Origin Of Huangjindong Gold Deposit,Jiangnan Orogen:Constraints From Texture And Compostion Of Gold-bearing Pyrite

The Huangjindong gold deposit is the most typical large-scale orogenic gold deposit in the Changsha-Pingjiang gold polymetallic metallogenic belt of the Jiangnan orogenic belt.It is stored in Neoproterozoic slate with a gold resource reserve of about85t.The predecessors have conducted a lot of research on the source of ore-forming materials in this deposit,but the controversy is still ongoing and the research is difficult.Therefore,this paper analyzes the structure and composition of the gold-bearing pyrite in this deposit using petrographic and geochemical methods,and obtains the following achievements and understanding:1.The ore types of Huangjindong gold deposit are mainly quartz sulfide vein type,altered slate type and quartz breccia type.The metallogenic process can be divided into three stages:quartz-scherichite,quartz-gold-polymetal sulfide,quartz-calcite-chlorite.Pyrite is an important gold-bearing mineral,which contains a lot of invisible gold,inclusion gold and fissure gold.2.Pyrites have several morphological types including euhedral pyrites and subhedral-anhedral pyrites.Some developed crushed structure and zoned texture which consists of a core that has a porous structure and overgrowth rim during ore stage.It indicated that the formation of pyrite in the Huangjindong gold deposit is the product of multi-stage/phase geological events.3.Data from Electron Probe Micro Analysis?EPMA?show that a high As content in pyrite with an average of 1.134 wt%.A negative relationship between As and S indicated a substitution of As of S in Au-bearing pyrites.Data from LA-ICP-MS show that compared with Neoproterozoic slate,the trace elements of pyrite in the orebody enriched in As,but poor in Cr and Tl;Compared with the magmatic rocks in the area,the trace elements of pyrite in the orebody enriched in As and Sb,but poor in Cr,Mo and Tl.High-resolution multiple elemental mapping?Mapping?shows that the pyrite ring zone is relatively enriched with Au,As,Cu,Ni,Co elements,indicating that the ore-forming fluid has Au-As-Cu rich characteristics.4.The in-situ sulfur isotope results show that?34S values limiting?³⁴S to-9±1‰is stable with a small range of variation and strong homogeneity in main stage of ore-forming phase.Sulfur and metal had a deeper and higher metamorphic grade source.