Using Gis As A Spatial Support Tool To Discriminate Between True And False Geochemical Anomalies At The Northern Margin Of The Asankragwa Gold Belt In The Paleoproterozoic Kumasi Basin, Ghana

This study uses Geographical Information Systems (GIS) as a support tool for gold exploration to distinguish between true and false soil geochemical anomalies at the northern segment of the Asankragwa gold belt in the Paleoproterozoic Kumasi Basin, Ghana. The main objective of this study is to identify potentially mineralized zones within the northern segment of the Asankragwa gold belt by integrating GIS, structural and soil geochemical datasets. To reduce the probability of delineating false anomalies as true anomalies, diverse graphical threshold determination methods, namely histogram, box plot, QQ plot, mean+2SD, Jenks Natural Break and Probability plot, as well as advanced threshold determination methods like the Mean Absolute Deviation (MAD) and double MAD were employed. The threshold values established from the graphical methods are 175 ppb, 96 ppb, 335ppb, 384 ppb and 100 ppb respectively. However, the MAD and double MAD methods produced threshold values of 74.5ppb and 130ppb respectively. Based on the high variability in the threshold values, anomalous areas were delineated using thresholds values of 100ppb and 130ppb respectively established from the Jenks Natural Break and Probability plot and double MAD method. About 40%, 35% and 20% of the selected anomalous areas are located within soils overlying volcanoclastic, clastic sedimentary and marine volcanoclastic rocks respectively. These anomalies are not lithologically controlled since they are not confined to a particular rock type. Superimposing the selected aanomalies over geological structures and Landsat imagery, 90% of the anomalies can be linked to the NE-SW geological structures. Upon integrating the anomalies with structural data and illegal mining activities and using the Booleon analysis, not all anomalies may be true anomalies. True gold anomalies within the Asankragwa gold belt are consistent with the central> northern> southern portions. Hence, the discovery of gold in the Asankragwa gold belt has been enhanced using GIS as a spatial support tool.