The Pb-Zn deposit is the largest and consists of three lodes (Enyigba, Ameri and Ameka). The Enyigba lodes stretched about 2 km long and 30 m wide. The mining in the Abakaliki lodes account for over 50 % of the total 10,000 tons of Pb-Zn ores mined between 1946 and 1974 in the Benue Trough and the estimated reserve of about 1.5 million tons of 7 % combined Pb-Zn ores. Recently, the mining activity is carried out by artisanal miners. The mineralization in Abakaliki is hosted by the Albian carbonaceous shales of the Asu River Group which is the earliest sediments and lie unconformably upon the basement complex. There is a report on the presence of a 300 m thick sandstone layer as the basal detrital suite directly resting on the basement graben. As a rule, mineralized veins are not closely associated with intrusive igneous bodies. However, the mineralized veins are structurally controlled, occurring as open space fillings in fracture and fault systems including the NS to N15E faults that cuts obliquely to the main structural trend (N50E) of the Benue Trough. Two main stages of ore formations have been identified. (1) The early digenetic stage which consists of traces of galena associated with pyrite and marcasite. (2) Syn-ore stage, consisting of siderite, quartz, sphalerite, pyrite and galena with minor bournonite and boulangerite. (3) Late ore stage associated with the introduction of copper sulphides and sulphosalts and quartz. Based on the field evidences the first Pb-Zn generation bears the imprint of syn-shear with a striated plane of mineralization and the second generation Pb-Zn ores are undeformed which usually sealed the first generation striations.

Other Regions, Features and Areas containing this locality

References