[01] Geoge Emeka Onyishi, Department of Industrial Physics, Enugu State, University of Science and Technology, Enugu, Nigeria. [02] Gabriel Zeruwa Ugwu, Department of Industrial Physics, Enugu State, University of Science and Technology, Enugu, Nigeria.

The aeromagnetic data over Lafia, Akiri, Makurdi and Akwana, parts of the Middle Benue Trough of Nigeria, were interpreted by source parameter imaging (SPI) and Euler deconvolution techniques in order to determine the sediment thickness of the area. The data were analyzed and interpreted using Oasis Montaj and PotentQ software. The regional fields were separated from the total magnetic intensity (TMI) fields to obtain the residual fields using first order polynomial fitting. The residual anomalies were also successively sharpened using first, second and horizontal derivatives. The result of the SPI interpretation revealed two depth models; the deep depth and the shallow depth. The depth to magnetic bodies estimated from the SPI ranged from 318.7 m (shallow magnetic bodies) to 4409.5 m (deep lying magnetic bodies. The depth estimates obtained from the Euler deconvolution technique, using two structural indices of 0 and 0.5, ranged from 902.3 m (out cropping magnetic bodies) to 4909.3 m (deep lying magnetic bodies). The maximum sediment thicknesses obtained from the two interpretation methods are in agreement with each other and indicate the possibility of hydrocarbon accumulation, especially at the northeastern (Akiri) part of the study area).

Aeromagnetic Data, Source Parameter Imaging, Euler Deconvolution, Sediment Thickness, Magnetic Anomalies and Hydrocarbon Prospect

[01] Biswas, A. (2016). Interpretation of gravity and magnetic anomaly over thin sheet- type structure using very fast stimulated annealing global optimization technique. Model. Earth Syst. Environ. 2 (1): 30. [02] Biswas, A. (2017). Inversion of source parameters from magnetic anomalies for mineral /ore deposits exploration using global optimization technique and analysis of uncertainty. Natural Resour. Res. 27 (1): 77-107. [03] Biswas, A. and Acharya, T. (2016). A very fast simulated annealing method for inversion of magnetic anomaly over semi- infinite vertical rod-type structure. Model. Earth Syst. Environ. 2 (4): 198. [04] Uzuakpunwa, B. A. (1974). The Abakaliki pyroclastics, Eastern Nigeria: new age and tectonic implications. Geol. Magazine, 111: 761-769. [05] Olade, M. A. (1975). Evolution of Nigeria’s Benue Trough (aulacogen): a tectonic model. Geological Magazine. 112: 575-583. [06] Olade, M. A. (1976). On the genesis of the lead-zinc deposits in Nigeria’s Benue Rift (aulacogen). A re-interpretation. J. Min. Geol. 13 (2): 20-27. [07] Hoque, M. (1984). Pyroclastics from lower Benue Trough of Nigeria and their tectonic implications. J Afr. Earth Sci. 2: 351-358. [08] Nwosu, O. B. (2014). Determination of Magnetic Basement Depth over Parts of Middle Benue Trough by Source Parameter Imaging (SPI) Techniques using HRAM. Int. J. Sc. Tech. Res. 3 (1): 262-271. [09] Ugwu, C. M. and Ugwu, G. Z. (2018). Euler deconvolution and forward and inverse modelling of aeromagnetic anomalies over Ogoja and Bansara areas of Lower Benue Trough, Nigeria. Amer. J. Geophy. Geochem. Geosyst., 4 (1): 1-12. [10] Ugwu, C. M., Ugwu, G. Z. and Alasi, T. K. (2018). Spectral analysis and source parameter imaging of aeromagnetic anomalies over Ogoja and Bansara areas of Lower Benue Trough, Nigeria. J. Geol. Min. Res., 10 (13): 28-38. [11] Reyment, R. A. (1965). Aspects of Geology of Nigeria, Ibadan University Press. Bull. Geol. Surv. Nig., 1: 1-95. [12] Offodile, M. E. and Reyment, R. A. (1978). Stratigraphy of the Keana-Awe area of the Middle Benue region of Nigeria. Bull. Geol. Inst. Univ. Upsala, 2: 37-66. [13] Cratchley, C. R. and Jones, G. P. (1965). An interpretation of geology and gravity anomalies of the Benue valley, Nigeria Geophysics Paper, Overseas Geol. Surv. London, 1: 1-26. [14] Offodile, M. E. (1976). A review of the Geology of the Benue Valley Geology of Nigeria. Elizabethan Publishing Company Lagos, 319-330. [15] Ayoola, E. O. (1978). Sedimentology of the Middle Benue Trough, Nigeria. Unpl. Ph.D thesis, University of London. [16] NGSA (1994). Geological map of Nigeria, Nigeria geological Survey Agency. [17] Obaje, N. G. (2004). Geology and mineral resources of Nigeria, Springer- Dordrecht Heidelbug, 10-30. [18] Thurston, J. B. and Smith, R. S. (1997). Automatic conversion of magnetic data to depth, dip, and susceptibility contrast using the SPI method. Geophysics, 62: 807-813. [19] Nabighian, M. N. (1972). The analytic signal of two-dimensional magnetic bodies with polygonal cross-sections: Its properties and use for automated anomaly interpretation. Geophysics, 37: 507-517. [20] Thompson, D. T. (1982): EUlDPH: A new technique for making computer-assisted depth estimates from Magnetic data, Geophysics, 47: 31-37. [21] Reid, A. B., Allsop, J. M., Granser, H., Millet, A. J., and Somerton, I. W. (1990). Magnetic interpretation in three dimensions using Euler deconvolution: Geophysics, 55: 80-9. [22] Ofoegbu, C. O. (1984). Aeromagnetic anomalies over the Lower and Middle Benue Trough, Nigeria. J. Afr. Earth Sci., 3: 293-2. [23] Wright, J. B., Hastings, D., Jones, W. B. and Williams, H. R. (1985). Geology and Mineral Resources of West Africa. George Allen and Unwin, London, 90-120.