Mapping Gold-Bearing Massive Sulfide Deposits in the Neoproterozoic Allaqi Suture, Southeast Egypt with Landsat TM and SIR-C/X SAR Images
Meta-volcanic sequences in the Neoproterozoic Arabian-Nubian Shield host auriferous massive sulfide deposits with surface expression in the form of clay and iron alteration zones. These are large enough (few hundreds of meters across) and have distinctive characteristic reflectance spectra to be mapped with the 30-m spatial resolution Landsat Thematic Mapper (TM) images. Landsat TM together with Shuttle Imaging Radar (SIR)-C/X-Synthetic Aperture Radar (SAR) images are used for finding and mapping the alteration zones in the western part of the east-trending Allaqi suture in the Southeastern Desert of Egypt. The 5/7-5/1-3/4*5/4 band-ratio Landsat TM image shows the Umm Garaiat alteration zone as sugary white; this appears red in the 5/7-4/5-3/1 band-ratio Landsat TM image. Geological and geochemical data indicate that the Umm Garaiat alteration zone is the surface expression of a massive sulfide deposit that contains up to 12 g/t gold. Density slicing using 5/7 and 3/1 Landsat TM band-ratios effectively maps clay and iron alteration. The 5/7 density slicing Landsat TM image suggests that the Umm Garaiat alteration zone is dominated by clay minerals. The 3/1 density slicing Landsat TM image shows little evidence for FeO minerals associated with the Umm Garaiat alteration zone. Analysis of Landsat TM images with supervised classification techniques using the Umm Garaiat alteration zone as the training site helped identify previously unknown alteration zones at Wadi Marahiq. Interpretation of Chh-Lhh-Lhv SIR-C/X-SAR images helped in understanding the lithological and structural controls on massive sulfide deposits in the study area. This demonstrates the utility of orbital remote sensing for finding ore deposits in arid regions.
T. M. Ramadan et al., "Mapping Gold-Bearing Massive Sulfide Deposits in the Neoproterozoic Allaqi Suture, Southeast Egypt with Landsat TM and SIR-C/X SAR Images," Photogrammetric Engineering and Remote Sensing (PE\&RS), vol. 67, no. 4, pp. 491-497, American Society for Photogrammetry and Remote Sensing, Apr 2001.
Geosciences and Geological and Petroleum Engineering
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