Radioelements Potentiality Around Gabel Nugrus Area, South Eastern Desert, Egypt: Geological and Mineralogical Implications

Abstract

The present study spotlights on the geological, petrographical, mineralogical and radiometric prospecting, which control the distribution of radioactive elements within the granitic rocks of Gabel Nugrus. The study area is composed of ultramafic rocks, ophiolitic metagabbros, biotite hornblende gneisses and granitic rocks. The granitic rocks are represented by monzogranite, syenogranite and garnetiferous muscovite granite. The minerals (uranophane, uranothorite, fergusonite, zircon, monazite, xenotime, allanite, sphalerite, gold, arsenopyrite and pyrite) were identified by Scanning Electron Microscope (SEM) and back-scattered electron imaging system. In monzogranite, the average eU and eTh contents in both north and south of Gabel Nugrus are 9.25ppm, 5.4ppm, 31.41ppm, 19.29ppm respectively. In the syenogranite, the average eU, eTh contents are 10.22ppm and 24.45ppm respectively. In the garnetiferous muscovite granite, the average eU and eTh contents are 7.82ppm and 13.33ppm respectively. The radioactive anomaly in the study area is confined to the fractures cutting through the garnetiferous muscovite granite at the northern part of Gabel Magal El Harami area. The average of eU, eTh and eUm contents within fractures are187.87ppm, 109.57ppm, 156.57, this reflects a strong addition of uranium from the surrounding rocks. While the radioelements have been dissolved from the surrounding rocks (different types of granites) by meteoric and/or surface water through joints and fissures and finally, it deposited/trapped along the fractures of garnetiferous muscovite granites (absorbed by iron oxides) and less impermeable mica lenses due to the change in the physicochemical conditions, Eh and Ph in the given medium.

The Geology and Mineral Chemistry of Beryl Mineralization, South Eastern Desert, Egypt: A Deeper Insight into Genesis and Distribution

“…These schistose rocks in Wadi Sikait comprise talc schists, graphite schists, mica schists, garnet-mica schists, and quartzo-feldspathic schists. The beryl mineralization is mainly hosted by mica schists, besides elongate crystals disseminated in amphibole schists [23].…”

“…The ophiolitic rocks and orthogneiss underwent progressive metamorphism and deformation along the NW-SE shear zone. The serpentinite was transformed into talccarbonate, while the metagabbro is thrusted over the ophiolitic mélange, forming a sheeted mass [23]. The deformed orthogneiss is represented by mylonite, and contains blocks of mafic-ultramafic rocks and bands of tremolite-actinolite.…”

“…Um Sleimat beryl mineralization is found in phlogopite schists, tourmaline schists, and in quartz veins at the intrusive contact between the ophiolitic mélange and muscovite granites (Figure 2a,b). Phlogopite zones around beryl-bearing quartz veins extend in the NW-SE direction, and dip 35 • -65 • to the NE [7,23,28]. The unmineralized quartz veins (beryl-free veins) are not surrounded by phlogopite schists and/or cut the ultramafic rocks.…”

Assessing environmental and radiological impacts and lithological mapping of beryl-bearing rocks in Egypt using high-resolution sentinel-2 remote sensing images

“…The ultramafic rocks are highly tectonized forming fold-thrust sheets over ophiolitic metagabbros (ENE-WSW) 38 , 39 . Ophiolitic mélange includes many varieties of schistose rocks such as graphite-biotite schist, garnet-hornblende-biotite schist, quartzo-feldspathic schist, and phlogopite schist, which contains the beryl mineralization 35 . The contact between the gneisses and schist rocks is usually sharp and variable mineralization such as radioactive minerals and columbite.…”