The Zaker iron deposit is located in northeastern Zanjan within the Tarom subzone and the Tarom–Hashtjin metallogenic belt, northwestern Iran. The study area is situated in the northern part of the deposit. Iron mineralization is mainly hosted by the Late Eocene Tarom intrusive body, which intruded the volcanic rocks of the Karaj Formation. Magnetite is the principal ore mineral, and the mineralization exhibits massive, vein-veinlet, stockwork, banded, and brecciated textures. Apatite is the most abundant associated mineral, accompanied by pyroxene, actinolite, pyrite, chalcopyrite, and late quartz and calcite veinlets. The host intrusive rocks display a granular texture and are composed mainly of plagioclase, alkali feldspar, quartz, and clinopyroxene. Geochemically, the intrusion is classified as quartz monzonite with shoshonitic affinity and belongs to the high-K calc-alkaline to alkaline series and I-type granitoids. Trace-element and rare earth element geochemistry indicates that the parental magma was generated in a subduction-related continental arc setting. Mineralization is interpreted as a magmatic–hydrothermal magnetite-apatite system formed during the late stages of magma evolution through the crystallization of magnetite and apatite from Fe- and P-rich magmatic fluids. Ore formation initiated with oxide mineralization, characterized by magnetite, apatite, and coarse-grained pyroxene precipitated within fractures and joints of the newly emplaced intrusion, followed by sulfide mineralization represented by pyrite and chalcopyrite. Structural investigations indicate that localized extensional tectonics controlled the emplacement of the ore bodies, producing fracture patterns comparable to en echelon extensional fractures developed within dextral strike-slip shear zones. Subsequent compressional, extensional, and dextral strike-slip deformation phases affected the region from the Late Paleogene to the Quaternary. The integration of petrographic, alteration, structural, and geochemical evidence confirms the magmatic–hydrothermal origin of the Zaker iron mineralization and its genetic relationship with high-K calc-alkaline magmatism in an active continental margin.