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21.
The estimation of finite strain in rocks is fundamental to a meaningful understanding of deformational processes and products on all scales from microscopic fabric development to regional structural analyses. The Rf/φ and Fry methods on feldspar porphyroclasts and mafic grains from 5 granite, 1 metavolcanic, 3 metasedimentary and 1 granodiorite samples were used in Wadi El Falek region. Finite-strain data shows that a high to moderate range of deformation of the granitic to metavolcano-sedimentary samples and axial ratios in the XZ section range from 1.60 to 4.10 for the Rf/φ method and from 2.80 to 4.90 for the Fry method. Furthermore, the short axes are subvertical associated with a subhorizontal foliation. We conclude that finite strain in the deformed granite rocks is of the same order of magnitude as that from metavolcano-sedimentary rocks. Furthermore, contacts formed during intrusion of plutons with some faults in the Wadi El Falek area under brittle to semi-ductile deformation conditions. In this case, finite strain accumulated during superimposed deformation on the already assembled nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain. 相似文献
22.
Rangeland hydrology and erosion model (RHEM) enhancements for applications on disturbed rangelands 总被引：2，自引：0，他引：2 
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下载免费PDF全文 Osama Z. Al‐Hamdan Mariano Hernandez Frederick B. Pierson Mark A. Nearing C. Jason Williams Jeffrey J. Stone Jan Boll Mark A. Weltz 《水文研究》2015,29(3):445-457
The rangeland hydrology and erosion model (RHEM) is a new process‐based model developed by the USDA Agricultural Research Service. RHEM was initially developed for functionally intact rangelands where concentrated flow erosion is minimal and most soil loss occurs by rain splash and sheet flow erosion processes. Disturbance such as fire or woody plant encroachment can amplify overland flow erosion by increasing the likelihood of concentrated flow formation. In this study, we enhanced RHEM applications on disturbed rangelands by using a new approach for the prediction and parameterization of concentrated flow erosion. The new approach was conceptualized based on observations and results of experimental studies on rangelands disturbed by fire and/or by tree encroachment. The sediment detachment rate for concentrated flow was calculated using soil erodibility and hydraulic (flow width and stream power) parameters. Concentrated flow width was calculated based on flow discharge and slope using an equation developed specifically for disturbed rangelands. Soil detachment was assumed to begin with concentrated flow initiation. A dynamic erodibility concept was applied where concentrated flow erodibility was set to decrease exponentially during a run‐off event because of declining sediment availability. Erodibility was estimated using an empirical parameterization equation as a function of vegetation cover and surface soil texture. A dynamic partial differential sediment continuity equation was used to model the total detachment rate of concentrated flow and rain splash and sheet flow. The enhanced version of the model was evaluated against rainfall simulation data for three different sites that exhibit some degree of disturbance by fire and/or by tree encroachment. The coefficient of determination (R2) and Nash–Sutcliffe efficiency were 0.78 and 0.71, respectively, which indicates the capability of the model using the new approach for predicting soil loss on disturbed rangeland. By using the new concentrated flow modelling approach, the model was enhanced to be a practical tool that utilizes readily available vegetation and soil data for quantifying erosion and assessing erosion risk following rangeland disturbance. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
23.
Osama M. K. Kassem Habes A. Ghrefat Haider Zaman Awni T. Batayneh Saad Almogren Yousef Nazzal Eslam Elawadi 《Journal of the Indian Society of Remote Sensing》2016,44(1):91-99
Geological and structural mappings of Tayyib Al-Ism area were carried out using the rocks finite strain data, the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) data and the field based observations. To analyze the finite strain in the studied rocks, the Rf /? and Fry methods are applied to feldspar porphyroclasts and mafic grains from nine metavolcano-sedimentary samples (Hegaf Formation), four diorite-gabbros suite samples (Sawawin Complex), two meta-granite samples (Ifal suite) and five Zuhd alkali granite samples. The obtained data indicate traces of high to moderate level of deformation in the meta-granite and metavolcano-sedimentary rocks. The axial ratios along the XZ section range from 1.70 to 4.80 for the Rf/? method and from 1.50 to 4.50 for the Fry method. A sub-vertical trend of short axes in association with sub-horizontal foliation is also observed. These informations allow us to conclude that a finite strain in the deformed granitic rocks is of the same order of magnitude as in the metavolcano-sedimentary rocks. The contacts between the metavolcano-sedimentary and granitic rocks in Tayyib al Ism area were formed during the granitic intrusions along some of the faults under brittle to semi-ductile deformation conditions. These faults have significantly influenced the geometry and style of rifting in the Red Sea during the Neogene. The finite strain was accumulated in the area during the process of deformation, which superimpose the already existed nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain. In addition to finite strain analysis, band ratio images (3/1, 5/3, 7/5) and Principal Component Analysis (PCA) technique have been used, which proved effective in mapping geological and structural features of various rock bodies exposed in the study area. 相似文献
24.
