Mapping Hydrothermal Alteration Targets from Landsat 8 OLI/TIRS and Magnetic Data Using Digital Image Processing Techniques in Garoua, North Cameroon

A geological based remote sensing study was carried out over the Poli group in Garoua (northern Cameroon), renowned for its hydrothermally occurring mineralizations (Gold and Uranium). In this study, Landsat 8 OLI/TIRS coupled with magnetic data were used in order to realize a regional litho-structural mapping of hydrothermal alteration targets, required for mineral exploration. Hence, the enhancement of both Landsat 8 and magnetic data was achieved via digital image processing (DIP) techniques notably Band rationing (BR), Principal Component Analysis (PCA), Horizontal gradient (HG), and lineament extraction algorithms. Based on reference band ratio combinations (Sultan’s and Kaufmann’s) and Crosta Technique (PCA analysis), hydrothermally altered minerals such as hydroxyl-bearing minerals and iron oxides were identified. The PCA map was shown to better illustrate hydrothermally altered areas than Band ratios. Thus, a classification map emphasizing on mineral targets was obtained from the PCA map. Besides, the CET grid analysis tool (horizontal gradient) from Geosoft software 8.4 and the line algorithm (pan band 8) from Geomatica 2013 allowed the extraction of subsurface and surface lineaments respectively. The resulting lineaments showed a predominant E-W trending direction, which suggests a major tectonic event having prevailed within the area. Other directions include NE-SW/ENE-WSW, and N-S. The generation of a target exploration map, via ArcGIS 10.4.1, was performed by the overlay of hydrothermal alteration mapping and structural mapping. New regional maps, providing a useful insight for further mining exploration, were obtained