Petrology of mantle peridotites and volcanic rocks of the narrowest Mesozoic ophiolitic zone from Central Iran (Surk area, Yazd province)

The Surk ophiolitic melange, as a narrow belt, is located between the southwest of the Central Iran and Urumieh-Dokhtar magmatic arc, along the Naein-Dehshir-Baft fault. This ophiolitic melange consists of mantle peridotites (harzburgite, lherzolite and dunite in decreasing order), gabbro, diabasic dykes, dacite, serpentinite, listvenite, rodingite, chert and Upper Cretaceous limestones. Petrography and mineral chemistry of mantle peridotites reveal formation of excess olivines by incongruent melting of orthopyroxenes, occurrence of K-free pargasitic amphibole in lherzolites and increasing value of Cr# of spinels from lherzolite to harzburgite to dunite. Whole rock chemistry of volcanics in this ophiolite suggests the effect of subducted oceanic slab on their productive magma, cause to presence of silica-oversaturated volcanic rocks (dacite). All above petrography and mineral chemistry evidences and field relationships (such as transitional succession of lherzolite-harzburgite-dunite, and absence of lherzolite-dunite contact) suggest melt/mantle peridotite reaction. This reactive melt originated from a subducted oceanic slab that decreases the melting temperature of the lithospheric mantle and leads to widespread ascending melt/rock reaction. The Surk ophiolitic melange is a HOT type ophiolite and has characteristics of supra-subduction zone (back arc basin) ophiolites.