SUBDUCTED BASALTS AND SEDIMENTS AS SOURCES FOR FELSIC DYKES IN THE MAWAT OPHIOLITE, NE IRAQ

In Press, Journal Pre-proof, Available online 24 October 2020

Abstract

The Mawat ophiolite is a fragment from the Neo-Tethyan oceanic lithosphere and is regarded as the largest and best-exposed ophiolite within the Zagros Suture Zone, northeast Iraq. Field work, petrology, and geochemical data of felsic intrusive rocks in Mawat ophiolite are investigated. The felsic dykes are classified into two types: oceanic plagiogranites in western (Mirza and Ismail, 2007), and leucogranites in central (Mohammad et al. 2014) Mawat ophiolite, here called tonalites and granites, respectively. Both types, but variously mixed, occur in the eastern felsic dykes. The tonalites are weakly peraluminous to metaluminous and are low in K₂O and TiO₂ and high in Na₂O. The granites are strongly peraluminous, moderate to high in K₂O and Na₂O, and very low in TiO₂. The western tonalites are similar to adakites and are interpreted to have derived from melts from subducted oceanic slab interacted with the mantle. The eastern tonalites have gone through hornblende and plagioclase fractionation in a shallow-level magma chamber modifying their original compositions. The granites are interpreted to have derived from the melted psammitic sediments on top of the subducted slab. The tonalitic and granitic melts were partially mixed and fractionated in shallow level in eastern Mawat.