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This study demonstrates the use of ASTER data for the mapping of gypsum deposits and associated geological formations that occurred in the Thumrait region of southern Oman. The measurement of spectra over samples of gypsum in the 1,300–2,500 nm wavelength using a PIMA spectrometer showed the presence of distinct absorptions at 1400–1600, 1750, 1940, 2,100, and 2,400 nm characteristics to O? H stretching, H2O combinations, and S? O bending overtones and stretching, respectively. Studying the unique spectral absorption characters of gypsum samples, we developed a false color composite (FCC) and an image by decorrelation stretch using the spectral bands 7, 3, and 2 of ASTER. The results FCC showed the regions of gypsum occurrences, and the decorrelated image discriminated the gypsum occurrences from other geological formations of the area. The study of surface mineralogy of the region using the VNIR‐SWIR bands by the spectral angle mapper method showed the presence of sulfate, carbonate, and clay minerals of the geological formations in the study area. We compared the results of ASTER with the results obtained using spectral bands 12, 8, and 4 of Sentinel‐2A processed by the same methods. The study showed that the spectral bands of ASTER can be used for mapping the gypsum and associated geological formations. 相似文献
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Geochemical and oxygen isotope perspective of a new R chondrite Dhofar 1671: Affinity with ordinary chondrites 
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下载免费PDF全文 Arshad Ali Sobhi J. Nasir Iffat Jabeen Ahmed Al Rawas Neil R. Banerjee Gordon R. Osinski 《Meteoritics & planetary science》2017,52(9):1991-2003
Dhofar 1671 is a relatively new meteorite that previous studies suggest belongs to the Rumuruti chondrite class. Major and REE compositions are generally in agreement with average values of the R chondrites (RCs). Moderately volatile elements such as Se and Zn abundances are lower than the R chondrite values that are similar to those in ordinary chondrites (OCs). Porphyritic olivine pyroxene (POP), radial pyroxene (RP), and barred olivine (BO) chondrules are embedded in a proportionately equal volume of matrix, one of the characteristic features of RCs. Microprobe analyses demonstrate compositional zoning in chondrule and matrix olivines showing Fa‐poor interior and Fa‐rich outer zones. Precise oxygen isotope data for chondrules and matrix obtained by laser‐assisted fluorination show a genetic isotopic relationship between OCs and RCs. On the basis of our data, we propose a strong affinity between these groups and suggest that OC chondrule precursors could have interacted with a 17O‐rich matrix to form RC chondrules (i.e., ?17O shifts from ~1‰ to ~3‰). These interactions could have occurred at the same time as “exotic” clasts in brecciated samples formed such as NWA 10214 (LL3–6), Parnallee (LL3), PCA91241 (R3.8–6), and Dhofar 1671 (R3.6). We also infer that the source of the oxidation and 17O enrichment is the matrix, which may have been enriched in 17O‐rich water. The abundance of matrix in RCs relative to OCs, ensured that these rocks would be apparently more oxidized and appreciably 17O‐enriched. In situ analysis of Dhofar 1671 is recommended to further strengthen the link between OCs and RCs. 相似文献
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Sobhi Samhan Kurt Friese Wolf von Tümpling Herbert Pöllmann Heinz Hoetzl Marwan Ghanem 《Environmental Earth Sciences》2014,71(4):1533-1539
Al-Qilt catchment, located east of both the Ramallah and Jerusalem districts is strongly influenced by waste waters discharged from Israeli settlements and Palestinian urban centers. In this research, our aim was to verify the chemical status of the surface sediments from the Al-Qilt catchment during 2008/2009. For this purpose, 36 surface sediment samples were collected and analyzed with ICP/MS within the fraction of below 63 μm. The extent of contamination of trace metals from Al-Qilt sediments sites were measured by evaluating the contamination factors (CF) from digestion by aqua regia and additionally by sequential extraction steps using the BCR-method. On the basis of the calculated CF, sediments appear particularly contaminated with Zn, Cu, Ag, Sn, Cd, Hg, Bi, and B. Three regions, Wadi Sweanit, Ras Al-Qilt, and Qalandiah have been identified as critical points of contamination. Trace metal inputs to the Al-Qilt catchment need to be kept under strict control in the future since Ras Al-Qilt is considered as one of the important springs in the area and is used for domestic purposes. Moreover, it will be susceptible to pollution if no action is taken to decrease the pollution at the upstream of Al-Qilt. 相似文献
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Abdulrahman Al-Safarjalani Sobhi Nasir Thomas Fockenberg Hans-Joachim Massonne 《Chemie der Erde / Geochemistry》2009,69(4):359-375
