Investigation of parent magma evolution and origin of chromites in Cheshmeh-Bid, in ophiolite of Neyriz, Fars

Cheshmeh-Bid chromite deposit is located in Nayriz ophiolite, about 200 km northeast of Shiraz. The ophiolite sequences in this area include ultramafic rocks (dunite, harzburgite, and pyroxenite). In this deposit, chromites are present in the mantle-crust transition zone and are enclosed by dunite. Based on chemical studies of major elements, chromite is depleted from Al and Ti elements and enriched by Fe, Cr and Mg. The calculated values of TiO2, Al2O3 and FeO/MgO indicates that the parent magma is the Boninite magma type with composition equilibrium to the podiform chromites. These chromitites are the result of relatively high melting of the mantle and Boninite melt, which are formed as a result of rising and mixing of magma with mantle harzburgites in the upper environment of the subduction zone. Variations in the chromite mineral composition along with the textural changes in host ores indicate the injection of at least two mineralizing melts in the study area.