Magnetic mineralogy of some ring complexes from the South Eastern Desert,Egypt     

N. Wassif  A. M. Kafafy  E. M. Abdel Aal  A. Abdeldayem  H. Odah  R. Mostafa 《Arabian Journal of Geosciences》2014,7(9):3455-3466

Ore microscopic study was carried out on a great number of samples collected from four well-dated alkaline rock masses (ring complexes), namely Gabal Mishbeh, Gabal Nigrub El Fogani, Gabal Nigrub El Tahtani, and Gabal El Gezira located in the Eastern Desert of Egypt. These rings consist mainly of wide variety of rock types ranging from basic to acidic and from under saturated to quartz bearing. The opaques of the basic rocks consist mainly of various ilmenite–magnetite intergrowths and differ essentially from those of the acidic rocks where minor amount of titanomagnetite is present. Numerous exsolution, replacement, and deformational textures were described. The distribution of opaque minerals and their intergrowths in the four well-defined ring complexes is described. Systematic rock magnetic measurements such as natural remanent magnetization intensity and initial susceptibility, Curie point, saturation magnetization, and coercive force were carried out, and their results were discussed in the light of opaque mineralogical studies.  相似文献   

Tectonic evolution of the Southern Gulf of Suez, Egypt: a comparison between depocenter and near peripheral basins   总被引：1，自引：0，他引：1  

Mohamed A. Omran  Mohamed S. El Sharawy 《Arabian Journal of Geosciences》2014,7(1):87-107

The sedimentary pattern of the southern Gulf of Suez, Egypt, especially during the Cenozoic rift stage, was controlled mainly by tectonic activities (subsidence and uplift) and sea level change. The stratigraphic record of the southern Gulf of Suez can be divided into two megasequences: pre-rift and syn-rift. The pre-rift megasequence can be viewed as two distinctive depositional regimes, clastic rocks of continental to braided stream environment during Cambrian and open marine transgression extended from Upper Cretaceous till Eocene. The syn-rift deposits showed a distinctive contrast between the depocenter and peripheral basins. This difference can be shown clearly on the sedimentary sequence of Hilal and Shoab Ali oilfields. The syn-rift megasequence can be differentiated in relation to rift evolution into the following stages: initial rift stage with low subsidence rate, main rift stage with maximum subsidence rate, quiescence stage with the slowest subsidence rate throughout the rift evolution, evaporite stage with restriction conditions, and Pliocene–Recent stage with shallow marine condition.  相似文献   

Hydrologic factors controlling groundwater salinity in northwestern coastal zone,Egypt     

Nahla A Morad  M H Masoud  S M Abdel Moghith 《Journal of Earth System Science》2014,123(7):1567-1578

The aim of this article is to assess the main factors influencing salinity of groundwater in the coastal area between El Dabaa and Sidi Barani, Egypt. The types and ages of the main aquifers in this area are the fractured limestone of Middle Miocene, the calcareous sandstone of Pliocene and the Oolitic Limestone of Pleistocene age. The aquifers in the area are recharged by seasonal rainfall of the order of 150 mm/year. The relationship of groundwater salinity against the absolute water level, the well drilling depth, and the ability of aquifer to recharge has been discussed in the present work. The ability of aquifer to locally recharge by direct rainfall is a measure of the vertical permeability due to lithological and structural factors that control groundwater salinity in the investigated aquifers. On the other hand, the fracturing system as well as the attitude of the surface water divide has a prime role in changing both the mode of occurrence and the salinity of groundwater in the area. Directly to the west of Matrouh, where the coastal plain is the narrowest, and east of Barrani, where the coastal plain is the widest, are good examples of this concept, where the water salinity attains its maximum and minimum limits respectively. Accordingly, well drilling in the Miocene aquifer, in the area between El Negila and Barrani to get groundwater of salinities less than 5000 mg/l is recommended in this area, at flow rate less than 10 m³/hr/well. In other words, one can expect that the brackish water is probably found where the surface water divide is far from the shore line, where the Wadi fill deposits dominate (Quaternary aquifer), acting as a possible water salinity by direct rainfall and runoff.  相似文献   

