Uranium/Thorium isotope evidence for ground-water history in the Eastern Desert of Egypt

Dabous, Adel A.; Osmond, J.K.; Dawood, Yehia H.

doi:10.1006/jare.2001.0861

Cited by 19 publications

(10 citation statements)

References 21 publications

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“…Our results are consistent with the experimental results of Lowson et al [16], Payne et al [17], and Dabous et al [18], which note the similarity of the 234 U: 238 U activity ratios in groundwater and in the most easily leached fractions of water-bearing rocks.…”

Section: Evolution Of Uranium Isotopic Compositionssupporting

confidence: 93%

“…Further, daughter nuclides pass most actively into water from surface coatings [15], increasing the uranium isotopes activity ratio in water. In addition, the similarity of the activity ratios of 234 U: 238 U in groundwater and in the most easily leached fractions of water-bearing rocks was noted in the experiments of Lowson et al [16], Payne et al [17], and Dabous et al [18], with the fractions being defined as sorbed elements, carbonate minerals and amorphous iron minerals [19] which could indicate the opposite process which is the transition of nonequilibrium nuclides from water to rock with an increase in the U isotopes activity ratio in the rock [20]. Under such conditions, it is difficult to estimate the rate of chemical weathering and to date natural processes by using the currently developed methods [21,22].…”

Section: Introductionmentioning

confidence: 66%

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Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer in Combination with Groundwater Data

Малов

Zykov

2019

Water

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This work is part of a research project that aims to develop a method for combined radiocarbon and uranium-isotope dating of groundwater. The specific objective of this study was to investigate the mobility of uranium isotopes in the various mineral phases of rocks of an aquifer of sandy-clay deposits of the Vendian in the northwest of Russia, for which a partial extraction procedure was used. Representative aliquots of each core sample were treated with various reagents: distilled water, low mineralized fresh natural groundwater, minopolycarboxylic acid chelating agent (0.05 M EDTA), 0.5M HCl, 15 M HNO 3 , as well as total digestion, and the U isotope data for each procedure are reported in this study. The following mineral phases of core samples were characterized: sorbed material, carbonate minerals, amorphous iron oxides, partially soluble aluminosilicates and crystalline iron oxides, totally digestible aluminosilicates and a clay/quartz resistate. Red-colored siltstones and sandstones were depleted in uranium in relatively readily soluble mineral phases. The concentration of sorbed uranium was established in the range 15.8 ± 2.1-30.5 ± 3.9 µg/kg and carbonate minerals contained even less uranium. For iron hydroxides and the most readily soluble aluminosilicates, uranium concentrations were in the range 168 ± 24-212 ± 28 µg/kg. The most insoluble fraction contained uranium in the range 1.65 ± 0.21-4.32 ± 0.45 mg/kg. In green-colored siltstones, the concentration of sorbed uranium was much higher in the range 106 ± 14-364 ± 43 µg/kg. Carbonate minerals and amorphous iron oxides contained uranium in the range 1.91 ± 0.21-2.34 ± 0.26 mg/kg. In aluminosilicates and a clay/quartz resistate, uranium concentrations were in the range 5.6 ± 0.5-16.8 ± 1.4 mg/kg. Elevated values of 234 U: 238 U activity ratio prevailed in the sorbed material and iron hydroxides. In aluminosilicates and clay/quartz resistate, the values decreased. This indicates the replacement of primary sedimentogenic uranium by secondary hydrogenic uranium sorbed on the surface of minerals and coprecipitation with iron hydroxides. The results obtained made it possible to carry out preliminary quantitative estimates of the retardation factor and recoil loss factor of uranium in the groundwater of siltstones and sandstones of the studied Vendian aquifer.

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Section: Evolution Of Uranium Isotopic Compositionssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 66%

Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer in Combination with Groundwater Data

Малов

Zykov

2019

Water

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“…The results obtained partially confirm previously expressed ideas about the evolution of U isotopic compositions of the Vendian rock near the study area [20]. Our results are consistent with the experimental results of Lowson et al [16], Payne et al [17], and Dabous et al [18], which note the similarity of the 234 U: 238 U activity ratios in groundwater and in the most easily leached fractions of water-bearing rocks.…”

Section: Evolution Of Uranium Isotopic Compositionssupporting

confidence: 92%

“…Further, daughter nuclides pass most actively into water from surface coatings [15], increasing the ratio of isotope activities in water. In addition, the similarity of the activity ratios of 234 U: 238 U in groundwater and in the most easily leached fractions of water-bearing rocks was noted in the experiments of Lowson et al [16] , Payne et al [17], and Dabous et al [18]. These fractions were defined as adsorbed elements, carbonate minerals and amorphous iron minerals [19].…”

