U series age and origin of two secondary uranium deposits, central Eastern Desert, Egypt

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

doi:10.2113/gsecongeo.94.2.273

Cited by 49 publications

(38 citation statements)

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“…This indicates relatively recent deposition of U from water with 234 U/ 238 U AR > 1 (Figure 3). This result is similar to the cases studied by [13,32,33]. Suksi et al [13] reported fracture calcites from the groundwaters with 230 Th/ 234 U AR = 3.22 in Almottu, Finland.…”

Section: Activity Ratios Of U-series Radionuclidesupporting

confidence: 83%

Uranium-Series Disequilibria in the Groundwater of the Shihongtan Sandstone-Hosted Uranium Deposit, NW China

et al. 2015

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Uranium (U) concentration and the activities of 238 U, 234 U, and 230 Th were determined for groundwaters, spring waters, and lake water collected from the Shihongtan sandstone-hosted U ore district and in the surrounding area, NW China. The results show that the groundwaters from the oxidizing aquifer with high dissolved oxygen concentration (O 2 ) and oxidation-reduction potential (Eh) are enriched in U. The high U concentration of groundwaters may be due to the interaction between these oxidizing groundwaters and U ore bodies, which would result in U that is not in secular equilibrium. Uranium is re-precipitated as uraninite on weathered surfaces and organic material, forming localized ore bodies in the sandstone-hosted aquifer. The 234 U/ 238 U, 230 Th/ 234 U, and 230 Th/ 238 U activity ratios (ARs) for most water samples show obvious deviations from secular equilibrium (0.27-2.86), indicating the presence of water-rock/ore interactions during the last 1.7 Ma and probably longer. The 234 U/ 238 U AR generally increases with decreasing U concentrations in the groundwaters, suggesting that mixing of two water sources may occur in the aquifer. This is consistent with the fact that most of the U ore bodies in the deposit have a tabular shape originati from mixing between a relatively saline fluid and a more rapidly flowing U-bearing meteoric water.

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Section: Activity Ratios Of U-series Radionuclidesupporting

confidence: 83%

Uranium-Series Disequilibria in the Groundwater of the Shihongtan Sandstone-Hosted Uranium Deposit, NW China

et al. 2015

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“…They are usually bright yellow in color, but they may be darker when mixed with reddishbrown iron oxides and black manganese oxides. The most important varieties are soddyite, kasolite, and uranophane (Attawiya, 1971;Osmond et al, 1999;Dawood et al, 2004). In addition, the unidentified secondary Zr -rich silicate mineral, betafite, and liandratite have been identified for the first time in the present study.…”

Section: Discussionmentioning

confidence: 49%

“…The second phase of alteration occurred near the surface when the late -stage hydrothermal fluids cooled to the temperature of meteoric water and possibly mixed with it; the pH of the fluids became more alkaline, and at these conditions, U and Eu were precipitated into the fracture system, mainly being adsorbed on the clay minerals and probably being co -precipitated with iron oxy -hydroxides. The disequilibrium state of the secondary uranium minerals in the El Atshan area is reported by many authors (Hussein et al, 1970;Osmond et al, 1999). …”

Section: Geological Backgroundmentioning

confidence: 62%

“…The geology of the El Atshan area has been investigated by Obrenovic et al (1966), Hussein and El Kassas (1972), Osmond et al (1999), and Dawood et al (2004). The main rock units are (from older to younger) metasediments, metavolcanics, Hammamat sediments, granites, and post -tectonic volcanics (Fig.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The secondary uranium minerals are represented by uranophane, kasolite, soddyite, gummite, schoepite, schroeckingerite, rutherfordine, zippeite, and uranopilite (Attawiya, 1971). However, only soddyite, kasolite, and uranophane have been confirmed to be present in El Atshan (e.g., Osmond et al, 1999;Dawood et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Role of geochemical alteration on the formation of secondary Zr- and U-bearing minerals in El Atshan trachyte, central Eastern Desert, Egypt

El‐Naby

2009

Journal of Mineralogical and Petrological Sciences

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El Atshan area, situated in the central Eastern Desert of Egypt, is a good location for studying the influence of high -and low -T alterations on the formation of Zr -and U -bearing minerals within a trachyte sill. These minerals are mainly represented by an unidentified secondary Zr -rich silicate mineral, betafite, and liandratite. The unidentified Zr -rich silicate mineral is considered to be an alteration product of the precursor zirconolite during high -T alteration. This is indicated by the changes in the composition marked by an increase in the amount of hydration (H 2 O), Si, and U and a decrease in the amount of Ca, Ti, Nb, and Fe. The morphology of this unidentified mineral is similar to that of zirconolite. For seven oxygen atoms, the calculated formula of the unidentified Zr -rich silicate mineral is (Si . With more extensive alteration, it was found that the unidentified secondary Zr -rich silicate mineral was unstable and it underwent re -equilibration with U -rich fluid, which led to alterations in betafite. The two possible mechanisms responsible for the alteration of the unidentified Zr -rich silicate mineral to betafite are as follows: (1) the dissolution of the unidentified Zr -rich silicate mineral and precipitation of betafite and (2) the ion -exchange between partially to fully amorphized zones and the U -rich fluid. Such alteration is indicated by a marked increase in the amount of U, Ti, and Nb and a decrease in the amount of Zr, Si, Ca, P, Y, and ΣREE.

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

Dabous

Osmond

Dawood

2002

Journal of Arid Environments

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U series age and origin of two secondary uranium deposits, central Eastern Desert, Egypt

Cited by 49 publications

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Uranium-Series Disequilibria in the Groundwater of the Shihongtan Sandstone-Hosted Uranium Deposit, NW China

Uranium-Series Disequilibria in the Groundwater of the Shihongtan Sandstone-Hosted Uranium Deposit, NW China

Role of geochemical alteration on the formation of secondary Zr- and U-bearing minerals in El Atshan trachyte, central Eastern Desert, Egypt

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

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