水银洞卡林型金矿载金黄铁矿含砷环带特征及砷赋存状态  

THE CHARACTERISTICS OF ARSENIC BEARING ZONING IN GOLD-BEARING PYRITE AND THE ARSENIC OCCURRENCE STATE IN THE SHUIYINDONG CARLIN-TYPE GOLD DEPOSIT

作　　者：徐亮 鲜海洋[1] 杨文淋 朱建喜[1] XU Liang;XIAN Haiyang;YANG Wenlin;ZHU Jianxi(CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou Guangdong510640,China;College of Materials and Chemistry&Chemical Engineering,Chengdu University of Technology,Chengdu,Sichuan 2610059,China)

机构地区：[1]中国科学院广州地球化学研究所中国科学院矿物与成矿重点实验室/广东省矿物物理与材料研究开发重点实验室,广东广州1510640 [2]成都理工大学材料与化学化工学院,四川成都610059

出　　处：《矿物岩石》2025年第1期55-64,共10页Mineralogy and Petrology

基　　金：国家自然科学基金青年项目(批准号:42402036);广东省自然科学基金杰出青年项目(编号:2022B1515020007);广州市科技计划项目(编号:202201010385);中国科学院青年创新促进会(编号:2021353)。

摘　　要：卡林型金矿中金主要以“不可见”金的形式赋存于含砷黄铁矿。黄铁矿中As的含量限制着以固溶体形式进入晶格的Au含量,As的掺入对黄铁矿的晶体结构和卡林型金矿中“不可见”金的形成机制的影响亟待研究。本文以贵州水银洞金矿作为典型卡林型矿床进行研究,利用扫描电镜(SEM)结合背散射(BSE)、电子背散射衍射(EBSD)、电子探针(EPMA)、聚焦离子束(FIB)以及三维电子衍射(3DED)技术等手段,对载金黄铁矿的含砷环带特征及砷赋存状态进行研究,发现大颗粒黄铁矿通常存在低As多孔的沉积-成岩黄铁矿核心和As震荡环带,反映了成矿流体的周期性剧烈波动;小颗粒黄铁矿的含砷环带大多为1~2层,且含砷环带的外侧As含量逐步降低,与高Au区域耦合;含As震荡环带的晶体取向与核部一致,说明了环带为核部黄铁矿外延生长形成;含砷黄铁矿中的As主要呈随机替代S位置的形式进入黄铁矿的晶格,黄铁矿晶格的整体结构并不发生改变,但由于Fe-S(As)键长、S(As)-S(As)键长均随As含量的增加而变大,黄铁矿的晶胞参数随之变大,其相关性为a0(nm)=0.5415+0.0031×CAs(at%)。含砷黄铁矿的晶胞参数变大为Au替代进入黄铁矿晶格提供了空间,提高了Au在黄铁矿晶格中的稳定性。In Carlin-type gold deposits,gold mainly exists as"invisible"gold within arsenopyrite,where the arsenic content affects the extent of gold that can be incorporated into the lattice in solid solution.This study employs scanning electron microscopy(SEM),backscattered electron(BSE)imaging,electron backscatter diffraction(EBSD),electron probe microanalysis(EPMA),focused ion beam(FIB),and three-dimensional electron diffraction(3DED)to investigate the formation mechanism of"invisible"gold in the Guizhou Shuiyindong gold deposit,a typical Carlin-type deposit.The research results show that large-grained arsenopyrite typically has a porous low-As core and As oscillation zoning,reflecting periodic and intense fluctuations of the ore-forming fluids.Small-grained arsenopyrite usually has 1~2 As-zoning bands,with the As content gradually decreasing toward the outer edge of the zoning bands,which are coupled with high Au areas.The crystal orientation of the As-zoning bands matches that of the core,indicating that the bands were formed by the outer growth of the core arsenopyrite.In arsenic-bearing arsenopyrite,As primarily enters the crystal lattice by randomly substituting for sulfur sites.The overall structure of the arsenopyrite lattice remains unchanged,but due to the increased bond length of Fe-S(As)and S(As)-S(As)bonds with increasing As content,the unit cell parameters of arsenopyrite expand.The correlation is given by a_0(nm)=0.5415+0.0031×C_(As)(at%).The expansion of the unit cell parameters of arsenopyrite provides space for the substitution of Au into the lattice,enhancing the stability of Au in the arsenopyrite lattice.

关 键 词：卡林型金矿 水银洞金矿 含砷黄铁矿 含砷环带 不可见金 

分 类 号：P571[天文地球—矿物学]