Dominik C. HEZEL Jochen SCHLÜTER Heiko KALLWEIT A. J. Timothy JULL Osama Y. AL FAKEER Mubarak AL SHAMSI S. STREKOPYTOV 《Meteoritics & planetary science》2011,46(2):327-336
We report on the first meteorite search campaign in the United Arab Emirates (UAE). The geology and proximity of our search region suggest that it is the north‐western extension of the Oman meteorite fields. We found 26 ordinary chondrites, bringing the total number of official meteorites from the UAE to 28. The campaign was organized and conducted in close cooperation with the UAE government and the main masses of the meteorites remained in the country where they will become part of an exhibition. The bulk composition of five meteorite and three soil samples indicates an uptake of U, Mo, Sr, Ba, Li, and Pb from the soil into the meteorites during terrestrial weathering. Terrestrial ages determined from 14C decay of 21 meteorites range from recent falls to 24.4 ka, with two meteorites having >37 ka and approximately 39 ka, respectively. Weak correlations between weathering degree, meteorite bulk chemical composition, and terrestrial age suggest highly localized weathering conditions, possibly related to abundant occurrences of sabkhas in the search region. 相似文献
25.
Osama E. A. Attia 《Arabian Journal of Geosciences》2013,6(6):2045-2059
Nabq sabkha exists 16 km north of Sharm El Sheikh City occupying the low land topography in the alluvial fan zone along the coastal area, Gulf of Aqaba, Sinai, Egypt. The long axis of the sabkha trends NW–SE receiving water from two different sources: meteoric water drained from the surrounding mountainous area and seawater seepage. Field observations help to divide the area into raised beach, hill slopes, sabkha basin, and coastal area. The sabkha basin can be subdivided from its center outward into (1) basin center hypersaline lake flourished with microbial mat and precipitation of halite as rafts, cumulates, and chevrons, (2) saturated saline sand and/or mud flat zone with the extensive growth of gypsum and halite crystals growing displacively as well as different forms of petee structures, and (3) an elevated marginal dry zone with tepee structures. Mineralogical analysis reveals that quartz, halite, and gypsum are the dominant minerals with subordinate amount of aragonite, anhydrite, thenardite, and/or polyhalite. In addition, clay minerals in the mudflat zone are presented by illite and smectite, indicating derivation of soil from the surrounding basement rocks. Chemical analysis of the collected brine samples reveals alkali character in the saline lake (pH?=?7.6) and high concentrations of Na+ (680 meq/l), Cl? (940 meq/l), Mg2+ (208 meq/l), Ca2+ (70 meq/l), SO 4 2+ (30 meq/l), and HCO 3 ? (6 meq/l). The high salinity values are due to the aridity of the area, which favors precipitation of halite. Using comparative sedimentological, chemical, and mineralogial methods between such modern and ancient evaporitic environments and by detailed field, petrographic and mineralogical studies of modern evaporite environments help to interpret paleo-depositional environments of ancient evaporites sequences still in debate. 相似文献
26.
A water harvesting system for research purposes has been established in the Lisan Peninsula of the Dead Sea in the middle of the Jordan Rift Valley, where no authorized guideline is available for designing water harvesting systems. Rainfall and runoff, which occurred as flash floods, were observed at the downstream end of a gorge with a 1.12 km2 barren catchment area from October 2014 through July 2019. Due to the extremely arid environment, runoff from the catchment is ephemeral, and the flash flood events can be clearly distinguishable from each other. Thirteen flash flood events with a total runoff volume of more than 100 m3 were successfully recorded during the five rainy seasons. Pearson and Spearman correlations between duration, total rainfall depths at two points, total runoff volume, maximum runoff discharge, bulk runoff coefficient, total variation in runoff discharge and maximum variation in runoff discharge of each flash flood event were examined, revealing no straightforward relationship between rainfall and runoff. The performance of the conventional SCS runoff curve number method was also deficient in reproducing any rainfall–runoff relationship. Therefore, probability distribution fitting was performed for each random variable, focusing on the lognormal distribution with three parameters and the generalized extreme value distribution. The maximum goodness-of-fit estimation turns out to be a more rational and efficient method in obtaining the parameter values of those probability distributions rather than the standard maximum likelihood estimation, which has known disadvantages. Results support the design of the water harvesting system and provide quantitative information for designing and operating similar systems in the future. 相似文献
27.
