The use of GIS/remote sensing in determining gold potential areas on the Paleoproterozoic Asankragwa gold belt, Ghana

Abstract

Remote sensing technique, which is not limited by accessibility, financial status, unusually large areal extent and climate when used at the initial stage, together with other geological data sets, will make an exploration process faster, easier and most importantly very efficient and cost-effective. There is limited information on this belt due to the size of the belt, complexity of the belt and the fact that it falls within the Kumasi Basin where mineralisation is not highly expected. Although the major structures on this belt are similar to that on the Ashanti belt, mineralisation on this belt has not been high as that on the Ashanti belt. This study seeks to use GIS to integrate geological methods with remote sensing methods to delineate mineralised zones on the Asankragwa gold belt (AGB) to produce information on anomalies which will entice exploration companies to explore further on this belt and to provide guidelines for grassroot explorers in areas where there is limited geochemical and geophysical information. Band combinations (bands 5, 4, 3 and 5, 6, 7), as well as band ratios (5/6, 5/7, 7/2 and 2/4), were implemented to the visible, near-infrared and shortwave infrared bands of Landsat 8, which were used to determine alterations in the study area. Lineaments were mapped from the Digital Elevation Model (DEM) of the area. About 80% of these lineaments were observed to be trending NE-SW. The structures contributed to about 70% of the anomalies observed in the area. The results of this investigation demonstrate the capability of the applied imagery enhancement methods in distinguishing different features, identifying hydrothermally altered rocks and structures as well as delineation of probable anomalies. It was observed that the effectiveness in the identification of mineralised zones was enhanced by integrating remote sensing data sets. Structures and alteration information obtained from remote sensing provided enough information for the delineation of gold potential areas on the entire belt.