卡林型金矿黄铁矿中金的赋存状态及微观富集机理：EPMA-NanoSIMS-FIB-SEM-(球差校正)TEM方法组合研究

金主要以“不可见金”赋存于含砷黄铁矿中是卡林型金矿的标志性特征之一。然而由于黄铁矿颗粒细、多期次、多环带，而早期研究因技术限制未能原位-微区开展TEM分析，金究竟以晶格金还是纳米金为主一直存在争议，进而导致金的微观富集机理仍不清楚。最近发展起来的EPMA-NanoSIMS-FIB-SEM-(球差校正)TEM方法组合为解决上述争议和问题提供了契机。本项目以贵州水银洞和锦丰、美国Getchell金矿为研究对象，首先利用SEM、EPMA和NanoSIMS研究不同类型、不同环带黄铁矿在微米尺度下的结构、精确成分及其变化规律；然后利用FIB-SEM原位-微区制备TEM样品，并利用TEM和球差校正TEM分析黄铁矿在纳米-原子尺度下的成分及分布、结构、晶格参数、元素占位等，最终揭示不可见金的赋存状态及其微观富集机理。研究成果有助于阐明巨量不可见金的微观精细卸载过程和机制，并为卡林型金矿成因提供重要约束。

Invisible Au in arsenian pyrite is one of the symbolic characteristic of Carlin-type Au deposit. However, because the pyrite is fine grained, multi-stage and multi-band, and previous studies failed to conduct in-situ TEM analysis due to technical limitation, the occurrence of invisible Au in arsenian pyrite is still debated (lattice Au dominated or Au nanoparticle dominated?), and the microscopic enrichment mechanisms of inviable Au is poorly understood. Recent development of EPMA-NanoSIMS-FIB-SEM-(spherical aberration-corrected) TEM techniques combination provides an opportunity to address the above debate and problem. In this study, we will take the Shuiyindong and Jinfeng deposits in Guizhou, and the Getchell deposit in USA as example, and analyze samples to determine the texture, and precise chemistry and its variation of different pyrite types and different pyrite sub-bands at the micrometer scale using SEM, EPMA, and NanoSIMS. We will then use FIB-SEM techniques to prepare the site-specific TEM foil, and analyze the pyrite’s chemistry and element distribution, texture, lattice parameter, and element occupation at the nanometer-atomic scale using TEM and spherical aberration-corrected TEM, and ultimately uncover the occurrence of invisible Au and its microscopic enrichment mechanism. Achievements attained in this study will contribute to illuminate massive invisible Au precipitation process and mechanism, and also provide constraints on the genesis of the Carlin-type Au deposits.