ASTER and Landsat TM remote sensing data application for chromite prospecting: case study from south Iran

Chromite deposits in Iran are located in the ophiolite complexes, which have mostly podiform types and irregular in their settings . Exploration for podiform chromite deposits associated with ophiolite complexes has been a challenge for the prospectors due to tectonic disturbance and their distribution patterns. Most of Iranian ophiolitic zones are located in mountainous and inaccessible regions. Remote sensing approach could be applicable tool for choromite prospecting in Iranian ophiolitic zones with intensely rugged topography, where systematic sampling and conventional geological mapping are limited. In this study, Landsat Thematic Mapper and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data were used for chromite prospecting and lithological mapping in Neyriz ophiolitic zone in the south of Iran. Image transformation techniques, namely decorrelation stretch, band ratio, principal component analysis (PCA) were applied to the datasets. The RGB decorrelated image of Landsat TM spectral bands 7, 5, and 4, and the principal components PC1, PC2 and PC3 image of ASTER VNIR-SWIR spectral bands showed the occurrence of major lithological units in the study area. The band ratios of 5/3, 5/1, 7/5 and 4/7, 4/1, 2/3*4/3 applied on ASTER VNIR-SWIR bands were used discriminate all rock types in the study and delineation of the transition zone in the ophiolitic complex. Spectral Angle Mapper (SAM) technique was used to detect minerals of rock units. Additionally, image processing results were verified by comprehensive fieldwork and laboratory analysis. Result of this investigation indicate that the integration of Landsat TM and ASTER datasets is one of the most effective tool for chromite prospecting and lithological mapping in mountainous and inaccessible regions such Iranian ophiolitic zones