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Acta Geochimica - Mineralogical and geochemical characteristics of stream sediments collected from 30 stations in the Dahab-Wadi Kid area (southeastern Sinai, Egypt) are presented. The studied... 相似文献
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Dahab stream sediments, southeastern Sinai, Egypt: a potential source of gold, magnetite and zircon 总被引：1，自引：0，他引：1
A. A. Surour A. A. El-Kammar E. H. Arafa H. M. Korany 《Journal of Geochemical Exploration》2003,77(1):25-43
The stream sediments of Dahab area, southeastern Sinai, Egypt, were studied for their content of economic minerals. These sediments are immature as indicated by poor sorting and other mechanical parameters. They are derived from Precambrian basement rocks, which are mostly represented by granitic rocks in addition to lesser amounts of volcanics and gabbros. The mineralogical investigation revealed that these sediments contain considerable amounts of placer gold, Fe–Ti oxides and zircon.The concentrated Fe–Ti oxides comprise homogeneous magnetite and ilmenite in addition to ilmeno-magnetite, hemo-ilmenite and rutile–hematite intergrowths. Isodynamic separation of some raw samples of SIZE=1 mm revealed that up to 15.12% magnetic minerals can be recovered. Zircon shows remarkable variations in morphology, colour, chemistry and provenance. U-poor and U-rich varieties of zircon were discriminated containing UO2 in the ranges of 0.04–1.19 and 3.05–3.68 wt.%, respectively. REE-bearing minerals comprise monazite, allanite and La-cerianite.On mineralogical basis, the present work suggests that Dahab stream sediments represent a promising target for further geochemical exploration for precious metals, especially gold. Fire assay data indicate that placer gold in the studied sediments sometimes reaches 15.34 g/t. Narrow gullies and valleys cutting the basement manifest the development and preservation of gold in this arid environment. Background concentration of gold and variation in lithology suggest multiple source of the metal in the investigated sediments. 相似文献
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R. Laouar A.J. Boyce M. Arafa A. Ouabadi A.E. Fallick 《Journal of African Earth Sciences》2005,41(5):445-465
Miocene igneous rocks (diorites, andesites, dacites, rhyolites and microgranites) of Chetaibi and Cap de Fer massif, NE Algeria, are high-K calc-alkaline to shoshonitic rocks. Fresh diorites have δ34S and δ18O values ranging between −2.5‰ and +5.9‰, +6.5‰ and +6.7‰ respectively, indicating a mantle origin. The relatively low δ34S values (−5.4‰ to −12.2‰) and high δ18O (+8.3‰ to +9.0‰) of altered diorites indicate the input of a crustal component to the initial magma. The microgranites’ I-type signature is indicated by the geochemical data and the δ34S and δ18O values of −1.2‰ and −3.6‰, and +7.8‰ to +10.4‰ respectively. The andesites show a large variation of δ34S, between −33.2‰ and +25.7‰. Massive andesites with δ34S between +6.8‰ and +7.6‰ preserve a 34S-enriched mantle signature. The δ34S of the lava flows between +25.7‰ and +25.8‰ are attributed to open system magma degassing, whereas the low δ34S of two andesitic dyke samples (−13.7‰ and −33.2‰) strongly suggest a crustal sulphur input. High δ18O (+9.2‰ to +15.7‰) of andesites indicate post-magmatic alteration (mainly silicification); the flyschs with δ18O between of +13.3‰ and +21.7‰ are most likely the contaminant. Quartz veins within the andesites gave a δ18O value of +23.0‰ while silica-filling vesicles yielded a value of +13.8‰. Initial Sr-isotope data are rather high for all the rocks (diorites: 0.707–0.708, andesites: 0.707–0.710, and microgranites and rhyolites: 0.717–0.719), and because geochemical and stable isotope data do not indicate a substantial amount of crustal assimilation, an extensive enrichment of the mantle source by subducted sediments is called for. A metasomatized-mantle source, characterized by high radiogenic Sr and relatively high δ18O, has also been indicated for the genesis of similar Tertiary igneous rocks in the Western Mediterranean basin, e.g. the Volcanic Province of southeasten Spain [Benito, R., Lopez-Ruiz, J., Cebria, J.M., Hertogen, J., Doblas M., Oyarzun, R., Demaiffe, D., 1999. Sr and O isotope constraints on source and crustal contamination in the high-K calc-alkaline and shoshonitic neogene volcanic rocks of SE Spain. Lithos 46, 773–802] and some plutons of northeastern Algeria [Ouabadi, A., 1994. Pétrologie, géochimie et origine des granitoïdes peralumineux à cordiérite (Cap Bougaroun, Béni-Touffout et Filfila), Algérie nord-orientale. Thèse de Doctorat, Université de Rennes I, France, 257p; Fourcade, S., Capdevila, R., Ouabadi, A., Martineau, F., 2001. The origin and geodynamic significance of the Alpine cordierite-bearing granitoids of northern Algeria. A combined petrological, mineralogical, geochemical and isotopic (O, H, Sr, Nd) study. Lithos 57, 187–216]. 相似文献
