Ophiolite gabbro from source to sink: A record of tectonic and surface processes in Central Anatolia

摘要

Ophiolitic rocks derived from Tethyan seaways are abundant in Anatolia; many are in arrays that mark sutures between Eurasia, Gondwana, and continental ribbons and island arcs. Ophiolitic fragments also occur dispersed between sutures, indicating tectonic transport of possibly hundreds of kilometers. Scattered fragments of the Central Anatolian Ophiolite (CAO) have been interpreted as originating in oceans to the north, west, and/or south of their current locations, with implications for the magnitude and direction of transport and the relation of ophiolite obduction to regional metamorphism of the underlying continental-margin terrane (Central Anatolian Crystalline Complex [CACC]). Ophiolitic clasts (primarily gabbro) are widespread in sedimentary basins and alluvial terraces, particularly in the southern CACC. Petrologic and geochemical data from (meta)gabbro outcrops, gabbro clasts in conglomerates, and gabbro cobbles on alluvial terraces near the Ni?de Massif, a metamorphic dome at the southern tip of the CACC, indicate paleosources and can be used to reconstruct the history of ophiolite emplacement, metamorphism, erosion, and dispersal. (Meta)gabbro at the northern margin of the Ni?de Massif is geochemically similar to CAO gabbro: both have low Ti/V and depleted high field strength elements, typical of boninitic (forearc) magma, although Ni?de mafic and associated ultramafic rocks were metamorphosed at middle to upper amphibolite facies, and the rest of the CAO were metamorphosed at (sub)greenschist-facies conditions. Amphibolite-facies mafic and ultramafic rocks near the contact with underlying CACC metasedimentary rocks have been ductilely deformed in mylonitic high-strain zones with top-to-south kinematics likely related to tectonic interleaving of ophiolitic and continental margin rocks at depth. The confinement of high-grade metaophiolite to the southern tip of the CACC may indicate oblique and diachronous obduction from south to north.Whole-rock trace-element data for gabbro clasts indicate that early to middle Miocene sediments were derived from mixed sources (CAO and Tauride ophiolites), whereas later Miocene sediments were sourced entirely from the CAO, even those on the opposite side (south) of the Ni?de topographic high. These results may indicate that late Miocene uplift and arching of the Tauride Mountains at the southern margin of the Central Anatolian plateau drove reorganization of sediment dispersal and topographic disconnection of Miocene depocenters from their CAO sources.