Geothermobarometry and petrogenesis of Chahar Dahane peridotites, West margin of Makran zone, Hormozgan province, Iran

The study area known as ‘Chahar-Dahaneh’ is part of the Iranian southeast ophiolites related to Alpian-Himalayan Mesozoic orogeny belt, and is located in the western margin of the Makran subduction zone. Chahar Dahaneh peridotite section consists of three major lithologies including: 1.dunite lenses 2. harzburgites and 3. Lherzolite. Based on electron microprobe analysis ,we estimated pressure of 5kb with 10%wt H2O for magma with temperature of about 1150-1200C for the origin of clinopyroxene crystallization and chrome spinels are ferrian palenaste in composition. Enrichment of Al3+ ratio to Fe3+ in spinels from lehrzolites suggest that they formed in lower oxygen fugacity and higher pressure than those spinels in dunites and olivines are forsterite in type with  88-91 Mg#. Based on microprobe datas, Chahar Dahaneh peridotites are related to back arc metasomatised mantle in SSZ tectonic setting.