川西里伍铜矿富钴磁黄铁矿的首次发现及结晶条件  

First Discovery and Crystallization Conditions of Co-rich Pyrrhotite From Liwu Copper Deposit in Western Sichuan Province

作　　者：张先泽 王昌南[1] 余祥龙 杨光源[1] ZHANG Xianze;WANG Changnan;YU Xianglong;YANG Guangyuan(Sichuan Liwu Copper Mining Company,Ganzi,Scichuan 626099,China)

机构地区：[1]四川里伍铜业股份有限公司,四川甘孜626099

出　　处：《中国锰业》2023年第2期47-53,共7页China Manganese Industry

基　　金：国家自然科学基金青年科学基金项目(编号:41902068);中国地质调查局成都地质调查中心项目(编号:CDG2019-KF-SK-001)。

摘　　要：江浪穹隆位于松潘-甘孜造山带东南缘,其核部产出的里伍式富铜矿床主要金属硫化物为磁黄铁矿、黄铜矿和闪锌矿。为了查明磁黄铁矿的化学组成和结晶条件,研究针对里伍铜矿致密块状和条带状矿石中的磁黄铁矿开展了显微观察与电子探针成分分析。结果显示这些磁黄铁矿:①主要元素组成为Fe和S,前者含量62.30%~59.13%,平均60.14%,后者含量39.33%~37.36%,平均38.59%,计算平均化学式Fe_(0.891)S;②具有极高的Co元素含量,介于0.79%~0.21%,平均0.49%,可能与Fe呈类质同象的形式存在;③属于高温六方晶系,结晶温度300~556℃,平均411℃;④产于较低的硫逸度环境,计算获得lg f(S_(2))介于-2.88~-11.50,平均-7.11。结合过去的成果资料,认为里伍式富铜矿床形成于中-高温热液作用,且低硫逸度条件可能更有利于富钴磁黄铁矿的形成。研究首次报道了里伍矿田磁黄铁矿富含战略性关键矿产之一的Co元素,对后续勘查找矿和综合评价具有重要指导意义。Jianglang dome is located on the southern margin of the Songpan-Garze orogenic belt with the high-grade Cu deposits in its core.The main metal sulfides are pyrrhotite,chalcopyrite and sphalerite.To explore the chemical composition and crystallization conditions of pyrrhotite grains in massive and banded ores by carrying out an analysis of microscopic observation and electron probe.The results show that these pyrrhotite grains:①It has major elements of Fe(62.30%-59.13%,with an average of 60.14%)and S(39.33%-37.36%,with an average of 38.59%)with calculated average chemical formula of Fe_(0.891)S.②It shows extremely high content of Co(0.79%-0.21%,with an average of 0.49%),which may exist in the form of isomorphism with Fe.③It belongs to high-temperature hexagonal system with crystallization temperatures of 300-556°C and an average of 411℃.④It is formed in low sulfur fugacity environment with calculated lg f(S_(2))between-2.88 and-11.50.And its average is-7.11.Combined with previous studies,it is considered that the Liwu-type high-grade copper deposit was formed in medium-high temperature hydrothermal process.The low sulfur fugacity condition was likely more conducive to the formation of Co-rich pyrrhotite.This paper firstly reports that pyrrhotite grains in Liwu ore field are rich in Co,which is one of the strategic key minerals.This discovery has important guiding significance for subsequent exploration and comprehensive evaluation.

关 键 词：富钴磁黄铁矿 化学组成 结晶条件 里伍铜矿 江浪穹隆 

分 类 号：P581[天文地球—岩石学]