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Geology and Radioactivity of the Pegmatitic Rocks of Gabal El Urf, Northern Eastern Desert, Egypt |
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PP: 1-13 |
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doi:10.18576/jrna/070101
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Author(s) |
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El Dabe, M. M,
Ismail, A. M,
Metwaly M,
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Abstract |
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| The pegmatitic rocks that intrude Monzogranites of Gabal El Urf, North Eastern Desert, are characterized by poly-phased mineralization. It is located southwest of the granitic pluton and consisting of three zones; the outer one is represented by potash feldspar, the middle by quartz, and the inner occupied with mica and accessory minerals. Two phases of mineralization are recorded; the earlier is characterized by colorful mineralization, nearly located at the inner zone along the N-S and intersection area between NE-SW and NW-SE trends. The latter is characterized by the dominance of opaque minerals spreading in the three zones of the pegmatite along with the NE-SW and E-W trends and filling the fractures. The earlier phase is characterized by the presence of radioactive minerals (thorite, xenotime, and zircon). The later phase is characterized by another array of accessory minerals (fluorapatite, cassiterite, atacamite, sulfides and Nb-minerals) beside the Th-minerals (thorite, uranothorite,), U-minerals (autunite and uranophane), REE-bearing minerals (pyrochlore and bastnasite) and iron oxides minerals. It possesses a net of fractures filled by iron oxides associated with the transported uranium and REEs. There are two levels of radioactivity; the first one is moderate (eU 26 ppm - eTh 245 ppm) and the second is (eU 45 ppm, eTh 1061 ppm) on average. Radioactivity of El Urf pegmatitic rocks is syngenetic and related to the late-stage magmatism, proved by the high Th-concentrations and presence of the radioactive minerals, followed by uranium migration. The high concentrations of thorium and the high values of Th/U ratio in the radioactive pegmatitic rocks rather than the world (3.5) indicated that the uranium migrated from a zone to another in the same pegmatite by a circulating hydrothermal solution. |
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