豆荚状铬铁矿中不同类型矿物包裹体成因及指示意义  

Genesis and significance of different types of mineral inclusions in podiform chromitite

作　　者：熊发挥[1,2] 徐向珍 杨胜标[1] 闫金禹 张博杨 曹楚奇 孙怡 杨经绥 XIONG Fa-hui;XU Xiang-zhen;YANG Sheng-biao;YAN Jin-yu;ZHANG Bo-yang;CAO Chu-qi;SUN Yi;YANG Jing-sui(Center for Advanced Research on Mantle,Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China)

机构地区：[1]地幔研究中心,自然资源部深地动力学重点实验室,中国地质科学院地质研究所,北京100037 [2]南方海洋科学与工程广东省实验室(广州),广东广州511458 [3]中国地质大学(北京),北京100083 [4]南京大学地球科学与工程学院,江苏南京210023

出　　处：《岩石矿物学杂志》2022年第2期413-436,共24页Acta Petrologica et Mineralogica

基　　金：南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0201);国家自然科学基金项目(92062215,42172069,41720104009);青藏高原第二次科学考察专项(2019QZKK0801);自然资源部深地动力学重点实验室自主研究课题(J1901-28);中国地质调查局项目(DD20221817,DD20221657)。

摘　　要：豆荚状铬铁矿是十分重要的战略资源,目前学者对它们的成因尚未形成统一的认识。先前的研究主要从岩石学、地球化学和地质年代学等方面对铬铁矿的成因进行了约束,但对铬铁矿包裹体类型及其反映的地质过程还缺乏系统的总结和研究。通过对不同岩体的铬铁矿中矿物包裹体进行详细的研究,发现铬铁矿中含有丰富的矿物包裹体,分为5大类:(1)无水硅酸盐类矿物包裹体,包括橄榄石、斜方辉石、单斜辉石等;(2)含水矿物,包括角闪石、绿泥石、蛇纹石等;(3)含铂族元素矿物和硫化物,包括Os-Ir合金、Pt-Fe合金、自然Os和自然Ir,以及黄铁矿、黄铜矿、磁黄铁矿等;(4)壳源矿物,包括锆石、金红石、石英、钙铬榴石等;(5)异常矿物,包括金刚石、碳硅石、柯石英等超高压矿物,以及自然镍、自然铬、自然铁和自然钛等。通过对比研究,确定它们形成于不同期次,进而初步拟定豆荚状铬铁矿形成过程存在4个阶段,分别为地幔深部的地幔柱/地幔对流、大洋岩石圈中地幔橄榄岩的部分熔融/岩浆结晶分异、俯冲带环境中的岩石-熔体反应和后期的热液蚀变/流体改造。认为铬铁矿中矿物包裹体记录了铬铁矿成矿各个时期的环境条件,针对铬铁矿中包裹体的详细研究可以更加准确地揭示铬铁矿的形成过程。Podiform chromite is a very important strategic resource,and scholars have not an unified understanding of its origin.Previous studies mainly constrained the genesis of chromitite from petrology,geochemistry and geochronology.It is still deficient in systematic summary and research about the inclusion types and their implications on geological processes.According to the detailed study of different chromitite bodies,the mineral inclusions can be divided into five catagories:(1)Anhydrous silicate mineral inclusions,including olivine,orthopyroxene,clinopyroxene,etc.;(2)Hydrous minerals,including hornblende,chlorite,serpentine,and apatite;(3)Platinum group minerals(PGM)and sulfides,including Os-Ir alloy,Pt-Fe alloy,natural Os and natural Ir,as well as pyrite,chalcopyrite,pyrrhotite,etc.;(4)Crust source minerals,including zircon,rutile,quartz,calcium chromium garnet,etc.;(5)Exotic minerals,including ultra-high pressure minerals such as diamond,moissanite,coesite,and natural nickel,natural chromium,natural iron and natural titanium,etc.Through comparative studies,it is determined that they were formed in different stages,and it is preliminarily proposed that there are four stages of the formation of podiform chromitite,which are the mantle plume/mantle convection in the deep mantle,partial melting/magma crystallization differentiation of the mantle peridotite in the oceanic lithosphere,melt-rock reaction in the super subduction zone,and hydrothermal alteration/fluid modification in the later stage.It is believed that the mineral inclusions in chromitite have recorded the environmental conditions of various periods of chromite formation,and can reveal the formation process of chromitite more accurately.

关 键 词：豆荚状铬铁矿 蛇绿岩 矿物包裹体 氧逸度 多阶段 成因 

分 类 号：P578.46[天文地球—矿物学] P588.125[天文地球—地质学]