Geochemistry and petrogenesis of mantle peridotites from the Nehbandan Ophiolitic complex, Eastern Iran

Ophiolitic exposures from the East and Northeast of Nehbandan. Eastern Iran, are remnants of a Cretaceous oceanic basin between Lui and Afghan continental blocks. Based on petrographic studies, they contain harzburgite. clinopyroxene-harzburgite and Iherzolite equilibrated in spinel peridotite fades. Chemistry of clinopyroxene in Iherzolite is characterized by low Na20 and TiO2, contents suggesting sub-oceanic origin. Spinel is a ubiquities accessory phase yielding chromium number [Cr# = l00*Cr/(Cr+Al)] in the range of 31-37 and 15-21 for harzburgite and Iherzolite. respectively. Melting degrees on the basis of spinel chemistry is 5 to 8% for Iherzolite and 12.5 to 14.2% for harzburgite. Cr# of magmalic spinel is 50-51 which correlate with Al-rich type of podiform chromitites. Whole-rock chemistry shows that most of the peridotitic samples exhibit evident U-shaped primitive mantle-normalized rare earth element patterns. In addition, in multi-element diagrams, relative to neighboring ra...