Capability of advanced spaceborne thermal emission and reflection radiometer (ASTER) on discrimination of carbonates and associated rocks and mineral identification of eastern mountain region (Saih Hatat window) of Sultanate of Oman

摘要

The present study demonstrates the capability of multi-spectral data acquired from advanced spaceborne thermal emission and reflection radiometer (ASTER) satellite to explore the areas of massive carbonate deposits and associated rock formations for geological application. The extent of interdependence among VNIR, SWIR and TIR bands of ASTER spectral regions has been studied for discrimination of rock formations and identification of minerals of eastern mountain region (Saih Hatat window) of Sultanate of Oman and processed through digital image analysis and classification. Visual interpretation techniques have been employed to discriminate major quartz-rich silicates, carbonates and mafic ophiolite rock formations on the satellite image by carrying out subsequent image enhancement technique and principal component analysis (PCA). Color composite using nine VNIR and SWIR ASTER spectral bands by exposing the results of band ratios of (band 7 + band 9)/band 8 for limestone (CaCO_3); (band 6 + band 8)/band 7 for dolomite (CaMgCO_3); and band 2/band 1 for mafic-rich (Fe~(3+)) rock formations differentiated the carbonates and ophiolite formations of the study region. The band ratios of 6/8 developed for quartz-rich silicates (shale, schist, sandstone, graywackes) of autochthonous Unit 'A' of Late Pro-terozoic to Early Ordovician and Tertiary age, 9/7 for the carbonates (limestone and dolomite) of Autochthonous rock Unit 'B' of Late Permian to Triassic age and 1/2 for mafic ophiolites (harzburgite, harzburgite with dunite) of Samail Nappe discriminated the different rock formations and increased the visual interpretations. It has well delineated thegray limestone and yellow dolomite of Autochthonous Unit 'A'. The subsequent PCA realized on the 6 SWIR spectral bands enables very good validation and discrimination of quartz-rich silicates, carbonates and mafic ophiolite rock formations defined on previous image rationing techniques and existing geological map, and provides information comparable to surficial formations previously not well recognized. It is capable of distinguishing the ancient and recent alluvial fans consisting of clay, silt, sand and conglomerate formations of Tertiary age from the Autochthonous Unit 'A'. Furthermore, the ASTER TIR spectral indices have been applied for assessing the effectiveness of TIR spectral bands on identification of quartz-rich silicates, carbonates and mafic-rich minerals and to evaluate the discriminated rock formations. The results agree well with existing geological maps and other published data. The study results show that the combination of visual interpretation, previous field knowledge and digital image processing techniques applied on the ASTER spectral regions have proved beneficial in studying carbonates and associated rock formations of eastern mountain region of Sultanate of Oman and can thus be used as a powerful tool to explore massive carbonate deposits or for geological mapping of other geographical regions where similar geological questions need to be resolved.