A B S T R A C TAeroradiometric data set of Isanlu sheet 225 (1:100,000) has been acquired with a view to analyze and interpret for the delineation of hydrothermally altered zones that favour gold mineralization. The acquired aero-radiometric data was subjected to filtering algorithm and enhancement techniques such as shaded relief enhancement, elemental ratio enhancement using Geosoft Oasis Montaj Software. Moreover, Golden Software Surfer was used to identify and present the revealed hydrothermally altered zones. The interpretation of the aero data set has enhanced the delineation of eight hydrothermally altered zones. Therefore, the areas that are hydrothermally altered are potential sites for gold mineralization, such as areas around Odogbe and Okolom in the north-central portion of the study area. Similarly, regions around Egbe in the western edge are suspected to be mineralized zones. Results obtained in this research study have shown that mapping of hydrothermally altered zones that favour gold mineralization is feasible even without the actual physical contact and visitation to the area. The research suggests that this method of delineation may compliment other geophysical exploration technique for possible gold bearing zones of an area. Moreover, due to the non-invasive nature of the method, large areas of space may be mapped within a limited time. Areas that are nonaccessible to ground geophysical exploration due to various factors can also be studied.

Potassium (K) response is associated with minerals that can be easily weathered, whereas uranium (U) is usually related to residual clay, oxides and accessory minerals. With a view to interpret for the detection of sulphide deposit based on similar responses exhibited by the various rock units, radiometric data set was interpreted. The study area is located within Latitude +8000’00’’to +8030’00’’ and Longitude +5030’00’’E to +6000’00’’E. The data was collected in most parts of the Nigeria by Fugro Airborne Services Ltd. Johannesburg in collaboration with the Nigerian Geological Survey agency using a light aircraft that was flown in NW-SE direction with a nominal terrain clearance of 80 m and at a speed of 70-80 m/s, with a flight line spacing of 500 m apart. The acquired data was subjected to elemental concentration enhancement using Geosoft Oasis Montaj Software. From the interpreted data, the red coloured portions indicate high uranium and low potassium formations (H-U/K), while the blue coloured portions indicate low uranium and high potassium formations (L-U/K). The regions L-U/K have recorded low U/K ratios, meaning that L-U/K have very low uranium count rates as compared to the count rates of potassium in these regions; this signifies potassium abundance. This also suggests igneous activities that usually culminate to the emplacement of the meta-volcanic lithologies. H-U/K and M-U/K (Moderate U/K formations) are seen to have patches of high U/K ratios within the central portions. This high U/K ratio was therefore, as a result of sulphide deposition.