Gypsum exploration using ASTER data in the Hormozgan province, south of Iran

Iran is the second largest gypsum producer in the world. There are still potential areas for the exploration of the new gypsum deposits. Regional scale investigation is an important preliminary step in mineral exploration. Advanced spaceborne thermal emission and reflection radiometer (ASTER) images were used for mapping of the gypsum deposits in Roydar basin, in southern Iran. The objective of this study is to identify gypsum-bearing areas with economic value using ASTER data. The present research utilized various image-processing techniques, including false color composite (FCC), band ratios (BR), and spectral angle mapper (SAM). Four reference spectra used in SAM method. Two reference spectra were selected from the USGS and IGCP libraries, respectively. Two other spectra extracted from ASTER images, corresponding to the known sampled locations. This study showed that FCC images of ASTER bands are quick, easy, and efficient method to identify gypsum-bearing areas. We proposed six different groups of the FCCs to separate gypsum layers. The use of extracted spectra from ASTER image, as the reference spectra, is better than IGCP and USGS spectra from the spectral libraries in identifying gypsum-bearing areas by SAM method. The [(B3 × B8)/(B5 × B6)]–(3/2) band ratio demonstrated that gypsum-bearing rocks are enhanced better than the FCC & SAM techniques. The results were evaluated for accuracy assessment by field checking and sampling.