Migration from Eastern Gezira into greater Khartoum     

Mohamed E. Abu Sin 《GeoJournal》1991,25(1):73-79

This paper is an attempt to investigate the role of rural-urban migration in the population integration process and national identity in Sudan. Although migration is considered as an important mechanism in integration, yet its effect cannot be easily detected if urban life fails to challenge the culture and norms of migrants. In this case study the role of migration is limited by the status of the urban and the purely traditional background of migrants. Population integration is a central issue in the Sudan with its high level of pluralism, ethnic and cultural complexity. It is assumed that migration is an essential factor to challenge such complexity. This paper is part of a research programme financed by the Deutsche Forschungsgemeinschaft (DFG) — Identity in Africa — Processes of Development and Change — initiated and sponsored by H. Ruppert and F. N. Ibrahim, University of Bayreuth.  相似文献   

Effects of soil-structure interaction on seismic response of elevated tanks   总被引：1，自引：0，他引：1  

Medhat A. Haroun  Mohamed K. Temraz 《Soil Dynamics and Earthquake Engineering》1992,11(2)

Models of two-dimensional x-braced elevated tanks supported on isolated footings are analyzed to investigate the effects of dynamic interaction between the tower and the supporting soil-foundation system. Static, dynamic elastic, and dynamic inelastic responses of towers under horizontal ground motions are evaluated. Effects of soil properties, represented by the shear wave velocity, on joint displacements and on member end actions are studied. In general, soil-tower interaction reduces member end actions except near the base of tower.  相似文献   

Palaeomagnetism of the Stephano-Autunian Lower Tiguentourine formations from stable Saharan craton (Algeria)   总被引：1，自引：0，他引：1  

Mohamed El-Messaoud Derder  Bernard Henry  Nacer-Eddine Merabet  Lucien Daly 《Geophysical Journal International》1994,116(1):12-22

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Radiospectrometric and magnetic signatures of a gold mine in Egypt     

Mohamed A. El-Sadek 《Journal of Applied Geophysics》2009,67(1):34-43

The purpose of this research is to study the signatures of a gold mine (Um Salim), located in the Eastern Desert of Egypt, using aeroradiospectrometric and aeromagnetic data. To achieve this goal, reduction-to-pole (RTP), high-pass filtering and analytical signal techniques were applied to the aeromagnetic data. Besides, interpretation of the total-count (TC) radiometric map, the three radioelements (K, eU and eTh) maps and the ternary radioelement composite image were carried out. Moreover, a two-dimensional trend analysis for the structural lineaments as traced from the geologic, total-count radiometric and reduced-to-pole magnetic maps was conducted to define the relationship which might exist between location of the gold mine, lithologies and major structures of the area under consideration.The study revealed that the known gold mine is associated with a high positive magnetic anomaly that trends in the NE direction and a high-amplitude analytic signal. The Um Salim gold mine is associated with very low aeroradiospectrometric levels on the four maps (TC, K, eU and eTh). The location of the gold mine is controlled by the intersection of both NW and NE trends. There are other particular radiospectrometric ratio signatures for gold deposits (eU/eTh, eU/K and eTh/K). Ternary radioelement maps can discriminate also alteration zones in various degrees that correlate with the gold mine. These zones can be used as a diagnostic exploration guide for various types of non-radioactive mineral deposits (e.g., copper and gold). Four major tectonic trends were identified that have the following directions: NE, NW, N–S and WNW.  相似文献   

An overview of the Late Cretaceous-Eocene positive inversions and Oligo-Miocene subsidence events in the foreland of the Tunisian Atlas: Structural style and implications for the tectonic agenda of the Maghrebian Atlas system   总被引：4，自引：0，他引：4  

Sami Khomsi  Mohamed Ghazi Ben Jemia  Chokri Maherssi  Riadh Mezni 《Tectonophysics》2009,475(1):38-207