The chemical bulk rock composition of 37 xenoliths, brought from depths of 25–30 km to the surface by penetrating Cenozoic alkali basaltic magma, from the Shamah Harrat, southwestern Syria, was determined by XRF spectroscopy. The geochemical character of these xenoliths points to original marls and within-plate igneous rocks. To obtain the mean chemical composition of the corresponding upper portion of the lower crust, the compositions of the 37 xenoliths were averaged and a leucogranitic and upper crustal component was added to account for assimilation by the Cenozoic magmas. This mean is more basic (SiO2—50.5 wt%) and richer in HFSE, LREE, and LILE compared to compositions of the lower crust given by Taylor and McLennan [1985. The Continental Crust: Its Composition and Evolution. Blackwell, Oxford, 312pp.] and Rudnick and Gao [2005. Composition of the continental crust. In: Rudnick, R.L. (Ed.), The Crust. Treatise on Geochemistry, vol. 3. Elsevier, Amsterdam, pp. 1–64]. Calculations of the seismic compressional-wave velocity from our compositional mean, using the PERPLE_X computer software, yielded values around 6.85 km/s, which are in accordance with reported seismic studies for the corresponding depth levels (6.7–7.1 km/s). 相似文献
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Mafic granulite and spinel lherzolite xenoliths from Cenozoic alkaline basalts near Al-Ashkhara, eastern Oman, have been selected for a systematic mineralogical, geochemical and Sr–Nd–Pb isotopic study. This is the only place in E Arabia where samples of both lower crust and upper mantle can be examined. Lower crustal xenoliths consist of two mineralogically and chemically distinct groups: gabbronorite (subequal abundances of ortho- and clino-pyroxene and plagioclase) and plagioclase pyroxenite (dominant pyroxene and subordinate plagioclase). Temperature estimates for lower crustal xenoliths using the two pyroxene geothermometer (T-Wells) yield 810–865 °C. The mineral assemblage (spinel–pyroxene–plagioclase) and Al content in pyroxene indicate that plagioclase-bearing xenoliths equilibrated at 5–8 kbar (13 and 30 km depth) in the lower crust. εNd and 87Sr/86Sr calculated at 700 Ma for Al-Ashkhara lower crustal xenoliths (+ 6.4 to + 6.6; 87Sr/86Sr = 0.7028 to 0.7039) are consistent with the interpretation that juvenile, mafic melts were added to the lower crust during Neoproterozoic time and that there was no discernible contribution from pre-Neoproterozoic crust. Upper mantle xenoliths consist of both dry and hydrous (phlogopite-bearing) lherzolites. These peridotites are more Fe-rich than expected for primitive mantle or melt residues and probably formed by pervasive circulation of melts that have refertilized pre-existing mantle peridotites. Mineral equilibration temperatures range from 990 to 1070 °C. Isotopic compositions calculated at 700 Ma are εNd = + 6.8 to + 7.8 and 87Sr/86Sr = 0.7016 to 0.7025, indicating depleted upper mantle. Pb isotopic compositions indicate that the metasomatism was relatively recent, perhaps related to Paleogene tectonics and basanite igneous activity. Nd model ages for the spinel peridotite xenoliths range between 0.59 and 0.65 Ga. The xenolith data suggest that eastern Arabian lower crust is of hotspot origin, in contrast to western Arabian lower crust, which mostly formed at a convergent plate margin. Geochemical and isotopic differences between lower crust and upper mantle indicate that these are unrelated, possibly because delamination replaced the E Arabian mantle root in Neoproterozoic time. 相似文献
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ASTER mapping of limestone formations and study of caves, springs and depressions in parts of Sultanate of Oman 总被引：1，自引：0，他引：1
Caves, springs, and large depressions of limestone karst formations are becoming more attractive tourist places and have potential importance on socio-economic development. The present study is a multi-scale point of view on limestone karst, from the space images to microscopic fabric. Here, the karst features consist of limestone formations of Cretaceous (Albian–Cenomanian) age of Tanuf Valley and Tertiary (Late Paleocene–Middle Eocene) age of Sur region of parts of Sultanate of Oman which are mapped in the visible near-infrared and shortwave infrared spectral bands of advanced spaceborne thermal emission and reflection radiometer (ASTER) using decorrelated stretch image processing technique and the occurrences of caves, springs, and depressions of the formations in the field were studied. The decorrelated RGB images of ASTER spectral bands 8, 3, and 1 discriminated well the limestone formations and associated lithology. The limestone formations of Tanuf valley (Natih formations of Hajar unit) are thick-bedded, massive, shallow marine limestone and clayey limestone, which have caves and springs. Large depressions are studied as collapsed structures at the boundary between Abat formations; they consist of gray to white marly or micritic limestone with chert nodules and Seeb Formation of bioclastic limestone, calcarenite, marl, and sandstone of Sur region. Interpretations of limestone formations, their occurrences and distributions of caves, springs and depressions of these regions are verified and confirmed in the field and studied in the laboratory. Occurrences of more springs and depressions in the limestone formations of the study sites are interpreted and located on the Google Earth image. The study proved the capability of ASTER sensor in mapping of limestone formations and recommends the technique to other geographical regions where similar geological questions need to be resolved. 相似文献
8.
