Petrological constraints of the Ediacaran magmatic intrusions, Homrit Mukpid area, southeastern Desert, Egypt: Bulk rock geochemistry and mineralogy

The study provides a comprehensive investigation into the evolution and petrogenesis of the Homrit Mukpid (HM) granitic suites, emphasizing their petrological characteristics. The HM granitic rocks comprise two main suites: the older granodioritic suite (GHM) and the younger alkali-feldspar granite suite (AHM). The GHM exhibits notable enrichment in TiO₂, MgO, CaO, Fe₂O₃, Sr, Ba, Cr, V, and Sc, and lower concentrations of Ta, Th, Rb, Y, Nb, Sn, Ga, U, Pb, Zn, and ∑REEs compared to the AHM. Geochemically, GHM is distinguished by pronounced negative P, Ti, and Nb anomalies, as well as a decrease in HREEs (avg. ≈ 11 ppm) relative to LREEs (avg. ≈ 83 ppm) and a moderately negative Eu anomaly (avg. ≈ Eu/Eu∗ = 0.78), characteristic of substantially fractionated, subduction-related I-type magmatic sources. In contrast, the AHM displays high SiO₂ (avg. ≈ 75 wt%), total alkalis (avg. ≈ 9 wt%), and higher FeO/MgO, and Rb contents. Their REEs pattern shows a strong negative Eu anomaly (av. Eu/Eu∗ ≈0.08) and HREEs enrichment, indicative of post-collisional A₂-type granites. Importantly, there is no evidence of M-type tetrad effect, as determined using both the lambda and Irber methods. The evoultion of the HM, as a part of the Arabian Nubian Shield, is marked by distinct stages of collision and post-collision, as inferred from the mineralogical and geochemical data of granitic rocks. The GHM is formed from the subducted slab dehydrating, which facilitated the melting of the upper mantle, providing underplating of high K-mafic melts. The GHM formation is attributed to the dehydration of a subducted slab, which triggered upper mantle melting and the generation of high-K mafic melts. This melt subsequently underwent melting and fractionation at elevated temperatures (avg. ≈ 809 °C, using zircon saturation temperature). Conversely, the AHM formed through slab delamination, inducing asthenospheric upwelling and the melting of tonalitic/clay-rich metapelite rocks, followed by extreme fractional crystallization processes during a post-collisional extension episode at low temperatures (avg. ≈ 784 °C) and shallow depths.