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Wadi Defeit area in the extreme South Eastern Desert of Egypt is occupied mainly by Precambrian ophiolitic and island-arc assemblages. The ophiolitic rocks are principally represented by serpentinite, talc-carbonate and listwaenite thrusted over the metasediments and island-arc schistose metavolcanics and intruded by syn to late tectonics intrusions of gabbro-diorite and monzogranite (G2). For discrimination of the basement rock units covering the study area, tracing the major structural features and identification of the mineralized alteration zones, the ETM+ with 7 bands composition and resolution about 15 m was processed where the geometric corrections and radiometric balancing to the image were carried out. The image enhancement techniques including spatial and spectral enhancement, ratioing and stretching have been applied and different band ratios were testes, the band selection for different ratio images used is based on the spectral signatures of these rocks. The study revealed that, based on the spectral signatures of the different basement rocks forming Gabal Al Adraq area, the RGB band ratio image (5/7, 5/1, 4) is proved to be very effective in the discrimination of the different basement rocks and the gold bearing alteration zones. The gold mineralization is introduced into the listwaenites, alteration zones and quartz veins during the sulfidization processes and the remobilization of gold took place along the thrust zones during listwaenization. This study indicates that the alteration zones in both the metavolcanics and the listwaenites are promising and need more detailed exploration for Au and Ag mineralizations to evaluate their potentiality.
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