Origin of wehrlite cumulates in the Moho transition zone of the Neoproterozoic Ras Salatit ophiolite,Central Eastern Desert,Egypt: crustal wehrlites with typical mantle characteristics     

Hisham?A.?GahlanEmail author  Shoji?Arai  Fawzy?F.?Abu El-Ela  Akihiro?Tamura 《Contributions to Mineralogy and Petrology》2012,163(2):225-241

Ultramafic cumulates, mainly crustal true wehrlites, were discovered and described in the mantle–crust transition zone (MTZ) and the extremely lower layered gabbro sequence of the Ras Salatit ophiolite, Central Eastern Desert, Egypt. They form either boudinaged lensoidal tabular bodies or interdigitated layers often concordant with the planolinear fabrics of the Ras Salatit ophiolite rocks. The contact between wehrlites and the host MTZ dunite or layered gabbro is razor sharp, lobate and/or sinuous, without chilled margins or any visible deformations. The Ras Salatit wehrlites are orthopyroxene-free and composed mainly of olivine and clinopyroxene. They are texturally equilibrated and show a characteristic poikilitic texture. Crystallization order of the Ras Salatit wehrlites is olivine/spinel followed by clinopyroxene with the absence of plagioclase. Olivine and clinopyroxene of the Ras Salatit wehrlites are compositionally uniform and conspicuously high in Mg#, mostly around 0.93 and 0.92, respectively. Moreover, the clinopyroxene shows low Ti and Al contents coupled with marked depletion in LILE. The calculated melt in equilibrium with clinopyroxene from the Ras Salatit wehrlites is largely similar to lavas from the Izu-Bonin forearc. Given the above characteristics, the Ras Salatit wehrlites were produced by crystal accumulation from a hydrous depleted basaltic/tholeiitic melt corresponding to temperatures between 1,000 and 1,100°C at the oceanic crustal pressure (~2 kbar). The involved hydrous tholeiitic melt has been probably formed by fluid-assisted partial melting of a refractory mantle source (similar to the underlying harzburgites) in a somewhat shallow sub-arc environment.  相似文献   

Water Purification Using Cost Effective Material Prepared from Agricultural Waste: Kinetics,Isotherms, and Thermodynamic Studies          下载免费PDF全文

Mu. Naushad  Mohammad Rizwan Khan  Zeid Abdullah ALOthman  Ala'a H. Al‐Muhtaseb  Md. Rabiul Awual  Ayoub Abdullah Alqadami 《洁净——土壤、空气、水》2016,44(8):1036-1045

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Morphodynamic evolution of a lower Mississippi River channel bar after sand mining          下载免费PDF全文

Brendan T. Yuill  Ahmed Gaweesh  Mead A. Allison  Ehab A. Meselhe 《地球表面变化过程与地形》2016,41(4):526-542

In‐channel sand mining by dredge removes large quantities of bed sediment and alters channel morphodynamic processes. While the reach‐scale impacts of dredging are well documented, the effects of the dredged borrow pit on the local flow and sediment transport are poorly understood. These local effects are important because they control the post‐dredge evolution of the borrow pit, setting the pit lifespan and affecting reach‐scale channel morphology. This study documents the observed morphological evolution of a large (1·46 million m³) borrow pit mined on a lateral sandbar in the lower Mississippi River using a time‐series of multibeam bathymetric surveys. During the 2·5 year time‐series, 53% of the initial pit volume infilled with sediment, decreasing pit depth by an average of 0·88 m yr^?1. To explore the controls of the observed infilling, a morphodynamic model (Delft3D) was used to simulate flow and sediment transport within the affected river reach. The model indicated that infilling rates were primarily related to the riverine sediment supply and pit geometry. The pit depth and length influenced the predicted magnitude of the pit bed shear stress relative to its pre‐dredged value, i.e. the bed‐stress reduction ratio (R*), a metric that was correlated with the magnitude and spatial distribution of infilling. A one‐dimensional reduced‐complexity model was derived using predicted sediment supply and R* to simulate patterns of pit infilling. This simplified model of borrow‐pit evolution was able to closely approximate the amount and patterns of sediment deposition during the study period. Additional model experiments indicate that, for a borrow pit of a set volume, creating deep, longitudinally‐shorter borrow pits significantly increased infilling rates relative to elongated pits. Study results provide insight into the resilience of alluvial river channels after a disturbance and the sustainability of sand mining as a sediment source for coastal restoration. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Bedload transport of small rivers in Malaysia     

