Iron isotopic constraints on the origin of peridotite and chromitite in the Kızıldağ ophiolite, southern Turkey

- The first Fe isotopic study of the Kızıldağ ophiolite
- Equilibrium Fe isotope fractionation between major minerals in harzburgites
- Large and disequilibrium Fe isotope fractionation in dunites and chromitites
- Fe isotopic constraints on the origin of the peridotites and chromitites

The first data set of high-precision Fe isotopic compositions of olivine, orthopyroxene and chromite from harzburgites, dunites and chromitites from the Kızıldağ ophiolite, southern Turkey is reported here. The Fe isotopic compositions of the minerals are variable, with δ56Fe ranging from 0.005‰ to 0.222‰ in olivine, from − 0.005‰ to 0.024‰ in orthopyroxene and from − 0.214‰ to 0.072‰ in chromite. The forsterite contents and δ56Fe values of the olivine in the harzburgites and dunites range from 90.5 to 90.9 and from 0.005‰ to 0.050‰, respectively, similar to the values of abyssal peridotites. The Fe isotope variations of the minerals together with petrological features and major elemental compositions, suggest a residual origin for the harzburgites and an accumulation process associated with the dunite formation. The δ56Fe of the chromite correlates positively with Fe3 +/Fetotal ratio and negatively with FeO content, indicative of correlations with mantle oxygen fugacity and fractional crystallization. Comparisons between the results from the Kızıldağ and those from Luobusa ophiolite indicate that these chromitites were most likely formed by the change of oxygen fugacity and magmatic differentiation.