Total Ground Magnetic Studies of Igarra Area, Akoko-Edo Local Government Area, Edo State

Abstract

The study area, Igarra which is North-West of Edo State, Nigeria, is underlain in the North by Precambrian Basement Complex and in the South by Cretaceous and Tertiary sediments. The ground magnetic study of the area was carried out. The investigation was aimed at studying the total components (i.e. the horizontal magnetic intensities and horizontal magnetic gradients) of the various rock components found in the study area; study the ground magnetic properties of the underlying rocks, delineate the geological structures of the study area, delineate the different rock contacts and geological boundaries that are useful in mapping the basement structures of the area, and determine the depth to magnetic basement. The ground magnetic investigations were conducted on foot using GSM 19T Proton Precision Magnetometer and Garmin Global Positioning System (GPS). Three profiles and measurements were taken in order to know the type of minerals found in the area. Closely spaced stations of 20 m interval were adopted for the magnetic survey to allow high resolution of near surface structures. The magnetic data were analysed using Grapher 11. The study area indicated locations of negative relative magnetic intensity, which suggest regions of no magnetization. It is where magnetic sediments, rocks and minerals are not present. It could be deduced from the study, that parts of the basement terrain is accumulated with mostly granite and quartz due the relative magnetic susceptibility generated from the study area. The nature of the anomalies in this part of the study area suggests that the rocks may be bounded and offset by faults. Although the results provide valuable insights into the subsurface geology, the interpretation of magnetic data is inherently non-unique and primarily reflects shallow subsurface conditions. Therefore, the integration of additional geophysical methods is recommended for more detailed characterization.