Diverse tectonic settings of formation of the metaigneous rocks in the Jurassic metamorphic accretionary complexes (Refahiye, NE Turkey) and their geodynamic implications

Abstract

Two isolated metamorphic accretionary complexes of Jurassic age, the Refahiye and Kurtlutepe metamorphic rocks, crop out as tectonic slices within the coeval suprasubduction-zone ophiolite at the southern margin of the Eastern Pontides (NE Turkey), close to the İzmir-Ankara-Erzincan suture. The Refahiye metamorphic rocks are made up of greenschist, marble, serpentinite, phyllite and minor garnet amphibolite, garnet micaschist and metachert. The whole unit was metamorphosed under garnet-amphibolite-facies conditions and strongly retrogressed during exhumation. The Kurtlutepe metamorphic rocks consist of subgreenschist-facies metavolcanics, metavolcaniclastics, marble, calc-phyllite, and minor serpentinite and metachert. Metabasites in the Refahiye metamorphic rocks are represented by four distinct geochemical affinities: (i) cumulate "flavor," (ii) alkaline oceanic island basalt (OIB), (iii) enriched mid-ocean ridge basalt (E-MORB) and (iv) tholeiitic island arc basalt (IAB). On the other hand, the Kurtlutepe metavolcanic rocks display only tholeiitic to calc-alkaline island arc geochemical affinities. The metabasic rocks with OIB affinities were interpreted as parts of the accreted oceanic islands, and those with E-MORB affinities as parts of accreted ridge segments close to oceanic islands and/or plume-distal mid-ocean ridges with a mantle previously metasomatized by plume components. The metabasic rocks with IAB affinities might have been derived from the overlying suprasubduction ophiolite and/or arc domain by a number of tectonic or sedimentary processes including tectonic slicing of accretionary complex and overlying fore-arc ophiolite, juxtaposition of the magmatic arc with subduction zone by strike slip faults, submarine gravity sliding and debris flows or subduction erosion. However, totally recrystallized nature of the metabasic rocks together with field relations does not allow any inference on the processes involved. The Kurtlutepe metavolcanic rocks might represent collided and accreted oceanic island arc with the subduction zone. Attempted subduction of an intraoceanic island arc may also explain the magmatic lull during Late Jurassic-Early Cretaceous in the Eastern Pontides.

40Ar-39Ar geochronology and petrogenesis of postcollisional trachytic volcanism along the İzmir-Ankara-Erzincan Suture Zone (NE, Turkey)*

“…Paleotectonic configurations of the southern part of the Pontides imply that the zone corresponding to the IAESZ was an old forearc mantle wedge at least since the beginning of the Mesozoic, which is documented by the overlapping subduction and accretion events (Göçmengil et al, 2013;Topuz et al, 2013;Delibaş et al, 2016;Gülmez et al, 2016). For that reason, the character of the mantle source area of the postcollisional magmatic units along the IAESZ was possibly dictated by highly metasomatized and subduction-related signatures even without any influence of an actively subducting slab, which has also been suggested by recent studies (Yücel et al, 2017).…”

Petrology and 40Ar-39Ar dating of paragneisses from the Devrekani Massif (Central Pontides, Northern Turkey): Implications for the Jurassic high-T metamorphism in an extensional tectonic environment

“…The petrochemical and geochronological results reported here for the Jurassic metamorphic rocks enable a re-assessment of the geodynamic evolution of the Central Pontides, in which there are oceanic subduction-accretion complexes, magmatic arcs and fore-arc sequences formed during the Triassic, Jurassic and Cretaceous (Akdoğan et al, 2017;Okay et al, , Çimen et al, 2018. The presence of the Jurassic subduction-accretion complexes along with the subduction zone ophiolites (Göçmengil et al, 2013;Topuz et al, 2013a,b), and the existence of Jurassic ophiolitic rocks in the Late Cretaceous mélanges, suggest that the subduction zone system was active during the Early to Middle Jurassic period (e.g., Dilek and Thy, 2006;Sarıfakıoğlu et al, 2009;Çelik et al, 2011;Gücer and Aslan, 2014).…”

Distribution of rocks in Pınarbaşı Ophiolite from central Anatolia (Turkey) based on analysis of ASTER and Landsat‐8 data

“…Ophiolites, which are parts of the oceanic lithosphere, contain a wide range of lithologies such as peridotites, gabbros, and basalts and can be observed on the continents and in the accretionary complexes of suture zones (e.g., Çelik, Chiaradia, Marzoli, Billor, & Marschik, 2013; Çelik et al, 2019; Coleman, 1984; Dilek & Furnes, 2009; Moores, 1982; Nicolas, 1989; Steinmann, 1927; Yang et al, 2019). Mapping of ophiolites and accretionary complexes reveals: (a) the plate tectonic history and the emplacement of former oceanic basins (e.g., Çelik et al, 2013, 2016; Çörtük et al, 2016; Göçmengil, Altıntaş, Topuz, Çelik, & Özkan, 2013; Özkan, Çelik, Soycan, Çörtük, & Marzoli, 2020; Topuz et al, 2013), (b) distribution of mantle and crustal rocks of the oceanic lithosphere, and (c) the spatial distribution of associated economic deposits of ore minerals (e.g., chromite, manganese; Aldanmaz, Meisel, Celik, & Henjes‐Kunst, 2012; Çelik et al, 2013, 2016; Çörtük et al, 2016).…”