Discriminative mapping of geological formations and silica-rich zones using ASTER images: A case study of Ardakan area, Iran

The Kalut-e-Ashrafa area is located in the north-east of Ardakan area in central Iran, Yazd province. This area promises copper mineralization. The most of the minerals in this study area are silica-rich veins and veinlets. Therefore, in order to identify geological formations with silica zones and to determine potential mineralization areas, ASTER images and remote sensing methods were used. Advanced Space-borne Thermal Emission and Reflection radiometer (ASTER) images helped to make discriminative maps of those geological formations and to spot silica rich zones in that area. For this purpose, Color-Ratio-Composite (CRC), False Color Composite (FCC) images of band4/band1 (Red), band3/band1 (Green), and band12/band14 (Blue) ratios were employed to enhance the FCC images and make them more distinctive, a decorrelation stretch procedure was applied to CRC images. Discrimination of silica-rich zones was performed using Matched Filtering methods applied to ASTER spectral bands. Geological formations were distinguishable in the FCC images of the study area, and the sand dunes were distinctive in the images with bluish pixels. Also, setting a threshold of x+2s on the digital numbers of the MF rule images provided implication that red areas had a high probability of being silica-rich zones.