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Dr. Adel Mady Afify Mohammed :: Publications:

Mineralogical and geochemical characterization of radioactive minerals and rare earth elements in granitic pegmatites at G. El Fereyid, South Eastern Desert, Egypt
Authors: G.M. Saleh, A.M. Afify, B.M. Emad, M.I. Dawoud, H.A. Shahin, F.M. Khaleal
Year: 2019
Keywords: Mineralogy Geochemistry Rare earth elements Radioactive minerals Granitic pegmatites Egypt
Journal: Journal of African Earth Sciences
Volume: 160
Issue: 103651
Pages: Not Available
Publisher: ELSEVIER
Local/International: International
Paper Link:
Full paper Adel Mady Afify Mohammed_Afify, Emad, 2019.pdf
Supplementary materials Not Available

The present work deals with the mineralogical and geochemical investigations of radioactive minerals and rare earth elements associated with granitic pegmatites at Gabal El Fereyid area exposed in the south Eastern Desert of Egypt. The study area is occupied by tonalite and monzogranites, the latter is intruded by pegmatites with a distinctive distribution of economically important mineralization. The studied pegmatitic bodies occur as veins that are ranging in size from few meters to 25m long and their width usually less than 7 m; although small pockets are present. The latter display zoning structure (concentric layering) consisting of feldspar-rich zones enveloping pockets of mica (mainly muscovite) and all zoning internal quartz core. Field work using gamma spectroscopy measurements over these pegmatites shows that some bodies are radiometrically anomalous, especially the muscovite-rich zones. The mineralogy and geochemistry (trace and rare earth elements contents) of the radioactive zones in such pegmatites were achieved. Mineral characterization of the highly radioactive zones shows enrichment in thorite, uranothorite, ishikawaite, samarskite and fergusonite minerals. The spectrometric measurements of the studied pegmatites show that they possess the highest content of radioelements as well. They show enrichment in large ion lithophile elements (LILE; Pb, Rb, Sr) and high field strength elements (HFSE; Y, Zr, Th, U, Nb) and depletion in K, P and Ti. The studied granitic pegmatites indicate moderate to large negative Eu anomaly and show clear M-type tetrad effect of REE. The mineralogical and geochemical signature of investigated pegmatites represents a NYF-type (Niobium–Yttrium–Fluorine family), whereas the enrichment of rare element is an indication of high degrees of fractional crystallization of a suite of volatile-rich magmas. Uranium and thorium mineralization in the studied pegmatite are related to magmatic (syngenetic) origin with hydrothermal (epigenetic) input. The magmatic mineralization is evidenced by occurrence of thorite and zircon, whereas the hydrothermal activity is represented by alteration of feldspars and formation of pyrite and iron oxides associated with the radioactive minerals. The high levels of radioactivity and rare earth elements mineralization in the studied granitic pegmatite bodies make them a target to exploration and to enlarge the potentiality of the highly mineralized localities.

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