Geochemistry, petrogenesis and radioactivity of El Hudi I-type younger granites, South Eastern Desert, Egypt     

Ashraf Emam  Nasser M. Moghazy  Anas M. El-Sherif 《Arabian Journal of Geosciences》2011,4(5-6):863-878

The present study deals with geochemical characteristics and petrogenesis of three younger granite varieties (coarse-grained biotite-muscovite granites (CBG), garnetiferous muscovite granites (GMG) and Abu Aggag biotite granites (AAG)) in El-Hudi area, east of Aswan, southeastern desert of Egypt. Mineral chemistry and whole rock chemistry data revealed that all granites have high SiO₂ (70.8-74.7 wt.%), Al₂O₃ (12.8-14.3 wt.%), Na₂O and K₂O (>3.2 wt.%) contents with high Na₂O/K₂O ratios (～>1). Plagioclase feldspars range in composition from albite to oligoclase (An_9-27) in CBG, oligoclase (An_13-18) in GMG and albite (An_2-6) in AAG. Potash feldspars are mainly perthitic microcline and exhibit chemical formulae as (Or_93-96 Ab_7-4 An₀) in CBG, (Or_95-98 Ab_5-2 An₀) in GMG and (Or_82-98 Ab_18-2 An₀) in AAG. Biotites from CBG and GMG are enriched in (Mg and Ti) and depleted in (Al, Fe, Mn and K) compared with those of AAG. Biotites from CBG and GMG had been derived from calc-alkaline magma, whereas those from AAG had been derived from peraluminous magma. Chlorites from CBG and GMG are Mg-Fe bearing, while that from AAG is Fe-rich chlorite (chamosite). The CBG and GMG are Mg-rich monzogranites originated from high-K calc-alkaline magma with metaluminous to mildly peraluminous nature. The AAG are Fe-rich monzogranites to syenogranites generated from high-K calc-alkaline peraluminous magma. Both CBG and GMG are late- to post-orogenic granites, while the AAG are post-orogenic granites. All three granite varieties are considered as evolved I-type granites, formed under low to moderate water pressures (～ 0.5-7 kbars) and relatively high ranges of crystallization temperatures (～700-890°C). They were generated from partial melting of crustal materials at lower (CBG >30 km depth) and intermediate (GMG & AAG ～20-30 km depth) levels. The crystal fractionation was the predominant process during differentiation of parent magmas of these granites. Geochemical characteristics manifest that AAG represent the highly fractionated member of magma cycle differs from that produced CBG and GMG. The CBG are relatively enriched in both U and Th existing only within the accessory minerals such as zircon, sphene, and allanite.  相似文献   

Spatio-temporal characteristics of precipitation and drought in Balochistan Province,Pakistan   总被引：1，自引：0，他引：1  

Muhammad Ashraf  Jayant K. Routray 《Natural Hazards》2015,77(1):229-254

  相似文献   

GIS‐evaluation of two slope‐calculation methods regarding their suitability in slope analysis using high‐precision LiDAR digital elevation models     

M. Irfan Ashraf  Zhengyong Zhao  Charles P.‐A. Bourque  Fan‐Rui Meng 《水文研究》2012,26(8):1119-1133

  相似文献   

Response of a tunnel deeply embedded in a viscoelastic medium     

Thomas J. Birchall  Ashraf S. Osman 《国际地质力学数值与分析法杂志》2012,36(15):1717-1740

This paper presents a three‐dimensional energy‐based solution for the time‐dependent response of a deeply embedded and unsupported semi‐infinite tunnel of circular cross‐section. The tunnel is taken to be excavated quasi‐instantaneously from an infinite rock body that initially exhibits an isotropic stress state and that is made up of a homogeneous, isotropic and viscoelastic material. The viscoelastic behaviour is modelled by means of Burger's model, and the rock is taken to behave volumetrically linear elastic and to exhibit exclusively deviatoric creep. This viscoelastic problem is transformed into the Laplace domain, where it represents a quasi‐elastic problem. The displacement fields in the new solution are taken to be the products of independent functions that vary in the radial and longitudinal directions. The differential equations governing the displacements of the system and appropriate boundary conditions are obtained using the principle of minimum potential energy. The solutions for these governing equations in the Laplace domain are then obtained analytically and numerically using a one‐dimensional finite difference technique. The results are then transformed back into the time domain using an efficient numerical scheme. The accuracy of the new solution is comparable with that of a finite element analysis but requires much less computation effort. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

CHEMICAL CHARACTERISTICS OF WETLAND′S INFLOW DRY DIFFUSE DUST AND DIRT FROM IMPERVIOUS SURFACE     

Azam Khan  Saadat Ashraf 《湿地科学》2005,(4)

1INTRODUCTIONIn impervious area dry dustand dirtbuildup con-tains heavy metals,nutrients,pesticides and organ-ics.Many studies(APWA,1969;Sartor and Boyd,1972;Pitt and Amy,1973;Pitt,1979,1985;Yousef and Wanielista,1990;Wanielista andYousef,1993,Ball,et al.…  相似文献   

Cretaceous Environments of Afghanistan:A Synthesis Based on Selected Sections     

Abdul Rahman Ashraf  Ashok Sahni 《东北亚地学研究》2003,(1)