Sobhi Nasir Hamad Al-Saad Abudlrazak Alsayigh Oliver Weidlich 《Journal of Asian Earth Sciences》2008,33(5-6):353-365
Geological investigations of the Halul and the Shraouh islands, offshore Qatar, indicate that most of their calcareous rocks, which display abundant stromatolitic bedding, belong to the Infra-Cambrian Hormuz Series. Mineralogical, petrological, and geochemical analyses show that these calcareous rocks consist dominantly of dolomite and have formed in a reducing depositional environment. Faint laminations and small streaks of organic matter furnish evidence for the involvement of algal mats in their genesis and indicate their formation in an intertidal to supratidal setting. The Halul and Shraouh dolomites experienced extensive recrystallization and sulfatization during the emplacement of the Halul and Shraouh salt domes that form the cores of the islands. During mobilization and ascent of the salt, the dolomite recrystallized, and its Sr initial ratios were abnormally enhanced by the incorporation of 87Sr from a source, which is more radiogenic than the attendant seawater at the time of the dolomite formation near the Proterozoic–Cambrian boundary. Geochemical analysis show that Si, Al, Ti Zr, and % of insoluble residue are highly correlative, suggesting the presence of detrital minerals such as rutile and zircon. A paleosabkha model may well agree with this chemical signature. However, the Infra-Cambrian age of the Hormuz rocks and the presence of stromatolitic layers containing organic materials in the studied rocks, suggest that organogenic dolomitization could be an alternative dolomitization model. 相似文献
9.
Tabea Broecker Vahid Sobhi Gollo Aryeh Fox Jörg Lewandowski Gunnar Nützmann Shai Arnon Reinhard Hinkelmann 《Ground water》2021,59(4):488-502
Transport processes that lead to exchange of mass between surface water and groundwater play a significant role for the ecological functioning of aquatic systems, for hydrological processes and for biogeochemical transformations. In this study, we present a novel integral modeling approach for flow and transport at the sediment–water interface. The model allows us to simultaneously simulate turbulent surface and subsurface flow and transport with the same conceptual approach. For this purpose, a conservative transport equation was implemented to an existing approach that uses an extended version of the Navier–Stokes equations. Based on previous flume studies which investigated the spreading of a dye tracer under neutral, losing and gaining flow conditions the new solver is validated. Tracer distributions of the experiments are in close agreement with the simulations. The simulated flow paths are significantly affected by in- and outflowing groundwater flow. The highest velocities within the sediment are found for losing condition, which leads to shorter residence times compared to neutral and gaining conditions. The largest extent of the hyporheic exchange flow is observed under neutral condition. The new solver can be used for further examinations of cases that are not suitable for the conventional coupled models, for example, if Reynolds numbers are larger than 10. Moreover, results gained with the integral solver provide high-resolution information on pressure and velocity distributions at the rippled streambed, which can be used to improve flow predictions. This includes the extent of hyporheic exchange under varying ambient groundwater flow conditions. 相似文献
10.
This study demonstrates the capability of the longer wavelength (L-band) and fine mode images of the Phased Array type L-band Synthetic Aperture Radar (PALSAR), and the optical spectral bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to map sedimentary formations and structures of the Marmul region, Central Oman. Results of study shows that the principal components image of the visible and near infrared–shortwave infrared (VNIR-SWIR) spectral bands of the ASTER have potential to discriminate the occurrence and distribution of marine and Quaternary sedimentary formations of the region. The color composite image developed using PALSAR data (R:HH?+?HV; G:HH; B:HV) has capable to differentiate the occurrence of the sedimentary formations and structures of the region. We developed ratios images by summing the HH intensity as a numerator and the HV intensity as a denominator (R:HH+(HH?+?HV)/HV, G:HH?+?HV, B:HH/HV), and by summing the HV intensity as a numerator and the HH intensity as a denominator (R:HV+(HH?+?HV)/HH, G:HV?+?HH, B:HV/HH) to study better the sedimentary formations and structures. The images discriminated well the occurrence of the limestones and shale formations of the marine deposits, the wadi alluvium of the Quaternary deposits and the manmade building structures of the region. We studied the minerals of the sedimentary formations using VNIR-SWIR spectral bands of the ASTER by spectral angle mapper (SAM) image processing method. The study showed presence of carbonates, silicates and OH bearing aluminosilicate minerals in the formations. The image interpretations are verified in the field and confirmed by the laboratory studies. 相似文献