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

Abstract

The first data set of high-precision Fe isotopic compositions of olivine, orthopyroxene and chromite from harzburgites, dunites and chromitites from the KIzIldag ophiolite, southern Turkey is reported here. The Fe isotopic compositions of the minerals are variable, with delta Fe-56 ranging from 0.005 parts per thousand to 0.222 parts per thousand in olivine, from -0.005 parts per thousand to 0.024 parts per thousand in orthopyroxene and from -0.214 parts per thousand to 0.072 parts per thousand in chromite. The forsterite contents and delta Fe-56 values of the olivine in the harzburgites and dunites range from 90.5 to 90.9 and from 0.005 parts per thousand to 0.050 parts per thousand, 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 delta Fe-56 of the chromite correlates positively with Fe3+/Fe-total ratio and negatively with FeO content, indicative of correlations with mantle oxygen fugacity and fractional crystallization. Comparisons between the results from the KIzIldag and those from Luobusa ophiolite indicate that these chromitites were most likely formed by the change of oxygen fugacity and magmatic differentiation. (C) 2015 Elsevier B.V. All rights reserved.