Application of Magnetic Geophysical Techniques in Investigating Subsurface Deposits in Parts of Kogi State, North-Central Nigeria

Abstract

The aeromagnetic data of the Idah and Angba areas were interpreted qualitatively and quantitatively. Source Parameter Imaging (SPI) and Forward and Inverse modeling techniques were employed in quantitative interpretation to determine the thickness of the sedimentary Basin and magnetic susceptibilities.  Qualitatively, the first vertical derivative map shows areas of higher intensity (higher signal) in the north-central, west, and east of the study area. In comparison, the south region has a lower intensity (lower signal). In addition, the reduction-to-pole map shows some elliptical bodies, indicating the shapes of magnetic anomalies centered symmetrically on the body. Results from SPI estimated depth ranges from 431.5 m (shallow magnetic bodies) to 6494.3 m (deep lying magnetic bodies). Forward and inverse modeling estimated depths for profiles 1-5 were 526 m, 461 m, 4347 m, 1751 m, and 6847 m, respectively, with respective susceptibility values of 0.0003, 0.0879, 0.0800, 0.0004 and 0.0700 which indicate intermediate and basic igneous rocks (diorite, andesite and gabbro or basalts) and basic sedimentary rocks (sandstone and limestone). The maximum depths obtained from the four methods applied show sufficiently thick sediments suitable for hydrocarbon accumulation.

Keywords: Aeromagnetic data, Idah and Angba, FVD, RTP, Upward continuation, SPI, forward and inverse modeling, anomalous source.