Study of mantle peridotites of Surk ophiolitic melange (Yazd province, Iran)

The Surk ophiolitic melange, as a narrow belt, is located in western part of Yazd province, between the southwest of Central Iran and Urumieh-Dokhtar magmatic arc, along Naein-Dehshir-Baft fault. This ophiolitic melange consists of mantle peridotites, gabbro, diabasic dykes, quartz andesite, dacite, serpentinite, listwaenite, rodingite, chert and Upper Cretaceous limestones. Petrography and mineral chemistry of mantle peridotites reveal incongruent melting of orthopyroxenes, the formation of excess olivines, the high value of Cr# in spinels of harzburgite and dunite and the occurrence of pargasitic amphibole in lherzolites in the studied ophiolite. All of these evidences suggest melt/oceanic lithosphere reaction. The reactive melt originated from a subducted slab that decreases the melting temperature of the lithospheric mantle and leads to widespread ascending melt/wall rock reaction. The peridotites of this ophiolitic melange consist of harzburgite, dunite and lherzolite in decreasing order. The ophiolite is a harzburgite type ophiolite (HOT) showing characteristics of supra subduction zone ophiolites (back-arc basin).