Uranium mineralization in the two mica granite of Gabal Ribdab area, South Eastern Desert, Egypt

Ibrahim, M. M.; Saleh, Gehad M.; El‐Naby, Hamdy H. Abd

doi:10.1016/s0969-8043(01)00122-1

Cited by 25 publications

(23 citation statements)

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“…The uranyl minerals precipitated along a reactive, chemically evolving flowpath (Lofvendahl, 1981;Korzeb et al, 1997;Ibrahim et al, 2001). At the microscale, precipitation was in response to systematic compositional change, and was thus analogous to the behavior of the reactive waste plume at the BX tank farm.…”

Section: Discussionmentioning

confidence: 99%

Microscale controls on the fate of contaminant uranium in the vadose zone, Hanford Site, Washington

McKinley

Zachara

Liu

et al. 2006

Geochimica et Cosmochimica Acta

103

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An alkaline brine containing uranyl (UO 2 2+ ) leaked to the thick unsaturated zone at the Hanford Site. We examined samples from this zone at microscopic scale to determine the mode of uranium occurrence-microprecipitates of uranyl (UO 2 2+ ) silicate within lithic-clast microfractures-and constructed a conceptual model for its emplacement, which we tested using a model of reactive diffusion at that scale. The study was driven by the need to understand the heterogeneous distribution of uranium and the chemical processes that controlled it. X-ray and electron microprobe imaging showed that the uranium was associated with a minority of clasts, specifically granitic clasts occupying less than four percent of the sediment volume. XANES analysis at micron resolution showed the uranium to be hexavalent. The uranium was precipitated in microfractures as radiating clusters of uranyl silicates, and sorbed uranium was not observed on other surfaces. Compositional determinations of the 1-3 lm precipitates were difficult, but indicated a uranyl silicate. These observations suggested that uranyl was removed from pore waters by diffusion and precipitation in microfractures, where dissolved silica within the granite-equilibrated solution would cause supersaturation with respect to sodium boltwoodite. This hypothesis was tested using a reactive diffusion model operating at microscale. Conditions favoring precipitation were simulated to be transient, and driven by the compositional contrast between pore and fracture space. Pore-space conditions, including alkaline pH, were eventually imposed on the microfracture environment. However, conditions favoring precipitation were prolonged within the microfracture by reaction at the silicate mineral surface to buffer pH in a solubility limiting acidic state, and to replenish dissolved silica. During this time, uranyl was additionally removed to the fracture space by diffusion from pore space. Uranyl is effectively immobilized within the microfracture environment within the presently unsaturated Vadose Zone.

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Section: Discussionmentioning

confidence: 99%

Microscale controls on the fate of contaminant uranium in the vadose zone, Hanford Site, Washington

McKinley

Zachara

Liu

et al. 2006

Geochimica et Cosmochimica Acta

103

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“…Radioactive pegmatites have been recorded in many localities in the Eastern Desert of Egypt (Sayyah et al, 1993;Ibrahim et al, 1997;Ali, 2001;Ibrahim et al, 2001;Ali et al, 2005;Abdel Warith et al, 2007;Raslan et al, 2010). Also, several studies worldwide have revealed the presence of granite-pegmatite-hosted rare-metal mineralizations (Matsubara et al, 1995;Hanson et al, 1998;Erict, 2005;William et al, 2006;Pal et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…the pegmatitic bodies of the Gabal Ras Baroud younger granites (Sayyah et al, 1993: Raslan et al, 2010 uranium and columbite mineralization in the pegmatites related to the Gabal Abu Dob younger granites (Ibrahim et al, 1997), and radioactive pegmatites related to the Gabal El-Sibai alkali feldspar granites (Ali, 2001). Anomalous pegmatites associated with granitic rocks have also been reported in the southern part of the Eastern Desert (Ibrahim et al, 2001;Ali et al, 2005;Abdel Warith el al., 2007). The high level of radioactivity of these rocks is attributed to the presence of accessory minerals such as zircon, monazite, thorite, uranothorite and allanite (Shurmann, 1966).…”

Section: Introductionmentioning

confidence: 91%

Mineralogy and radioactivity of pegmatites from South Wadi Khuda area, Eastern Desert, Egypt

2010

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Radioactive minerals in pegmatites associated with granitic rocks are commonly encountered in the south of the Wadi Khuda area and found as dyke-like and small bodies. They are observed within garnet-muscovite granites near the contact with older granitoids. Field surveys indicated that the studied pegmatites vary in dimensions ranging from 2 to 10 m in width and from 10 to 500 m in length. They are composed mainly of intergrowth of milky quartz, reddish-pink K-feldspar and plagioclase together with small pockets of muscovite.Field radiometric measurements indicated that radioactivity in pegmatites is more than twice that of their enclosing country rocks. Radionuclide measurements revealed that the average contents of U and Th increase gradually from rocks of dioritic to granodioritic composition (1.5×10 -6 U and 4.3×10 -6 Th) and increase significantly in biotite granites (5.8×10 -6 U and 15.2×10 -6 Th) but drastically decrease in muscovite granites (2.2×10 -6 U and 5.6×10 -6 Th). The average contents of U and Th of anomalous pegmatites are 95.3×10 -6 and 116.9×10 -6 , respectively, indicating their uraniferous nature. In the south of the Wadi Khuda area, pegmatites are low in average Th/U (1.4) and high in average U/K (35.6), which suggests that uranium concentrating processes did not affect the pegmatites, indicating poor source-rocks.Mineralogical investigations of the studied pegmatites revealed the presence of secondary uranium minerals (kasolite and autunite), in addition to zircon, thorite, apatite, garnet and biotite. Primary and secondary radioactive mineralizations indicated that the mineralization is not only magmatic, but also post-magmatic. Electron microprobe analyses showed distinct cryptic chemical zoning within thorite where UO 2 decreases from core to rim. This feature in thorite is sporadic, suggesting non-uniform redistributions of UO 2 within thorite during magmatic processes.