Zahra ZANGENEH SIRDARI  Aminuddin AB GHANI  Zorkeflee Abu HASSAN 《国际泥沙研究》2014,29(4):481-490

Numerous time-consuming equations, based on the relationship between the reliability and representativeness of the data utilized in defining variables and constants, require complex parameters to estimate bedload transport. In this study the easily accessible data including flow discharge, water depth, water surface slope, and surface grain diameter （ds0） from small rivers in Malaysia were used to estimate bedload transport. Genetic programming （GP） and artificial neural network （ANN） models are applied as complementary tools to estimate bed load transport based on a balance between simplicity and accuracy in small rivers. The developed models demonstrate higher performance with an overall accuracy of 97% and 93% for ANN and GP, respectively compared with other traditional methods and empirical equations.  相似文献   

Adaptive state estimation of groundwater contaminant boundary input flux in a 2-dimensional aquifer     

Muhammad Malik Nauman  Murtuza Mehdi  Asif Iqbal  Muhammad Saifullah Abu Bakar  Brahim Aissa  Dk Nur Afiqah Jalwati Puteri  Amer Farhan Rafique 《地下水科学与工程》2019,(4):373-382

In many circumstances involving heat and mass transfer issues,it is considered impractical to measure the input flux and the resulting state distribution in the domain.Therefore,the need to develop techniques to provide solutions for such problems and estimate the inverse mass flux becomes imperative.Adaptive state estimator(ASE)is increasingly becoming a popular inverse estimation technique which resolves inverse problems by incorporating the semi-Markovian concept into a Bayesian estimation technique,thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters.The ASE is particularly designed for a system that encompasses independent unknowns and/or random switching of input and measurement biases.The present study describes the scheme to estimate the groundwater input contaminant flux and its transient distribution in a conjectural two-dimensional aquifer by means of ASE,which in particular is because of its unique ability to efficiently handle the process noise giving an estimation of keeping the relative error range within 10%in 2-dimensional problems.Numerical simulation results show that the proposed estimator presents decent estimation performance for both smoothly and abruptly varying input flux scenarios.Results also show that ASE enjoys a better estimation performance than its competitor,Recursive Least Square Estimator(RLSE)due to its larger error tolerance in greater process noise regimes.ASE's inherent deficiency of being slower than the RLSE,resulting from the complexity of algorithm,was also noticed.The chosen input scenarios are tested to calculate the effect of input area and both estimators show improved results with an increase in input flux area especially as sensors are moved closer to the assumed input location.  相似文献   

Geophysical interpretation of the Rashidpur structure Surma Basin,Bangladesh     

Abu Sohel  Shamaun Kabir  Delwar Hossain 《Journal of the Geological Society of India》2009,74(1):39-48

The Rashidpur structure is located in the southern part of the Surma Basin, Bangladesh. This paper presents an integrated interpretation of seismic and other geophysical data considering the available geologic information in terms of hydrocarbon potential of this structure. The study area lies within a gravity high and a high magnetic intensity. Fifteen seismic sections of the study area have been analyzed to interpret the subsurface geology, structure and stratigraphy. Based on the analysis of seismic sections and correlation with well data, four prominent reflecting horizons have been identified. The litho-stratigraphy of the Rashidpur structure is prepared on the basis of well information. The lithological sequences encountered in the Rashidpur structure range in age from Miocene to Plio-Pliestocene. The gas producing sands of the structure are within Bokabil to Bhuban Formations of the Miocene age. The seismic study indicates that the Rashidpur structure is a narrow, NS elongated anticline affected by a major reverse fault on the eastern flank. It is an asymmetrical anticline with the axis swinging slightly to the east on the northern plunge and thus attaining a slight concavity to the east. There are various geophysical indications of hydrocarbons in this structure.  相似文献   