Structural interpretation of surface and subsurface data in the Eastern foreland basins of Tunisia, allows us to recognize positive inversion structures, i.e. related to compressional events, expressed and recorded in the Paleogene sedimentary pile of the Atlas domain. These episodes are followed by a period of relative tectonic quiescence during Oligocene-Early Miocene with development of extensional structures with slightly tilted panels, grabens and locally the development of listric normal faults branched at depth on “décollement” levels.Comparison of the seismic interpretations and field data collected along the South Atlas Front as well as in the Atlas belt, allows us to propose a tectonic scenario at the scale of Eastern Tunisia Atlas. In particular, we emphasise the role of the so-called “Atlas event” (Middle-Late Eocene), which was initially defined in Algeria but poorly outlined in Tunisia. We will show that the tectonic agenda defined in Eastern Tunisia is consistent with the one proposed elsewhere in the Maghreb allowing us to propose a unified view of the geodynamic evolution of the whole Atlas system during this period.The negative inversion recorded during Oligocene-Early Miocene along with the occurrence of synsedimentary normal faults are related to an increase of the subsidence rate in the frame of continuous shortening coeval to basin formation in the front of the Atlas. The whole Oligo-Miocene evolution results from two different mechanisms: flexuration in the front of the Atlas and the onset of the extension of the Pantelleria-Linosa-Malta rift system of central Mediterranean, which attained a climax stage later during Pliocene-Quaternary.  相似文献   

Liberation-limited grade/recovery curves from X-ray micro CT analysis of feed material for the evaluation of separation efficiency     

Jan D. Miller  Chen-Luh Lin  Lukasz Hupka  Mohamed I. Al-Wakeel 《International Journal of Mineral Processing》2009,93(1):48-53

Procedures for 3D mineral liberation analysis by X-ray micro CT (XMT) are presented and discussed including the construction of liberation-limited grade/recovery curves for specific feed materials. In this way, actual separation efficiencies can be compared to what might be expected for a perfect separation limited only by the extent of liberation. It is shown that 3D mineral liberation analysis based on XMT is preferred to 2D section analysis which overestimates the extent of liberation. By way of example, procedures and experimental results are presented and discussed for feed material in the case of phosphate rock flotation.  相似文献   

Petrogenesis of the Nesryin gabbroic intrusion in SW Sinai, Egypt: new contributions from mineralogy, geochemistry, Nd and Sr isotopes     

Mohamed M. Abu Anbar 《Mineralogy and Petrology》2009,95(1-2):87-103

The Wadi Nesryin gabbroic intrusion is part of the Neoproterozoic Pan-African basement cropping out in southern Western Sinai of Egypt. The intrusion comprises hornblende gabbro, pyroxene–hornblende gabbro, diorite and appinitic varieties. It exhibits chilled margins against the older rocks represented by fine-grained gabbro and dolerite and belongs to what is known throughout Egypt as the “younger gabbro suite”. Mineralogy, mineral chemistry and whole rock geochemistry indicate that these rocks were derived from tholeiitic magmas with minor calc-alkaline affinity. They have chemical signatures of subduction related arc rocks formed at an active convergent plate margin. They were formed by 15–30% of partial melting of a garnet lherzolite and to a minor extent of spinel-garnet lherzolite sources, modified by fluids related to a subducting slab. Pressure estimates using the amphibole geobarometer indicate that the gabbroic rocks crystallized at pressures between 2.8 and 5.6 kbar (average?=?4.3 kbar). Diorites record lower formation pressures between 1.8 and 3.7 kbar (average?=?3.0 kbar). The temperature estimates calculated by several geothermometers yielded crystallization temperatures ranging from 674°C to 961°C, with an average of about 817°C. The whole rock Rb–Sr isochron age of the Nesryin gabbroic intrusion is 617?±?19 Ma with initial ⁸⁷Sr/⁸⁶Sr?=?0.70322?±?0.00004. This age indicates that the mafic–ultramafic plutons in the Pan-African belt in southern Sinai belong to the Egyptian younger gabbros and not to the older metagabbro–diorite complexes or ophiolitic suites. The rocks have low ⁸⁷Sr/⁸⁶Sr initial ratios ranging from 0.703141 to 0.703338 and negative ? Sr ranging from ?6.34 to ?9.14. The initial ¹⁴³Nd/¹⁴⁴Nd ratios range from 0.511944 to 0.512145 with positive and high ? Nd values (1.93 to 5.86) reflecting a mantle contribution in their petrogenesis.  相似文献   

U–Pb TIMS age constraints on the evolution of the Neoproterozoic Meatiq Gneiss Dome,Eastern Desert,Egypt     

