الفهرس 
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Abstract
The present thesis provides the geology, petrography, geochemistry and radioactivity of the different Neoproterozoic basement rocks exposed at the areas surrounding Wadi Um Sidra and Wadi Um Asmer in the northern Eastern Desert of Egypt.
The investigated area is located at about 50 km northwest of Hurghada City in the North Eastern Desert of Egypt between Latitudes 27° 14´ and 27º 26´ N and Longitudes 33º 8´ and 33º 22´ E. Geologically, The area (about 570 km2) is covered mainly by Neoproterozoic basement rocks. These rocks include metavolcanics, Dokhan Volcanics, monzogranites, syenogranites and alkali feldspar granites. The post-granitic dykes and veins penetrate all the previous rock types and represent the last igneous manifestation in the study area.
The metavolcanics are the oldest exposed rock type in the area and cropping out at G. Kherm Al Asmar. They range in composition from metabasalts to meta-andesites, which commonly exhibit porphyroblastic textures. The chemical composition of these rocks classified them as younger metavolcanics (YMV). The metabasalts originated from low-K tholeiitic magma in an immature island arc environment and the meta-andesites originated from a medium-K calc-alkaline magma in an immature island arc environment.
The Dokhan Volcanic rocks are represented by a successive sequence of lava flows of basaltic andesites, andesites, dacites and rhyolites interlayered with their related pyroclastics. Geochemically the studied Dokhan volcanic rocks span the entire range from basaltic andesite to rhyolite and have calc-alkaline nature. The basaltic andesites and andesites are classified as medium to high-K volcanic rocks, whereas the dacites and rhyolites are more high-K rocks. They are characterized by large ion lithophile elements (LILE)-enrichment relative to high field strength elements (HFSE) and display negative P and Ti anomalies, implying apatite and Fe-Ti oxides fractionation. These volcanics have LREE-enriched chondrite-normalized REE patterns. The REE patterns of the rhyolites are characterized by wing shape with strong negative Eu anomaly, reflecting plagioclase fractionation. The calc-alkaline nature, LILE enrichment and the marked Ta-Nb troughs shown by their spider diagrams indicate that, the studied Dokhan volcanic rocks are developed in subduction environment.
Based on the field, petrographical and geochemical investigations, the younger granites are categorized into monzogranite, syenogranite and alkali feldspar granite. Monzogranite is medium to coarse-grained, porphyritic varieties are common. Syenogranite is massive, medium to coarse-grained, pinkish white in color, holocrystalline and equigranular with hypidiomorphic textures. The alkali feldspar granite is medium to coarse-grained, pink to pinkish red color.
Monzogranites and syenogranites have calc-alkaline nature, whereas the alkali feldspar granites have alkaline nature. These granites under study have metaluminous to slightly peraluminous character and highly fractionated I-type granites. These granites were generated under low to moderate water pressures at 0.5-10 kbars and exhibit crystallization temperatures vary from about 650 ºC to 670 ºC.
Structurally the E-W to ENE-WSW and NW-SE trending faults are the oldest ones, since they were cut and dislocated by the N-S, NNE-SSW and NNW-SSE as well as NE-SW trending faults. This study demonstrates that NE-SW, NNW-SSE and N-S trending strike-slip faults and their intersections have played critical roles in distribution of the uranium mineralizations.
The highly enriched granites in uranium and/or thorium are the alkali feldspar granites. The high background of U (av. 8.29 ppm) classified this type of granite as uraniferous uranium source for the genesis of the secondary uranium minerals by the hydrothermal fluids. The mineralogical investigation confirmed that, the secondary uranium minerals are chiefly consisting of uranophane and kasolite.