Application of ASTER SWIR data on detection of alteration zone in the Sheikhabad area, eastern Iran

Abstract

This research was focused on different techniques of remote sensing to identify the external alteration structures at Sheikhabad region, especially mining exploration of hydrothermal alteration of typical structure using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. We have applied the ASTER data, including three visible and near infrared (VNIR), six shortwave infrared (SWIR), and five thermal infrared (TIR) bands to determine the alteration minerals of Sheikhabad area. Spectral analysis of the surface reflectance SWIR manifests absorption in 2.20 and 2.33 μm wavelength regions. Absorption at 2.20 μm (band 6), due to Al-OH anionic agent is consistent with the presence of clay minerals (illite, kaolinite) and sericite, whereas absorption at 2.33 μm (band 8) due to Mg-OH anionic agent and carbonates is consistent with the occurrence of chlorite, epidote, and calcite minerals. In this research, by using the satellite image processing of ASTER sensor, different methods such as false color composite (FCC), band ratio (BR), and principal component analysis (PCA) as well as the direct data from the Mokhtaran geological map (1:100,000) were applied. The results obtained from ASTER data are compatible with the conclusions inferred from petrology and X-ray diffraction (XRD) studies of the surface samples. Based on petrographic studies, these rocks have different compositions and include trachyandesite, andesite, rhyodacite, and porphyric diorite. According to petrology and chemical analysis (XRD) and remote sensing results, six alterations zones consisting of kaolinitization, silicification, alunitization, carbonatization, sericitization, and propylitic are distinguished; thus, it is suggested to explore Cu-Au mineralization.