Geochemical and Geological Assessment of Lead-Zinc Deposits at Enyigba and its Environs, Southeastern Nigeria

Abstract

This study investigates the geology and grade of lead-zinc (Pb-Zn) mineralization within the Enyigba area of the Lower Benue Trough, Southeastern Nigeria, with the objective of evaluating the economic potential and geological controls of mineralization. The research adopted an integrated approach combining geological field mapping and geochemical evaluation. Field investigations involved mapping lithological units, and measuring fracture orientations. The field mapping revealed that the local geology of Enyigba is dominated by sedimentary rocks belonging to the Asu River Group, which is the oldest stratigraphic unit in the Lower Benue Trough and it consists mainly of dark grey to black shales, siltstones, fine to medium grained sandstones, and thin limestone interbeds. A total of ten representative ore samples was collected from two mineralized locations in the study area at an average depth of 1.2 meters and laboratory analyses were conducted using X-ray fluorescence (XRF) and wet chemical methods (Aqua Regia digestion and EDTA titration) to determine the concentrations of lead and zinc. The results show that lead content ranges from 1.13 to 5.25 wt% with a mean of 3.31 wt%, while zinc content ranges from 1.31 to 3.96 wt% with a mean of 2.50 wt%. The spatial variation of Pb and Zn suggests a metal zonation pattern typical of Mississippi Valley-Type (MVT) mineralization, where galena (PbS) is concentrated in central veins and sphalerite (ZnS) occurs in peripheral zones. Structural features such as faults and fractures provided conduits for hydrothermal fluids, which precipitated Pb-Zn sulfides within the Albian Asu River Group sediments. Comparison with other deposits in the Lower Benue Trough, such as Ishiagu, Ameri, and Ameka, revealed similar grade ranges and paragenetic trends, confirming the genetic and structural consistency of mineralization across the region. The study concludes that the Enyigba Pb-Zn ores are moderately rich and economically viable for small to medium scale mining, particularly given their shallow occurrence and accessibility. It is therefore recommended that subsurface exploration involving drilling and geophysical surveys be conducted to delineate ore continuity and assess deeper sulfide zones, which may contain higher metal concentrations. Additionally, environmental monitoring and remediation programs are advised to mitigate potential heavy metal contamination associated with lead mining.