Ilmenite and titanomagnetite geochemistry of the XV Fe–Ti oxide deposit, Bafq–Saqand Metallogenic Province, Central Iran Microcontinent: Implications for Fe–Ti oxide mineralization

The XV Fe–Ti oxide deposit occurs in gabbroic and pyroxenitic rocks of the Bafq–Saqand Metallogenic Province, Central Iran Microcontinent, and is related to a mafic–ultramafic magmatic episode dated at 363 ± 67 Ma. This contribution uses in situ LA–ICP–MS trace–element analyses of titanomagnetite and ilmenite to evaluate the origin, physicochemical evolution, and metallogenic significance of the Fe–Ti oxide assemblage. Titanomagnetite contains 42.73–91.97 wt.% FeO t , 0.91–50.66 wt.% TiO 2 and 0.10–1.19 wt.% V 2 O 3 , whereas ilmenite contains 15.74–48.11 wt.% FeO t , 49.10–60.02 wt.% TiO 2 and 0.01–0.24 wt.% V 2 O 3 . The two minerals are enriched in Si, Al, Ca, Mg, Mn, Ti and V and show comparatively low Ni, Cr, Co and Ga. Titanomagnetite mostly plots in high–temperature magmatic Fe–Ti–V fields, with restricted overlap toward Kiruna–type and porphyry–related compositions, indicating that the original magmatic signal was largely retained but was not completely immune to post–crystallization effects. Ilmenite lamellae in titanomagnetite record two sub–solidus stages: relatively coarse trellis– and sandwich–type lamellae related to high–temperature oxidation–exsolution of ulvöspinel–rich titanomagnetite, and later fine intergrowths produced during lower–temperature re–equilibration below the magnetite–ulvöspinel solvus. These data indicate an evolution involving fractional crystallization, enrichment of Fe, sub–solidus unmixing, and limited oxidative modification. We infer that differentiation of a hydrous, oxidized, P–bearing mafic magma generated an Fe–Ti–rich melt that separated from the silicate liquid and accumulated as disseminated to net–textured titanomagnetite–ilmenite among earlier silicate minerals. The XV system is therefore interpreted as dominantly magmatic, with late–stage liquid immiscibility and oxide accumulation as the main ore–forming mechanisms and only localized fluid–related overprinting.