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<p>The region of Um Ara-Wadi Murrah is situated in Egypt's arid Southeastern Desert. The region contains a variety of tectono-stratigraphic units, with the earliest being ultramafic rocks, serpentinite, metavolcanics, metasediments, monzogranite, and syenogranite. Strong shearing, fracturing, and jointing control the high radioactivity in the anomalous areas. Uranophane, kasolite, and autunite make up the majority of visible secondary uranium mineralization. A variety of rare earth minerals, including monazite, bastnäsite, allanite, chernovite and xenotime were recorded in the study area. Betafite, ishikawaite, columbite, fergusonite and samarskite were recorded as radioactive bearing-minerals (Nb–Ta minerals). Finally; base metals represented by gold, bismite, cassiterite and wolframite. Secondary processes primarily influenced the post-magmatic addition of uranium to these granitic sites, known as uranium enrichment. We can identify the three types of ore minerals (magmatic, hydrothermal, and supergene) using a suggested paragenetic sequence. The latter comprises secondary uranium minerals and altered uranothorite. There are several ways that rare metal enrichment can happen, such as ascending hydrothermal solutions (alkaline solutions first, then acidic hydrothermal solutions) and descending acidic meteoric water during supergene enrichment processes. Changes in physicochemical conditions and the fugacity of oxygen and sulfur led to the initial precipitation of gold in mesothermal and epithermal solutions. Mineralogical and geochemical evidence confirms the different stages of mineralization. The study area has been enriched in uranium and rare earth elements (av. 3451.4, 273 ppm, respectively). The calculated values of the tetrad effect are 1.12. The chondrite-normalized REE patterns for syenogranite are M-type tetrad. The Th–U variation diagram reveals that all samples fall within the supergene enrichment field, with all Th/U ratio values being less than 0.1. Regarding the correlations between U and trace elements, we observe positive correlations with Zr, Y, and very weak to ill-defined correlations with LREEs, Nb, and F, indicating partially magmatic processes followed by post-magmatic processes.</p>

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Study of rare metal mineralization of granitoids at South Um Ara-Wadi Murrah area, Southeastern Desert, Egypt: implications for a characterization of mineral paragenesis

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  • 发表日期：

    2025年5月2日

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  • Amira M. El Tohamy

摘要

The region of Um Ara-Wadi Murrah is situated in Egypt's arid Southeastern Desert. The region contains a variety of tectono-stratigraphic units, with the earliest being ultramafic rocks, serpentinite, metavolcanics, metasediments, monzogranite, and syenogranite. Strong shearing, fracturing, and jointing control the high radioactivity in the anomalous areas. Uranophane, kasolite, and autunite make up the majority of visible secondary uranium mineralization. A variety of rare earth minerals, including monazite, bastnäsite, allanite, chernovite and xenotime were recorded in the study area. Betafite, ishikawaite, columbite, fergusonite and samarskite were recorded as radioactive bearing-minerals (Nb–Ta minerals). Finally; base metals represented by gold, bismite, cassiterite and wolframite. Secondary processes primarily influenced the post-magmatic addition of uranium to these granitic sites, known as uranium enrichment. We can identify the three types of ore minerals (magmatic, hydrothermal, and supergene) using a suggested paragenetic sequence. The latter comprises secondary uranium minerals and altered uranothorite. There are several ways that rare metal enrichment can happen, such as ascending hydrothermal solutions (alkaline solutions first, then acidic hydrothermal solutions) and descending acidic meteoric water during supergene enrichment processes. Changes in physicochemical conditions and the fugacity of oxygen and sulfur led to the initial precipitation of gold in mesothermal and epithermal solutions. Mineralogical and geochemical evidence confirms the different stages of mineralization. The study area has been enriched in uranium and rare earth elements (av. 3451.4, 273 ppm, respectively). The calculated values of the tetrad effect are 1.12. The chondrite-normalized REE patterns for syenogranite are M-type tetrad. The Th–U variation diagram reveals that all samples fall within the supergene enrichment field, with all Th/U ratio values being less than 0.1. Regarding the correlations between U and trace elements, we observe positive correlations with Zr, Y, and very weak to ill-defined correlations with LREEs, Nb, and F, indicating partially magmatic processes followed by post-magmatic processes.