Alteration Mapping by Remote Sensing: Application to Hasandağ – Melendi̇z Volcanic Complex, Central Turkey

Certain alteration minerals are used to identify the hydrothermally altered rocks. In volcanic rocks, mainly potassic, phyllic (sericitic), propylitic, argillic alteration and silicification are observed. The role of remote sensing in alteration mapping is the differentiation of the minerals that are unique for different alteration types. In this study, Landsat TM 5 images are used. General alteration trend in the area is mapped by conventional methods of color composite, band rationing, principal component analysis and multi-linear regression analysis. Detailed mineral mapping is carried on by using the United States Geological Survey (USGS) spectral library data. Spectral reflectances of selected minerals are analyzed according to the TM band intervals and appropriate band ratios are selected. TM bands 1,2,3,4,5 and 7 are used. Outputs of mineral maps are investigated for zonal distribution. Mineral maps that are obtained by the mineral separation method reveal that the youngest volcanic complex Hasandağ is poorly altered. Instead, Keçiboyduran, Melendiz and Tepeköy volcanic complexes are found to be highly altered with the pattern of clay dominant in the center and increasing oxidation towards flanks. Also the alteration along the previously mapped buried faults is a proof that the method can provide information about the alteration source.