Geochemistry, mineral paragenesis and geothermal conditions of oreforming fluids from the Ain El Bey Cu–Fe deposit: potential occurrence of native gold and precious metal traces (North African orogenic belt, Northern Tunisia)

The Ain El Bey abandoned mine, in North-West Tunisia, fits into the geodynamic context of the European and African plate boundary. Ore deposit corresponds to veins and breccia of multiphase Cu–Fe-rich mineralization related to various hydrothermal fluid circulations. Petromineralogical studies indicate a rich mineral paragenesis with a minimum of seven mineralization phases and, at least, six pyrite generations. As is also the case for galena and native silver, native gold is observed for the first time as inclusion in quartz which opens up, thus, new perspectives for prospecting and evaluating the potential for noble metals associated with the mineralization. Scanning Electron Microscope--Energy Dispersive Spectroscopy and Transmission electron microscopy analyses show, in addition, a large incorporation of trace elements, including Ag and Au, in mineral structures such as fahlores(tetrahedrite-tennantite) and chalcopyrite ones. The mineral/mineral associations, used as geothermometers, gave estimated temperatures for the mineralizing fluids varying from 254 to 330 ℃ for phase Ⅲ, from 254 to 350 ℃ for phase Ⅳ, and from 200 to 300 ℃ for phases Ⅴ and Ⅵ. The seventh and last identified mineralization phase, marked by a deposit of native gold, reflects a drop in the mineralizing fluid’s temperature(< 200 ℃) compatible with boiling conditions. Such results open up perspectives for the development of precious metal research and the revaluation of the Cu–Fe ore deposit at the Ain El Bey abandoned mine, as well as at the surrounding areas fitting in the geodynamic framework of the Africa-Europe plate boundary.

广东那程银金矿床地质特征及成矿规律浅析

那程银金矿区位于吴川—四会大断裂中部主断裂东南侧,次级NE向运塘—三屋排断裂南东,黄岭顶—合水口断裂北西之复合部位。矿区内共发现含银金矿脉16条,均产于蚀变破碎带中。矿脉在空间排列上呈相互近于平行的雁行式左行排列的特点,圈定工业矿体2个。银金矿床的形成是原岩经构造破碎和蚀变作用后,金银富集含量明显增加,在多期次而强烈的地质作用改造后,大面积活化迁移,在有利部位富集,形成工业矿体,是构造活动、变质作用、交代作用和岩浆活动共同作用的结果,属中—低温热液破碎蚀变岩型银金矿床。

广东那程银金矿床地质特征

那程银金多金属矿床位于广东省阳春地区。通过采用路线地质调查、构造填图、矿床(点)考察和岩石地球化学等方法,详细总结了矿区地质特征。震旦系云开群和寒武系八村群是区内主要含矿地层,但震旦系Ag元素丰度值明显偏高,因此震旦系形成的矿床规模比寒武系大;矿区整体为一背斜构造,北翼具有低温元素组合特点,南翼具有中温元素组合特点,反映出褶皱的南翼处于抬升,而褶皱的北翼处于下降,因此,北翼矿体的埋藏深度大于南翼;矿区燕山期侵入岩出露处一般都有较好的矿化,加里东期白云母—绢云母不等粒变质砂岩质条带状混合岩出露处矿化较好,而碎裂—糜棱岩化似斑状黑云母钾长石花岗岩出露处矿化一般。