Prospecting for metallic mineral deposits using integrated electromagnetic and electrical resistivity tomography in Agbede, Edo State Nigeria

Abstract

This study involves the application of Very Low Frequency-Electromagnetic (VLF-EM) and Electrical Resistivity Tomography (ERT) in locating and mapping of metallic mineral deposit potential in Agbede and its environs, Edo State Nigeria. The field geometry was made up of four traverses measuring 200 m, 210 m, 320 m and 310 m carried out in four localities (Kilometres 50, 54, 86 and 92 respectively along Okene-Benin Road) at a mean separation of 10 m with frequency band of 18.8 KHz and signal strength of 13 db. Two traverses in Kilometres 86 and 92 were utilized by ERT investigation due to VLF- EM results. The results of the qualitative interpretation of VLF-EM identified areas suspected to be of Metallic Ore importance. These form the basis for Electrical Resistivity Tomography (ERT) investigation. Results of the resistivity model and surfer plot geologic sections show that metallic mineral signatures of ERT imaging in Kilometre 86 are not well defined probably due to low data density records. However, the ERT images obtained from Kilometre 92 and line crosses of the electromagnetic anomalies, c₁, c₂, c₃ and C₄ revealed c₄ as metallic mineral. The ERT interpretations indicate that the c₄ anomalies in the VLF-EM curve are responses from closely separated conductors. These inferred metallic mineral deposits occur at 4.8 m and 7.5 m below the surface extending to depths of 8.5 m and 9.3 m respectively. The geologic section shows that they are laterally located at 123m, 128 m, 133 m and 137 m respectively along the transverse.

Keywords: VLF – EM, Resistivity tomography, Metallic mineral deposits, Geologic interface, Agbede Edo State Nigeria