Key Laboratory of Computational Geodynamics, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
Development Research Center, China Geological Survey, Beijing 100037, China.
J Nanosci Nanotechnol. 2021 Jan 1;21(1):246-261. doi: 10.1166/jnn.2021.18744.
The mineralogical and compositional characteristics of gold-bearing minerals and the occurrence of gold are not only of great significance to exploring the sources of ore-forming materials and their formation mechanisms but also helpful for designing reasonable beneficiations and smelting schemes and achieving remarkable economic benefits. This paper presents an integrated study on the crystal characteristics, elemental composition and distribution of pyrite (the main gold-bearing minerals), on the basis of electron probe microanalysis (EPMA), scanning electron microscopy (SEM), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and nano-secondary ion mass spectrometry (NanoSIMS). The occurrence of gold in the Shuiyindong gold deposit and Ashawayi gold deposit has been studied by means of microscopy, SEM, and EPMA images, elemental correlations, S-Fe-As ternary diagrams, logAs-logAu diagrams and Au/As ratios. The gold in pyrite of the Shuiyindong deposit is in the form of nano gold inclusions and lattice gold. The gold in pyrite of the Ashawayi deposit dominantly exists in the form of nano gold inclusions or is present as micro-nano gold particles in the cracks or edges of pyrite, some of which can exist as lattice gold. The ore-forming hydrothermal solution of the Shuiyindong gold deposit is mainly underground hot brine, but it may be reformed by a deep magmatic hydrothermal solution or volcanic-subvolcanic hydrothermal solution. The ore-forming hydrothermal solution of the Ashawayi gold deposit is mainly derived from the metamorphic hydrothermal solution formed during the orogenic process, and the ore-forming process or post-mineralization process may be reformed by the leaching of underground hot brine. Finally, the characteristics of ore-forming fluids and evolution of the two types of deposits are determined via pyrite element surface scanning. This paper shows that micro-nanoscale study of gold-bearing pyrite is of great significance to understanding the gold mineralization process and is worth further study.
载金矿物的矿物学和成分特征以及金的赋存状态不仅对探索成矿物质来源及其形成机制具有重要意义，而且有助于设计合理的选矿和冶炼方案，实现显著的经济效益。本文通过电子探针微分析（EPMA）、扫描电子显微镜（SEM）、激光烧蚀-电感耦合等离子体质谱（LA-ICP-MS）和纳米二次离子质谱（NanoSIMS）等手段，对主要载金矿物黄铁矿的晶体特征、元素组成和分布进行了综合研究。本文还通过显微镜、SEM 和 EPMA 图像、元素相关性、S-Fe-As 三元图、logAs-logAu 图和 Au/As 比值等手段，对水因洞金矿和阿沙威金矿中金的赋存状态进行了研究。水因洞矿床黄铁矿中的金呈纳米金包裹体和晶格金形式存在。阿沙威矿床黄铁矿中的金主要以纳米金包裹体形式存在，或呈微纳米金颗粒存在于黄铁矿的裂隙或边缘，部分以晶格金形式存在。水因洞金矿的成矿热液主要为地下热卤水，但可能受到深部岩浆热液或火山-次火山热液的改造。阿沙威金矿的成矿热液主要来源于造山过程中形成的变质热液，成矿过程或成矿后可能受到地下热卤水的淋滤改造。最后，通过黄铁矿元素表面扫描确定了两种类型矿床成矿流体的特征及其演化。本文表明，载金黄铁矿的微纳米尺度研究对认识金矿化过程具有重要意义，值得进一步研究。
