Mapping Hydrothermal Alteration Minerals using Landsat 8 and ASTER Data: A Case Study from the Red Sea Hills, NE Sudan

Hydrothermal alteration minerals provide key indicators for mineral exploration, particularly in arid and inaccessible regions where field surveys are constrained. This study integrates remote sensing and GIS techniques to map alteration zones in the Red Sea Hills, NE Sudan, using Landsat 8 OLI and ASTER datasets. Preprocessing included FLAASH atmospheric correction and Minimum Noise Fraction (MNF) transformation to enhance spectral integrity. For Landsat 8 diagnostic band ratios and density slicing were applied to highlight ferric/ferrous iron oxides and clay/hydroxyl-bearing minerals, followed by supervised Parallelepiped classification of Sabins band ratios and Crosta transformations to delineate prospective alteration zones. ASTER VNIR-SWIR data enabled higher resolution mapping through Mineral Indices and Spectral Angle Mapper (SAM) classification against USGS spectral library endmembers. These approaches revealed three principal hydrothermal alteration zones: phyllic (muscovite, illite), argillic (kaolinite, alunite), and propylitic (epidote, chlorite). Results demonstrate that Landsat 8 is effective for regional-scale reconnaissance, but ASTER’s superior spectral resolution provides more accurate and mineralogically de-tailed alteration mapping. The study underscores the value of ASTER data for early-stage exploration in structurally complex, mineralized terranes such as the Arabian-Nubian Shield. Keywords: Hydrothermal alteration; Mineral exploration; ASTER; Landsat 8; Crosta; Band Ratio; Spectral indices; SAM classification; Arabian-Nubian Shield