Tonian mafic–intermediate and Late Ediacaran ferroan–alkalic granitoid magmatism along the Ad Damm fault Zone, western Arabian Shield

The Arabian–Nubian Shield preserves an episodic record of Neoproterozoic crust formation and reworking. Here we integrate zircon U–Pb geochronology and Lu–Hf isotopes with zircon typology, whole-rock geochemistry, petrography, and field relationships to constrain the magmatic evolution of intrusive rocks along the Ad Damm Fault Zone (ADFZ), western Arabian Shield. Zircon U–Pb ages identify two magmatic episodes. Khasrah hornblende gabbros crystallized at ∼ 846 ± 5 Ma and quartz diorite at 830 ± 4 Ma, recording Tonian mafic–intermediate magmatism with broadly arc-like geochemical characteristics. Their zircon populations are dominated by S-type morphologies, and positive mean εHf(t) values (+4.84 ± 1.39 to + 8.54 ± 1.32) indicate relatively juvenile isotopic sources. A distinct Late Ediacaran episode is recorded by the Nu’man granitoids at 604–––599 Ma and the Ad Damm sheared granite at 586 ± 3.5 Ma. These felsic rocks are ferroan–alkalic, enriched in HFSE and REE, and marked by pronounced negative Eu anomalies and contrasting T-, P-, K-, and N-type zircon populations. Positive mean εHf(t) values (+5.46 ± 1.31 to + 5.76 ± 1.54) again point to juvenile isotopic sources, though they cannot uniquely distinguish new mantle input from reworking of previously accreted juvenile crust. The > 200 Myr age gap, together with contrasting geochemical and zircon characteristics, precludes interpreting the two episodes as a continuous differentiation sequence or a direct genetic lineage. The 586 Ma age of the sheared granite dates crystallization and provides a maximum age for its deformation fabric. The ADFZ thus preserves discrete records of Tonian, broadly arc-like mafic–intermediate magmatism and Late Ediacaran evolved felsic magmatism involving differentiation and/or reworking of isotopically juvenile crust, providing new constraints on the episodic tectono-magmatic evolution of the western Arabian Shield.