الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The area under investigation is a part of South Western Sinai massif. It is bounded by longitudes 33˚50’15” to 34˚5’15” E and latitudes 28˚1’30” to 28˚18’30” N and covers an area of 624.25 Km2. Field relationships and petrographic studies revealed the rock existence of three rock varieties arranged from the oldest as follows; older granites (tonalite and granodiorite), younger granites (alkali feldspar granite, syenogranite and monzogranite) and post granite dykes (rhyolite, andesite and basalt). Older granites form an elongated batholithic belt and occupy a limited exposure (12.7 km2) at the northwestern part of the study area. They form high to moderate rugged relief, strongly weathered and exfoliated. Locally, they have subjected to hydrothermal alteration especially along fault planes and joints. They are exposed along Wadi Isla and Wadi Tulaa. The generation of enclaves and synplutonic intrusions of mafic magmas in granite batholiths have important petrogenetic implications. First, is that felsic and basic magmatism are not accidentally produced at the same time, implying that the processes involved in the generation of the basic magmas are also related to the process of generation of felsic magmas. Second, is the interpretation of basic magmas that represent top-to-down intrusions implying, that these basic magmas reached the level of emplacement before the granitic magma. The most plausible hypothesis, in agreement with the field observations and rheological explanations, is that the mafic magma was formed a part of a composite intrusion in which the core was formed by granite magma and the rim was formed by basic magma. The implication of this reversely stratified magma chamber, is that the acidic magma must have originated at a source deeper than the source of mafic one. It is clear that these mafic magmas are originated in a hydrated mantle source, possibly mantle wedge above subduction zone and probably with contribution of continental crust. The petrological inversion, in which the crustal source is below the mantle source, is offered by the well contrasted cold plume hypothesis.The reversely stratified magma chamber observed in this pluton and being responsible of the top-to-down synplutonic intrusions. Younger granite suite are the most predominant rock unit exposed in the study area, covering about 373.35 km2 and represent about 60 % of the total area. Based on the petrological and field observations the rocks are classified into two phases: Phase-I (rapakivi granites) and Phase-II granites (syenogranite and alkali feldspar granite).Phase-I (rapakivi granites) of the study area forms moderate- to high-relief mountains. They are intruded into the older granites and latter intruded by off-shoots of alkali feldspar granites with sharp contacts. Sharp contacts indicate lack of reaction between the magma and country rocks. Rapakivi granites crop out in the central and southern parts of the study area. They exposed at Wadi Muraykh, Wadi Thuman, Wadi Al-Mahash, Wadi Gargir and Wadi Badr. Rapakivi granites attain medium- to coarse–grained with pinkish color. They attain moderately jointed and shows moderate to high degree of weathering especially along joint planes. The cavernous and block weathering is occasionally developed. Quartz plugs and pegmatite veins are also common in the rapakivi granites. They are traversed by basalt and rhyolite dykes. Phase-II granites are of limited occurrence and crop out especially at northern and central part of the study area. The rocks are hard, massive and medium- to coarse-grained of reddish pink color. They show hypidiomorphic- granular texture and belong to hypersolvous granites. These granites send off-shoots through rapakivi granites as observed at Wadi Al-Mahash. Phase-II granites are intruded into rapakivi and older granites with sharp contact. The pluton is traversed by post granite dykes that are represented by basalt, andesite and rhyolite varieties.