Mineral imaging with Landsat Thematic Mapper data for hydrothermal alteration mapping in heavily vegetated terrane

A mineral imaging methodology, which involves processing of Landsat Thematic Mapper (TM) images and integration of ground data, is tested in the Baguio district of the Philippines to map hydrothermally altered zones in heavily vegetated terranes. Based on published reflectance spectra, two band ratio images are created and input into principal components analysis to map each predominant hydrothermal alteration mineral into separate mineral images. Digitized map data of known hydrothermal alteration zones are used for identifying training pixels for the known alteration zones. The mineral images and the training pixels are used in a supervised classification to map hydrothermally altered zones; classification accuracy reaches 69%. Inclusion of an image of a digital elevation model improves the classification accuracy to 82%. The mineral imaging methodology proved more successful in remote mapping of known hydrothermally altered zones in the Baguio district than remote mapping of limonitic and clay alteration using previously developed techniques.