The possible source of uranium mineralization in felsic volcanic rocks, Eastern Desert, Egypt of the Arabian-Nubian Shield: Constraints from whole-rock geochemistry and spectrometric prospection

Abstract

The present work deals with the detailed geology, mineralogy, geochemistry, and spectrometric prospection of the felsic volcanic rocks at the Eastern Desert, Egypt of the Arabian-Nubian Shield. Felsic volcanic rocks are an essential source for rare earth elements (REEs) and uranium occurrences in this area. They are compositionally uniform with tholeiitic to calc-alkaline affinities, peraluminous and belong to the series of rhyolite with high-K melt. They exhibit more enrichment in high field strength elements (HFSE, e.g. Zr, Ta, Nd, Th, and U) and large-ion lithophile elements (LILE, e.g. Pb and Rb) compared to the country rocks of the studied area, with REE ranging from 188.20 to 442.70 ppm and strong depletion in Ti, Sr, P with deep negative Eu oddities. The felsic volcanic rocks were mostly generated from the partial melting of quartz-amphibolite facies accreted during the Neoproterozoic. Positive oddities of Zr- U- Th for the felsic volcanic rocks determine the involvement of crustal materials. Felsic volcanic rocks are found in A-type suites of magma and represent highly fractionated rocks derived from rhyolitic magma, with insignificant interaction with continental crust in the low-pressure environment and during fractional crystallization. Felsic volcanic rocks have higher values of radioactivity in which eU range from 0.5 to 121 ppm and eTh from 1.0 to 415.10 ppm. The high values of eU and eTh can be ascribed to the mineralization of uranium and the presence of accessory minerals of radiogenic nature such as uranophane, uranothorite, zircon, and monazite. Uranophane is considered as the mineral with most enriched uranium contents in the studied felsic volcanic rocks in which (UO2 = 87.30 wt %). Also, they are enriched with REE-bearing accessory minerals comprising allanite, titanite, and apatite. The geological investigations of the felsic volcanic rocks in the studied areas are inappropriate to clear the feasible economic potentialities of rare earth elements and U occurrences; itemized and invaluable explorational work is as yet needed. Whilst, the environmental impact of mineralization, owing to U and Th and their radiogenic daughter products, is observed and must be elaborated minutely.