EVALUATION OF AEROMAGNETIC ANOMALIES OF ABUJA SHEET 186 AND GITATA SHEET 187, NORTHCENTRAL NIGERIA

Abstract

Interpretations of High-Resolution Aeromagnetic Data of Abuja Sheet 186 and Gitata Sheet 187,
Northcentral Nigeria, were carried out with the aim to determine Curie Point Depth, Geothermal
Gradient, Heat Flow, and depth to a magnetic source. Euler Deconvolution method was adopted,
and the software used for analysis include: Oasis Montaj Version 8.4, Matlab Version R2020a,
Grapher 5, SUFER 11, Georient, and Microsoft Excel. The Total Magnetic Intensity ranges from
32919.5 to 33083.5 nT, and the residual magnetic values range from -392.5 to -171.6 nT. The
depth estimates were obtained from the Euler deconvolution technique, using four structural
indices of 0.0, 1.0, 2.0 and 3.0. The structural index (0.0) represents contacts and ranges from
60.2 to 318.3m while 1.0 stands for dyke and sill and ranges from 200.7 to 762.2m. Cylinder
has structural index of 2.0 and ranges from 206.3 to 1167.0 m. Structural index, 3.0 represents
the presence of spheres and ranges from 151 to 1588m. The depth of magnetic sources varies
across the study area due to underlying topography. The depth to the Centroid (Zo) ranges from
11.60 to 13.56 km and the depth to the top boundary (Zt) of magnetic sources ranges from 0.311
to 2.16 km. The equivalent curie depth obtained ranges from 22.89 to 25.64 km and could be as a
result of the intruded Older Granite suite in the area. The average heat flow (59.32 mWm-2) and
geothermal gradients (23.720C km-1) indicate that the heat flows and geothermal gradients were
not uniform, which possibly revealed that the magma conduits were randomly distributed and
thus could be considered as typical of the continental crust.