This study aimed to evaluate the radiological hazards of uranium (238U), thorium (232Th), and potassium (40K) in microgranitic rocks from the southeastern part of Wadi Baroud, a northeastern desert of Egypt. The activity concentrations of the measured radionuclides were determined by using a gamma-ray spectrometer (NaI-Tl-activated detector). The mean (238U), (232Th), and (40K) concentrations in the studied rocks were found to be 3680.3, 3635.2, and 822.76 Bq/kg, respectively. The contents in these rocks were elevated, reaching up to 6.3 wt%. This indicated the alkaline nature of these rocks. The high ratios of Th/U in the mineralized rocks could be related to late magmatic mineralization, suggesting the ascent of late magmatic fluids through weak planes such as faults and the contact of these rocks with older granites. The present data were higher than those of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) guideline limits. All the radiological hazard results indicated high human health risks. This confirmed that this area is not radiologically safe, and care must be taken when working in this area. This study showed that the area under investigation had high U content suitable for uranium extraction that could be used in the nuclear fuel cycle.
Ras Baroud area has several rock units arranged from the oldest to the youngest as: older granites, younger granites, pegmatites, dykes and quartz veins. Yo u nger granite of Ras Baroud is exposed as small semirounded isolated mass, which is medium to coarse grained and pink to reddish pink in color. This granite is dissected with several types of dykes ranging from basic to acidic ones. Pegmatite body is encountered at the peripheral parts of this granite. It is compositionally zoned, being composed of massive milky quartz in the core and pink color blocky K-feldspars with subordinate nest like aggregates of yellowish white mica the outer rim. Ras Baroud granite is composed mainly of K-feldspars, plagioclase quartz and micas (biotite and muscovite) associated with zircon, titanite, and opaque as accessory minerals. On the other hand, the secondary minerals are represented by sericite and chlorite. The pegmatite bodies at the northern periphery of Gabal Ras Baroud consist essentially of orthoclase, quartz, plagioclase and mica (muscovite and biotite). The accessory minerals include zircon, allanite, fluorite and opaques. Compared to the parent granitic pluton, the pegmatite body has higher concentrations of Zr, Rb, Y, Ba, Pb, Nb and lower Cu, Sr concentrations. It is important to notice that the variation in the concentration of trace elements in the studied pegmatite samples may be due to the difference in the mineralogical composition of these samples. Uranium content in pegmatite body ranges from 10 ppm to 235 ppm with an average 84 but the thorium content range from 1 ppm to 309 ppm with an average 95. Pegmatite body of Ras Baroud has several important rare-metal bearing minerals include; samarskite-Y, columbite, cassiterite, zircon, fluorite and rutile in addition to some opaque minerals as magnetite and ilmenite.
Aswan granites are divided into two types: 1) granite extends from Aswan north to El Shellal south and 2) granodiorite-quartz monzodiorite form two separated elongated and parallel bodies extending in N-S direction. At the contact between the two types there are some enclaves and ferromagnesian minerals. Aswan granite is composed mainly of alkali-feldspars, plagioclase, quartz, biotite, hornblende. Allanite, zircon , monazite, fluorite, apatite, titanite and opaques are the main accessory minerals. Secondary minerals are muscovite, chlorite and carbonates. Two generations of quartz which included in hornblende, microclinization of plagioclase, presence of skeletal apatite, presence of secondary titanite in granite due to the presence of high titanium content which derived from granodiorite-quartz monzodiorite, the presence of zircon included in biotite and both of them mantled with hornblende and the presence of different types of textures, all the previous are some criterias for magma mixing. There are some criteria in the geochemistry of the trace elements for magma mixing, presence of low content of Ba and Sr in granite as compared with granodiorite-quartz monzodiorite, low Zr content in granite but high in granodiorite-quartz monzodiorite, presence of high Zn and Pb in granite and the presence of small gab between the two rock samples which may be attributed to absence of complete spectrum of samples to causes such gabs. This study revealed that the uranium content in granite is lower than that of granodiorite-quartz monzodiorite and the thorium content in granite is greater than that of granodiorite-quartz monzodiorite which give an indication for the mixing magma. On the other hand, the uranium content in both types are suitable for using this granite as ornamental stones.
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