The Source Parameter Imaging (SPI) method for estimation of depth to buried magnetic sources from gridded digital data of the Sokoto Basin, Nigeria: Implications in exploration Geophysics

Abstract

Analysis of high resolution aeromagnetic data over the study area has been carried out using Source Parameter Imaging SPITM to explore for hydrocarbon potential in the entire Sokoto basin of Nigeria. It is bounded by longitudes 3.50 oE and 7.00 oE and latitudes 10.00 oE and 14.00 oN. Three grids (dx, dy and dz) were obtained before the SPI was calculated. Those grids were use of Oasis Montaj by carefully using appropriate cut-off wavelength of the area. Those grids later serve as input grids for SPI calculations. The result shows that the Sedimentary thicknesses in the north central part is much higher than those of the southern part of the study area, the SPI values vary gradually within these sub-basins in the northcentral. As one traverses the basin from the north towards the southwest the sedimentary thickness decreases and rest directly on the Precambrian basement. However, profiles across these sub-basin in the north, revealed that Sedimentary thickness range from 460 m to 3009.5 m. The profile 1 corresponds to the Gwandu Formation, which forms the Post-Paleocene continental terminal and occurs in the northwestern part of Sokoto. While the profile 2 corresponds to Kalambaina and Dange Formations, which constitute the Sokoto group and is of marine origin. This marine sedimentary layer dips gently and thickens gradually towards the northcentral, with a maximum thickness of over 3000 m near border with Niger Republic, is attributed to deep seated volcanic and magnetic sources. While areas of shallow seated magnetic bodies in the southern part attributed to presence of sandstones, ironstones, shales, graphites, limestones, intrusives and other near-surface magnetic minerals, ranges from 154. 0 m to 1000 m. The general trend in the orientation of the TMI and SPI map are found to be predominantly in the NE-SW and NW-SE related to the Pan – African Orogeny trends. Therefore, Dange and Kalmalo with sedimentary thickness of over 3.0 km could be sufficient for hydrocarbon maturation