Assessment of Image Ratio Technique for Gold Exploration in Arid Region Using Landsat ETM+7: Limitations and Possible Source of Misinterpretations

Abstract

In modern exploration program, the use of multispectral satellite images is one of the standard procedures during the early stages of gold exploration, due to its high efficiency and low cost. The main goal of the present study is to assess the efficiency of image ratio technique for gold mineralization in arid region. The area around the third cataract, northern state, Sudan has been selected for the current purpose. Landsat ETM+7 images have been used in the current study. The patterns recognized in the digitally processed satellite images showed a clear discrimination of granitic rocks, Sandstone from mafic metavolcanics, as well as delineate the structural features in the region. The spectral properties of band ratios have successfully been used to delineate alteration zones. Common false color composite ratio images have been applied by combining band ratio images in RGB. From these entire analyses through visual interpretation and ground truthing the results show that more than 60% of the image mask with iron alteration due to the dominantly ferruginous Sandstone formation in the study area and addition to clay-rich wadies deposits. From field observation very narrow hydrothermally alteration zone has been detected along highly sheared metavolcanics and their margin with syn-orogenic granites in the central part of the study area. This study clearly concluded that nevertheless, the significance of image ratio technique for gold exploration in early stage of exploration program, care should be taken during image interpretation in such geological condition.