Tracking the transition from subduction‐related to post‐collisional magmatism in the north Arabian–Nubian Shield: A case study from the Homrit Waggat area of the Eastern Desert of Egypt

Abstract

Field and geochemical observations of the granitoids of the Homrit Waggat area in the central Eastern Desert of Egypt reveal two magmatic phases. The early phase of weakly deformed subduction-related calc-alkaline rocks includes tonalite and granodiorite. We name the later phase the Homrit Waggat Pluton (HWP); it includes undeformed syenogranite, alkali feldspar granite, and minor albitized granite. The tonalite and granodiorite have distinct negative Nb-Ta anomalies and lower alkalis, REE, Nb, Zr, and Hf than the HWP. The early magmatic pulse is a subduction-related suite, likely generated by underplating of mantle-derived magmas that triggered partial melting of mafic lower crust; mixing of these melts led to intermediate magma that further fractionated to tonalite and granodiorite. The HWP granites of the late magmatic pulse are transitional from a subduction-related to an anorogenic within-plate environment, plausibly generated by post-collisional lithosphere delamination. Although the parent magma of the HWP was I-type, extensive fractional crystallization produced residual liquids with A 2 -type character. Albitized granites are found only along the outer margin of the HWP, and contacts with the alkali feldspar granite are gradational, suggesting fluid interactions at a late stage of crystallization. The original textures of the albitized granites are preserved, but their bulk composition was modified by the production of Narich minerals and the removal of K, REE, and some trace elements by fluids.

Geochemistry and Petrogenesis of Late Ediacaran Rare‐metal Albite Granites of the Arabian‐Nubian Shield

“…The ADAG in particular has likewise been assigned by different authors to either magmatic (Asran, 1985;Mohamed, 1993;Jahn, 1996;Renno, 1997) or metasomatic origins (Sabet et al,1976;Kamel and E1 Tabbal, 1980). In fact, the distinction between magmatic and metasomatic processes may not be as absolute as once thought (Lundstrom, 2016;Azer et al, 2019aAzer et al, , 2020Seddik et al, 2020).…”

Constraints of Mantle and Crustal Sources Interaction during Orogenesis of Pre‐ and Post‐collision Granitoids from the Northern Arabian‐Nubian Shield: A Case Study from Wadi El‐Akhder Granitoids, Southern Sinai, Egypt

“…Accordingly, the best model for explaining the origin of the studied post-tectonic granites is the partial melting and anatexis of lower crustal rocks. The required heat for crustal rock anatexis can be assigned by the contribution of intraplating mantle-derived; volatile-rich melt (Azer and Farahat, 2011;Azer et al, 2020). Moreover, the northern parts of the ANS were subjected to oblique compressional force, which led to the activity of Najd Fault System (Abu-Alam and Stüwe, 2009).…”

“…Recently, it is well-known that contribution of pre-Neoproterozoic crust in the formation of the OG and YG groups is insignificant (e.g. Hargrove et al, 2006;Moussa et al, 2008;Ali et al, 2012;Azer et al, 2020). Although the granitoid rocks from the ANS have been subjected to numerous investigations concerning their petrogenesis and geotectonic evolution, but much controversy still persists for their source, regional geotectonic regimes and peculiar individual petrogenetic paths such as the role of fractional crystallization against crustal anatexis (e.g., Stern and Gottfried, 1986;Beyth et al, 1994).…”

Magmatic and hydrothermal evolution of highly-fractionated rare-metal granites at Gabal Nuweibi, Eastern Desert, Egypt

“…One of the most striking features of the Eastern Desert of Egypt, the northwestern segment of the ANS, is the abundance of post-collisional felsic plutons (Azer et al, 2019(Azer et al, , 2020Seddik et al, 2020;Abuamarah et al, 2021). The evolution of the Nuweibi intrusion is discussed here in light of the current data and post-collisional magmatism in the northern ANS.…”

“…Generally, post-orogenic granites J o u r n a l P r e -p r o o f evolved from calc-alkaline (630-600 Ma) to alkaline (610-590 Ma) character, with some overlap in their ages (Ali et al, 2009;Eliwa et al, 2014). They include a number of discrete, shallowlyemplaced A-type and highly fractionated I-type igneous complexes, with significant enrichment in some ores (Helba et al, 1997;Abou El Maaty and Ali Bik, 2000;El Hadek et al, 2016;Abu El-Rus et al, 2017;Sami et al, 2017Sami et al, , 2018Heikal et al, 2019;Azer et al, 2019Azer et al, , 2020Seddik et al, 2020, Abuamarah et al, 2021. The abundance of these post-orogenic granites is of geodynamic interest, as they represent a significant addition of material into the juvenile crust of the ANS over a relatively short time interval.…”