆演化、流体出溶和热液演化过程中铁同位素地球化学行为的研究现状。岩浆演化过程中铁同位素会发生显著分馏,如部分熔融过程中,熔体相比残余固相富集重铁同位素;矿物分离结晶会引起残余熔体铁同位素组成的变化,主要受含Fe2+或Fe3+矿物结晶的影响,如磁铁矿分离结晶会导致残余熔体铁同位素组成变轻,总体反映岩浆氧化还原状态对铁同位素分馏的主要控制作用,因此,含矿岩体铁同位素组成及其变化可用于确定岩浆的氧化还原状态。流体出溶是含矿岩浆演化成为岩浆热液矿床的关键过程,出溶流体相对于母岩富集轻铁同位素,但实验研究表明出溶流体铁同位素组成可能受其中铁的迁移形式、与流体平衡的含Fe2+或Fe3+矿物的比例、相分离和流体混合等多种因素影响。热液演化过程中,含铁热液矿物沉淀会引起流体铁同位素组成的变化,磁铁矿沉淀会导致流体富集轻铁同位素,而含铁硫化物(如磁黄铁矿)沉淀则会使得流体逐渐富集重铁同位素,显示热液流体氧化还原状态对铁同位素分馏的控制作用。由于黄铜矿被认为可以有效记录流体的铁同位素组成,其铁同位素值被用于区分热液流体氧化还原状态。铁元素作为岩浆-热液成矿系统中直接参与成矿的元素,为直接示踪成矿物质来源提供了可能性,然而,岩浆演化、流体�Iron element is one of the important metal elements involved in mineralization in the magmatic-hydrothermal metallogenic system.The δ^(56)Fe values of iron-rich minerals(pyrite,magnetite,chalcopyrite,pyrrhotite,bornite,arsenopyrite,siderite)in magmatic-hydrothermal deposits vary considerably(-2.07‰~+1.58‰),indicating that the iron isotope has obvious fractionation during the magmatic evolution,fluid exsolution and hydrothermal evolution,therefore,it has great application potential in constraining the migration-enrichment-precipitation process of ore-forming metals and tracing the source of ore-forming materials in the magmatic-hydrothermal metallogenic system.Based on sorting out and analyzing the data of previous studies,this paper summarizes the research status of iron isotope geochemical behavior in magmatic evolution,fluid exsolution and hydrothermal evolution of magmatic-hydrothermal metallogenic system.The iron isotope will undergo significant fractionation in the process of magmatic evolution,and the melt phase is enriched in heavy iron isotope than the residual solid phase during partial melting;the iron isotope composition of the residual melt is changed due to the separation and crystallization of minerals,which are mainly affected by the crystallization of minerals containing Fe^(2+) or Fe^(3+),for example,separation and crystallization of magnetite will lead to enrichment of light iron isotope composition in the residual melt,which generally reflects the main control of the redox state of magma on the fractionation of iron isotopes.Therefore,the composition and variation of iron isotope in ore-bearing rocks can be used to determine the redox state of magma.Fluid exsolution is a key process in the evolution of ore-bearing magma into magmatic hydrothermal deposits,the exsolution fluid is rich in light iron isotope relative to the host rock,however,the experimental studies show that the iron isotope composition of the exsolution fluid may be affected by many factors,such as the migration form of iro

关 键 词：FE同位素 岩浆-热液成矿系统 地球化学行为 应用研究现状 

分 类 号：P618.31[天文地球—矿床学]