Mineralogy, M-type tetrad effect and radioactivity of altered granites at the G. Abu Garadi shear zone, central Eastern Desert, Egypt

Abstract

The G. Abu Garadi area is covered mainly by metasediments, alkali feldspar granites and stream sediments. The alkali feldspar granite is traversed by a major strike-slip fault trending in an N-S direction as well as two subordinate sets of faults trending NW to WNW for the first one and NE for the second one. These faults represent the shear zones affected by magmatic (syngenetic) as well as hydrothermal (epigenetic) activities causing alteration of the granitic rocks. The most common alteration features are albitization, greisenization and koalinitization. The mass balance calculations of the studied altered samples show enrichments in Zr, Y, Ni, U, Th and Ga and depletions in Zn, Sr, Nb, Ba, Pb, Cu and V. Only the greisenized samples exhibit a significant enrichment in Nb, ∑REE budget and pronounced lanthanide tetrad effect (M-type), especially TE 1,4 , while weakly expressed tetrad effects are for the other albitized and koalinitized samples. Mineralogically, the common accessory minerals in the altered samples include samarskite-(Y), betafite, uranothorite, zircon, fluorite and cassiterite. The greisenized granites contain high eU and eTh than the other altered types, where they are characterized by an assemblage of the radioactive minerals; samarskite-(Y), betafite, uranothorite in addition to zircon. The inter-element relationships between U and Th and also their ratios illustrate that the radioelement distribution in these granites is mainly governed by magmatic processes, in addition to post-magmatic ones. The distribution of chemical elements and the fractionation of some isovalents within the shear zone are largely controlled by the newly formed mineral phases. With respect to uranium mobilization, uranium migrated from the host alkali feldspar granites of G. Abu Garadi, while the shear zones acted as traps for the migrated uranium. Moreover, U migrated in the shear zone during greisenization and albitization, and migrated out during koalinitization.

Mineralogy and Geochemistry of Uraniferous Sandstones in Fault Zone, Wadi El Sahu Area, Southwestern Sinai, Egypt: Implications for Provenance, Weathering and Tectonic Setting

“…Abedini et al (2018) indicated that the co-existence of W-and Mshape tetrad-effects in the Kanigorgeh residual horizon of bauxite deposits in Iran supports the idea that penetration of low-pH surface waters into the upper part caused destruction of REE-bearing minerals, leaching and transportation of REE downwards and their ultimate concentration in the lower part. Conjugate types of this effect (M-and W-shape) have been reported from different environments, such as the Qahr-Abad fluorite deposit and other deposits worldwide (El Nahas et al, 2011;El Mezayen et al, 2019, Ibrahim et al, 2015El-Tohamy, 2019). The latter indicates that the existence of both W-and M-type tetrad effects in the same deposit can be related to weathering, leaching by groundwater and/or mixing of fluids and/or waters or combinations of these.…”

Radionuclide Content and Radiation Dose Rates of Uraniferous and Mineralized Granites at GV Occurrence in Gabal Gattar, Northeastern Desert, Egypt.

“…Secondary generated quartz and uranium mineralization show an intimate intergrowth in microfractures. In some parts, the amorphous silica coating the mineralized surface, and may protect them from alteration (El Feky, 2011).…”

Spectrophotometric determination of Uranium through complex formation with roxarsone

“…4). (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) were assayed to determine the variation of concentrations with pH on this protocol. The concentrations determined using this modified method was not affected significantly with the variation in the pH from 2 to 8.…”

“…Uranium ore always contains other metal impurities 5 , so the leaching, adsorption, or biosorption of Uranium vary according to the type of the rock 6,7 . Many techniques have been previously developed for the determination of Uranium; these methods include inductively coupled plasma spectrometry (ICP-AES) 8 , inductively coupled plasma-mass spectrometry (ICP-MS) 9,10 , ion chromatography (I.C.)…”