Groundwater of Egypt: “an environmental overview”   总被引：1，自引：0，他引：1  

M. R. El Tahlawi  A. A. Farrag  S. S. Ahmed 《Environmental Geology》2008,55(3):639-652

Although Egypt has the great Nile River, which is the main supply of water, Egypt’s water is limited to 55.5 billion m³ per annum. Owing to the rapid growth of the population and the increasing consumption of water in agriculture, industry, domestic use, etc., it is expected that Egypt will rely to some extent on groundwater to develop the new projects such as Tushka in Upper Egypt and East Oweinat. Issues related to groundwater in Egypt are identified with the common geological features associated with formation of the aquifers and demonstrating the location of the main resources of groundwater, followed by the main objective of this paper, which is addressing the environmental issues related to groundwater in Egypt. Several studies have been reviewed and personal communication made with the authorities to introduce this work and provide an overview of the groundwater quality problems in Egypt with examples from different parts of the country.  相似文献   

Magmatic unmixing in spinel from late Precambrian concentrically-zoned mafic–ultramafic intrusions, Eastern Desert, Egypt     

Ahmed Hassan Ahmed  Hassan Mohamed Helmy  Shoji Arai  Masako Yoshikawa 《Lithos》2008,104(1-4):85-98

Spinel is widespread in the ultramafic core rocks of zoned late Precambrian mafic–ultramafic complexes from the Eastern Desert of Egypt. These complexes; Gabbro Akarem, Genina Gharbia and Abu Hamamid are Precambrian analogues of Alaskan-type complexes, they are not metamorphosed although weakly altered. Each intrusion is composed of a predotite core enveloped by pyroxenites and gabbros at the margin. Silicate mineralogy and chemistry suggest formation by crystal fractionation from a hydrous magma. Relatively high Cr₂O₃ contents are recorded in pyroxenes (up to 1.1 wt.%) and amphiboles (up to 1.4 wt.%) from the three plutons. The chrome spinel crystallized at different stages of melt evolution; as early cumulus inclusions in olivine, inclusions in pyroxenes and amphiboles and late-magmatic intercumulus phase. The intercumulus chrome spinel is homogenous with narrow-range of chemical composition, mainly Fe³⁺-rich spinel. Spinel inclusions in clinopyroxene and amphibole reveal a wide range of Al (27–44 wt.% Al₂O₃) and Mg (6–13 wt.% MgO) contents and are commonly zoned. The different chemistries of those spinels reflect various stages of melt evolution and re-equilibration with the host minerals. The early cumulus chrome spinel reveals a complex unmixing structures and compositions. Three types of unmixed spinels are recognized; crystallographically oriented, irregular and complete separation. Unmixing products are Al-rich (Type I) and Fe³⁺-rich (Type II) spinels with an extensive solid solution between the two end members. The compositions of the unmixed spinels define a miscibility gap with respect to Cr–Al–Fe³⁺, extending from the Fe³⁺–Al join towards the Cr corner. Spinel unmixing occurs in response to cooling and the increase in oxidation state. The chemistry and grain size of the initial spinel and the cooling rate control the type of unmixing and the chemistry of the final products. Causes of spinel unmixing during late-magmatic stage are analogous to those in metamorphosed complexes. The chemistry of the unmixed spinels is completely different from the initial spinel composition and is not useful in petrogenetic interpretations. Spinels from oxidized magmas are likely to re-equilibrate during cooling and are not good tools for genetic considerations.  相似文献   

Structural controls,temperature–pressure conditions and fluid evolution of orogenic gold mineralisation at the Betam mine,south Eastern Desert,Egypt     

