Petrology of ultramafic to mafic cumulate rocks from the Goksun (Kahramanmara) ophiolite, southeast Turkey

The Goksun (Kahramanmaras) ophiolite (GKO), cropping out in a tectonic window bounded by the Malatya metamorphic unit on both the north and south, is located in the EW-trending lower nappe zone of the southeast Anatolian orogenic belt (Turkey). It exhibits a complete oceanic lithospheric section and overlies the Middle Eocene Maden Group/Complex with a tectonic contact at its base. The ophiolitic rocks and the tectonically overlying Malatya metamorphic (continental) unit were intruded by I-type talc-alkaline Late Cretaceous granitoid (similar to 81-84 Ma). The ultramafic to cumulates in the GKO are represented by wehrlite, plagioclase wehrlite, olivine gabbro and gabbro. The crystallization order for the cumulate rocks is as follows: olivine +/- chromian spinel -> clinopyroxene -> plagioclase. The major and trace element geochemistry as well as the mineral chemistry of the ultramafic to mafic cumulate rocks suggest that the primary magma generating the GKO is compositionally similar to that observed in the modern island-arc tholeiitic sequences. The mineral chemistry of the ultramafic to mafic cumulates indicates that they were derived from a mantle source that was previously depleted by earlier partial melting events. The highly magnesian olivine (Fo(77-83)), clinopyroxene (Mg# of 82-90) and the highly Ca-plagioclase (An(81-89)) exhibit a close similarity to those, which formed in a supra-subduction zone (SSZ) setting. The field and the geochemical evidence suggest that the GKO formed as part of a much larger sheet of oceanic lithosphere, which accreted to the base of the Tauride active continental margin, including the Ispendere, Komfirhan and the Guleman ophiolites. The latter were contemporaneous and genetically/tectonically related within the same SSZ setting during the closure of the Neotethyan oceanic basin (Befit Ocean) between the Taurides to the north and the Bitlis-Pfitfirge massif to the south during the Late Cretaceous. (C) 2019, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.