The Kighal porphyry Cu deposit, in the Arasbaran magmatic belt (AMB), is hosted by Late Eocene to Oligocene volcanic rocks and Miocene high-K calc-alkaline subvolcanic intrusions. The Miocene quartz monzonite stocks host porphyry-style Cu mineralization characterized by potassic, phyllic, argillic, and propylitic alteration zones and an advanced argillic lithocap. The Ar-Ar dating of secondary biotite from the potassic alteration and alunite from the lithocap yields precise ages of 20.10 +/- 0.18 Ma and 19.15 +/- 0.21 Ma, respectively, documenting the evolution of the hydrothermal system over similar to 1 Myr. Hydrothermal rutile occurs in the deposit from the proximal potassic to distal propylitic alteration zones, and their Ti-Fe-Cr-V-W contents can be used as a fertility indicator which suggests a decrease from the proximal zones towards the distal zones. The geochemical fingerprints of the Kighal (and in general the AMB) igneous rocks reflect a post-collisional arc setting. Their distinctly high Th/Yb and Ta/Yb ratios are typical of high-K calc-alkaline intrusions, suggesting that their parental melts were derived from an enriched upper mantle source modified by slab-derived components. Their Sr-87/Sr-86((i)) (0.70427 to 0.70452) and Nd-143/Nd-144((i)) (0.512712 to 0.512754) ratios reveal that the magmas experienced moderate crustal assimilation during their magmatic evolution, also supported by increasing Th/La and Sr-87/Sr-86((i)) and decreasing epsilon Nd-(i) values with increasing SiO2 content. The Pb-206/Pb-204, Pb-207/Pb-204, and Pb-208/Pb-204 ratios of the intrusions (18.67 to 18.84, 15.60 to 15.66, and 38.83 to 39.06, respectively) reveal a crustal origin. Hence, a post-collisional arc setting is proposed for NW Iran, in which mantle-derived mafic melts underwent a MASH process and ascended into shallow magma chambers in the upper crust associated with moderate crustal contamination, which account for the formation of large-scale porphyry Cu mineralization in the AMB.