Major-Trace Element Signatures of Sulfides and Oxides and Implications for Ore-Forming Mechanisms in the Northeast Saveh Epithermal System, Central Urumieh–Dokhtar Magmatic Arc (Iran)

We have investigated the major- and trace-element composition of hydrothermal pyrite, magnetite, and titanomagnetite, and of the principal Cu-minerals chalcopy-rite and chalcocite, to constrain ore-forming processes in the northeastern Saveh district (central Urumieh–Dokhtar magmatic arc, Iran). Our data provide new con-straints on the magmatic–hydrothermal evolution and subsequent hydrothermal–supergene modification of the ore system. Titanomagnetites hosted in shallow monzo-dioritic intrusions are enriched in Ti–V–Al, plot below the magnetite–ulvöspinel join and record high crystallization temperatures (< ~500 °C) under rela-tively low oxygen fugacity. By contrast, magnetites from silica-rich hydrothermal veins are relatively Fe-rich, have very low TiO₂, formed at intermediate tempera-tures (~200–300 °C) under higher fO₂, and show pronounced depletion in Ti and V relative to monzo-dioritic oxides. Textures and oxide systematics (Al+Mn vs Ti+V; V/Ti–Fe) document repeated hydrothermal pulses, Fe²⁺ leaching and element redis-tribution during cooling and fluid–rock interaction. Geochemical trends indicate progressive evolution from a magmatic fluid to later meteoric water overprint, with decreasing As contents reflecting mixing with oxidizing meteoric waters. Vertical elemental zoning suggests that most samples represent mid- to deep-level sections of the epithermal system. Elevated Cu contents (up to 0.95 wt.%) highlight pyrite as a significant Cu host. Co/Ni ratios between 1 and 10 further corroborate a magmatic–hydrothermal origin. Chalcopyrite is the principal economic Cu carrier at Northeast Saveh. Replacement follows a temperature- and fluid-controlled pathway (chalco-pyrite → covellite → chalcocite/digenite). At lower temperatures (< ~200 °C) re-placement proceeds more slowly, producing chalcocite/digenite under prolonged reaction conditions. Chalcocite commonly occurs as thin replacement rims and fracture fills that concentrate remobilized copper. Collectively, the investigated oxide and sulfide proxies provide robust discriminants for separating magmatic versus hydrothermal domains and for vectoring toward higher-temperature feeders and zones of remobilized copper.