Basem A. Zoheir 《Mineralium Deposita》2008,43(1):79-95

The Betam gold deposit, located in the southern Eastern Desert of Egypt, is related to a series of milky quartz veins along a NNW-trending shear zone, cutting through pelitic metasedimentary rocks and small masses of pink granite. This shear zone, along with a system of discrete shear and fault zones, was developed late in the deformation history of the area. Although slightly sheared and boudinaged within the shear zone, the auriferous quartz veins are characterised by irregular walls with a steeply plunging ridge-in-groove lineation. Shear geometry of rootless intra-folial folds and asymmetrical strain shadows around the quartz lenses suggests that vein emplacement took place under a brittle–ductile shear regime, clearly post-dating the amphibolite-facies regional metamorphism. Hydrothermal alteration is pervasive in the wallrock metapelites and granite including sericitisation, silicification, sulphidisation and minor carbonatisation. Ore mineralogy includes pyrite, arsenopyrite and subordinate galena, chalcopyrite, pyrrhotite and gold. Gold occurs in the quartz veins and adjacent wallrocks as inclusions in pyrite and arsenopyrite, blebs and globules associated with galena, fracture fillings in deformed arsenopyrite or as thin, wire-like rims within or around rhythmic goethite. Presence of refractory gold in arsenopyrite and pyrite is inferred from microprobe analyses. Clustered and intra-granular trail-bound aqueous–carbonic (L_CO2 + L_aq ± V_CO2) inclusions are common in cores of the less deformed quartz crystals, whereas carbonic (L_CO2 ± V_CO2) and aqueous H₂O–NaCl (L + V) inclusions occur along inter-granular and trans-granular trails. Clathrate melting temperatures indicate low salinities of the fluid (3–8 wt.% NaCl eq.). Homogenisation temperatures of the aqueous–carbonic inclusions range between 297 and 323°C, slightly higher than those of the intra-granular and inter-granular aqueous inclusions (263–304°C), which are likely formed during grain boundary migration. Homogenisation temperatures of the trans-granular H₂O–NaCl inclusions are much lower (130–221°C), implying different fluids late in the shear zone formation. Fluid densities calculated from aqueous–carbonic inclusions along a single trail are between 0.88 and 0.98 g/cm³, and the resulting isochores suggest trapping pressures of 2–2.6 kbar. Based on the arsenopyrite–pyrite–pyrrhotite cotectic, arsenopyrite (30.4–30.7 wt.% As) associated with gold inclusions indicates a temperature range of 325–344°C. This ore paragenesis constrains f _S2 to the range of 10⁻¹⁰ to 10^−8.5 bar. Under such conditions, gold was likely transported mainly as bisulphide complexes by low salinity aqueous–carbonic fluids and precipitated because of variations in pH and f _O2 through pressure fluctuation and CO₂ effervescence as the ore fluids infiltrated the shear zone, along with precipitation of carbonate and sericite. Wallrock sulphidation also likely contributed to destabilising the gold–bisulphide complexes and precipitating gold in the hydrothermal alteration zone adjacent to the mineralised quartz veins.  相似文献   

Genesis of secondary uranium minerals associated with jasperoid veins,El Erediya area,Eastern Desert,Egypt     

