Petrography and Geochemistry of ophiolitic peridotite from Marivan-Kamyaran region, Zagros (western Iran)

The peridotites from Marivan-Kamyaran ophiolite suite (MKO), outer Zagros ophiolite belt, western Iran, are studied for the petrological and geochemical characteristics. Both mantle and crustal peridotites are present in the Marivan-Kamyaran ophiolitic sequence. Extensive compositional variations in MgO, Al2O3, Cr, Ni and Al2O3 / SiO2, combined with the abyssal (MOR) and supra-subduction zone (SSZ) nature of the peridotites, are indicative of variant degrees of depletion of the mantle peridotites. Various degrees of depletion are consistent with a wide range of partial melting percentages (10-15%) obtained from non-modal backward partial melting models. The enrichment in HFSE such as Hf, Ti, Ta and Th indicates melt-rock interaction in the mantle peridotites; while, the enrichment in U and LIL elements such as Cs, Rb, Pb is most probably related to the fluid-rock interaction. It is suggested here that MOR nature of a part of the mantle peridotites in the region has been changed to SSZ characteristics in later stages through processes such as melt-rock interaction. It is likely that, similar to other occurrences of outer Zagros ophiolite belt, mantle peridotites from MKO with MOR and SSZ characteristics had been originated in MOR setting, before their composition were modified in a SSZ environment.