Sedimentology and depositional environments of the Ordovician Umm Sahm Sandstone Formation in southern Jordan     

Issa Makhlouf  Abdalla Abu Hamad  Basem Moh’d 《Arabian Journal of Geosciences》2017,10(7):178

The Ordovician Umm Sahm Sandstone Formation of Jordan comprises approximately 200-m-thick succession of fluvial quartzarenites with subordinate claystone and siltstone lithologies of shallow marine conditions. The Umm Sahm Formation is characterized by its dark brown color, frequent jointing, and steep scarps. The Umm Sahm Formation is bounded by the marine claystones of Hiswah Formation at the top and the fluvial sandstones of the Disi Formation at the bottom. The Umm Sahm Formation is composed of two main facies: fluvial facies and tidal facies. The fluvial facies constitutes about 93% of the total thickness. The lower few meters of the succession passes upward from the Disi Sandstone Formation into similar massive white sandstone facies exhibiting similar white color, fine- to coarse-grained sandstone, with round-shaped pebbles. Trough and planar cross-bedding show a northwest unidirectional palaeocurrent trend. Light brown colored quartzarenites similar to those of the Cambrian Umm Ishrin Sandstone Formation are most common in the upper part of the succession. The tidal facies occupies three intervals in the middle part of the succession. It is composed of laminated and thin-bedded sandstones, siltstones, and claystones. They are rippled and varicolored with abundant trace fossils (Cruziana, Harlania, ruzophycus). The presence of hummocky cross stratification indicates the earliest short-lived tempestite conditions during the Paleozoic erathem of Jordan. The first appearance of Graptolites in the Ordovician rocks of Jordan was recorded during this study in the tidal facies of the Umm Sahm Formation. The vertical arrangement of both fluvial and tidal facies indicates three successive short-lived transgressions and regressions. These marine incursions indicate the successive shoreline advances of the Tethys Ocean, which was located northward, and inundated the southern braid plain. The three short-lived transgressive events took place, and the Tethys marine margin was displaced southward, giving rise to deposition of tidal facies in an open coast tidal flat. Following the transgressive events, renewed progradation and strandline retreat took place, fed by large amounts of siliciclastics derived from the continent and transported by braided streams across the intertidal zone.  相似文献   

Validation of TRMM 3B42 V6 for estimation of mean annual rainfall over ungauged area in semiarid climate     

Abolghasem Akbari  Farshid Daryabor  Azizan Abu Samah  Mohsen Fanodi 《Environmental Earth Sciences》2017,76(15):537

This research compares data from the Tropical Rainfall Measuring Mission 3B42 V6 with data obtained from 19 synoptic rain gauges during the period 1998–2010 over the semiarid climate of Khorasan Razavi, Iran. Validation was performed using three spatial extents, including 1 TRMM grid face from the synoptic station (1PTRM), 3 TRMM points surrounding the synoptic station (3PTRM) and 5 TRMM points surrounding the synoptic station (5PTRM), using ArcGIS 10.2 software. The perfect and poor r were obtained at stations S08 and S19, with values of 0.92 and 0.26, respectively. According to the Nash–Sutcliffe efficiency coefficient, the TRMM satellite can predict the spatial variation of the mean annual rainfall by 0.23, 0.43 and 0.38 for 1PTRM, 3PTRM and 5PTRM, respectively, at 19 stations. The agreement significantly increases by 0.88, 0.83 and 0.80 for 1PTRM, 3PTRM and 5PTRM, respectively, when gauges S05, S07, S11 and S13 are excluded from the dataset, which may be associated with orographic or instrumental error at the stations.  相似文献   

