Petrology of the Ispendere, Kömürhan and Guleman Ophiolites (Southeast Turkey): Subduction Initiation Rule (SIR) Ophiolites and Arc Related Magmatics

DOI: 10.5176/2251-3353_GEOS14.31

Authors: Melahat Beyarslan and A.Feyzi BİNGÖL

Abstract: The Ispendere, Kömürhan and Guleman ophiolites situated in the central part of the southeastern Taurus, are remnants of late Cretaceous suprasubduction zone (SSZ) oceanic lithosphere that was developped in Southern Tethys. All these ophiolites are coeval in age and contain crustal sequences of an ideal ophiolites. Guleman ophiolite contains mantle peridotites while, due to intense tectonic, the mantle peridotites are missing in the Ispendere and Kömürhan ophiolites. The ophiolites are related with the Elazig magmatics composed of basaltic-andesitic pillow lavas ans lava flows, andesitic pyroclastics, dacite intruded by calc-alkaline plutonic rocks. The crustal section of the Ispendere and Kömürhan ophiolites contain ultramafic and mafic dykes and stocks in the gabbros. The ultramafic intrusive rocks including wehrlite and clinopyroxenite gradually passing to plagioclase wehrlite and mafic gabbro. The crystallization order of the cumulate rocks is characterized by olivine-chlinopyroxene-plagioclase. The harzburgitic mantle peridotite, the presence of ultramafic dykes and stocks in layered gabbros, the crystallization order of cumulates indicate a forearc and an island arc settings. The basaltic pillow lavas and lava flows have MORB-like features while, the andesite and plutonic rocks composed of diorite-tonalite-granodiorite-granite, have calc-alkaline features, because subduction initiation progressed until establishment of a mature subduction zone. This chemostratigraphic evolution reflects formation of what ultimately becomes forearc lithosphere as a result of mantle melting that is progressively influenced by subduction zone enrichment during subduction initiation. MORB-like lavas result from decompression melting of upwelling asthenosphere and are the first magmatic expression of subduction initiation. The fluids from dehyrating oceanic crust and sediments result melting in depleted harzburgitic residue and form the ultramafic stocks in gabbros. With subduction stabilization, island arc forms. The ophiolites formed these prosesses are called “subduction initiation Rule” ophiolites.

Keywords: Ispendere, Kömürhan, Guleman, ophiolite, suprasubduction zone, subduction initiation rule, island arc