The Majid Abad Cu prospect, located 32 km northeast of Ahar (northwestern Iran), lies within the Arasbaran metallogenic zone, characterized by subduction-related Cenozoic magmatism and diverse mineralization. The area consists of Eocene lava flows and pyroclastic rocks intruded by Oligocene gabbroic and monzodioritic bodies, the latter closely linked to hydrothermal alteration and copper mineralization. This study integrates field observations, petrography, geochemistry, ore mineralogy, and fluid inclusion data to elucidate the petrogenesis and mineralization processes. Geochemical features of igneous rocks indicate calc-alkaline to high-K calc-alkaline compositions. Enrichment in LREE and LILE with negative Nb, Ta, and Ti anomalies suggests low-degree partial melting of a metasomatized mantle source in a continental arc setting. Hydrothermal alteration shows well-defined potassic, phyllic, argillic, and propylitic assemblages, with quartz–sulfide stockwork mineralization concentrated in the phyllic and potassic zones. The potassic–phyllic transitional zone hosts the main mineralization, consisting primarily of pyrite and chalcopyrite, with minor bornite. Fluid inclusions yielded homogenization temperatures of 142–567 °C and salinities of 4–53 wt% NaCl eq., indicating magmatic–hydrothermal fluids typical of porphyry Cu systems. In this regard, Majid Abad represents a low-grade porphyry-type Cu, with an average Cu grade of 0.2 wt.% and an average Au grade of 0.2 ppm.

Keywords: Majid Abad, Porphyry copper, Geochemistry, Hydrothermal alteration, Fluid inclusion.