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S. M. Salem Sultan Awad Arafa T. M. Ramadan El Sayed A. El Gammal 《Arabian Journal of Geosciences》2013,6(2):321-335
Three types of hydrothermal alterations are recorded in Wadi El Regeita area, argillic, phyllic, and propylitic. Whole-rock analysis of representative samples of the alteration halo (1) shows a Cu, Au, and Ag content up to 1.7 wt.%, 1.6 g/t, and 4 g/t, respectively; in the alteration halo (2), these metal contents are up to 1.3 wt.%, 1.4 g/t, and 3 g/t, following the same order. The integrated remote sensing and geophysical data, as well as geological field verification, show that Wadi El Regeita area includes promising Cu ores within two hydrothermal alteration haloes. Spatial data analyses of lineaments from Landsat Enhanced Thematic Mapper (ETM) band ratio image (7/5, 5/4, 3/1) reveal the presence of alteration haloes that potentially may host Cu mineralization at south and north of El Regita Cu mine. Gravity interpretation indicates that the surveyed area is dissected by NE–SW fault zones in the central part, near Wadi El Regeita Cu mine. Ground magnetic survey data revealed that the surveyed area includes six magnetic bodies at depths ranging from 32 to 90 m, possibly recording the presence of mineralized and hydrothermally altered andesitic dykes. The half length of these dykes ranges from 600 to 1,070 m; their half thickness from 30 to 123 m and their half width from 48 to 531 m. Dyke locations coincide with surface alteration haloes (1) and (2) as indicated by the ETM band ratio image processing. The final assessment of the area, however, needs more detailed geological and geophysical studies with contributions of remote sensing techniques. 相似文献
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Electron magnetic resonance spectra of specimens of two crystalline rocks (12021-55 and 12075-19) and of four specimens of fines < 1 mm (12001-16, 12030-16, 12033-50 and 12070-125) have been obtained as a function of spectrometer frequency (9 and 35 GHz), temperature (78 to 300K), heat treatments (to 960°C), and mineral phases (plagioclase, olivine, pyroxferroite, glass, and basaltic fragments). Three paramagnetic ions, Fe3+, Ti3+ and Mn2+, are identified on the basis of spectral characteristics in plagioclase fractions, with concentrations 1019 ions g–1. Spectral components of at least two phases with exchange coupling of unpaired spins are resolved in whole rock samples of the crystalline rock specimens. These disappear upon heat treatment in air at 250°C and are presumably the result of an oxidation of the phases. It is suggested that these are non-stochiometric iron-rich oxide phases which approach stochiometry with heating in air. Some of the spectral properties of the characteristic resonance in fines are shown to be inconsistent with the hypothesis that the resonance is due to spherical iron particles. Another intense spectral component observed in samples of 12033-50 (H ~ 3000 Oe,g ~ 4 at 9 GHz andH ~ 3000 Oe,g ~ 2.2 at 35 GHz) is also observed in basaltic appearing fragments selected from 12001-16. It is estimated that the source of this component has concentrations in 12001-16, 12030-16, and 12075-125 that are < 2% the concentration in 12033-50. A similarity of this component to one observed in a crystalline rock sample from 12021-55 heat-treated in air and then left in air for 27 days and to one observed in a sample of fines heat treated at low pressure (< 10–3 mm Hg) to 800°C is the basis for suggesting that it is also due to a ferromagnetic oxide phase. The spectrum of a ferromagnetic metal platlet from 12001-16, in which the resonance and antiresonance were well resolved, was used to calculate the saturation magnetization and gave a value in reasonable agreement with that of iron as expected.Deceased.American University in Cairo, Cairo, EgyptResearch sponsored by the U.S. Atomic Energy Commission and supported by NASA Contract MSC-T-76458. 相似文献
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The Ba2+ ion adsorption isotherms on β-MnO2 were of the Langmuir type. The endothermic heat of adsorption (40 kJ mol?1) is ascribed to entropy contributions associated with the ion-exchange mechanism. The Ba2+ ion adsorption density was higher at pH 10 than that at pH 7, due to the more negative surface charge at the higher pH. Ba2+ ions were found to reverse the sign of the ζ potential of the MnO2 particles.More oleate was adsorbed by β-MnO2 in the presence of Ba2+ ions than in their absence. The oleate adsorption isotherms on Ba2+-activated MnO2 were of the Freundlich type and indicated an exothermic process. Hallimond flotation recovery of Ba2+-activated MnO2 was higher at pH 10 than at pH 7, although less oleate was adsorbed at the higher pH. At pH 7, Mn2+-activation led to higher recoveries than Ba2+-activation. It seems that the attraction between the surface and the activator plays an important rôle in determining the flotation recovery. 相似文献
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