MULTIFACETED INVESTIGATION OF PORPHYRY CU-AU-MO DEPOSIT IN HYDROTHERMAL ALTERATION ZONES WITHIN THE GOLD FIELD OF ILESHA SCHIST BELT

Abstract

This study was carried out to map the distribution of porphyry systems within Ilesha Schist belt Southwestern Nigeria for easy accessibility of commercial gold as well as copper and molybdenum deposits to boost exploitation activities within the area. Airborne magnetic and radiometric data of the area were utilized. The acquired total magnetic intensity map of the field was enhanced with reduction to equator, vertical derivative, analytic signal and spectral analysis. Enhanced total magnetic intensity map of the study area revealed magnetic anomalies related to concealed intrusive rock associated with Cu-Au-Mo deposit at depth ranges from 306 – 421 m. Vertical derivative map revealed shallow magnetic bodies in the southern and western parts, which are probable zones for Cu-Au-Mo deposit. Analytical signal map, with magnetic zones of high intensity value between 0.1 nT/M and 1.7 nT/M highlighted faulted basement blocks impregnated with porphyry the Cu-Au-Mo deposit. Airborne radiometry image shows radioelement distributions for different lithologies. High concentration of potassium signatures observed over some parts of the area revealed hydrothermal alteration zones favourable to concentration of Cu-Au-Mo deposits. Computed Th/k ratio and composite potassium maps enhanced the signature of potassium enrichment associated with hydrothermal alteration zones. Validation of airborne results using geochemical analyses confirms the presence of copper-gold-molybdenum elements within the mapped hydrothermal alteration zones. This research has identified other valuable ore deposit, such as copper and molybdenum, to enhance exploitation activities within the area.