REMOTE SENSING AND GEOPHYSICAL MAPPING OF MINERALIZATION POTENTIAL OF IPERINDO AND ITS ENVIRON, SOUTHWESTERN NIGERIA

Abstract

Land Sat, Aeromagnetic, ground magnetic, Very Low Frequency Electromagnetic (VLF-EM), Vertical Electrical Sounding (VES), Combine Horizontal Profiling and Vertical Electrical Sounding and Induced Polarization techniques were interpreted for delineating basement structures and their implications on mineralization in Iperindo and its environ. Lineaments were extracted from the satellite image and it shows extremely major trends in NE-SW direction. The pattern of the lineaments extracted from Landsat data suggests that the study area is a potential area of mineralization. Aeromagnetic data (sheet 243) was acquired from Nigeria Geological Survey Agency (NGSA.1965) in which total magnetic intensity map was generated. In order to attenuate the noise and improve the quality of signal for better enhancement of the anomaly, the total magnetic intensity map was subsequently enhanced by reduction to equator filter, derivatives filter, continuation filter, and analytic signal. The lineament of aeromagnetic map was generated from derivative filters using structure index of 0.0 and 2.0. The processed image shows the lineaments trends majorly toward NE-SW directions. General coincidence of both Landsat and aeromagnetic lineaments trends were observed in the study area, which means that these lineaments reflect real continuous fractures in depth. The 3-D euler deconvolution and radial spectral analysis were applied to locate and estimate the depth to anomalous bodies, impregnated with mineral deposit, which shows varying depth between 50 m and 500 m. Five ground magnetic and VLF-EM traverses were established in the study area. The aeromagnetic and ground magnetic data presented in form of maps and profile revealed the existence of magnetized bodies (interpreted as fracture, fault, veins and dykes ) in the study area and provided information on the geological contact difference from those shown on earlier geological map of the area. The VLF-EM interpretation revealed the existence of linear features, which are interpreted as fault and fractures. These linear features across the study area run approximately NE-SW, W-E, and NW-SE directions. The linear features were observed in the near surface between the depth of 40 m and 200 m. Thirteen Vertical Electrical Sounding (VES) stations were occupied. Quantitative interpretations of the VES curve were carried out using partial curve matching techniques which revealed maximum of five (5) subsurface layers such are top soil, weathered layer, fresh basement and fractured basement. Combined vertical electric sounding and horizontal profiling (VES&HP) was acquired concurrently with induced polarization (IP) using dipole-dipole array. Low resistivity and high IP-chargeability anomalies were delineated in the study area. Mineral hosted by sulphide-bearing quartz veins within schist was also targets of interest for mineralization. Therefore, the high resistivity observed in this study is attributed to the presence of quartz veins. The relatively low resistivity areas that are suspected to be fault/fracture zone with a depth of over 150 m of varying length, which correlated with high chargeability zones, are indicative of disseminated mineral deposits. The consistent NE-SW trends associated with all the anomalies suggest a unique structural and mineralized body. The mineralization potential map generated from the combination of results of the study area shows high mineralized and non mineralized zones of depth to mineralized bodies varies between 30 m and 500 m.