Standard Global Journal of Geology and Explorational Research (SGJGER)

053- 073

Authors: Hatem M. El-Desoky, Ahmed M. El Mezayen and Akram E. Serag

The present study embodies the results of field work and laboratory investigations and attempts to present the geology, petrography, geochemistry and petrogenesis of the Ediacaran Dokhan Volcanics at Wadi Zareib, Central Eastern Desert, Egypt. The investigated area is located along the Red Sea Coast and most common rock types among the Dokhan Volcanics are rhyolites and trachyandesites are commonly interbedded with lava flows successions. Microphenocrysts of quartz, alkali feldspars and plagioclase set in a fine-grained groundmass of microcrystalline to felsitic aggregates of quartz and plagioclase together with chlorite, epidote, sericite and hematite. Major element oxides and trace element data suggest that the trachyandesites are genetically related through crystal fractionation. The trace elements Y, Pb, Cu, Zr and Ga show negative anomalies (enriched) relative to Sr and Ba element. Wadi Zareib Dokhan Volcanics were originated from typical calc-alkaline reflecting the magmatic differentiation of metaluminous to peraluminous magma type. The geochemical trends of major oxides and trace elements of the studied volcanic rock varieties may suggest their co-magmatic nature. The Wadi Zareib Dokhan Volcanics display geochemical characteristics of both orogenic arc-type and anorogenic within-plate environments, suggesting eruption in a transitional “post-collisional tectonic setting. These rocks were derived from a single magma and suffered subsequence fractional crystallization. Keywords: Dokhan Volcanics, geochemistry, Neoproterozoic, petrogenesis, petrography and tectonic setting

009-026

Authors: Gehad M. Saleh, Doaa A. Mostafa, Mostafa E. Darwish and Ibrahim A. Salem

The granitoid rocks in G. El Faliq area, southeastern Desert of Egypt, consist of granodiorites, tonalities, monzogranites and alkali feldspar granites. The G. El-Faliq area is composed of ophiolitic mélange, gneisses, older granitoids, younger granitoids and post granitic dykes and veins. Altered granites are encountered at shears and fault zones at G. El Faliq, they rich by uranium and base metals mineralization. Geochemically, the older granitoids are peraluminous to metaluminous granites and fall in volcanic arc granites, while the younger granitoids are calc-alkaline and metaluminous to peralkaline granites and display most of the chemical characteristics of within plat granites setting. The altered granites show argilic facies with a relative depletion in K2O and Na2O + CaO oxides. The comparison between the average of the major oxides of the fresh samples of younger granitoids related to altered ones in the studied area shows that, the younger granitoids rich in SiO2, Na2O and K2O but depleted in TiO2, Al2O3, Fe2O3, FeO, MnO, CaO, MgO and P2O5 related to altered ones. Also, regard to trace elements they are rich in Sr and depleted in Ni, Zn, Zr, Y, Ba, Nb, U and Th. The mineralization of G. El Faliq can be classified on the basis of mode of occurrence and lithological associations into: a) secondary uranium minerals (uranophane), b) niobium-tantalum minerals, c) sulphide minerals and d) accessory minerals. The spectrometric survey revealed the presence of enriched zones with a maximum eU content of 650 ppm and the maximum eTh is 350 ppm. The evidence of hydrothermal mineralization in the alteration of rock-forming minerals such as feldspars and the formation of secondary minerals such as uranophane and pyrite. The pre-existing primary uranium minerals are the source of the present secondary uranium minerals by the action of oxidizing fluids, mobilization of uranium and then redeposition in other forms. Redistribution by circulating meteoric waters might have taken place. Keywords: G. El-Faliq, altered granites, uranium mineralization, spectrometric prospecting

001- 008

Authors: Marzouk Lazzez, Ramla Ben Rabah and Abdallah Maazaoui

In the Jeffara area, the Upper Jurassic M'rabtine member is constituted by platform carbonates interbedded with sand and shale. The sand levels form a good reservoir with a porosity of 17 % and a permeability of 130 md. The Lower Cretaceous reservoirs are hydrocarbon producer in the northeastern part of the Jeffara basin. Barremian sandstones (Sidi Aïch Fm.) have tested oil in some wells. Cenomanian Zebbag carbonates are hydrocarbon bearing in the Ezzaouia field and tested oil in El Bibane. The latter and also in some adjacent wells tested oil in the Aptian Orbata carbonates. Commonly, the Jeffara Basin has proven / moderate hydrocarbon play. In the central and northwest part of the basin, based on some control points, the area prospectivity is likely to moderate. Outcrop data as well as petrographical studies, tectono-stratigraphic overview and sedimentological investigation were used to exhibit exploration targets for hydrocarbons and form the proven reservoirs of significant oil-fields (e.g. Ezzaouia, El Bibane and Robbana). The Jaffara basin displays variety of siliciclastic and carbonate reservoirs, most likely extending from Ordovician to Cretaceous time. Source rock kitchens, regionally known within the Ordovician, Silurian, Carboniferous, Permian, Jurassic and Cretaceous successions, are locally deeply buried and fully mature in various parts of the basin. Traps are mainly structural; anticlines at Jurassic and Cretaceous level, forming the hydrocarbon pool in the Ezzaouia oil field. The siliciclastic deposits display substantial heterogeneity resulting from depositional environment and may hold basin-ward structural / stratigraphic traps. These lithofacies are showing hydrocarbon potential and could promote the poorly explored zone where locally several objectives within Jurassic and Cretaceous series are penetrated. Key words: Cretaceous, Jeffara Basin, wells tested, prospectivity