几内亚锡吉里盆地Bereko金矿床地质特征、矿床成因及找矿前景分析

Geological characteristics,deposit genesis,and prospecting prospect analysis of Bereko Gold Deposit in Sigiri Basin,Guinea

近年来,几内亚已成为西非地区金矿投资勘查的热点地区之一,而锡吉里盆地是几内亚主要的金矿产区。Bereko金矿床位于锡吉里盆地的西北部,矿区内地层由古元古代比利姆系变质沉积岩、火山碎屑岩、火山岩和侵入岩组成;矿体呈平行或近平行状赋存于古元古代比利姆系变质沉积岩和花岗闪长岩体内的次级韧脆性剪切带中,与石英脉关系密切;矿区内主要发育脉状金矿化、角砾状金矿化和浸染状金矿化3种类型;与金成矿关系密切的蚀变类型为硅化、黄铁矿化、黄铜矿化和碳酸盐化(铁白云石化)。该矿床受古元古代比利姆系地层,北东向、北西西向、近南北向、近东西向断裂(剪切带)和花岗闪长岩体共同控制。矿床类型为造山型+热液型。该矿床形成于埃伯尼安造山运动时期(2 060~2 160 Ma),成矿流体具有多源、多期次性。通过土壤地球化学测量,圈定了Au-Ⅰ、Au-Ⅱ、Au-Ⅲ和Au-Ⅳ4处Au异常,为下一步工作提供了找矿靶区。

In recent years,Guinea has become one of the hot spots for gold investment and exploration in West Africa.At present,the Siguiri Basin is the main gold mining area in Guinea.Beroko Gold Deposit is located in the northwest of the Siguiri Basin,and the stratum is composed of Paleoproterozoic Birimian metamorphic sedimentary rocks,pyroclastic rocks,volcanic rocks,and intrusive rocks;the ore bodies are mainly hosted in the subordinate ductile-brittle shear zone of the Birimian metamorphic sedimentary rocks and granodiorite,and it is closely related to quartz veins;there are mainly three types of gold mineralization:vein gold mineralization,breccia gold mineralization,and disseminated gold mineralization.The alteration types closely related to gold mineralization are silicification,pyritization,chalcopyritization and carbonation(ankeritization).The deposit is jointly controlled by the Paleoproterozoic Birimian stratum,NE,NWW,nearly NS,nearly EW trending fault structures(shear zones),and granodiorite bodies.The deposit type is classified as"orogenic+hydrothermal"gold deposits.The deposit was formed during the Eburnean orogeny(2060-2160Ma),and the ore-forming fluid has multiple sources and multiple phases.Four anomalous zones,Au-Ⅰ,Au-Ⅱ,Au-Ⅲ,and Au-Ⅳwere delineated through soil geochemical survey,which provided target areas for prospecting.