Spectral analyses of basement rocks in El-Sibai-Umm Shaddad area, Central Eastern Desert, Egypt, using ASTER thermal infrared data

Abstract

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) level 1B (five thermal infrared (TIR) bands) data have been used to discriminate the exposed rock units in the Wadi El-Sibai-Umm Shaddad area in the Central Eastern Desert of Egypt. The quantitative and qualitative spectral characteristic analyses of the exposed rock units have been applied using the data of ASTER TIR bands (8–12 μm) in order to explain the relationship between emissivity of these rock units and their mineralogical composition. The exposed rock units comprise a variety of granitic rocks intruded into the ophiolitic and island arc metavolcanic assemblages of the Pan-African basement. The ophiolitic serpentinites talc-carbonate rocks, metavolcanics and granitic rocks are well discriminated by applying the ASTER thermal band ratios (12/13, 10 × 11/13 × 14, 12/14) in RGB. In this study, the principal component analyses (PCA) of the five ASTER thermal bands are applied for the first time to discriminate the basement rocks in the study area. The method effectively discriminates between three granitic varieties forming the El-Sibai-Abu El Tiyur intrusion. They are biotite granite, leucocratic alkali-feldspar granite and riebeckite granite. These granitic varieties were previously mapped as one unit, namely alkali-feldspar granite. This study reveals that the applied data of ASTER thermal ratio bands produced a new geological map with well-discriminated rock units.