Radiological and Environmental Impacts of El Sela-Qash Amer Granites, South Eastern Desert, Egypt

Abstract

El Sela area is mainly covered by ophiolitic mélange (Sul Hamed), biotite granite, two-mica granite (El Sela), muscovite granites (Qash Amer), and cross cut by microgranite dolerite and bostonite dikes as well as quartz and japser veins. These granitic rocks are hydrothermally altered, especially around El Sela ENE-WSW shear zone, that causing hydrothermal alterations accompanied by radioactive mineralization. These rocks are mainly composed of alkali feldspar, quartz, muscovite, and biotite with zircon, fluorite, apatite and iron oxides as an accessory minerals. The radioactive minerals are represented by uranophane, autunite, meta-autunite and phurcalite which are restricted in the highly sheared microgranite, dolerite dikes as well as jasper veins. Uranium contents (eU) range from 10.1 to 17.7 ppm at Qash Amer with their thorium contents (eTh) vary from 5.8 to 22.7 ppm. El Sela granites have uranium contents (eU) range from 6.4 to 19.7 ppm with equivalent thorium content (eTh) range between 14.0 and 44.9 ppm. The eU-eTh, (eU/ eTh)-eU and eU-[eU+(eTh X 3.5)] diagrams show depletion of uranium for both the Qash Amer and El Sela granitic samples, suggesting that uranium may be leached out of the original rock towards the ENE-WSW and NNW-SSE shear zones. The migrated uranium (Um) amount was calculated and indicated as either migration out or migration in at Qash Amer and El Sela granites, mostly to the shear zone cutting through the area. Absorbed Dose Rate (D), annual effective dose equivalent (AEDE), radium equivalent activity (Raeq), external (Hex) and internal (Hin) hazard index, in addition to activity gamma index (Iγ) caused by gamma emitter natural radionuclide were determined from the obtained values of 238 U, 232 Th and 40 K. Most of the studied samples have radiological parameters values higher than the international recommended values suggesting that El Sela and Qash Amer granitic rocks are hazardous and not recommended for use as ornamental stones with respect to workers and human beings.