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

Abstract

Paleozoic rocks in the Wadi El Sahu area are affected by many major faults in different directions. A reverse fault trending NE‐SW is exposed for about 300 m of its length as it cuts through the Abu Hamata and Adedia formations on the south side of Wadi El Sahu. A secondary ascending hydrothermal solution carrying heavy metals and radioactive minerals passed through the fault plain and the surrounding fractures, forming mineralized and radioactive zone. The mineralized zone thickness ranges from 60 cm to 200 cm along the fault plain. These rocks were analyzed radiometrically using a portable gamma‐ray spectrometer, chemically by employing ICP‐ES and ICP‐MS, as well as mineralogically by both binocular and Environmental Scanning Electron microscope. Gold content was also determined by fire assay. REE and U contents reached up to 2682 and 1216 ppm, respectively. Mineralogical investigations indicated the presence of uraninite, torbernite, autunite, sklodowskite, kasolite as uranium minerals, thorite as a thorium mineral, monazite, allanite and xenotime as REE‐bearing minerals, zircon and columbite as accessory minerals, gold and nickel as precious and base metals, in addition to cassiterite, chalcopyrite, chalcocite and chrysocolla. High REE and U contents are attributed to the circulation of epigenetic U and REE‐bearing hydrothermal solutions along the fault plain and its surrounding fractures. Hydrothermal alteration processes could then be confirmed by the presence of the M‐type tetrad effect in the REE‐patterns of the ferruginous sandstone. The non‐chondritic ratio of Nb/Ta, Zr/Hf and Y/Ho in the studied sandstone may be attributed to the tetrad effect. The Ce and Eu anomaly with unusual REE‐patterns was represented by the presence of conjugated M‐W tetrad effects, indicating either the dual effect of hydrothermal solutions or groundwater with seawater. The results clarify that the tetrad‐effects could be used as evidence for the environment of deposition and as an indication for gold mineralization.

Radioactivity, Petrogenesis and Rare Earth Elements Tetrad Effect of the Mineralized Granite of Gabal Gattar, North Eastern Desert, Egypt

“…All samples of the studied mineralized granites have La/Y ratio values (<1), indicating that the mineralizing solution is mainly acidic. This may suggest that these acidic solutions have high ability for solubilizing uranium and REEs-bearing minerals which may be precipitated due to pH changes by the presence of alkaline carbonate solutions as indicated from Y/Ho ratio (Sallam et al, 2020).…”

Petrogenesis and geological implications of the trachytic rocks in the South Eastern Desert, Egypt: Mineralogical, geochemical, and radioactivity insights

“…The composition of Palaeozoic and Mesozoic volcanic rocks ranges from olivine basalt to trachyte, whereas tertiary volcanic formations are mostly basaltic. There have been numerous prior research on these alkaline volcanic systems conducted by (Heikal 2003; Dawood et al 2003; Saleh et al 2004, 2007, 2015, 2020, 2021; Ibrahim et al 2005; Abdalla 2001; El Tohamy 2011; Gharib et al 2012; Nabawy and El Sharawy 2018; Sadek et al 2020; Sallam et al 2021; Abuamarah and Nabawy 2021; Kamar et al 2022; Oraby et al 2022; Ali-Bik et al 2022; Abdalla et al 2023; Dessouky and Ali 2018; Dessouky et al, 2023; Khaleal et al 2022, 2023).…”