Petrogenesis of El-Aradyia late-Ediacaran fluorite-bearing granites, Central Eastern Desert of Egypt

Abstract

El-Aradyia fluorite-bearing granites (EFBGs) are exposed in the Central Eastern Desert of Egypt. EFBGs have a range of composition from syenogranite to alkali-feldspar granites. They display ferroan, high-K calc-alkaline and weakly peraluminous granites characters. Based on their K/Rb ratios and high SiO 2 contents, EFBGs are categorised as highly differentiated and highly evolved granites. Thermobarometric measurements refer to the crystallisation of EFBGs under magma conditions include, temperatures between 679 and 766 °C, pressures between 2 and 5 kbars, and log f O2 between − 17 and − 15. The low oxygen fugacity values of EFBGs along with appearance of normative ilmenite, indicates their crystallisation under reducing conditions. Trace elements classified EFBGs as A 2 -subtype granites, which were formed during post-collisional crustal extensional stage of the Pan-African Orogeny. EFBGs were derived by partial melting of lower crustal source (i.e. tonalites-granodiorite) with limited mantle contribution. Subsequently, the generated magmas were evolved through extensive fractional crystallization by K-feldspar and other accessory minerals. Concurrently, the volatiles/fluids enhanced the partial melting of the pre-existing tonalite-granodiorite source. The REEs tetrad effect and non-CHARAC elemental behavior in EFBGs samples support the role of magmatic and melt-fluid interaction processes in their magmatic evolution. The textural features of the accessory fluorite, along with the change in the Y concentration from the core to the rim, support their magmatic-hydrothermal origin.