Aero-magnetic and Aero-radiometric Prospecting for Potential Gold Mineralisation over Ilesa and its Environs Southwest, Nigeria.

Abstract

The mapping of potential gold mineralization zones in a part of southwestern Nigeria was carried out from the analyses and interpretation of airborne magnetic and radiometric data. Some enhancing filters, such as analytic signal and first vertical derivative were applied on the Total Magnetic Intensity map to delineate near-surface structures that might host the potential mineral zones within the study area. The analytic signal shows three magnetic zones delineated with low magnetic zone ranging from 0.008 to 0.026 nT/m, moderate with amplitude 0.117 to 0.029 nT/m and high with amplitudes above 0.109 nT/m. In the First vertical derivative, NE-SW structural trends, considered to be the orientation of gold mineral deposits dominate. The depth obtained from the source parameter imaging ranges from 89.03 to 574.76 m. The results from the analysis of aero-radiometric data revealed that the concentration of the radioelements ranged from 0.16 – 3.25 %, 0.80 – 33.27 ppm and 0.13 – 7.24 ppm for potassium, thorium, and uranium, respectively. The K/eTh ratio maps reveal the presence of hydrothermal alteration zones at the north-eastern, central, and southern parts of the study area corresponding to the amphibolite schist and quartz schist, respectively, source rocks for gold deposits. This study has shown that the structures (faults and fractures) and hydrothermal alteration zones delineated within the study area are favourable features to host gold mineralization in the study area.