Effect of the mineralogical composition on the radioactivity of the younger granites and pegmatites at Gabal al-Dob area, northern eastern desert, Egypt

الملخص EN

Gabal El-Dob area is located at the Northern Eastern Desert of Egypt.

The late pan-African El-Dob pluton is one of the well exposed granitic batholith at the Northern part of Eastern Desert of Egypt.

It comprises starting from oldest: metavolcanics, older granites, Dokhan volcanics, younger gabbro and younger granites.

All rock types of Gabal El-Dob area are cross-cut by various pegmatites, quartz veins, acidic and basic dykes.

The younger granites can be differentiated into three main phases: monzogranites, syenogranites and alkali feldspar granites.

They form oval to elongate plutons extending in the N-S and NNE-SSW directions.

Pegmatitic rocks are exposed at Wadi Abu Zawal, Gabal El-Urf and Gabal El-Dob nearby or enclosed in the granitic rocks and present as dykes or vein like bodies.

X-ray diffraction analysis (XRD) as well as Environmental Scanning Electron Microscope (ESEM) was used in the mineralogical studies of the various rocks of Gabal El-Dob area which clarified that the common heavy minerals can be classified into: 1) uranium minerals, 2) thorium minerals 3) U, Th and REE bearing minerals 4) sulphides minerals and 5) oxides and silicate minerals.

Wadi Abu Zawal pegmatites are considered as the most radioactive and uranium mineralized rocks due to presence of uranophane, metaautunite, thorianite, monazite, cheralite, allanite, bastnaesite and uranopolycrase.