The study of north Makran ophiolitic mélange tectonic setting based on mineral chemistry, southeast of Iran

The study area, as a part of north Makran ophiolitic melange, is located in Southeast of Iran. This ophiolitic complex contain a relatively complete sequence of oceanic lithosphere with well preserved mantle and crust sequences. The dominant structures are WNW-ESE thrust faults with north-northeast dip resulting a SSW-ward transportion. Peridotite (harzburgite, dunite and lherzolite) is the most abundant rock type in mantle sequence of this complex. Olivine, orthopyroxene, clinopyroxene and a few spinels are the main rock forming minerals, and granular, poikilitic and mesh are their main textures. Electron microprobe analyses of olivine, orthopyroxene, clinopyroxene and spinel in harzburgites and dunites show that olivine is forsterite (Fo:87-90), orthopyroxene is enstatite (En:88-91), clinopyroxene is diopside (En:44-48, Wo:48–52), and spinel is Al-Cr bearing (Spl:54-69, Chr:21–36) type. The mean values of Mg# (Mg#=Mg/(Mg+Fe+2) in olivine, clinopyroxene, respectively are 0.86, 0.92, 0.96 and Cr# (Cr#=Cr/Cr+Al+Fe3+) in spinel is 0.27. The chemical composition of olivine and spinel indicate that the peridotites are of abyssal type, belong to sub-oceanic crust mantle, and endured 10 to 15 % partial melting. Based on discriminant diagrams, Makan peridotites represent mid oceanic ridge affinities with no distinguishable and conclusive subduction influence. Therefore, north Makran ophiolite formed in an extensional basin between the central Iranian microcontinents (Lut block), to the north-northeast, and the continental sliver of Bajkan-Durkan complex to the south-southwest.