GEOLOGY, SPECTROMETRY AND EVALUATION OF THE RADIATION EXPOSURES AT EL GIDAMI-EL GARRA AREA, CENTRAL EASTERN DESERT, EGYPT

El Gidami- El Garra area lies between latitudes 26o 24’– 26o 27’ N and longitudes 33o 20’– 33o 29’ E,
in the central Eastern Desert of Egypt, 3 km south of the midpoint of Qena-Safaga highway. The area is
covered by younger granites intruded into amphibolites, and syn-tectonic granites. It represents one of the
most promising uranium occurrences in the Eastern Desert. The main granitic types forming this pluton as
defined from their mineral composition and textures comprise pegmatitic perthite granite, perthite granite
and fluorite perthite granite.
Petrographically, these three types of younger granites are similar. The three types are perthitic in
composition and medium to very coarse grained, even pegmatitic. Quartz, potash feldspar and plagioclase,
with small amount of biotite and opaque minerals constitute the mineral assemblage in these types. Fluorite,
zircon, allanite, titanite, apatite and monazite are accessory minerals. Chlorite, epidote, saussurite and
muscovite are secondary constituents. In addition, there are some important radioactive minerals in the
studied granites such as uranophane, xenotime and metamict zircon.
Locally, the estimated values of the external absorbed -radiation dose rate are 221.4±43.87, 242±51.16,
190.6±56.24 and 294.9±39.81 (nGy/h) for the granitic rocks; fluorite perthite, Syn-tectonic, perthite and
pegmatite perthite, respectively. These values are much higher than the worldwide average. Fortunately,
neither public activities nor residential centers are recognized around the studied granites at El Gidami
area.
The activity concentrations of the studied rocks are below the regulated values. As a result, all the
occupational activities during surface exploration or transportation of the studied granitic rocks are excluded
from the regulations and no need for any recommendations about the resulting effective doses.
Generally, the slabs of thickness of 4cm from the different locations and granitic rock types exhibit an
annual effective dose up to 2.41 (mSv/y). This value is below the action level and the studied granitic rock
types may be used safely as decorative materials.