Pan-African younger granitoids of the southern Eastern Desert, Egypt: Geology, geochemical constraints, and mineralization

Younger granitoids of the Gabal El Farayid-Gabal El Marafawy district in the southern Eastern Desert Egypt are compositionally syenogranites. Based on petrological and geochemical studies, they are classified as two distinct types: the biotite-hornblende subsolvus EI-Marafaway I-type syenogranite: and the biotite-bearing hypersolvus El-Farayid A-type syenogranite: The subsolvus El-Marafawy syenogranite is characterized by low Rb/Sr ratios and high field strength element (HFSE) concentrations (Nb, Ta,Y), fractionated LREEs with flat HREEs. high LREE/HREE ratios, negative Nb-Ta anomalies, and lack of negative Ba and Eu anomalies. The hypersolvus El-Farayid syenogranite (HFS) is characterized by high Rb/Sr ratios and HFSE concentrations, slightly fractionated (HFSI) to onfractionated (HFSII) LREE with a positive slope for the HREE, absence of negative Nb-Ta anomalies and significant negative Ba, Ce, Zr and Eu anomalies. Based on field and geochemical data, the late-tectonic subsolvus El-Marafawy syenogranite may have been produced by dehydration partial melting of all amphibolitic source, followed by high-pressure fractionation. The post-tectonic hypersolvus El-Farayid syeriogranite probably formed from a residual magma by crystallization of biotite, plagioclase, K-feldspar and accessory monazite. allanite, and titanite in a shallow-level magma chamber emplaced along strike-slip faults of a convergent margin. Generally, the syenogranites were generated during a period of rapid tectonic transition from crustal thickening during subduction (subsolvus El-Marafawy syenogranite) to crustal thinning during extension (hypersolvus El-Farayid syenogranite), which represents the final magmatic stage of all extensive are system. U and Thl contents in the above rock types are comparable, indicating that these elements are mainly contained in accessory minerals that controlled their distributions.