Section: Introductionmentioning

confidence: 75%

<strong></strong>Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer Using Methods for the Extraction of Uranium with Different Strength Reagents in Combination with Groundwater Data

Ai¹,

Sb²

2019

Preprint

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A partial extraction procedure was used to study the distribution of uranium in the mineral phases of rocks of an aquifer of sandy-clay deposits of the Vendian in the northwest of Russia. This work is a part of a research project to develop a method for combined radiocarbon and uranium-isotope dating of groundwater. Representative aliquots of each core sample were subjected to five "partial" extractions by treatment with: distilled water, low mineralized fresh natural groundwater, minopolycarboxylic acid chelating agent (0.05M EDTA), 0.5M HCl, 15M HNO3, and a total digestion, with U isotopes reported in this study for each procedure. The following mineral phases of core samples: adsorbed material, carbonate minerals, amorphous iron oxides, aluminosilicates partial digestion and a crystalline iron oxides, aluminosilicates total digestion and a clay/quartz resistate were characterized. Red-colored siltstones depleted in uranium in relatively readily soluble mineral phases. The concentration of adsorbed uranium was established in the amount of 15.8±2.1 - 30.5±3.9 μg/kg. Carbonate minerals contain even less of this element. In iron hydroxides and the most readily soluble aluminosilicates, its concentrations are in the range 168±24 - 212±28 μg/kg. The most insoluble fraction contains 1.65±0.21 - 4.32±0.45 mg/kg of uranium. In green-colored siltstones, the concentration of adsorbed uranium is much higher: 106±14 - 364±43 μg/kg. Carbonate minerals and amorphous iron oxides contain 1.91±0.21 - 2.34±0.26 mg/kg of uranium. In aluminosilicates and a clay/quartz resistate, uranium concentrations are 5.6±0.5 - 16.8±1.4 mg/kg. Elevated values of 234U:238U activity ratio prevail in the adsorbed material and iron hydroxides. In aluminosilicates and clay/quartz resistate, the values decrease. This indicates the replacement of primary sedimentogenic uranium by secondary hydrogenic uranium adsorbed on the surface of minerals and coprecipitated with iron hydroxides. The results obtained made it possible to carry out preliminary quantitative estimates of the retardation factor and recoil loss factor of uranium in the groundwater of siltstones of the studied Vendian aquifer.

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“…In most terrestrial water systems, the 234 U/ 238 U activity ratio is greater than 1 and in some deep aquifers as much as 10 or 20. Moreover, high activity of 234 U was reported from groundwater in contact with granitic rocks (Dabous et al, 2002 andMarques, 2008). In general, the 234 U/ 238 U ratios are discussed in terms of the activity ratio even though the isotope ratio is now the measured quantity (Cheng et al, 2000).…”

Section: U-th Isotopic Fractionationmentioning

confidence: 99%

Radiogenic Isotope Fractionation as an Indication for Uranium Mobility in the Granites of El Shallal Area, West Central Sinai, Egypt

Dawood¹

2009

ear

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The granitic rocks at Wadi El Shallal area are categorized into metaluminous hornblende-biotite granites and peraluminous twomica granites. The chemical analyses indicate that the two-mica granites are slightly altered and characterized by high uranium and thorium contents (averages 20.27 and 27.12 ppm, respectively). Compared to the hornblende-biotite granites, the 230 Th/ 234 U and 234 U/ 238 U activity ratios of the two-mica granites display values that depart significantly from equilibrium. The sample plots of the two granitic types are distributed in a trend reflecting more 234 U loss from the two-mica granites. Leaching experiments confirmed that the area around mineral grain boundaries are more enriched in 234 U relative to its parent 238 U as a result of α-recoil process that displaces the daughter nuclei outside the grain surface. This daughter (234 U) is ejected from the grain into the open spaces and therefore, subjected to leaching by fluids. The observed uranium series disequilibrium in the granitic rocks from El Shallal area reflects isotopic fractionation and a recent migration of uranium in the two-mica granites. The high uranium contents and U-Th isotopic composition of the two-mica granites fairly suggest that these rocks are probably the source for uranyl mineralization of the nearby Um Bogma Formation reflecting a history of leaching, mobilization and precipitation by meteoric and groundwater. However, more intensive investigations for uranium

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Uranium/Thorium isotope evidence for ground-water history in the Eastern Desert of Egypt

Cited by 19 publications

References 21 publications

Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer in Combination with Groundwater Data

Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer in Combination with Groundwater Data

<strong></strong>Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer Using Methods for the Extraction of Uranium with Different Strength Reagents in Combination with Groundwater Data

Radiogenic Isotope Fractionation as an Indication for Uranium Mobility in the Granites of El Shallal Area, West Central Sinai, Egypt

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