Geophysical study of Ubiaja and Illushi area in northern Anambra basin, Nigeria, using combined interpretation methods of aeromagnetic data

The aeromagnetic data of Ubiaja and Illushi area which falls within latitude 6 degrees 30 ' N-7 degrees 00 ' N and longitude 6 degrees 00 ' N-7 degrees 00 ' E were qualitatively and quantitatively interpreted. The qualitative interpretation revealed that the area is intensely faulted with major anomalies (faults) trending in the northeast and southwest directions. Standard Euler deconvolution, source parameter imaging (SPI) and modeling (forward and inverse) methods were employed in the quantitative interpretation. The aim of the quantitative interpretation includes determination of the thickness of the sedimentary basin, magnetic susceptibilities and possible type of mineralization prevalent in the area. The SPI depth result ranges from - 258.2 to - 3497.7m. The depth result from standard Euler deconvolution method for the structural index SI=0.5 ranges from 1377.3 to - 2510.9m; for SI=1, the depth to magnetic sources ranges from 1482.0 to - 3003.3m; for SI=2, the depth to magnetic sources range from 1627.8 to - 2984. 3m; and for SI=3, the depth ranges from 1853.9 to - 3089.9m. The results from forward and inverse modeling for profiles 1, 2, 3 and 4 showed depths of - 4118m, - 3611m, - 2964m and - 5489m, respectively (- signs signify subsurface depth). The susceptibility values of 0.0100 obtained for profiles 1 and 2 are associated with group of minerals such as hematite, gneiss, granite or gabbro. Profile 3 with susceptibility value of 0.0613 is typical of igneous rock porphyry. Profile 4 with susceptibility value of 0.0288 depicts minerals such as slate and hematite.