1IntroductionThe Late Mesozoic sequences of Afghanistan are important in understanding the geodynamic evolu-tion of the northwestern part of South Asia, in par-ticular the transgressive and regressive history of the northwestern part of the Tethys connecting Iran to the west and the northern Indian Subcontinent to the east. Jurassic to Upper Cretaceous sedimentary seque-nces were initially studied by Griesbach (1885 ~1887) and Hayden (1880~1901) through several traverses in northern an…  相似文献   

Study of Aerosol Direct and Indirect Effects and Auto-conversion Processes over the West African Monsoon Region Using a Regional Climate Model     

Zeinab SALAH  Ahmed SHALABY  Allison L.STEINER  Ashraf S.ZAKEY  Ritesh GAUTAM  Mohamed M.ABDEL WAHAB 《大气科学进展》2018,35(2):182-194

This study assesses the direct and indirect effects of natural and anthropogenic aerosols(e.g., black carbon and sulfate)over West and Central Africa during the West African monsoon(WAM) period(June–July–August). We investigate the impacts of aerosols on the amount of cloudiness, the influences on the precipitation efficiency of clouds, and the associated radiative forcing(direct and indirect). Our study includes the implementation of three new formulations of auto-conversion parameterization [namely, the Beheng(BH), Tripoli and Cotton(TC) and Liu and Daum(R6) schemes] in Reg CM4.4.1,besides the default model's auto-conversion scheme(Kessler). Among the new schemes, BH reduces the precipitation wet bias by more than 50% over West Africa and achieves a bias reduction of around 25% over Central Africa. Results from detailed sensitivity experiments suggest a significant path forward in terms of addressing the long-standing issue of the characteristic wet bias in Reg CM. In terms of aerosol-induced radiative forcing, the impact of the various schemes is found to vary considerably(ranging from-5 to-25 W m~(-2)).  相似文献   

Sorption of lead by chemically modified rice bran     

T. Fatima  R. Nadeem  A. Masood  R. Saeed  M. Ashraf 《International Journal of Environmental Science and Technology》2013,10(6):1255-1264

In this work, the effectiveness of native and chemically modified rice bran to remove heavy metal Pb(II) ions from aqueous solution was examined. Chemical modifications with some simple and low-cost chemicals resulted in enhancement of the adsorption capacities and had faster kinetics than native rice bran. Experiments were conducted in shake flasks to monitor the upshot of parameters over a range of pH, initial Pb(II) concentrations and contact times using a batch model study. The sorption capacities q (mg g^?1) increased in the following order: NaOH (147.78), Ca(OH)₂ (139.08), Al(OH)₃ (127.24), esterification (124.28), NaHCO₃ (118.08), methylation (118.88), Na₂CO₃ (117.12) and native (80.24). The utmost uptake capacity q (mg g^?1) was shown by NaOH-pretreated rice bran. The results showed that, using NaOH-modified rice bran, the chief removal of Pb(II) was 74.54 % at pH 5, primary Pb(II) concentration 100 mg L^?1 and contact time 240 min. Equilibrium isotherms for the Pb(II) adsorption were analyzed by Langmuir and Freundlich isotherm models. The Langmuir isotherm model, showing Pb(II) sorption as accessible through the high value of the correlation coefficient (R ² = 0.993), showed a q _max value of 416.61 mg g^?1. The kinetic model illustrated adsorption rates well, depicted by a second order, which gives an indication concerning the rate-limiting step. Thermodynamic evaluation of the metal ion ?G ^o was carried out and led to the observation that the adsorption reaction is spontaneous and endothermic in nature. NaOH chemically modified rice bran was a superb biosorbent for exclusion of Pb(II) and proved to be excellent for industrial applications.  相似文献   

Mineralogy and microchemistry of the Egat gold deposit, South Eastern Desert of Egypt     

Ashraf Emam 《Arabian Journal of Geosciences》2013,6(12):4619-4634

Gold-bearing quartz lodes from the Egat gold mine, South Eastern Desert of Egypt, are associated with pervasively silicified, highly sheared ophiolitic metagabbro and island-arc metavolcanic rocks. The mineralized quartz veins and related alteration haloes are controlled by NNW-trending shear/fault zones. Microscopic and electron probe microanalyses (EPMA) data of the ore and gangue minerals reveal that fine-grained auriferous sulfarsenides represent early high-temperature (355–382 °C) phases, with formation conditions as (fS₂?=??10, and fO₂ around ?31). A late, low-temperature (302–333 °C) assemblage includes coarse pyrite, arsenopyrite, and free-milling gold grains (88–91 wt.% Au), with formation conditions as (fS₂?=??8 and fO₂ around ?30). Gold was impounded within early sulfarsenides, while free-milling gold blebs occur along microfractures in quartz veins and as inclusions in late sulfides. Infiltration of hydrothermal fluids under brittle–ductile shear conditions led to mobilization of refractory Au from early sulfarsenide phases and reprecipitated free gold, simultaneous with silicification of the host rocks. The positive correlation between Au and As favors and verifies the use of As as the best pathfinder for gold targets, along the NNW-trending shear zones.  相似文献   

Astrophysical parameters of ten poorly studied open star clusters     

Ashraf Latif Tadross  Reda El-Bendary  Anas Osman  Nader Ismail  Abdel Aziz Bakry 《天体物理学报》2012,(1):75-83

  相似文献