Geology, geochemistry, and radioactivity of El Maghrabiya young granites, Central Eastern Desert, Egypt

Abstract

The young granites of El Maghrabiya area located at the Central Eastern Desert, the southwestern part, are intensively altered along faults, fractures, and shear zones. Microscopically, the studied granites are classified as syenogranite and the altered portion exhibits features of ferrugination and episyenitization. This granite belongs to the high silica and low calcium, iron, and magnesium granites reflecting their origin from highly fractionated potassium-rich crustal material. El Maghrabiya syenogranites are generally uraniferous especially the altered portion that is characterized by high radioactivity. The hydrothermal activity is responsible for the formation of the anomalous zone characterized by extensive episyenitization and ferrugination processes. The ferruginated syenogranite has higher concentrations of uranium and thorium than the other altered granites (episyenitized). The present study revealed that zircon, fluorite, fluorapatite, and iron oxides are the most predominant U-bearing minerals in addition to uranophane that recorded in the ferruginated variety. The studied syenogranites characterized by two thorium ranges where the fresh granite exhibits the low range (22–45 ppm) and the altered granite characterized by the higher range (68–185 ppm) indicating that there are two pulses of the magma generating El Maghrabiya young granites. Uranium and thorium of the first generation are mostly attributed to the accessory minerals and related to the magmatic processes while the second generation is characterized by low Th/U ratio and high uranium content that is enriched by the hydrothermal solutions.