Alp Transit: Crossing Faults 44 and 49     

M. El Tani  R. Bremen 《Rock Mechanics and Rock Engineering》2014,47(3):1037-1048

  相似文献   

Performance of Foundations in Sabkha Soil: Numerical Investigation   总被引：1，自引：1，他引：0  

Ahmed M. Alnuaim  M. H. El Naggar 《Geotechnical and Geological Engineering》2014,32(3):637-656

Sabkha or salt flat soil is one of the most unpredictable and potentially dangerous soils in the Middle East. This soil covers a large and strategically important area of the Arabian Gulf coast, as it contains the world biggest oil reserve and a number of petrochemical plants are either have been built or are scheduled to be built in this area. The performance of shallow and deep foundations in the Eastern Province of Saudi Arabia’s sabkha soil is investigated numerically using the finite element method. The parameters used to simulate this soil in the numerical models were based on a large number of laboratory tests to determine the shear strength and stiffness parameters of the sabkha soil. In addition, the characteristics of the interface between the foundation and soil used in the numerical model were established from shear box tests that were conducted to evaluate the concrete-sabkha soil interface properties. The developed numerical model was calibrated/verified using the results of full-scale pile load testing program from an ongoing project to further enhance the accuracy of the results. A parametric study was then conducted using the verified model to establish the performance characteristics of foundations constructed in sabkha soil and provide guidelines for their design.  相似文献   

Factors and processes of permanent gully evolution in a Mediterranean marly environment (Cape Bon,Tunisia)     

A. El Khalili  H. Habaeib  J. M. Lamachère 《水文科学杂志》2013,58(7):1519-1531

Abstract

Gully erosion is considered to be one of the most important soil erosion processes in Mediterranean marly environments, but its actual contribution to total soil loss is still under discussion. The objectives of this paper are: (a) to acquire the distributed value of erosion rate in a permanent gully developed on a marly substratum in a Mediterranean environment; and (b) to quantify the key factors responsible for the spatial and temporal differences in erosion rates observed within the gully. A permanent gully located in Cap Bon (northeastern Tunisia) has been intensively and regularly monitored over a 7-year period with electronic survey equipment (total station) to give five field topographic surveys, as well as hydrological measurements at the gully outlet. The net soil loss for the 7-year period comprised a denudation of 51 m³ of sediment on the gully bank slopes, which corresponds to a mean soil loss of 61 m³ ha^?1 year^?1 or 6.1 mm year^?1. Denudation was observed on bed units with a slope gradient greater than 20%, while the remainder showed deposition. By confirming the factors involved in gully evolution, and by refining the statistical link between factors and erosion rates within the gully, the results provide important information to predict gully erosion rates in Mediterranean marly environments.

Editor Z.W. Kundzewicz; Associate editor G. Mahé

Citation El Khalili, A., Raclot, D., Habaieb, H., and Lamachère, J.M., 2013. Factors and processes of permanent gully evolution in a Mediterranean marly environment (Cape Bon, Tunisia). Hydrological Sciences Journal, 58 (7), 1519–1531.  相似文献   

Origin of EL3 chondrites: Evidence for variable C/O ratios during their course of formation—A state of the art scrutiny          下载免费PDF全文

A. El Goresy  Y. Lin  M. Miyahara  A. Gannoun  M. Boyet  E. Ohtani  P. Gillet  M. Trieloff  A. Simionovici  L. Feng  L. Lemelle 《Meteoritics & planetary science》2017,52(5):781-806

