Utilizing of ASTER multispectral data in alteration zones and granitic rock types discrimination at Gabal Abu El-Tiyur area, central Eastern Desert, Egypt
Keywords:Gabal Abu El-Tiyur, Relative Band Depth, Band Ratios, Minimum Noise Fraction, Matched Filtering, Mixture Tuned Matched Filtering, geological mapping, radioactivity
The present work aims at examining the capability of ASTER VNIR-SWIR bands to discriminate the granitic rocks and detection of alteration types within them, which could be a possible hosting for Umineralization in the arid climate. The applied image processing techniques comprising relative band depth, band ratios, minimum noise fraction and color band composites supervised classification as well as two spectral mapping methods (matched filtering and mixture tuned matched filtering) were efficient in the granitic rocks discrimination and alteration end-members (hematite, muscovite, kaolinite and chlorite) identification. These results easily ifferentiate the mélange matrix into a) metasediments rich in blocks and b) metasediments poor in blocks. Also, the granitic rocks are
classified into granodiorite, monzogranite, syenogranite, alkali-feldspar granite and alkaline (riebeckite) granite. The associated abnormal level of radioactivity exhibits 18 ppm and 31 ppm for eU, eTh respectively and mainly restricted to the alkali-feldspar granites, which significantly have higher hematite and muscovite content rather than the other exposures. A detailed geologic map of
scale 1:100,000 is constructed from the interpretation of the processed ASTER images, fieldwork and petrographic studies. The results confirmed the ability of ASTER data and recommended it as a rapid and cost-effective tool in geological and mineralogical mapping in arid climate especially when the processing based on a detailed knowledge of the rock mineral assemblages.
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