INTERPRETATION OF HIGH-RESOLUTION AEROMAGNETIC DATA OVER ILESHA AND ENVIRONS IN SOUTHWESTERN NIGERIA

Abstract

The total magnetic intensity data, 1:100,000 high resolution aeromagnetic sheets 242 (Iwo), 243 (Ilesha), 312 (Okigwe) and 262 (Aponmu) and 263 (Ondo) lies between latitudes 4^o - 5^oE and longitudes 7^o-8^oN, Abuja, Nigeria, was analyzed and interpreted both quanlitatively and quantitavely by subjecting total magnetic intensity data to filtering and analytical techniques to determine the structural pattern, mineralization potential, depth to the basement, variation in the sedimentary thickness. Results derived from the first vertical derivative, horizontal derivative and analytical signal magnetic maps revealed the occurrence of numerous structures with dominant trends in the ENE-WSW, NE-SW and NNE-SSW directions across the study area. Prominent NE-SW magnetic gradation due to the presence of mega faults are observed around Ife North to Ilesha west and to Odo-Oti through Osogbo area on the residual and high pass magnetic maps. The mega faults are also highlighted on the first vertical derivative, horizontal derivative and analytical signal maps of the area. A major NE-SW trending mega fault mapped from the aeromagnetic data, in this study, is believed to be the prominent Ifewara fault. Lineament density map also produced from the extracted lineaments showed that areas with high density of lineaments have undergone more geologic activities than the others in the study area. Depths to deep magnetic sources obtained through the application of the SPI depth estimation method to low pass magnetic map vary from -751.3 to -9515.5m, while the depths to shallow magnetic sources obtained from high pass magnetic map vary from -127.6 to -492.5m. The prominent high mineralization zones are those found near and/or close to major fault zones and other minor structures mapped in this study. The research helped in mining and identification of zones with high and distinct mineralization potentials