TITLE:
Petrology, REE Geochemistry and Tetrad Effect of Some Muscovite Granites at Wadi El Gemal Area, South Eastern Desert, Egypt
AUTHORS:
Ahmed S. Shalan
KEYWORDS:
Wadi El Gemal, Umm El Kheran, REE Geochemistry, Tetrad Effect, Egypt
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.10 No.2,
February
25,
2022
ABSTRACT: The muscovite granites at the study area are being emplaced into biotite
granites and ophiolitic mélange settings. They occur in four exposures namely;
Umm Seleimat, Sikait, Umm El Kheran and Umm Addebaa exposure. The presence of
garnet and muscovite flakes may reflect the peraluminous nature of the studied
muscovite granites. Petrographically, the studied granites are mostly subsolvus
and consist of plagioclase, K-feldspars, quartz, muscovite and biotite. Garnet,
zircon, allanite and opaques are accessories. The textural features of these
granites are expressed by bent plagioclase lamellae, distorted microcline
twinning, deformed mica flakes and development of myrmekite and
recrystallization of feldspars into fine-grained aggregates. Umm Seleimat and
Sikait exposures are more differentiated due to the presence of high content of
K-feldspar and LREEs. The REE budget decreased from Umm Seleimat-Sikait
exposures to Umm El Kheran-Umm Addebaa exposures as (514.5 - 495.6)
to (195.9 - 197.7), respectively. Umm Seleimat-Sikait exposures have lower HREE/LREE (0.12 - 0.67), relative to Umm El Kheran-Umm Addebaa exposures (0.99 - 2.06). The studied granites revealed that the chondrite normalized REE
patterns are the normal M-type of tetrad effect, where TE1,3 tetrad effect is
higher than 1 in all samples which implies that there was an interaction between
melt and water-haloid-rich fluid when these granites are crystallized from magma.
Spectrometric values of Umm Seleimat and Umm Addebaa indicate that U content is
more than Th content. Applying the U mobilization equation proved that the
studied granites have been originated from a late magmatic phase of magma very
rich in radioelements, also the majority of measurements lie above the zero
line indicating that the studied granites affected with hydrothermal solutions
rich in uranium than thorium which indicates uranium addition.