Origin of a late Neoproterozoic (605 ± 13 Ma) intrusive carbonate–albitite complex in Southern Sinai, Egypt     

Mokhles Kamal Azer  Robert J. Stern  Jun-Ichi Kimura 《International Journal of Earth Sciences》2010,99(2):245-267

New geochemical, isotopic, and geochronological data and interpretations are presented for late Neoproterozoic intrusive carbonates and related rocks of southern Sinai, Egypt (northernmost Arabian–Nubian Shield). The Tarr carbonates are coarsely crystalline and related to explosive emplacement of hypabyssal and volcanic albitite at 605 ± 13 Ma. The carbonates associated with the albitites are divisible into two types: primary dolomitite and secondary breunneritite (Fe-rich magnesite). The dolomitite was clearly intrusive but differs from classic igneous carbonatites, containing much lower abundances of incompatible elements, such as REE, U, Th, Rb, Nb, Y, P, Sr, Zr, Ba, and total alkalies. The breunneritite is a secondary replacement of dolomitite, probably marking the roots of a vigorous hydrothermal system. Albitites show pristine abundances of major and trace elements and were not subjected to a major metamorphic overprint. They are relatively more fractionated, alkaline and related to within-plate A-type magmas, were emplaced in an extensional or non-compressive tectonic regime in the cupola of high-level A-type granite. Tarr albitites may represent residual magma remaining after near-total crystallization of an A-type granite pluton at depth, forcibly emplaced into the roof above the cooling pluton. The intrusive dolomitite exsolved from highly differentiated albitite melt, in the apical regions of a still-buried alkaline “A-type” granite pluton that was rich in CO₂; these volatiles migrated upwards and towards the cooler margins of the magma body. Late NNE-SSW extension allowed a shallow-level cupola to form, into which albitite melts and carbonate fluids migrated, culminating in explosive emplacement of albitite breccia and intrusive carbonate. Isotopic compositions of Tarr dolomitite and albitite indicate these are consanguineous and ultimately of mantle origin. Magmatic volatiles fenitized the wall rock, while submarine hydrothermal activity transformed some of the dolomitite into breunneritite. Recognition of Tarr-type should encourage similar hypabyssal complex intrusions to be sought for in association with A-type granitic plutons elsewhere.  相似文献   

Stochastic modeling of length of day and universal time     

Kamal Hamdan  Li-Yu Sung 《Journal of Geodesy》1996,70(6):307-320

We propose a general stochastic model for the UT1/LOD system and derive the corresponding Kalman filter model. This stochastic model consists of an arbitrary sum of continous time autoregressive moving average (ARMA) processes, each chosen to characterize a different frequency band. The transition matrix which corresponds to the overall system and the time-dependent process noise covariance matrix are derived.Based on the general formulation, several models for UT1 were derived from spectral analysis of the Space 92 UT1 series (Gross,1993). Using Space 92 as the reference series, the candidate models were compared based on their ability to predict UT1 and LOD up to 30 days in the absence of data. These candidate models were compared with the JPL operational Kalman Earth Orientation Filter (KEOF) which assumes a random walk model for LOD (Morabito et al.,1987). The results of the comparison revealed that autoregressive modeling the 40–50 day oscillation in the LOD reduces the LOD prediction error by 10prediction.  相似文献   

Bentonite as a Natural Adsorbent for the Sorption of Iron from the Ground Water Exploited from Aswan Area, Egypt     

Gharib M. Taha  Kamal Abou Elmagd 《Ground Water Monitoring & Remediation》2004,24(1):47-52

Sorption of dissolved Fe²⁺ on bentonite was studied using a batch technique. The distribution coefficient, K_d , was evaluated for a bentonite-iron system as a function of contact time, pH, sorbent and sorbate concentrations, and temperature. Sorption results were interpreted in terms of Freundlich's and Langmuir's equations. Thermodynamic parameters for the sorption system were determined at three temperatures: 298°, 308°, and 318°K. The values of ΔH°(-4.0 kjmol⁻¹) and ΔG°(-2.46 Kjmol⁻¹) at 298°K (25°C) suggest that sorption of iron on bentonite is an exothermic and a spontaneous process. The ΔG° value became less negative at higher temperatures and, therefore, less iron was sorbed at higher temperatures. The desorption studies with 0.01 M CaCl₂ and deionized water at iron loading on bentonite showed that more than 90 wt% of the iron is irreversibly sorbed, probably due to the fixation of the iron by isomorphous replacement in the crystal lattice of the sorbent.  相似文献   

Contribution de la gravimétrie à l'étude de la structure du bassin de Tadla (Maroc) : Implications hydrogéologiques     

Abdessamad Najine  Mohammed Jaffal  Kamal El Khammari  Tahar Aïfa  Driss Khattach  Mahjoub Himi  Albert Casas  Said Badrane  Hicham Aqil 《Comptes Rendus Geoscience》2006,338(10):676-682

This study is based on the analysis and the interpretation of the gravity data of the Tadla basin. Its purpose is to increase the knowledge of this basin structure. A residual anomaly map was first calculated from the Bouguer anomaly data witch are strongly affected by a regional gradient. The computed map provides information on the ground density variation but it does not bring enough of new elements. Data filtering allows us to emphasize the structures affecting the basin. We chose the horizontal gradient coupled to the upward continuation techniques that permit to highlight news structures and to give information on their dip. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the Tadla basin. To cite this article: A. Najine et al., C. R. Geoscience 338 (2006).  相似文献   

Site response assessment of an urban extension site using microtremor measurements,Ahud Rufeidah,Abha District,Southwest Saudi Arabia     

