الفهرس 
ACKNOWLEDGMENTS
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Abstract
Kroner (1993) noted that in NE Africa and Arabia, the Pan African terrain is generally referred to as Arabian- Nubian Shield (ANS) and consist to a large degree of juvenile crustal material accreted to the ancient African margin during the period ~ 900-700 Ma ago (Greenwood et al., 1980, Kroner et al., 1992 a). He also pointed out that in the Eastern Desert of Egypt and Sinai, Pan African juvenile island arc assemblages were formed between~ 800 and ~640 Ma ago, and the River Nile demarcates the approximate boundary between the juvenile and ancient, partly reworked, African craton (Kroner et al., 1987). He added that there has been much debate, largely based on Pb isotopic data, on the involvement of older continental crust in the orogenic history of the Eastern Desert of Egypt, but to date no pre-Pan African rocks have been identified.
Neumayr et al. (1996) presented a generalized geological history for the Meatiq Dome area, based on the work of Habib et al. (1985b), Fritz et al. (in review, and their own work).
On the basis of recent available data (e.g., Andresen et al., 2009), the present author introduced a new concept regarding the intervention of isotopic ages, deformational phases, tectonic evolution, magmatic activities and metamorphic events.
II. Subduction
The tectonic evolution of the present area started with the subduction processes of a segment of an oceanic crust under another one in a NW- dipping direction. This led finally to development of a strongly folded (D1) and highly foliated and metamorphosed (M1) mountain belt, which comprised principally amphibolites and gneisses. The former were represented mainly by ortho-amphibolites derived from oceanic crust. Para-amphibolites were also present, but of subordinate abundance and appear to have been resulted from calcareous sediments. The gneisses included subequal proportions of ortho- and paragneisses, probably derived from volcanic and pelitic to semipelitic sediments.
In the deeper part of the folded belt, partial melting was happened resulting in the formation of migmatites. Also, a huge granitoid mass, namely Um Baanib granite-gneiss derived from depleted asthenosphere mantle sources., was synkinematically emplaced into the folded belt. According to Liegeois et al. (2010), the age of the Um Baanib granite-gneiss is controversial. Andresen at al. (2009) obtained a concordant TIMS U-Pb zircon age of 631±2 Ma, which agrees reasonably well with a Five-point Rb-Sr whole rock isochron of 626±2 Ma (initial 87Sr/86Sr = (0.7030+0.0001) reported by Sturchio et al. (1983) for the orthogneiss.
The Um Baanib granite-gneiss intrusion captured many xenoliths of migmatitic amphibolites which are laterly concentrated in its eastern and western margins. from the geochemical point of view, these xenoliths are found to be interrelated with the Abu Fannani amphibolites.
Some of the partially melted material, together with the invading magma had been arisen along the tensional cracks developed at the crests of anticlines of the folded mountain belt. This arising magma led to the formation of intraoceanic island arc assemblages, from which volcanic ashes of various composition were added and/or intermingled with the pelitic oceanic sediments.
Neumayr et al. (1998) noted that M1 metamorphic event (T≥750 oC) is restricted to the migmatized amphibolite xenoliths and mentioned that metamorphic event occurred at about 780 Ma, namely prior to the intrusion of the Um Baanib Granite protolith.
III. Obduction
NW-ward obduction event (D2) was followed, where thick thrust nappes overrided the strongly folded and highly metamorphosed mountain belt causing development of high-to medium- grade mylonites. These mylonites possessed an upper amphibolite-facies metamorphism M2(620-690o C; see Neumayr et al., 1998)
At the mouth of Wadi Murr, an older relict structure has been recognized, where the Abu Fannani mylonitic amphibolites are thrown into overturned minor folds whose axial planes dipping steeply SE, and the fold axes plunge at 60 NE. Also, at 5 km south of the previous point, the same relict structure is detected where boudinaged quartz veins intercalating the mylonitic amphibolites show overturned folds whose axial planes dipping steeply S. This attitude was due to a clockwise rotation because of later tectonics connected with the ENE-WSW Najd compressive stresses.
Andresen et al. (2009) noted that the original elongation lineation of the mylonitic rocks was oriented NW-SE to NNW-SSE, and that shear-sense indicators within these mylonites are sparse but where observed indicate top-toward-NW displacement described by Sturchio et al. (1983).
In the latest phases of obduction event, a group of magmatic bodies having the composition of diorite and tonalite were synkinematically emplaced along the shear zones of the mylonites. According to Andresen et al. (op.cit.), these bodies have the crystallization ages of 609±1 Ma and 606.4 ±1 Ma.