Fe-Ti oxide minerals geothermometry and oxygen fugacity at the Dar Gaz anomaly, Kahnuj

In the southeast of Iran, occurrence of titaniferous magnetite deposits associated with the gabbroic rocks occur in Kahnuj ophiolitic complex. Petrogenetic studies have revealed the primary and secondary mineral constituents of the ores such as titanomagnetite, ilmenite, hematite, goethite, martite, pyrite, chalcopyrite, pyrrhotite and silicate gangue minerals. Various crystallographic intergrowths such as trellis - sandwich textures and ilmenite-titanomagnetite intergrowths are resulted from oxidation of former Ti-rich magnetite at different temperatures. Chemical analyses show that the ilmenite and magnetite (titanomagnetite) contains 46.51 to 52.68 and 4.00 to 19.71 wt.% TiO2 and 1.00 to 2.98 and 0.00 to 1.74 wt.% V2O3, respectively. The ulvöspinel component (Fe2TiO4) in titanomagnetite shows a composition ranging from 4.58 to 56.87 wt.%, and ilmenite lamellae are varying thickness and ilmenite type 1 to 3 contain of 88.23 to 93.94, 93.04 to 99.80 and 99.09 to 99.73 wt.% of the ilmenite component, respectively. Compositions of intergrowth Tm-Ilm pairs (type 2) were plotted on T/fO2 diagrams. The Tm-Ilm pairs show varying degrees of re-equilibration to subsolidus temperatures (551 to 830°C) and fO2 (-21.6 to -23.97), thus depicting the T/fO2 trajectory as the rocks cooled. The Tm-Ilm pairs from Dar Gaz cluster around the QFM buffer curve for 1.5 kbar total pressure.