SPECTRAL DISCRIMINATION OF URANIUM-BEARING TRACHYTE IN WADI KAREIM-WADI EL ATSHAN AREA, CENTRAL EASTERN DESERT OF EGYPT USING LANDSAT ENHANCED THEMATIC MAPPER DATA (ETM+)

The basement rocks around Wadi Kareim-Wadi El Atshan in the Central Eastern Desert of Egypt
represent a structurally and metamorphic complex assemblage of folded and faulted metasediment,
metavolcanic and Hammamat sedimentary rocks into a series of trends. Geological mapping in this region
is challenging, primarily due to difficult access, complexity of structures, and lack of resolution and
areal integrity of lithological differentiation using conventional mapping techniques. Spectral analysis of
selected bands of Landsat-7 ETM+ data covered the studied area, in synergy with previous geological field
observation, proved effective resolving of geological mapping problems in the study region, with emphasis
on discrimination and mapping the trachyte that exposed in the area which considered as favorable host
rock for uranium and/or thorium mineralization .
A variety of remote sensing processing techniques of the digital data of Landsat-7 ETM+ were
applied successfully for lithologic mapping in W. Kareim-Wadi El Atshan area, showing improvement in
discrimination of sill, dyke and plug trachyte rocks. Not all Red, Green and Blue (RGB) band combination
was useful to obtain basic knowledge of the study area. The traditional RGB (3,2,1 true color image and
7,4,2 false color image) band combination could not distinguished between some outcropping units, and not
delineate a definite contacts between them as well as delineation of the uranium bearing trachyte.
The adopted composite ratio image produced from combination of 3/1(Red), 5/4(Green) and 5/7(Blue)
band ratios were successfully used to discriminate the uranium-bearing trachyte and demonstrate the
benefit of the enhance ETM+ remote sensing data for lithologic and structural mapping. While Principal
Component analysis and decorrelation stretching techniques add further successful tools to outline and
define the uranium-bearing trachyte that extend all over W. Kareim-W. El Atshan area.
Interpretation and observation of small exposed bodies like trachyte rocks using remote sensing
techniques could help in detecting and delineating more than one localities of uranium mineralization,
especially, when these data compiled and integrate with the data of favorable structural and geochemical
conditions of uranium deposition.