GEOCHEMISTRY, PETROGRAPHY AND RADIOACTIVITY OUTLINE OF HAMRAT AL-JIRJAB GRANITIC PLUTON, ESH EL MELLAHA RANGE, NORTH EASTERN DESERT, EGYPT

Document Type : Original Article

Authors

1 Nuclear Materials Authority

2 Petrological Studies, Research Division, Nuclear Materials Authority.

3 Geology of Isotops

4 Research Sector

5 Isotopes geology Department

Abstract

Esh El Mellaha range is an uplifted block that is located in the North Eastern Desert of Egypt. It is the western extension of the Arab-Nubian Shield. It occurs as an elongated ridge parallel to the Gulf of Suez in the NW-SE direction. Gabal (G.) Hamrat Al-Jirjab crops out in the form of elliptical younger granitic pluton and considered as post-orogenic granite. It is an alkali feldspar granite type originated from peraluminous Calc-alkaline highly fractionated magma. This magma is rich in Rb but lake in Ba which reflects low pressure conditions. It was intruded at crustal depth greater than 20km at water pressure between 1 and 3 Kb. It was crystallized at temperatures ranging from 800 to 850°C. The alkali feldspar granites of Hamrat Al-Jirjab pluton is uraniferous granites originated from highly fractionated U-rich magma. They show high U and Th contents and low Th/U ratio due to high concentrations of U in the accessory minerals (Zircon, apatite, sphene and fluorite). The studying samples were investigated by using NaI(Tl) detector to evaluate the radiological hazards and compare them with the world average values. The average activity concentrations for 238U,232Th, 226Ra and 40K with an average value of (208.2), (138.6), (115,8), (1091.9) respectively. The obtained values were higher than the recommended values. Radiological hazard parameters were estimated based on the activity concentrations of 238U, 232Th, 226Ra and 40K and compared with the internationally approved values and the recommended safety limit. 

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