APPLICATIONS OF REMOTE SENSING IN LITHOLOGICAL MAPPING OF EAST GABAL ATUD AREA, CENTRAL EASTERN DESERT, EGYPT

The east of Gabal Atud area is covered by a variety of Precambrian basement rocks including Atud Formation, Atud tectonized mélange, metavolcanics, and serpentinites-talc-carbonates. These rocks were later intruded by the island arc metagabbro- diorite complex which in turn is invaded by some dykes. Operational Land Imager (OLI) and Sentinel-2A were applied for the first time for lithological discrimination of the exposed rocks. Five image enhancement techniques are applied including optimum index factor, false color composites, band rationing, principal component analysis, and minimum noise fraction for the interpretation of OLI and Sentinel-2A datasets. The integrated image-processing techniques allow the effective lithological discrimination of the east of Gabal Atud area, Central Eastern Desert, Egypt. The acid metavolcanics have been effectively discriminated from basic metavolcanics and serpentinites through FCC S2 b12-b11-b1, OLI PCA b4 -b3-b2, S2 PCA b5-b2-b3, and OLI band ratio (b4/b2, b6/b7, b4/b6). The sandstone facies highlight the fantastic (folding and faulting) structures of the Atud Formation on OLI and S2 images including OLI PCA of b1-b2-b3, S2 PCA of (b2), and S2 PCA of b5-b2-b3. Conglomerate facies can be differentiated from diamictite facies using the band ratio of the S2 (b7/b12). Although, the serpentinites and diamictite have different lithological compositions, they show similar colors in some OLI and S2 images (e.g. OLI PCA b1-b2-b3, S2 PCA b2) but they can be discriminated using other OLI and S2 techniques as OLI PCA b4-b2-b1, S2 PCA b5-b2-b3, and band ratio applications (e.g. OLI b6/b7 and OLI (b6/b7, b5/b6, b4/b2)).