Sr–Nd isotopes and geochemistry of the infrastructural rocks in the Meatiq and Hafafit core complexes, Eastern Desert, Egypt: Evidence for involvement of pre-Neoproterozoic crust in the growth of Arabian–Nubian Shield     

Ali A.  Khudeir  Mohamed A.  Abu El-Rus  Samir  El-Gaby  Osman  El-Nady  Wagih W.  Bishara 《Island Arc》2008,17(1):90-108

Abstract Meatiq and Hafafit core complexes are large swells in the Eastern Desert of Egypt, comprising two major tectono‐stratigraphic units or tiers. The lower (infrastructure) unit is composed of variably cataclased gneissose granites and high‐grade gneisses and schists. It is structurally overlain by Pan–African ophiolitic mélange nappes (the higher unit). The two units are separated by a low‐angle sole thrust, along which mylonites are developed. Major and trace element data indicate formation of the gneissose granites in both volcanic arc and within‐plate settings. Nevertheless, all analyzed gneissose granites and other infrastructural rocks, exhibit low initial ratios (Sr_i) (<0.7027), positive ε_Nd(t) (+4.9 to +10.3) and Neoproterozoic Nd model age (T_DM) (592–831 Ma for the gneissose granite samples). Although these values are compatible with other parts of the Arabian– Nubian Shield considered to be juvenile, the ε_Nd(t) values and several incompatible element ratios of the gneissose granites are too low to be derived from a mantle source without contribution from an older continental crust. Our geological, Sr–Nd isotopic and chemical data combined with the published zircon ages indicate the existence of a pre‐Neoproterozoic continent in the Eastern Desert that started to break up at ca 800 Ma. Rifting and subsequent events caused the formation of oceanic crust and emplacement within‐plate alkali basalts in the hinterland domains of the old continent. The emplacement of basaltic magma might have triggered melting of lower crust in the old continent and resulted in emplacement of the within‐plate granite masses between 700 Ma and 626 Ma. The granite masses and other rocks in the old continent have been subjected to deformation during the over‐thrusting of Pan–African nappes, probably because of the oblique convergence between East and West Gondwanaland. Rb–Sr isotopes of the gneissose granites in both Meatiq and Hafafit core complexes defines an isochron age of 619 ± 25 Ma with Sr_i of 0.7009 ± 0.0017 and mean squares of weighted deviates = 2.0. We interpret this age as the date of thrusting of the Pan–African nappes in the Eastern Desert. Continued oblique convergence between East and West Gondwanaland could have resulted in the formation northwest–southeast‐trending Meatiq and Hafafit anticlinoriums.  相似文献   

Exploration of the extension of two lava tubes,faults and dikes using very low frequency-electromagnetic technique in NE Jordan     

Ahmad Al-Oufi  Hakam A. Mustafa  Eid Al-Tarazi  Jafar Abu Rajab 《Acta Geophysica》2008,56(2):466-484

The very low frequency-electromagnetic (VLF-EM) technique was used to delineate two sub-parallel lava tubes, faults and dikes in Umm El-Quttein area, NE Jordan. The investigation of the lava tubes was conducted through 22 VLF-EM profiles across lava strike; the length of profiles ranged from 700 to 1700 m. The lava tubes outcrop at two sites: Azzam cave and Al-Howa tunnel, characterized by slightly weathered basalt, columnar joints and fissure zones; qualitative interpretation of Fraser and Karous-Hjelt maps differentiate those zones as linear, elongated and circular anomalous zones. The 2-D tipper inversion of VLF-EM data and resistivity imaging had the potential to screen out three anomalous zones of likely resistivity contrast: the lava tube body with resistivity over 2500 Θ·m, the fractured zones with resistivity less than 500 Θ·m, and the host vesicular basalt with resistivity of 1500 Θ·m. The strike of lava tubes varied from SW to NE direction with depth less than 20 m and width from 10 to 30 m.  相似文献