Magnetic Studies of Kagoro and Environs, North Central Nigeria

Abstract

Magnetic data were compiled from four aeromagnetic maps. A submap for the study area was produced from the four magnetic sheets in an ILWIS environment. Magnetic intensity values vary between 32,600 and 33,160 nT. The lowest magnetic contour values closure is centred over the Kagoro granite rocks at the central part. This closure is structurally aligned along the NE - SW direction. Regional field values vary between7789.1 and 7896.6 mGal. The residual contour values range from -180 to +160 nT. The main closure of the residual map is located on the central part of the area. A slipper-shaded closure centred over the Kagoro Granite is oriented along the NNE - SSW direction. Some of the closures in the study area are aligned along the NE - SW and E - W directions. Patterns of the closures of the magnetic maps are in conformity with those of the Nigeria basement and younger granite rocks. Isolations and magnitudes of the closures suggest that the various rock bodies occur separately and at different levels. The regional fields along nine profiles were obtained by third degree polynomial fitting using OriginLab7 software so as to obtain the residuals used for the models. The residual anomalies were accounted for by Mag2dc (2.5D) algorithms. The four profiles that traversed the Kagoro younger granite complex were estimated at maximum thicknesses of 14.1, 15.2, 9.5 and 10.4 km. These suggest that the Kagoro younger granite complex was emplaced at depths between 9.5 and 15.2 km. The volcanic rocks and their associates were formed from depths between 4.7 and 13.0 km.