Mineral inventories of enstatite chondrites; (EH and EL) are strictly dictated by combined parameters mainly very low dual oxygen (fO₂) and sulfur (fS₂) fugacities. They are best preserved in the Almahata Sitta MS‐17, MS‐177 fragments, and the ALHA 77295 and MAC 88136 Antarctic meteorites. These conditions induce a stark change of the geochemical behavior of nominally lithophile elements to chalcophile or even siderophile and changes in the elemental partitioning thus leading to formation of unusual mineral assemblages with high abundance of exotic sulfide species and enrichment in the metallic alloys, for example, silicides and phosphides. Origin and mode of formation of these exotic chondrites, and their parental source regions could be best scrutinized by multitask research experiments of the most primitive members covering mineralogical, petrological, cosmochemical, and indispensably short‐lived isotopic chronology. The magnitude of temperature and pressure prevailed during their formation in their source regions could eventually be reasonably estimated: pre‐ and postaccretionary could eventually be deduced. The dual low fugacities are regulated by the carbon to oxygen ratios estimated to be >0.83 and <1.03. These parameters not only induce unusual geochemical behavior of the elements inverting many nominally lithophile elements to chalcophile or even siderophile or anthracophile. Structure and mineral inventories in EL3 and EH3 chondrites are fundamentally different. Yet EH3 and EL3 members store crucial information relevant to eventual source regions and importantly possible variation in C/O ratio in the course of their evolution. EL3 and EH3 chondrites contain trichotomous lithologies (1) chondrules and their fragments, (2) polygonal enstatite‐dominated objects, and (3) multiphase metal‐rich nodules. Mineralogical and cosmochemical inventories of lithologies in the same EL3 indicate not only similarities (REE inventory and anomalies in oldhamite) but also distinct differences (sinoite‐enstatite‐graphite relationship). Oldhamite in chondrules and polygonal fragments in EL3 depict negative Eu anomaly attesting a common cosmochemical source. Metal‐dominated nodules in both EL3 and EH3 are conglomerates of metal clasts and sulfide fragments in EH3 and concentrically zoned C‐bearing metal micropebbles (≥25 μm ≤50 μm) in EL3 thus manifesting a frozen in unique primordial accretionary metal texture and composition. Sinoite‐enstatite‐diopside‐graphite textures reveal a nucleation and growth strongly suggestive of fluctuating C/O ratio during their nucleation and growth in the source regions. Mineral inventories, sulfide phase relations, sinoite‐enstatite‐graphite intergrowth, carbon and nitrogen isotopic compositions of graphite, spatial nitrogen abundance in graphite in metal nodules, and last but not least ¹²⁹I/¹²⁹Xe and ⁵³Mn/⁵³Cr systematics negate any previously suggested melting episode, pre‐accretionary or dynamic, in parental asteroids.  相似文献   

Parameters affect foaming and foam stability during foam drilling     

Hazaea Mohammed  Youhong SUN  Ould El Houssein Yarbana 《世界地质(英文版)》2007,10(2)

The authors presented indoor practice experiments of parameters affect on foaming and foam stability. Experiments were carried out and special equipments were used to determine foaming and foam stability; tests were tabulated and charted. The effects of chemical and physical parameters on foaming and foam stability have been conducted.  相似文献   

Dynamics of shock waves in a contracting cloud     

M. Y. Amin  M. S. El-Nawawy  M. A. El Shalaby 《Astrophysics and Space Science》1991,185(2):195-209

The contraction of an interstellar cloud is followed. The results indicates that there are shock waves appear during contraction. In order to study the effect of shock waves, two models have been studied. The post-shock temperature for the two models are, respectively, 3006 K and 2984 K. The density increases by more than three orders of magnitude. The gas is generally cooled by atoms, molecules, and grains. The dominant cooling process changes according to the chemical composition and the temperature of the gas. The thermal equilibrium depends on the existing physical conditions.  相似文献   

New magnetic chemically peculiar stars     

V. G. El’kin  D. O. Kudryavtsev  I. I. Romanyuk 《Astronomy Letters》2002,28(3):169-173

Our observations with the 6-m telescope revealed six new magnetic chemically peculiar (CP) stars among objects with large depressions in the continuum: HDE 293764, BD+17°3622, HD 169887, HDE 231054, HDE 338226, and HDE 343872. The presence of a magnetic field is suspected in several other CP stars. The maximum longitudinal field component B _e exceeds 1.5 kG for all six stars; in HDE 293764 and HDE 343872, it reaches 3.8 kG. For each object, we present our magnetic-field measurements and published data on previous studies. The method of searching for magnetic stars based on an analysis of spectrophotometry shows its efficiency.  相似文献