Hamdy H. Abd El-Naby 《Mineralium Deposita》2008,43(8):933-944

Uranium mineralization in the El Erediya area, Egyptian Eastern Desert, has been affected by both high temperature and low temperature fluids. Mineralization is structurally controlled and is associated with jasperoid veins that are hosted by a granitic pluton. This granite exhibits extensive alteration, including silicification, argillization, sericitization, chloritization, carbonatization, and hematization. The primary uranium mineral is pitchblende, whereas uranpyrochlore, uranophane, kasolite, and an unidentified hydrated uranium niobate mineral are the most abundant secondary uranium minerals. Uranpyrochlore and the unidentified hydrated uranium niobate mineral are interpreted as alteration products of petscheckite. The chemical formula of the uranpyrochlore based upon the Electron Probe Micro Analyzer (EPMA) is . It is characterized by a relatively high Zr content (average ZrO₂ = 6.6 wt%). The average composition of the unidentified hydrated uranium niobate mineral is , where U and Nb represent the dominant cations in the U and Nb site, respectively. Uranophane is the dominant U⁶⁺ silicate phase in oxidized zones of the jasperoid veins. Kasolite is less abundant than uranophane and contains major U, Pb, and Si but only minor Ca, Fe, P, and Zr. A two-stage metallogenetic model is proposed for the alteration processes and uranium mineralization at El Erediya. The primary uranium minerals were formed during the first stage of the hydrothermal activity that formed jasperoid veins in El Eradiya granite (130–160 Ma). This stage is related to the Late Jurassic–Early Cretaceous phase of the final Pan-African tectono-thermal event in Egypt. After initial formation of El Erediya jasperoid veins, a late stage of hydrothermal alteration includes argillization, dissolution of iron-bearing sulfide minerals, formation of iron-oxy hydroxides, and corrosion of primary uranium minerals, resulting in enrichment of U, Ca, Pb, Zr, and Si. During this stage, petscheckite was altered to uranpyrochlore and oxy-petscheckite. Uranium was likely transported as uranyl carbonate and uranyl fluoride complexes. With change of temperature and pH, these complexes became unstable and combined with silica, calcium, and lead to form uranophane and kasolite. Finally, at a later stage of low-temperature supergene alteration, oxy-petscheckite was altered to an unidentified hydrated uranium niobate mineral by removal of Fe.  相似文献   

Automatic detection of near surface geological and hydrological features and investigating their influence on groundwater accumulation and salinity in southwest Egypt using remote sensing and GIS   总被引：1，自引：0，他引：1  

Samy Ismail Elmahdy  Mohamed Mostafa Mohamed 《国际地球制图》2015,30(2):132-144

This study employs two automated algorithms, the topographic fabric and the deterministic eight-node (D8), to reveal near surface geological fractures and their associated paleodrainages network from a 90?m DEM of the Shuttle Topographic Radar Mission sensor. The topographic fabric algorithm, which calculates the slope and aspect which define a vector normal to the earth’s surface and then compute direction cosines of normal vector at each point, was used to auto-detect fault zones. The deterministic eight-node (D8) algorithm, which determines in which neighbouring pixel any water in a central pixel will flow naturally, was used to delineate paleodrainages concealed beneath sand sheets. Seven sets of geological structures were recognized. Their major trends were found to be in the S46°W, S58°W, S81°W, N107°W, N–S, E–W and N152°W and share similar trends of the revealed paleodrainages. The results suggest a strong spatial relationship between the features extracted from DEM and groundwater potential.  相似文献   

Geographical Publications     

《The Journal of geography》2012,111(4):170-176

Abstract

Project Marco Polo provided the opportunity for teachers and students to experience Egypt and the eastern Mediterranean firsthand through the lens of a geographer, archeologist, and oceanographer. The National Geographic Society and U.S. Navy collaborated to provide meaningful applied geography field experiences for teacher and student participants. In addition, participants developed a global perspective which enabled them to better understand the interrelationship of the region's diverse cultures and lands.  相似文献   

New Tricks with Old Maps: Urban Landscape Change,GIS, and Historic Preservation in the Less Developed World     

Dona J. Stewart 《The Professional geographer》2001,53(3):361-373

This article presents a methodology for a more detailed investigation of urban landscape change in rapidly growing cities of the less developed world beyond typical macrolevel approaches. This research is an attempt to bridge the gap between traditional landscape analysis and geographic information science (GIS). The article presents the preliminary results from a pilot project in Zamalek, Egypt, highlighting the benefits and drawbacks of the two techniques. Rarely used to study the less developed world, these techniques are utilized to assess change within a portion of Cairo's urban landscape. Large‐scale historic maps and high‐resolution satellite imagery, combined with field attribute collection, are the major data sources in this applied landscape analysis. A motivating factor in the desire to examine landscape change at such a large scale is the need to create monitoring systems for historic preservation in cities of the less developed world.  相似文献   

