Exploration for Base Metal Mineralization in the Southern Part of the Central Iranian Volcanic Belt Using Aster and ETM+Data

Abstract: The study area is located in the southern part of the Central Iranian Volcanic belt. Many base metal deposits are located in these areas which are mainly associated with porphyry systems. The area is having a semi-arid type of climate and a poor vegetation cover. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Enhanced Thematic Mapper Plus (ETM)+ images have been used here in order to find proper image processing techniques for enhancement of the hydrothermally altered areas. Different image processing techniques such as band ratios, principal component analysis and supervised classification are used for enhancing the altered areas. The analysis of the ASTER data over this area showed that the false color composite of the ratios 4/9 (red), 4/8 (green) and 4/5 (blue) can enhance the altered areas. In addition to the hydroxyl minerals, the chlorite and epidote rich rocks are also enhanced in the False Color Composite (FCC) of ratio images. As the vegetation cover in the area is poor, this image processing technique is suitable for enhancement of the hydrothermally altered areas in the arid and semi-arid areas. The selected Principal Components (PCs) that enhance the altered areas are chosen for making FCC by using PC4 (ASTER data in red, hydroxyl image), Principal Components (PC5) (ASTER data in green, hydroxyl image) and PC6 (ETM^ data in blue, iron oxide image). Supervised image classification showed that for the semi-arid type of climate where vegetation cover is poor, the altered and unaltered rocks can be classified successfully.