Petrology and Geochemistry of Noor abad ophiolite (Lorestan province, west Iran): an evidence of intra-oceanic subduction

Abstract

The Noorabad ophiolite is part of Kermanshah ophiolites in NW of Lorestan province, west Iran. The Kermanshah ophiolite complex with NW-SE trending is located in the SSW of the main Zagros thrust fault within the high Zagros zone. Rocks of the Noorabad ophiolite include diabases dikes, basalts lava and andesite that outcropped in the south of the Noorabad. These rocks are intensly altered and fractured that led to hydrothermal alteration and replacement of primary minerals such as pyroxene, plagioclase and opaque minerals by secondary minerals. Based on geochemical studies, the rocks of this area have tholeiitic and calc-alkaline signature. Also the plotted rock samples in geochemical discrimination diagrams, occur in island arc basalt (IAB) field. These rocks show depletion in HREE and HFSE and also are enriched in LILE and LREE. These patterns suggest that these rocks formed in intra-oceanic subduction zone. These geochemical characteristics along with comparison with other ophiolitic rocks in east Mediterranean reveal a subduction zone environment for genesis of the intermediate and mafic rocks of the Noorabad ophiolite.