西藏甲玛铜多金属矿床角岩中黑云母矿物化学特征及地质意义  

Mineral Chemical Characteristics of Biotites from Hornfels in the Jiama(Gyama) Polymetallic Copper Deposit of Tibet and Their Geological Significance

作　　者：王崴平[1] 唐菊兴[2] 应立娟[2] 

机构地区：[1]中国地质科学院研究生部,北京100037 [2]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《地球学报》2012年第4期444-458,共15页Acta Geoscientica Sinica

基　　金：国家973项目(编号:2011CB403103);危机矿山接替资源找矿专项典型矿床及成矿规律总结研究项目(编号:20089932);青藏专项(编号:1212010012005)联合资助

摘　　要：甲玛铜多金属矿床角岩中黑云母按其产状可区分为原生黑云母和热液黑云母,本文采用扫描电镜对两类产出状态的黑云母进行了观察,采用电子探针(EPMA)对这两类黑云母进行了微区原位成分分析,并根据电子探针数据计算了黑云母的矿物化学式。角岩中的原生黑云母和热液黑云母均属于镁质黑云母,二者都经受了热液流体的改造作用。从原生黑云母到热液黑云母Fe3+和Fe2+分异程度加大,Fe3+含量升高,Fe2+含量降低,指示了岩浆-热液流体逐渐向氧化态过渡。相比于原生黑云母,Cu元素更易于在热液黑云母中富集。角岩型矿石中的Cu含量与热液黑云母的Fe2+/(Fe2++Mg2+)比值呈正相关,与其Fe3+/Fe2+比值呈负相关,对于热液黑云母所在的角岩型岩矿石样品,其矿化强度或可以黑云母的Fe2+/(Fe2++Mg2+)比值来衡量;而Mo元素在两类黑云母中均广泛分布,不具有选择性赋存的特征。Biotite from hornfels in the Jiama（Gyama） polymetallic copper deposit can be classified into primary biotite and hydrothermal one. Two sorts of biotite were observed by SEM and measured by EMPA. The authors calculated the chemical formula of biotite on the basis of EMPA data. Both primary and hydrothermal biotites are magnesian biotites and have experienced hydrothermal alterations. Magma-hydrothermal fluids were gradually converted into oxidation state, as evidenced by the increase of Fe^3＋ and decrease of Fe^2＋, the increasing differentiation between Fe^3＋ and Fe^2＋, and the decrease of K, Na and Ca content from primary biotite to hydrothermal one. Compared with things of primary biotite, more Cu was likely to be concentrated in hydrothermal biotite. The Cu content of rocks has positive correlation with Fe^2＋/（Fe^2＋＋Mg^2＋） of biotite, and negative correlation with Fe^3＋/Fe^2＋ in hydrothermal biotites, which suggests that the mineralization intensity of hornfels-type ores containing hydrothermal biotites might be judged by Fe^2＋/（Fe^2＋＋Mg^2＋） ratio of hydrothermal biotites; nevertheless, Mo is spread in two sorts of biotite diffusely, and doesn＇t have characteristics of selective occurrence.

关 键 词：角岩 原生黑云母 热液黑云母 镁质黑云母 化学特征 Cu Mo 成矿指示 SEM EMPA 

分 类 号：P578.959[天文地球—矿物学] P588.311[天文地球—地质学]