Mineral chemistry and thermobarometry of Kurdistan ophiolitic peridotites, Zagros, western Iran

The mineralogical composition and geothermobarometry of the peridotites from the Marivan-Kamyaran ophiolitic complex, as a part of the Neo-Tethyian ophiolites in the Zagros Mountains, western Iran, are investigated. The studied samples are belonged to mantle and crustal peridotite types. Results of electron probe microanalysis in peridotites indicate that olivine is forsterite (Fo87-Fo92), clinopyroxene is augite-diopside (En48-56Fs3-6Wo39-49) and orthopyroxene is enstatite (En90-91). Cr-number (Cr#) and Al-number (Al#) in spinels of the mantle peridotites are 33-59 and 41-67, respectively. The same values in spinels of the crustal peridotites are 67-98 and 2-32, respectively. Geothermobarometry calculations for the mantle peridotites show average temperature of ~1104°C and average pressure of ~14 kbar. The crustal peridotites are formed at ~900 °C and ~7 kbar. Two distinct mineral chemistry of the mantle peridotites indicate existence of two types of mantle peridotites in the area, suggesting the possibility of the influence of melt-rock interaction on the chemical composition of the mantle peridotites in the area.