鄂东北金鸡坳金矿成矿流体性质及物质来源:来自矿床地质、流体包裹体及S同位素证据

Ore-forming fluid characteristics and ore-forming material sources of the Jinji’ao gold deposit in Northeastern Hubei Province: evidence from mineral deposit,fluid inclusion and sulfur isotope studies

金鸡坳矿区位于湖北省大崎山地区团风县,大地构造位置上位于北大别造山带南部,处于桐柏-浠水断裂与商麻断裂的交汇部位。其金矿体呈脉状或者透镜状赋存于北西向和近东西向断裂构造中,厚度和产状较稳定,但金品位及矿化类型不均匀;金品位一般在浅部高,在深部低;蚀变强度与金矿化存在正相关关系;流体包裹体研究表明,成矿流体为中高温-中低温(184.8~314.7℃)、低盐度(14.02~17.75 wt%)流体,密度约0.86~0.98 g/cm^3,成矿压力约21.54~40.07 MPa,成矿深度约2~5 km,属于中深成构造环境。在成矿作用过程中,流体有温度降低、盐度减小、密度增大、压力减小的趋势。矿石中黄铁矿的δ34S为3‰~4.2‰,数值比较集中,表明成矿物质硫源具有岩浆硫的特征,指示可能有深源硫参与金成矿。

Jinji’ao mining area is located in Tuanfeng County,Daqishan area,Hubei Province,in the southern part of North Dabie terrane and in the intersection of the Tongbai-Xishui Fault and Shangma Fault.The ore bodies are veins or lenticular and distributed in the NW and near EW fault structures with stable thickness.However,the gold grade and mineralization types are various.Gold grade is generally high in the shallow part and low in the deep part;gold mineralization is closely related to alteration intensity.Fluid inclusion studies showed that the ore-forming fluids are characterized by moderately high-low temperature(184.8~314.7℃)and low salinity(14.02~17.75 wt.%).The calculated density,pressure and depth fluids rang from 0.86 to 0.86 g/cm^3,21.54 to 40.07 Mpa and 2.0 to 5.0 km,respectively and are inferred to originated from a certain depth.Additionally,the results also show that the estimated temperature and salinity of the ore-forming fluids tended to decrease,while the density and pressure increase during the oreforming process.Theδ34 S values of the pyrite form the ores range from 3.0‰to 4.2‰,indicating the sulfur is of magmatic origin,most likely deep-source sulfur.