Arild Andresen  Mohamed Ali Abu El-Rus  Per Inge Myhre  Gamal Y. Boghdady  Fernando Corfu 《International Journal of Earth Sciences》2009,98(3):481-497

Ages are used to constrain the temporal evolution of the Meatiq Gneiss Dome, Eastern Desert, Egypt, by dating (ID-TIMS) pre-, syn-, and post-tectonic igneous rocks in and around the dome. The Um Ba’anib Orthogneiss, comprising the deepest exposed structural levels of the dome, has a crystallization age of 630.8 ± 2 Ma. The overlying mylonites are interpreted to be a thrust sheet/complex (Abu Fannani Thrust Sheet) of highly mylonitized metasediments (?), migmatitic amphibolites, and orthogneisses with large and small tectonic lenses of less-deformed intrusives. Two syn-tectonic diorite lenses in this complex have crystallization ages of 609.0 ± 1.0 and 605.8 ± 0.9 Ma, respectively. The syn-tectonic Abu Ziran diorite, cutting across the tectonic contact between mylonite gneisses of the Abu Fannani Thrust Sheet and a structurally overlying thrust sheet of eugeoclinal rocks (“Pan-African nappe”), has a magmatic emplacement age of 606.4 ± 1.0 Ma. Zircons from a gabbro (Fawakhir ophiolite) within the eugeoclinal thrust sheet yielded a crystallization age of 736.5 ± 1.2 Ma. The post-tectonic Fawakhir monzodiorite intrudes the ophiolitic rocks and has an emplacement age of 597.8 ± 2.9 Ma. Two other post-tectonic granites, the Arieki granite that intrudes the foliated Um Ba’anib Orthogneiss, and the Um Had granite that cuts the deformed Hammamat sediments, have emplacement ages of 590 ± 3.1 and 596.3 ± 1.7 Ma, respectively. We consider formation of the Meatiq Gneiss Dome to be a young structural feature (<631 Ma), and our preferred tectonic interpretation is that it formed as a result of NE–SW shortening contemporaneous with folding of the nearby Hammamat sediments around 605–600 Ma, during oblique collision of East and West Gondwana.  相似文献   

Sedimentary processes and provenance of Quaternary marine formations from the Tangier Peninsula (Northern Rif, Morocco)     

Khadija Aboumaria  Mohamed Najib Zaghloul  Maria Battaglia  Francesco Loiacono  Diego Puglisi  M&#x;hamed Aberkan 《Journal of African Earth Sciences》2009,55(1-2):10

This work deals with new lithostratigraphic, sedimentological, petrographic and geochemical data collected from coastal Quaternary formations of the Tangier Peninsula along the Northern Atlantic and Mediterranean coasts in the southern side of the Gibraltar Strait (Morocco).The sedimentological features of the analyzed sections reflect a palaeoenvironment evolution from a submerged beach-type to a high energy littoral depositional system, namely lower shoreface to beachface environment with a regressive trend to thickening- and coarsening-upward sequences. Other successions, located nearby Larache city and in the Sidi Kankouch area, are also characterized by a positive trend to fining- and thinning-upward sequences, reflecting an evolution from lower beachface or upper shoreface to lower shoreface. It is possible that the transgressive to regressive trend inversion could be related to fluctuations of sediment input rate versus accommodation space during the progradation of a coastal palaeoenvironment.The lateral and vertical evolution of the studied marine formations is related to late Quaternary neotectonics, mainly to the last repercussions of isostatic rebound of the External and Flysch Basin Domains, during a period of relatively uniform sea level between 280,000 and 125,000 years B.P.The provenance of arenites of these Quaternary marine formations, studied by means of modal counting and geochemical analysis, seems to be linked mainly to Middle-Upper Miocene and Pliocene terrigenous successions, unconformably resting on various formations of the Neogene accretionary prism. The latter has been built by the stacking of Flysch Nappes and External Units of the Northern Rif Chain.  相似文献   

Utilization of geoinformation tools for the development of forest fire hazard mapping system: example of Pekan fire, Malaysia     

Ahmad Rodzi Mahmud  Iwan Setiawan  Shattri Mansor  Abdul Rashid Mohamed Shariff  Biswajeet Pradhan  Ahmed Nuruddin 《Central European Journal of Geosciences》2009,1(4):456-462

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