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“…The best interpretation to explain the weak chemical variations in each granitic unit is crystal fraction of early mineral phases (biotite or plagioclase). More welldefined geochemical evolution in other tow mica peraluminous granitoids of southern Egypt clearly results from crystal fractionation phenomena (Ibrahim et al, 2001). Two different interpretations can be suggested to explain the chemical variation between each granitic unit (1) these units might be the result of successive magma pulses, derived from a single great deeper situated magma chamber or (2) might correspond to unrelated magma batches generated from distinct source rocks or under different melting conditions.…”

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confidence: 99%

“…Many papers have been devoted to tow mica peraluminous granitoids and related intrusive rocks (Clarke, 1981). Syn-collicion tow mica peraluminous granitic segregations are commonly associated with regionally metamorphosed terranes (LoNoo, 1992, Ibrahim et al, 2001, Saleh et al, 2002, Clarke et al, 2004, Moghazi et al, 2004, Stevens et al, 2008, Chudík et al, 2008, Tartèse and Boulvais, 2009. Numerous mechanisms have been proposed to explain the derivation of these segregations from the metamorphosed host -rock, but partial melting of metapelites (Barbey et al, 1990) is still the most widely accepted model for the generation of these tow mica peraluminous leucogranites.…”

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confidence: 99%

Untitled

2013

GJGES

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Tow mica granites of the Abu Rusheid -Eir Arib district in the Southeastern Desert of Egypt, cut pre-existing faults, and their contacts with the country rocks are sharp and lack contact metamorphism. They were intruded into a low -to high grade metamorphosed ophiolitic mélange and a high -grade metamorphosed meta-sedimentary succession of biotite schist. Petrographically, the phase is strikingly similar and consists of alkali feldspar, quartz, plagioclase, muscovite and biotite. Zircon, garnet, apatite, allanite, titanite and opaque's are accessories. Abu Rusheid -Eir Arib tow mica granites are characterized by strongly peraluminous compositions; contain miarolitic cavities and pegmatitic patches, suggesting the release of aqueous fluids from the down going slab during subduction. The investigated rock has low K/Rb and high Zr /Y ratios reflecting a typical mature continental -arc environment. The REEs pattern is characterized by fractionated LREEs and relatively flat HREEs with pronounced negative Eu anomalies. The geochemistry of REEs reflects the behavior of accessories and key major minerals such as garnet and feldspars, and may therefore give valuable information about the conditions of partial melting, melt segregation and crystallization of granite magmas in different crustal regimes. The study presents the surface distribution of the total gamma radiation Tc, K, U and Th in Abu Rusheid -Eir Arib two -mica peraluminous granites. The geochemistry of Zr/U, Zr/Th, Ce/U and Ce/Th against either U or Th in suite exhibits significant negative correlations, indicating that both elements are not preferentially hosted in accessory zircon or monazite, but could be associated with major rock forming minerals such as biotite, muscovite, plagioclase and quartz, or U is situated within labile sites within the granites. The distribution of uranium, thorium and their ratios in the garnetiferous granite reveal that this granite is considered as fertile granites and reflects the amount of remobilization that took place within the granites.Keywords: Tow mica granites, Magmatic differentiation, Total gamma radiation and Egypt. INDROUDUCTIONTow mica peraluminous granitoids are present and in some cases abundant in orogenic belts of various ages. The Neoproterozoic mobile belts of the Arabian-Nubian Shield (ANS) have been recognized as a typical example of an accretionary orogen defined by juvenile terranes. They yield Neoproterozoic Nd model ages (Stern, 2002) and have experienced a complete Wilson cycle (Stern, 1994). Although strongly tow mica peraluminous leucogranites are of limited distribution in the Egyptian Shield, they have close spatial association with gneisses and migmatites. They may be used to relate high-grade metamorphism and magmatism with tectono-metamorphic events in the Eastern Desert of Egypt. Many papers have been devoted to tow mica peraluminous granitoids and related intrusive rocks (Clarke, 1981). Syn-collicion tow mica peraluminous granitic segregations are commonly associated with regionall...

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Uranium mineralization in the two mica granite of Gabal Ribdab area, South Eastern Desert, Egypt

Cited by 25 publications

References 10 publications

Microscale controls on the fate of contaminant uranium in the vadose zone, Hanford Site, Washington

Microscale controls on the fate of contaminant uranium in the vadose zone, Hanford Site, Washington

Mineralogy and radioactivity of pegmatites from South Wadi Khuda area, Eastern Desert, Egypt

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