Abstract

This study aimed to estimate the depth of magnetic source bodies in Lafia and Akiri areas which fall within the middle Benue trough, Nigeria. Aeromagnetic data were used and spectral analysis and source parameter imaging were used for the quantitative interpretation of the data. The total magnetic intensity (TMI) contour map obtained from gridding of the data ranging from -39.5 to 100.0 nT was separated into regional and residual contour maps; it was done by polynomial fitting to produce the residual aeromagnetic intensity contour map. The residual intensity varies from -78.9 to 55.0 nT while the regional intensity varies from -39.18 to 39.84 nT. Depth results obtained from spectral analysis revealed two depth sources: the shallower magnetic source bodies and the deeper magnetic source bodies. The depth of shallower magnetic sources ranges from 0.557 to 1.261 km, with an average depth value of 0.899 km, whereas the depth of deeper magnetic sources varies from 2.419 to 5.732 km with an average depth value of 4.105 km. The SPI depth result ranges from -0.5638 km (shallow magnetic bodies) to 5.8381 km (deep lying magnetic bodies). The two methods showed depth estimation within the same range. The sedimentary thickness obtained from the different methods indicates the possibility of hydrocarbon accumulation if other conditions for hydrocarbon generation are satisfied.

Key words: Magnetic source bodies, depth estimation, spectral analysis, SPI, Lafia and Akiri areas, aeromagnetic data.