Geochronology and Geochemistry of Ediacaran A‐Type Granitoids From Central Iran: Post‐Collisional Magmatism During the Final Stages of the Cadomian Orogeny

ABSTRACT The late Cadomian magmatic evolution of the Central East Iranian Microcontinent (CEIM) remains a critical yet debated aspect of northern Gondwana tectonics. The Khezr‐Abad granitoids, exposed within the CEIM, preserve key records of late Neoproterozoic–early Palaeozoic crustal reorganisation along the northern Gondwana margin. Zircon U–Pb geochronology indicates crystallisation at ca. 550 Ma, coinciding with the terminal stage of Cadomian magmatism during the Ediacaran–early Cambrian transition. The granitoids are highly evolved, characterised by high SiO 2 and total alkalis, very low MgO, CaO and TiO 2 , and display pronounced depletion in Ba, Sr, Eu and Ti, coupled with enrichment in large‐ion lithophile elements and marked negative Nb–Ta–Ti anomalies. Chondrite‐normalised REE patterns show strong negative Eu anomalies, indicating advanced fractional crystallisation dominated by feldspar ± biotite. Elevated Ga/Al ratios, together with high Y/Nb and Ce/Nb values, classify the Khezr‐Abad suite as highly evolved A2‐type granitoids. Zircon Lu–Hf isotopic data yield ε Hf ( t ) values from −30.2 to +3.9 and two‐stage model ages (T DM2 = 1.3–3.4 Ga), indicating derivation predominantly from reworked Paleoproterozoic–Archean continental crust with minor juvenile mantle input. The widespread occurrence of 550 Ma felsic magmatism across the CEIM and adjacent peri‐Gondwanan terranes reflects a regional post‐collisional extensional regime that followed the Cadomian continental collision and crustal thickening. The Khezr‐Abad granitoids record post‐orogenic collapse and lithospheric thinning during the transition from Cadomian convergence to tectonic stabilisation along the northern Gondwana margin.