TITLE:
Space-Borne Imagery and Geochemical Characters of Post-Orogenic Dyke Swarms, Fatirah-Abu Zawal District, Eastern Desert of Egypt
AUTHORS:
Ezzat Abdel Rahman, Ashraf Emam
KEYWORDS:
Dyke Swarms, Fatirah, ETM+, Band Ratios, PCA, Geochemistry
JOURNAL NAME:
Open Journal of Geology,
Vol.4 No.5,
May
27,
2014
ABSTRACT:
The Precambrian rocks in Wadi Fatirah-Wadi Abu Zawal area, Eastern
Desert of Egypt, are crosscut by numerous post-orogenic dyke swarms. Image
processing techniques are applied to the enhanced Thematic Mapper plus (ETM+)
data for lithological mapping and spectral characterization of these dyke
swarms. Band ratios and principal component analysis (PCA) yield conspicuously
effective results. Depending on mineralogical and geochemical data, two
petrogenetic groups of dyke swarms have been recognized: the first group (mafic
dykes) comprises basalt, basaltic andesite and andesite, while the second group
(felsic dykes) corresponds to dacite and rhyolite in composition. The mafic
dykes are tholeiitic to calc-alkaline, while the felsic dykes display
significant calc-alkaline affinity. The Na2O, K2O, Ba, Y, Rb, Zr and Th contents increase from basic to
acidic dykes and vice versa relative to CaO, MgO, Fe2O3, Sr, V, Co and Ni contents. These dyke swarms have been
emplaced in post-collisional, destructive plate margin settings during periods
of extension. The basic dykes have characteristics of volcanic arc setting,
whereas the acidic dykes display geochemical features of within plate rocks.
The chemical differences between the mafic and felsic dyke swarms favor that the
two groups of dyke swarms cannot be related to the same magma source, but they
are formed from two different parental magmas.