沉积岩成岩及变质过程中硫化物的结构和组成变化与造山型金矿床的成因：以西秦岭八卦庙金矿床为例

多数造山型金矿床的形成可能与沉积岩或火山-沉积岩的变质脱流体作用有关。金在各类沉积岩和火山-沉积岩中的赋存状态及其在区域变质和相关热液活动过程中的释放、转移、搬运、富集机制是造山型金矿床成因研究的关键科学问题。本项目以西秦岭八卦庙超大型金矿床为研究对象，首先开展金矿石、蚀变岩和未蚀变围岩中不同产状黄铁矿-磁黄铁矿的矿物学研究，厘定从沉积-成岩到区域变质和热液成矿过程中硫化物的结构变化和成因机制，进而对不同类型黄铁矿和磁黄铁矿的微量元素组成进行微区原位分析，揭示黄铁矿结构变化及黄铁矿向磁黄铁矿转变过程中微量元素的释放、迁移和富集机制及其对形成含金流体的贡献。在此基础上开展各类黄铁矿-磁黄铁矿硫-铅同位素组成的原位分析、含水蚀变矿物羟基的氢-氧同位素组成分析和高精度的成矿年龄测定，阐明八卦庙金矿床金的来源、转化和富集过程及其控制因素，完善八卦庙金矿床成因模式，促进西秦岭造山型金矿床的研究。

There is a consensus that orogenic gold deposits formed largely due to metamorphic devalotization of Au-rich sedimentary and volcanic rocks. Core scientific issues in the genesis of orogenic gold deposit are how Au and associated trace elements occur in the source rocks, how they were liberated, transported, and gradually enriched to form ore-fluids. These questions, however, remains not well understood. To further address these issues, we propose an integrated textural, compositional, and isotopic study of the Baguamiao giant sediment-hosted orogenic gold deposits in the West Qinling orogen. We first characterize the mineralogy, paragenesis, and textures of variopus pyrite and pyrrhotite from the ores, alteration assemblages, and unmineralized coutry rocks of the Baguamiao gold deposit. The reuslts will provide significant insights into the transformation and evolution of the sulfide minerals during diagenesis, regional metamorphism and associated hydrothermal activities. We further use laser ablation ICP-MS to analyze gold and associated trace elements in various pyrites and pyrrhotites to document their geochemical behavior during recrystallization and dissolution-reprecipitation of pyrite and replacement of pyrite with pyrrhotite, processes critically important to form auriferous fluids. In-situ S and Pb isotope analysis of distinct generations of pyrite and pyrrhotite and contrast areas of within single grains are cthen onducted to provide additional evidence supporting a metamorphic source of gold, sulfur and other elements for the Baguamiao orogenic gold deposit. This study will yield significant new insights into the ore genesis and refine the genetic model of the Baguamiao gold deposit, enabling a bettter understanding of gold metallogeny of the entire West Qinling orogen and other sediment-hosted orogenic gold deposits in the world's Phanerozoic orogenic belts.