Citation: Lashin, A.; Anbar, M.A.; Aboud, E.; Zaidi, F.; Al-Bassam, A.; Al Arifi, N.; Al-Homadhi, E. Geochemistry and Petrogenesis of the Ediacaran Post-Collisional Granitoid Rocks in the Midyan Terrain, Northern Arabian Shield, Saudi Arabia. Minerals 2023, 13, 379. https://doi.org/10.3390/ min13030379 Academic Editor: Jaroslav Dostal Received: 31 January 2023 Revised: 27 February 2023 Accepted: 6 March 2023 Published: 8 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). minerals Article Geochemistry and Petrogenesis of the Ediacaran Post-Collisional Granitoid Rocks in the Midyan Terrain, Northern Arabian Shield, Saudi Arabia Aref Lashin 1, * , Mohammed Abu Anbar 2, *, Essam Aboud 3 , Faisal Zaidi 4 , Abdulaziz Al-Bassam 4 , Nassir Al Arifi 4 and Emad Al-Homadhi 1 1 Petroleum and Natural Gas Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia 2 Geology Department, Faculty of Science, Tanta University, Tanta 31527, Egypt 3 Geohazards Research Centre, King Abdulaziz University, P.O. Box 80206, Jeddah 21589, Saudi Arabia 4 Geology and Geophysics Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia * Correspondence: arlashin@ksu.edu.sa (A.L.); mmanbar@science.tanta.edu.eg (M.A.A.) Abstract: Midyan granites are located in the northern Arabian shield, northwest Saudi Arabia, in the Midyan terrain. They represent the most northerly segment of the Arabian–Nubian shield, which comprises the northern part of the East African orogeny. Consequently, understanding the origin of post-collisional and anorogenic magmatism in the Midyan terrain has significant geodynamic implications. Midyan granites are mainly composed of alkali feldspar granite, syenogranite, and rarely of granodiorite and diorite. Most of the studied granites are alkali-calcic, calc-alkaline, and metaluminous to peraluminous magma types. They are characterized by enrichment with light rare earth elements (LREEs), large-ion lithophile elements (especially Rb and Th), and some high-field strength elements (HFSE, e.g., Nb, Ta, Zr, and U), and the slight depletion of heavy rare earth elements (HREEs). Therefore, the Midyan granites and Hael granites studied in this paper represent good sources of geothermal heat, uranium–thorium, and REE mineralization. The studied granites have moderately strong negative Eu anomalies and a distribution pattern that is very consistent with that of the upper crust, indicating the presence of plagioclase or potassium feldspar cumulates. They have a Th/Ta ratio similar to that of the source of the crust, which may be derived from the upper crust following the collision between East and West Gondwana in the final stage of the Arabian Shield evolution. The data presented in this study are therefore consistent with the post-collisional intraplate magmatism that occurred at the beginning of the transition from convergent to extensional tectonics. The studied granites are derived from melt generated at a crystallization temperature of around 750 ◦ C at a pressure of around 0.2–0.5 GPa, emplaced at relatively shallow to moderate depths of between 20 and 30 km. Keywords: Arabian–Nubian Shield; whole-rock geochemistry; granite petrogenesis; Midyan Terrain; Saudi Arabia 1. Introduction The Arabian–Nubian Shield (ANS) is one of the largest regions of the juvenile con- tinental crust [1] and was mostly formed during the Neoproterozoic era, as indicated by the ages of U–Pb zircon and isotopic data on Sr, Nd, and Pb [2,3]. It is covered by Pre- cambrian metamorphic and igneous rocks around the Red Sea in northeast (NE) Africa (Egypt, Eritrea, Ethiopia, Somalia, and Sudan) and western Arabia (Saudi Arabia and Yemen). The Arabian Shield (AS) is composed mainly of well-preserved Neoproterozoic assemblages that have been slightly metamorphosed. These assemblages were generated between 900 and 550 Ma through the successive accretion of inter-oceanic island arcs along Minerals 2023, 13, 379. https://doi.org/10.3390/min13030379 https://www.mdpi.com/journal/minerals