Geochemical and petrogenetic evolution of the basement rocks of the Ha’il terrane, Arabian Shield: A snapshot of the Gondwana assembly

The Ha’il terrane is one of eight terranes that amalgamated in the Neoproterozoic to form the Arabian Shield during the protracted assembly of Gondwana. Large portions of the terrane are composed of plutonic rocks, but the timing and mechanisms of their formation remain poorly constrained. This study presents whole-rock major and trace element concentrations and zircon in-situ U-Pb-Hf isotope data for the Ha’il monzogranite (Dayra suite), Kilab monzogranite (Shuwayman suite), and the Ha’il diorite (enclaved within the Ha’il monzogranite) of the Ha’il terrane. The Ha’il diorite is highly metaluminous, shows I-type affinity, and was emplaced at 650 ± 3 Ma during syn-orogenic magmatism. The Ha’il monzogranite and Kilab monzogranite are transitional metaluminous-peralkaline and exhibit ferroan, A-type, and alkalic granite affinities. They were emplaced at 640 ± 3 Ma during post-orogenic magmatism. The initial Hf-isotope compositions of the Ha’il diorite (εHf(t) = +7.9 to + 9.0), Ha’il monzogranite (εHf(t) = +8.2 to + 11.1), and the Kilab monzogranite (εHf(t) = +8.7 to + 9.8) suggest their origin by partial melting of isotopically similar and juvenile crustal sources. The crustal sources were derived from a depleted mantle approximately 1000 Myr ago, coinciding with the initial rifting that led to the opening of the Mozambique Ocean. Furthermore, this study captures a tectonomagmatic transition from compressional, syn-orogenic to extensional, post-orogenic magmatism in the Ha’il terrane at around 640 Ma.