Study of chromite-hosting peridotites from Neyriz ophiolite, Abadeh Tashk area, Fars province by using mineralogical data


Department of Earth Sciences, Faculty of Sciences, Shiraz University, Iran


The Neyriz ophiolite in Abadeh-Tashk area is mainly comprised of ultramafics that are residuals after partial melting in upper mantle. The partial melting degree of the rocks increases from lherzolite to harzburgite and then to dunite that is indicated by mineralogical modal composition of the rocks. Variation in the modal composition is accompanied by the chemical changes in composition of olivines and spinels in these rocks. Fo in olivines increases from lherzolite (91.5-90.79) to harzburgite (91.56-91.23) and then to dunite (94.86-91.75). Increases of Cr# from 56.34 in lherzolite to 79.36 in dunite and decreases in Mg# from 41.05 in lherzolite to 32.56 in dunite are determined in spinels from the same rocks. Cr#, Mg#, Al2O3 and TiO2 values in chromian spinels indicate that the peridotites of Neyriz ophiolite are formed by high degree of partial melting in forearc environment at a supra-subduction setting zone (SSZ).   


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