Subduction-related magmatism (SRM) and its effect on magma fertility: Oligocene–Miocene plutonism evolution in the centre of Urumieh–Dokhtar magmatic arc, Iran

This study explores the Oligocene–Miocene subduction-related plutonic rocks (OMPs) from the central Urumieh–Dokhtar Magmatic Arc (UDMA) in the centre of the Alpine–Himalayan Orogenic Belt (AHOB). OMPs range in composition from gabbro/diorite ( c. 34–32 Ma) to tonalite ( c. 20 Ma) with geochemical signatures of metaluminous calc-alkaline I-type granitoids. Geochemical analyses reveal enrichment in large ion lithophile elements and light rare earth elements relative to high-field-strength elements and heavy rare earth elements (La N /Yb N = 3.05–4.45). Mineral and whole-rock chemical variations reflect lower crust melting to crustal contamination over time, and magmatic chamber evolution. OMP chemical evolution can be attributed to two key factors: (1) incorporation of Th-rich sediment/crustal components from progressive lower crustal melting and (2) injection of fertile mantle melts altering magma chamber composition. These factors rendered the OMPs barren in Cu-mineralization but suggest a possible potential Cu mineralization in Miocene intrusive rocks, where the enriched mantle fluids, derived from the subducted slab, were more pronounced. This study proposed a geodynamic model to improve our understanding of the UDMA magmatic evolution. Comparison of subduction-related magmatism plutonic rocks from the central UDMA, southern Tibet and western Anatolia highlights the evolution of slab dynamics, crustal thickening and extensional processes in ‘Oligocene–Miocene’ magmatism during the eastward closure of Neotethys along the AHOB.