Almadani  Sattam  Abdelrahman  Kamal  Ibrahim  Elkhedr  Al-Bassam  Abdulaziz  Al-Shmrani  Awad 《Arabian Journal of Geosciences》2015,8(4):2347-2357

Arabian Journal of Geosciences - Microtremor horizontal-to-vertical spectral ratio (HVSR) method has been conducted at 33 sites in Ahud Rufeidah urban expansion zone in order to assess the...  相似文献   

Hydro-climatic aspects of Indus River flow propagation     

Syed Ahmad Hassan  M. Rashid Kamal Ansari 《Arabian Journal of Geosciences》2015,8(12):10977-10982

  相似文献   

Experiments on integral length scale control in atmospheric boundary layer wind tunnel   总被引：2，自引：1，他引：1  

Kapil Varshney  Kamal Poddar 《Theoretical and Applied Climatology》2011,106(1-2):127-137

Accurate predictions of turbulent characteristics in the atmospheric boundary layer (ABL) depends on understanding the effects of surface roughness on the spatial distribution of velocity, turbulence intensity, and turbulence length scales. Simulation of the ABL characteristics have been performed in a short test section length wind tunnel to determine the appropriate length scale factor for modeling, which ensures correct aeroelastic behavior of structural models for non-aerodynamic applications. The ABL characteristics have been simulated by using various configurations of passive devices such as vortex generators, air barriers, and slot in the test section floor which was extended into the contraction cone. Mean velocity and velocity fluctuations have been measured using a hot-wire anemometry system. Mean velocity, turbulence intensity, turbulence scale, and power spectral density of velocity fluctuations have been obtained from the experiments for various configuration of the passive devices. It is shown that the integral length scale factor can be controlled using various combinations of the passive devices.  相似文献   

Post-collisional magmatism in the northern Arabian-Nubian Shield: The geotectonic evolution of the alkaline suite at Gebel Tarbush area, south Sinai, Egypt     

Esam Sadek Farahat  Mokhles Kamal Azer 《Chemie der Erde / Geochemistry》2011,71(3):247-266

Post-collisional alkaline magmatism (∼610–580 Ma) is widely distributed in the northern part of the Neoproterozoic Arabian-Nubian Shield (ANS), i.e. the northern part of the Egyptian Eastern Desert and Sinai. Alkaline rocks of G. Tarbush constitute the western limb of the Katharina ring complex (∼593 ± 16 Ma) in southern Sinai. This suite commenced with the extrusion of peralkaline volcanics and quartz syenite subvolcanics intruded by syenogranite and alkali feldspar granite. The mineralogy and geochemistry of these rocks indicate an alkaline/peralkaline within-plate affinity. Quartz syenite is relatively enriched in TiO₂, Fe₂O₃, MgO, CaO, Sr, Ba and depleted in SiO₂, Nb, Y, and Rb. The G. Tarbush alkaline suite most likely evolved via fractionation of mainly feldspar and minor mafic phases (hornblende, aegirine) from a common quartz syenite parental magma, which formed via partial melting of middle crustal rocks of ANS juvenile crust. Mantle melts could have provided the heat required for the middle crustal melting. The upper mantle melting was likely promoted by erosional decompression subsequent to lithospheric delamination and crustal uplift during the late-collisional stage of the ANS. Such an explanation could explain the absence or scarce occurrence of mafic and intermediate lithologies in the abundant late- to post-collisional calc-alkaline and alkaline suites in the northern ANS. Moreover, erosion related to crustal uplift during the late-collision stage could account for the lack or infrequent occurrence of older lithologies, i.e. island arc metavolcanics and marginal basin ophiolites, from the northern part of the ANS.  相似文献   

Strong ground motion attenuation in Aswan area, Egypt     

A. Deif  Azza Abed  Kamal Abdel-Rahman  Enayat Abdel Moneim 《Arabian Journal of Geosciences》2011,4(5-6):855-861

Recent and paleo seismicity indicate that moderate seismic activity is relatively large for Aswan area. This is a warning on the possibility of occurrence of earthquakes in the future too. No strong motion records are available in Aswan area for engineers to rely upon. Consequently, the seismological modeling is an alternative approach till sufficient instrumental records around Aswan become available. In the present study, we have developed new ground motion attenuation relationship for events spanning 4.0?≤? M _w?≤?7.0 and distance to the surface projection of the fault up to 100 km for Aswan based on a statistically simulated seismological model. We generated suites of ground motion time histories using stochastic technique. The ground motion attenuation relation describes the dependence of the strength of the ground motions on the earthquake magnitude and distance from the earthquake. The proposed equation for peak ground acceleration (PGA) for the bed rock is in the form of: $ {\mathbf{log}}{\text{ }}\left( {{\mathbf{PGA}}/{\mathbf{gal}}} \right){\text{ }} = {\mathbf{1}}.{\mathbf{24}} + {\mathbf{0}}.{\mathbf{358}}{M_{\mathbf{w}}} - {\text{ }}{\mathbf{log}}\left( {\mathbf{R}} \right){\text{ }}-{\text{ }}{\mathbf{0}}.{\mathbf{008}}{\text{ }}{\mathbf{R}}{\text{ }} + {\text{ }}{\mathbf{0}}.{\mathbf{22}}{\text{ }}{\mathbf{P}} $ . Where PGA is the peak ground acceleration in gal (cm/s²); M_w, its moment magnitude; R is the closest distance between the rupture projection and the site of interest; and the factor P is a dummy variable. It is observed that attenuation of strong motion in Aswan is correlated with those used before in Egypt.  相似文献   

Time-series maps of aboveground biomass in dipterocarps forests of Malaysia from PALSAR and PALSAR-2 polarimetric data     

Hamdan Omar  Muhamad Afizzul Misman 《Carbon balance and management》2018,13(1):19

  相似文献