ANALYSIS AND INTERPRETATION OF HIGH RESOLUTION AEROMAGNETIC DATA OF ABUJA SHEET 186 AND GITATA SHEET 187, CENTRAL NIGERIA

Abstract

Analysis of high resolution aeromagnetic data of Abuja Sheet 186 and Gitata Sheet 187, North Central Nigeria were carried out. The geomagnetic gradient was removed from the aeromagnetic data using the International Geomagnetic Reference Field (IGRF) and the obtained result was shown as Total Magnetic Intensity (TMI) maps. Software used for the analysis include: Oasis Montaj Version 8.4, Matlab Version R2010a, Grapher 5, SUFER 11, Georient and Microsoft Excel. The regional magnetic values range from 33213.0 to 33361.4 nT. The SW region is associated with lower magnetic values ranging from 33213.0 to 33222.0nT while the NE portion of the map is marked with higher aeromagnetic values ranging from 33352.3 to 33361.4nT. The residual field values range from -392.5 to -171.6 nT and the negative residuals dominate the study area because the study area is dominated by sediments and located at the western part of the magnetic equator. The reduced-to-equator map shows similar features with the crustal field map except for re-alignment of anomalies. The magnetic intensity ranges from -177.1 to -388.9 nT and first vertical derivative ranges from -0.190 to 0.161 nT/km. The fractures largely trend in the NE-SW and NW-SE directions. The Source Parameter Imaging revealed depth ranging from 45.0 to 378.3 m and the dominant geological features are sills and dykes. The depth (D2) to the shallow magnetic sources varies from 0.253 to 0.728 km while the depth (D1) to the magnetic basement varies from 0.479 to 3.36 km.