Location Mapping of Hydrothermal Alteration Using Landsat 8 Data: A Case of Study in Prestea Huni Valley District, Ghana

Utilization of multispectral satellite images is an excellent approach in the reconnaissance stage of gold prospecting due to its high effectiveness and low cost. This research used Landsat 8 Remote Sensing data and Geographical Information System to identify, delineate and map hydrothermal alteration zone relating to gold pattern mineralization in Prestea Huni Valley District in the Western Region of Ghana. Principle Component Analysis (PCA), three band combinations, spectral rationing and Crosta techniques are used in this study. For three band combinations, bands 5, 4, 3 and 5, 6, 7 are used to map location of hydrothermal alterations. Band ratios (7/5and6/7), (6/5) and (4/2) are used to identify presence of clay, ferrous and iron oxide minerals respectively. Sabin's ratio 4/2, 6/7 and 6/5, Kaufmann ratio 7/5, 5/4 and 6/7, and 4/2, 6/7 and 5 are used to identify vegetation, outcrop and hydrothermal alterations respectively. Crosta and PCA techniques were used to suppress the interference of vegetation in delineating the alteration zones. Results revealed that the three band combinations and spectral ratioing clearly depicts hydrothermal deposit of ferrous minerals, clay and iron oxide minerals. PCA identifies presence of iron-oxide and hydroxyl minerals as bright pixels. The first three high order principal components (PC1, PC2 and PC3) of input spectral bands gave more than 98% of the spectral information. Thus, the results from satellite images an effective and efficient way of mapping hydrothermal alteration zones at regional scale.