The present study aims to evaluate a relationship between the mineralogy and structural analysis in the Halaban area and to document the tectonic evolution of Halaban and Al Amar faults. The collected samples were taken from deformed granitiods rocks (such as granite, gneisses and tonalite), metasedimentary, metavolcanic, metagabbro and carbonate rocks are trend to NE-SW with low dip angle in the Halaban area. These samples were 8 from granite, 14 metagabbro, 6 metavolcanics, 5 tonalite, 6 metasedimentary, 10 gneisses and 8 carbonate rocks. Our results are described for the different axial ratios of deformed rocks as the following: XZ sections range from 1.10 to 4.60 in the Fry method and range from 1.70 to 2.71 in the Rf/? method. YZ sections range from 1.10 to 3.34 in the Fry method and range from 1.62 to 2.63 in the Rf/Phi method. In addition, XY sections range from 1 to 3.51 in the Fry method and range from 1 to 1.27 in the Rf/? method for deformed granite rocks, metasedimentry rocks, and metagabbro. The stretch axes for measured samples in the X direction axes (SX) variety from 1.06 to 2.53 in the Fry method and vary from 1.20 to 1.45 in the Rf/? method. The values of the Y direction axes (SY) vary from 0.72 to 1.43 in the Fry method, which indicates contraction and extension in this direction and vary from 1.13 to 1.37 in the Rf/? method which indicates extension in this direction. Furthermore, the Z direction axes (SZ) varies from 0.09 to 0.89 in the Fry method and from 0.52 to 0.71 in the Rf/? method. The stretches axes in the Z direction (SZ) show a vertical shortening about 11% to 91% in the Fry method and show vertical shortening about 29% to 48% in the Rf/? method. The studied rock units are generally affected by brittle-ductile shear zones, which are sub-parallel to parallel NW or NNW trend. It assumed that different rock types of have similar deformation behavior. Based on these results, it is concluded that the finite strain is accumulated during the metamorphism after that was started the deformation by thrusting activity. The contacts between the different rock types were deformed during thrusting under semi-brittle to ductile deformation conditions by simple shear. A component of vertical shortening is also involved causing subhorizontal foliation in the Halaban area. 相似文献
28.
Kassem Osama M. K. Hamimi Z. Aboelkhair H. Abdelhalim A. Al-Gabali M. 《Geotectonics》2019,53(1):125-139
Geotectonics - Estimation of finite strain and microstructural analysis of deformed rocks are keys to better understanding deformational processes and related structures in a variety of scales... 相似文献
29.
A hydrologic regression sediment-yield model was established to determine the relationship between water discharge and suspended sediment discharge at the Blue Nile and the Atbara River outlet stations during the flood season. The model consisted of two main submodels: (1) a suspended sediment discharge model, which was used to determine suspended sediment discharge for each basin outlet; and (2) a sediment rating model, which related water discharge and suspended sediment discharge for each outlet station. Due to the absence of suspended sediment concentration measurements at or near the outlet stations, a minimum norm solution, which is based on the minimization of the unknowns rather than the residuals, was used to determine the suspended sediment discharges at the stations. In addition, the sediment rating submodel was regressed by using an observation equations procedure. Verification analyses on the model were carried out and the mean percentage errors were found to be +12.59 and –12.39, respectively, for the Blue Nile and Atbara. The hydrologic regression model was found to be most sensitive to the relative weight matrix, moderately sensitive to the mean water discharge ratio, and slightly sensitive to the concentration variation along the River Nile's course. 相似文献
30.
The Lower Carboniferous sediments at Wadi Abu El Mogheirat consist of four stratigraphic formations, from base upwards: Um Bogma, El Hashash, Magharet El Maiah and Abu Zarab formations. The most-concentrated radioactive anomalies at Wadi Abu El Mogheirat are in the middle member of the Um Bogma Formation. The gibbsitic marl in this formation shows the highest uranium contents (around 710 ppm). Gibbsitic marl and black gibbsite of the middle Um Bogma Formation show higher enrichment in Co, Cu, Mn, Ni, Pb, Zn, U, V, Ce and Th. Black gibbsite contains the highest total rare earth elements concentration, especially in terms of LREEs, while gibbsitic marl contains the highest content of HREEs. Anomalous contents of gold at Wadi Abu El Mogheirat are recorded for the first time in the gibbsitic marl (content: 10.4 ppm), black gibbsite (2.8 ppm) of the middle member of the Um Bogma Formation and in the siltstones of the El Hashash Formation (0.6 ppm). Gibbsitic marl shows the presence of uranothorite, celestite, zircon, atacamite, barite, xenotime and rutile. These characteristic demonstrate that the middle member of the Um Bogma Formation constitutes a potential source for gold. This conclusion is reinforced by the potential to exploit other metals such as Co, Cu, Mn, Ni, Pb, Zn, U, V, Th and Ce as by-products. 相似文献