金山金矿热液蚀变粘土矿物特征及水-岩反应环境研究  

CHARACTERISTICS OF CLAY MINERALS DERIVED FROM HYDROTHERMAL ALTERATION IN JINSH AN GOLD DEPOSIT:IMPLICATION FOR THE ENVIRONMENT OF WATER-ROCK INTERACTION

作　　者：华仁民[1] 李晓峰[1] 张开平 季峻峰[1] 张文兰[1] 

机构地区：[1]南京大学地球科学系成矿作用研究国家重点实验室,江苏南京210093 [2]江西省金山金矿,江西德兴334200

出　　处：《矿物学报》2003年第1期23-30,共8页Acta Mineralogica Sinica

基　　金：国家自然科学基金重点项目 (批准号 :4973 3 12 0 )

摘　　要：粘土矿物是流体作用过程中水 岩反应的产物 ,因此其特征反映了流体活动的特征和水 岩反应的环境。金山金矿蚀变粘土矿物主要由伊利石和绿泥石组成 ,其中 ,蚀变糜棱岩中的伊利石含量大于绿泥石含量 ;而蚀变超糜棱岩中的绿泥石含量大于伊利石含量。蚀变糜棱岩中伊利石的多型为 2M1,超糜棱岩中为 2M1和 1M。金山金矿蚀变绿泥石的成份分析结果表明其为富铁绿泥石 ,由蠕绿泥石、铁镁绿泥石和密绿泥石组成 ,绿泥石中Fe、Mg质组分不仅来自围岩 ,而且也有一部分来自流体。利用地质温度计计算绿泥石的形成温度为 2 0 6～ 2 5 8℃ ,流体的f(O2 )为 1 0 -2 9.56～ 1 0 -3 1.48。本文认为金山金矿热液蚀变为酸性蚀变 ,其环境为还原环境 ,流体作用的水/岩比较高 ;在水 岩反应过程中 ,流体中的Fe、Mg、Si为带出组分。粘土矿物的形成机制为溶解 迁移 沉淀。Clay minerals are the products of water rock interaction in many geol ogical processes, e.g. weathering, diagenesis, and hydrothermal alteration at lo wer middle temperatures. Their characteristics can be used as indicators of th e features of fluid flow and the environment and mechanism of water rock intera ction. In the Jinshan gold deposit clay minerals consist mainly of illite and c hlorite. Illite is more abundant than chlorite in altered mylonite, but less th an that in altered ultramylonite. Most of illite is of the 2 M 1 polytype, whereas some 1 M polytype is present in altered ultramylonite. Based on elec tronic microprobe analyses, chlorite in the Jinshan gold deposit is Fe rich and can be divided into three types, i.e., ripidolite, brunsvigite and pycnochlorit e. The Fe and Mg components of chlorite are derived not only from mudstone, but also from fluid. The calculated formation temperatures of chlorite lie between 206℃ and 258℃ as measured by chlorite geothermometry, and the calculated oxyge n fugacity of the environment is 10 -29.56 ～10 -31.48 . It is conclude d that hydrothermal alteration in the Jinshan gold deposit occurred in a reductive and acid environm ent with a relatively high fluid/rock ratio. Fe, Mg and Si were lost from fluid during water rock interaction. Dissolution transport precipitation is the fo rming mechanism of both illite and chlorite.

关 键 词：粘土矿物 流体作用 水-岩反应 金矿床 伊利石 绿泥石 形成机制 

分 类 号：P618.51[天文地球—矿床学] P578.94[天文地球—地质学]