Review of Late Proterozoic sutures,ophiolitic mélanges and tectonics of eastern Egypt and north-east Sudan     

R. M. Shackleton 《International Journal of Earth Sciences》1994,83(3):537-546

The distribution, structural relations and ages of ophiolites and ophiolitic melanges in the Eastern Deserts of Egypt and north-east Sudan, and their relation to arc and post-arc magmatism, are used to infer the probable positions of sutures and the directions of obduction and subduction. The ages of the successive tectonic stages in the terranes decrease northwards, by about 100 Ma in the region discussed. Obduction was north-westwards. The obducted sheets of ophiolite and ophiolitic melange, extending about 500 km north from the Onib-Sol Flamed suture, may all represent a single back-arc basin. The direction of subduction is still not clearly proved: more geochemical evidence of arc-magmatic polarity is needed. The late tectonic north-westward thrusting, the NW - SE stretching lineation, the transpressional north-south Hamisama Shear Zone and the NW-SE sinistral Najd faults are all attributed to north-westward movement (present coordinates) of terranes towards the older craton west of the Nile. The Najd faults are interpreted as intracontinental transform faults.  相似文献   

Observations from the 12 October 1992 Dahshour earthquake in Egypt   总被引：1，自引：0，他引：1  

Hossam S. Badawi  Sherif A. Mourad 《Natural Hazards》1994,10(3):261-274

An earthquake of local magnitude 5.3 (duration magnitudeM _d ) on the Richter Scale occurred at Dahshour, 18 km south of Cairo, Egypt, on Monday, 12 October 1992 at 3:09 pm (local time). Numerous aftershocks followed the main event during the following weeks with magnitude up to 4.3. The earthquake occurred in an area that has had no recent seismic activity, and affected many cities in Egypt. Many buildings and monuments were severely damaged or collapsed. Modern concrete skeletal structures suffered minor nonstructural damage. Earthquake physical damage was estimated at about one billion U.S. Dollars. The severity of the damage was mainly due to poor construction materials and detailing, aging, inferior workmanship, and inadequate maintenance. Egypt was generally considered to be an area of moderate seismic activity. In 1989, earthquake provisions were first introduced in the Egyptian Code of Practice for Reinforced Concrete Structures only. The earthquake clearly showed the urgent need for an assessment and rehabilitation program to mitigate seismic risk hazard in existing structures. In addition, future development planning, and earthquake preparedness strategies should implement lessons learned from the event. In this paper, an overview discussion about the observations from the 12 October earthquake is presented.  相似文献   

A model for the three-dimensional evolution of continental rift basins,north-east Africa     

William Bosworth 《International Journal of Earth Sciences》1994,83(4):671-688

Large areas of north-east Africa were dominated by regional extension in the Late Phanerozoic. Widespread rifting occurred in the Late Jurassic, with regional extension culminating in the Cretaceous and resulting in the greatest areal extent and degree of interconnection of the west, central and north African rift systems. Basin reactivation continued in the Paleocene and Eocene and new rifts probably formed in the Red Sea and western Kenya. In the Oligocene and Early Miocene, rifts in Kenya, Ethiopia and the Red Sea linked and expanded to form the new east African rift system.This complex history of rifting resulted in failed rift basins with low to high strain geometries, a range of associated volcanism and varying degrees of interaction with older structures. One system, the Red Sea rift, has partially attained active seafloor spreading. From a comparison of these basins, a general model of three-dimensional rift evolution is proposed. Asymmetrical crustal geometries dominated the early phases of these basins, accompanied by low angle normal faulting that has been observed at least locally in outcrop. As rifting progressed, the original fault and basin forms were modified to produce larger, more through-going structures. Some basins were abandoned, others experienced reversals in regional dip and, in general, extension and subsidence became focused along narrower zones near the rift axes. The final transition to oceanic spreading was accomplished in the Red Sea by a change to high angle, planar normal faulting and diffuse dike injection, followed by the organization of an axial magma chamber.  相似文献