Mineralogy, Geochemistry and Thermobarometry of Gneisses from Soltanabad Metamorphic Complex (NE Sabzevar)

Soltanabad metamorphic complex cropped out in the ophiolitic range of NE Sabzevar. There is a distinict gneissic body in this complex associated with metabasite, serpentinite and adakitic intrusions. Quartz, albite, epidote, amphibole, garnet and chlorite are rock forming minerals of gneissic samples. On the basis of abundance of light and dark minerals, different types of felsic, intermediate and mafic gneisses are distinguishable. Average metamorphic conditions of gneisses from Soltanabad complex is calculated as 462 (±39)°C at pressure of 12.4 (±2.15) kb which can be predominant in hot thermal regime of a subduction setting. Whole rock chemistry of investigated gneisses indicates their plagiogranitic composition that produced by partial melting of mafic sequence of oceanic crust. Isotopic ratios of Hf from Zr and REE pattern confirm MORB affinity of these gneisses. The gneisses from Soltanabad metamorphic complex display considerable compositional similarity with plagiogranite fron Iran and Cyprus ophiolitic zones. Geochemical characteristics of these gneisses are comparable with plagiogranites of supra-subduction zone setting as well. Probably gneisses and blueschists of Soltanabad metamorphic complex represent plagiogranites and mafic rocks of Sabzevar oceanic lithosphere that have experienced subduction zone metamorphism.