富钴黄铁矿中钴微-纳米尺度赋存状态:以大横路铜钴矿为例  

Micro-to nanoscale cobalt occurrence in Co-enriched pyrite:A case study from Dahenglu Cu-Co deposit

作　　者：谢士稳[1] 刘福来[1] 王慧宁 王舫[1] 龙涛[1] XIE ShiWen;LIU FuLai;WANG HuiNing;WANG Fang;LONG Tao(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2024年第10期3028-3036,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(92062214);国家重点研发计划项目(2022YFC2903502);中国地质科学院基本科研业务费专项经费(JKYQN202312);中国地质调查项目(DD20242528)联合资助.

摘　　要：黄铁矿是重要的载钴矿物,自然界钴矿床中富钴黄铁矿的Co含量可达10%~20%,明显超出实验岩石学和理论计算获得的黄铁矿溶解Co的能力。目前,这些富钴黄铁矿溶解过饱和Co的机制以及Co过饱和黄铁矿是否出溶方硫钴矿尚不清楚。为探讨以上问题,本文选取吉林大横路Cu-Co矿中富钴黄铁矿为研究对象。能谱元素面扫描和电子探针分析结果显示,大横路富钴黄铁矿中Co呈不均匀分布且无规律,单颗粒Co含量变化范围较大(Py108为4.31%~9.74%、Py110为4.54%~8.83%),Co的不均匀很可能与黄铁矿的生长过程和结晶环境有关。透射电镜和原子探针分析结果显示,纳米尺度富钴黄铁矿中Co呈均匀分布,未见富Co的包裹体和方硫钴矿出溶体,Co以类质同象的形式替换Fe存在于富钴黄铁矿中。根据以上结果,我们认为大横路富钴黄铁矿中溶解过饱和的Co很可能与微晶尺寸效应有关,亚稳态Co过饱和FeS_(2)-CoS_(2)固溶体可以长期保持不变。Pyrite is an important Co-bearing mineral.The Co content of Co-enriched pyrite in natural cobalt deposits can reach 10%~20%,which is significantly higher than the solid solubility limit of Co in pyrite obtained from experimental and theoretical methods.At present,the mechanism of the dissolution of supersaturated Co in pyrite and whether the Co-supersaturated pyrite underwent cattierite exsolution are not clear.In order to solve the above issues,Co-enriched pyrite from Dahenglu deposit in Jilin Province was selected in this study.EDS elemental mapping and EPMA results show that Co distribution in Dahenglu Co-enriched pyrite is heterogeneous and irregular,and the Co contents of single pyrite grain are variable(4.31%~9.74%for Py108,4.54%~8.83%for Py110).The heterogeneity of Co distribution is probably related to the growth process and crystallization environment of pyrite.The results of TEM and APT show that Co distribution in Dahenglu Co-enriched pyrite is homogeneous at the nanoscale,and no Co-enriched inclusions and cattierite exsolution are identified,implying that Co is incorporated into Co-enriched pyrite by isomorphic substitution for Fe.According to the above results,we propose that the incorporation of supersaturated Co in Dahenglu Co-enriched pyrite is probably related to the crystallite size effect,and the metastable state of Co-supersaturated FeS_(2)-CoS_(2) solid solution can remain unchanged over a long period of time.

关 键 词：富钴黄铁矿 大横路铜钴矿 黄铁矿-方硫钴矿固溶体 钴赋存状态 微-纳米尺度 

分 类 号：P578.292[天文地球—矿物学] P618.62[天文地球—地质学]