滇东南茶花寨金矿床载金黄铁矿LA-ICPMS原位微量元素组成与地质意义  

The in-situ LA-ICPMS analyses of trace element compositions of gold-bearing pyrites in the Chahuazhai gold deposit,SE Yunnan and their geological significances

作　　者：陈威鸿 刘玉平[1] 杨昌毕 叶霖[1] 刘仕玉 苏文超[1] CHEN Weihong;LIU Yuping;YANG Changbi;YE Lin;LIU Shiyu;SU Wenchao(State Key Laboratory of Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of the Chinese Academy of Sciences,Beijing 100049,China;Yunnan Geological and Mineral Exploration and Development Bureau second geological team,Wenshan 663000,China;School of Resources and Environmental Engineering,Guizhou University,Guiyang 550025,China)

机构地区：[1]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵州贵阳550081 [2]中国科学院大学,北京100049 [3]云南省地质矿产勘查开发局第二地质大队,云南文山663000 [4]贵州大学资源与环境工程学院,贵州贵阳550025

出　　处：《矿物学报》2024年第1期122-132,共11页Acta Mineralogica Sinica

基　　金：云南省地质矿产勘查开发局第二地质大队项目(编号:E1FP003000)。

摘　　要：右江盆地是世界上卡林型金矿床最集中的地区之一,盆地南缘的滇东南地区是其重要组成部分。茶花寨金矿床为滇东南地区产于印支运动不整合面附近的代表性金矿床,黄铁矿为主要的载金矿物,其环带特征明显,为认识该区卡林型金矿成矿作用提供了理想的实例。本文在野外考察及镜下观察的基础上,通过LA-ICPMS分析技术,对茶花寨金矿床中不同期次黄铁矿开展了原位微量元素组成分析,以总结不同成矿阶段金的富集特征与关键控制因素。研究结果表明,该矿床黄铁矿存在3个期次:沉积成因的Py1,包括草莓状黄铁矿Py1a和环带状黄铁矿核部Py1b,交代成因的中间环带Py2,热液成因最外侧环带Py3。其中,Py1b富集Sb、Pb、Zn等元素,Py2富集As、Co、Ni,Py3则具有较高的Au、As、Cu、Sb含量和稍高的Se、Hg、Tl含量。三者对比显示,Py2中As含量最高,Py1b和Py2除As以外的其他微量元素含量接近或Py2中含量稍低,二者Co/Ni比值均在0.1附近,表明Py2为Py1b受热液交代改造形成;而Py3中微量元素组成与Py1b和Py2差异明显,指示其热液成因,且Py3中Co、Ni含量相较Py1b和Py2更低,Co/Ni比值在0.01~0.1之间,表明成矿流体温度较低且不富集Co、Ni,Py3中Co、Ni主要继承自Py1b和Py2。该矿床Au主要以晶格金的形式赋存在Py3中,其进入黄铁矿晶格与As、Sb、Cu、Se等元素相关。综上所述,茶花寨金矿床成矿流体为富集Au、As、Cu、Sb、Se、Tl等元素的低温热液流体,在到达赋矿地层后,交代Py1b形成高砷的中间环带Py2,流体中Au受高砷的Py2吸附聚集,在Py3形成过程中沉淀下来,最终以固溶体的形式赋存其中。The Youjiang Basin is one of the most concentrated areas of Carlin-type gold deposits in the world,and the SE Yunnan area on the southern margin of the basin is its important part.The Chahuazhai gold deposit is a representative gold deposit which occurred near the unconformity of Indosinian movement in the SE Yunnan.Pyrite is the main gold-bearing mineral with obvious zoning characteristics.This deposit provides an ideal example for understanding the Carlin-type gold mineralization in this area.In this paper,based on the field investigation and optical microscopy observation,and application of the in-situ laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)analytical technique,trace element compositions of pyrites in different stages have been analyzed,in order to summarize gold enrichment characteristics and key controlling factors of the gold mineralization in different stages of the Chahuazhai gold deposit.The results show that there are three types of pyrites in the deposit.They include the sedimentary originated pyrite(Py1),including framboidal pyrite(Py1a)and the core of zonal pyrite(Py1b),the middle zone of zonal pyrite(Py2)with the metasomatic origin and the rim of zonal pyrite(Py3)with the hydrothermal origin.Especially,the Py1b is enriched in Sb,Pb,Zn and other elements,whereas the Py2 is enriched in As,Co,and Ni.The Py3 has high contents of Au,As,Cu,and Sb,with relative slightly high contents of Se,Hg,and Tl.The comparison of those three types of pyrites shows that the Py2 has the highest As content,while the Py1b has similar or relative slightly low contents of trace elements comparing to the Py2 with the exception of As.The Py1b and Py2 have Co/Ni ratios around 0.1,indicating that the Py2 was formed by hydrothermal metasomatic transformation of the Py1b.The Py3 has significantly different trace element compositions to those of the Py1b and Py2,indicating its hydrothermal origin.Moreover,the Py3 has relatively low Co and Ni contents comparing to the Py1b and Py2,with Co/Ni ratios ran

关 键 词：黄铁矿 LA-ICPMS 微量元素 茶花寨金矿床 滇东南 

分 类 号：P579[天文地球—矿物学] P618.51[天文地球—地质学]