Application of integrated geophysical techniques in investigating Pb-Zn sulphide ore mineralization potential in part of the Benue Trough

The Abakaliki Lead-Zinc province is associated with four lodes, namely Ishiagu, Enyigba, Ameri and Ameka, as documented by the Nigerian Geological Survey Agency. Speculative mining activities in between and outside these lodes often result in abrupt termination of ore veins. The present study is at Ukawu, between the Ishiagu and the Ameka prospects and is aimed at reassessing and mapping areas of economic deposits. Integrated geophysical techniques involving magnetics, induced polarization (IP) and electrical resistivity tomography (ERT) were employed for the study with the objectives of determining ore habitat patterns and trends of mineralization. Areas with high peak positive magnetic anomaly corresponding to subsurface areas with anomalous high chargeability and relatively low resistivity structures are mapped as suspected areas of Pb-Zn mineralization across the study area. The results revealed that the suspected mineralization occurs as (mildly) disseminated stockwork that is relatively epigenetic in nature and not as elongated and laterally continuous veins. Total magnetic field intensity varies from - 17 to 29 nT with series of both magnetic low and high anomalies. Results of the parametric magnetic profile within the area where lead mineralization was previously mined show a flat (magnetic quiet) response parallel to the strike of the mine pit, which is the suspected trend of mineralization. The resistivity varied from 1.54 to 319 ohm-m while chargeability ranged from - 910 to 811 ms. Areas for further exploratory drilling or pitting were delineated based on the conjunctive interpretation of these methods. The lineament density agrees with the areas reported as Pb-Zn mineralized by indicating high lineament density in such regions of the study area. The study has regional application in other parts of the world in the search for metallic mineral occurrence as this study has added the Ukawu prospect to the existing records.