GEOPHYSICAL MAPPING OF AGBAJA IRON ORE DEPOSIT, AGBAJA VILLAGE, SOUTHERN BIDA BASIN, NIGERIA

Abstract

Geophysical mapping of Agbaja iron deposit was carried out by integration of geophysical methods, remote sensing and validated by geochemically analyzed borehole data of the study area. Landsat 8 image was acquired/downloaded from the U.S. Geological Survey site of the United States in TIFF format covering the study area. The Landsat 8 data was pre-processed for geometric, radiometric and atmospheric correction and then UTM geo- referenced using ARCGIS10.3 software which includes the application of pre-defined models which reduced the effect of the earth’s rotation. The image was then enhanced to improve the appearance of it features. Analysis such as band combination, False Color Composite (FCC), Principal Component Analyses (PCAs) and Band ratio was applied in mapping the iron deposit in the study area. Also, aeromagnetic data was obtained from Nigeria Geological Survey Agency (NGSA). Aeromagnetic data processing was done using Oasis montaj software, and the following maps were generated; Total Magnetic Intensity (TMI), Residualization, Analytic Signal and Total Horizontal Derivative (THD). A mineralized prospective map that shows mineralization of the study area trending NW- SE was generated by reconciling the thematic maps using a data driven model (entropy model). Weightage assigning was done through aforementioned model. For confirmation of the features observed on the mineral prospective map generated, ground truthing survey was carried out using both ground magnetic and electrical resistivity (VES). The results from both ground magnetics and VES were qualitatively and quantitatively interpreted and juxtaposed for comparison. The geochemically analyzed borehole data, ground magnetic data, and VES data interpretations validated the earlier entropy produced mineralization prospectivity map of the study area, and established that the Agbaja iron deposit in the study area exist as a flat or almost a flat lying deposit and laterally continuous, which are exposed in some areas and covered by lateritic top soil in other areas. It shows the depth to the top of the iron deposit ranges from 0 m-8 m, while the thickness of the deposit ranges from 25 -36 m and also depth to the bottom of iron deposit is 40 m at most. Hence, a validated iron ore mineralization potential map of the study area is produced.