Neo-Tethyan Tectonic Evolution: Implications from Petrogenesis of Mafic Rocks in the Bulfat Complex, Zagros Suture Zone, Northeast of Iraq

The Bulfat Complex in the Penjween-Walash Subzone of the Zagros Suture Zone, northeast of Iraq, comprises mafic, granitoid, and ultrabasic rocks over an area of 100 km². This study investigates the petrogenesis and tectonic setting of mafic rocks from the Kela suite, located northeast of Darshmana village in the Qala Diza area, through petrography, mineral chemistry, and geochemistry. The studied mafic rocks of the Bulfat Complex predominantly consist of plagioclase, pyroxene, and olivine minerals and are classified as gabbro, olivine gabbro, and troctolite. Those rocks display a wide range of igneous textures, including granular, ophitic, sub-ophitic, poikilitic, corona, porphyroclastic, exsolution, and mesh textures. Mineral chemistry Electron Probe Micro Analyses analyses show plagioclase (bytownite–labradorite), diopside clinopyroxene, chrysolite olivine, and secondary calcic amphibole, mainly pargasite. Whole-rock ICP-MS analysis reveals high SiO2, MgO, Al2O3, Fe2O3, CaO, and low alkalis and TiO2 with calc-alkaline to subalkaline affinity. The REE patterns show enrichment in LREEs (La/Sm)n=1.43, compared to HREEs. The enrichment in LILE (Sr and Ba) and depletion in HFSEs (Nb and P) indicate an island arc environment. Tectonic discrimination diagrams, together with negative Nb-Zr anomalies and positive Sr-Ba-K anomalies further support formations in subduction-related arc setting. Whole-rock geochemical data, Fe-Mg enrichment, and trace element characteristics suggest fractional crystallization from mantle-derived magmas. Geothermobarometry yields crystallization temperatures of 750-1016˚C (average 890˚C) and a pressure of 5-10 kbar (average 6.5 kbar), corresponding to an emplacement depth of 19-21 km under a warm subduction zone. These conditions reveal a low-angle subduction of old Neo-Tethyan (Albian-Cenomanian) and a slow convergence rate (< 2 cm/ year), yielding an estimated total convergence distance of the Neo-Tethyan Ocean to be around 324 km during Paleogene subduction.