Geochemistry and Radioactivity of Gabal El Monagah A-Type Granites, South Sinai Peninsula, Egypt

Gabal El Monagah granites form roughly an oval shaped pluton with NW-SE orientation in the
central part of Katharina Complex. It comprises two types of granites, syenogranites and alkali granites
Petrographically, the alkali granites of G. El Monagah are medium- to coarse-grained, and are mainly
composed of well-developed perthitic orthoclase, microcline, quartz, and albite as well as biotite and
amphiboles as accessory minerals.
Mineralogical studies using X-Ray diffraction (XRD) and Environmental Scanning Electron
Microscopy (ESEM), revealed the presence of spessartine garnet, zennwaldite, titanite (sphene) and apatite.
Geochemically, G. El Monagah alkali granites are A-type granites of alkaline nature, generated in an
extensional within plate (WPG) environment. They originated from calc-alkaline highly fractional
crystallization of mafic magma. This magma is also rich in Rb and Nb indicating low pressure condition.
Radiometrically these granites are characterized by their high uranium content (eU range from 8 to 21
ppm), and hence they are considered as uraniferous granites (≥ 4ppm), originated from highly fractionated
uranium-rich magma with trapping high concentration of uranium in accessory minerals; such as zircon,
allanite, apatite and sphene in these granites of Gabal El Monagah.