From subduction initiation to oceanic core complex formation: a tale of two ophiolites in the Kurdistan, NW Iran

The processes of subduction initiation and oceanic core complex (OCC) formation are essential to understanding plate tectonic evolution. The Kermanshah–Walash Ophiolitic Complex (KWOC) in Kurdistan, NW Iran, preserves a unique record of both mechanisms in spatially parallel but temporally distinct Late Cretaceous (Razab) and Eocene (Sarv-Abad) ophiolites. These ophiolites comprise peridotite, gabbroic bodies, a dike complex, and pillowed and massive basaltic lavas. Whole-rock geochemistry, U–Pb zircon geochronology, and field structures reveal distinct ages and tectonic settings for the two ophiolites. While radiolarian cherts constrain the Razab ophiolite to the Cretaceous, new U–Pb zircon (42–38 Ma) geochronology firmly places the formation of the Sarv-Abad oceanic core complex in the Eocene. The Cretaceous Razab unit contains high-Cr# spinel chromitite (0.77–0.82), forearc, and island arc tholeiitic (IAT) lavas, supporting formation during subduction initiation. In contrast, the Eocene Sarv-Abad unit features mylonitized gabbros, syn-extensional dikes, and contemporaneous D-MORB/E-MORB magmatism derived from heterogeneous mantle melting, diagnostic of an Oceanic Core Complex (OCC) in an extensional back-arc. Our results demonstrate that the KWOC was shaped by two distinct geodynamic mechanisms: subduction initiation in the Cretaceous and oceanic core complex formation in the Eocene. Despite ∼50 Myr separation, both units were emplaced during the Miocene closure, suggesting how contrasting mechanisms may have shaped the KWOC. The OCC model also offers a potential resolution to prior ambiguities in the geodynamic evolution of Peri-Arabic ophiolites.