Neoproterozoic U‐Th‐REE‐bearing Pegmatites in Wadi Ibib, South Eastern Desert, Egypt: Structural and Geochemical Measures for a Syn‐Tectonic Anatectic Model of Formation

Abstract

Pegmatites may form significant reservoirs of rare metals (Linnen et al., 2012;Dill, 2015), rare earth elements (REE) and radioactive metals (U and Th). Nevertheless, the origin of pegmatites and the associated mineralization is still a matter of debate (Černý and Ercit, 2005). Mineralized pegmatites can be classified into two suites (end-members): i) pegmatites with concentrations of niobium-yttrium-fluorine (referred to as the NYF suite); and ii) pegmatites with concentrations of lithium-cesiumtantalum (referred to as the LCT suite) (Černý et al., 2012). Two hypotheses are posited for the generation of pegmatitic melts: 1) continued fractionation of granitic magmas during plutonism and 2) limited partial melting of crustal sources, with inputs from circulating hydrothermal fluids (e.g., Martin and DeVito, 2005;London, 2005). These hypotheses can practically represent two endmembers of pegmatite formation. Generally, the host lithology, tectonic setting and geological setup of pegmatite swarms are important parameters that may control their formation and element budget.In the Egyptian Eastern Desert, most of the abundant pegmatite sets are spatially associated with post-tectonic Pan-African granites (e.g., Abd El-Naby and Saleh, 2003;Saleh et al., 2008;Ghazaly et al., 2015). Alternatively, the pegmatite sets associated with amphibolite facies gneissic and schistose rocks across the southern Eastern Desert are rarely recorded in some localities, e.g., Hafafit and Nugrus areas (e.g., Raslan and Ali, 2011;Ibrahim et al., 2015Ibrahim et al., , 2017.The structural pattern of Neoproterozoic rocks (e.g., propagation of thrusts and sutures) along the south Eastern Desert reveals a polyphase deformation history (Abd El-

Rare Earths in Egypt: Occurrence, Characterization and Physical Separation, A Review

“…Itis existed as anhedral cluster. This area was reported by Many authors such as Ibrahim et al [31], Ibrahim [32], Attawiya et al [33], and Ammar [34].…”