Textural records and geochemistry of the Kermanshah mantle peridotites (Iran): implications for the tectonic evolution of southern Neo-Tethys

Abstract

Kermanshah Ophiolite Complex (NW Iran), located along the Main Zagros Thrust Zone, marks the ophiolitic suture between the Arabian and Sanandaj-Sirjan continental blocks. N-MORB-normalized multielement patterns and chondrite--normalized REE patterns in the Kermanshah mantle restites show depletion in incompatible elements concentrations with respect to the depleted MORB mantle (DMM). In the V vs. Yb diagram, Harsin-Sahneh-Norabad and Miyanrahan peridotites (Kermanshah Ophiolite Complex), due to their relatively low V contents, fall close to the QFM buffer. Calculated TiO 2 and Al 2 O 3 compositions in the parental melt that were in equilibrium with chromian spinel are consistent with supra-subduction zone-type compositions. Besides, calculated FeO/MgO ratios in the parental melts are comparable with those in boninites from Oman ophiolites. Olivine from the peridotite restites is highly magnesian (Fo 89-93 ) with NiO contents of 0.2-0.4 wt. %, consistent with formation in a forearc environment. This is also proven by the Cr# and Mg# values as well as TiO 2 , Cr 2 O 3 , and Al 2 O 3 concentrations in chromian spinel of ultramafic rocks. Accordingly, petrogenetic modeling indicates that the Kermanshah ultramafic rocks may represent the residual mantle after extraction of 13-23% of boninitic-type melts. Decompression, melting and melt-rock reaction related textures are widespread in the Kermanshah mantle restites. Field relationships and geochemical evidence reveal that the studied ophiolites were a part of a rifted basin at the ocean-continent transition zone formed in the south Neo-Tethyan Ocean.

Effect of Water on the Dislocation Creep of Enstatite Aggregates at 300 MPa

“…The flow behavior of Earth's upper mantle is determined mainly by rheological properties of its constituent minerals such as olivine, orthopyroxene, and garnet. Orthopyroxene (opx) is an important mineral in mantle rocks such as peridotite, harzburgite, and lherzolite (Boyd, 1989;Moradpour et al, 2017). Its content in pyrolite model is as high as 17 wt% (Ringwood, 1975), and its abundance is second only to olivine in the upper mantle.…”

Petrographic characteristics of deep marine turbidite sandstones of the Upper Cretaceous Tanjero Formation, Northwestern Sulaimaniyah, Iraq: implications for provenance and tectonic setting

“…Zagros Suture Zone is the one of the main tectonically active part of the area. In the recent decade some tectonic and evolution studies of Neotethys were done by Alavi (2004Alavi ( , 2007, Karim and Taha (2009), Lawa et al (2013), Sissakian (2013), Malekzade et al (2016), Motaghi et al (2017), Moradpour et al (2017), Koshnaw et al (2018Koshnaw et al ( , 2019.…”