Early–Middle Jurassic intra-oceanic subduction in the İzmir-Ankara-Erzincan Ocean, Northern Turkey Ömer Faruk Çelik a, ⁎, Andrea Marzoli b , Robert Marschik c , Massimo Chiaradia d , Franz Neubauer e , İlknur Öz a a Kocaeli Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği Bölümü, 41380 Kocaeli, Turkey b Dipartimento di Geoscienze, Università di Padova, 35100-Padova, Italy c Department of Earth and Enviromental Sciences, Ludwig-Maximilians Universität, 80333 Munich, Germany d University of Geneva, Section des Sciences de la Terre, CH-1205 Geneva, Switzerland e Department Geography and Geology, University of Salzburg, Hellbrunner Str. 34, A–5020 Salzburg, Austria abstract article info Article history: Received 8 July 2010 Received in revised form 4 June 2011 Accepted 9 June 2011 Available online 2 July 2011 Keywords: Geochronology Intra-oceanic subduction Mélange Ophiolite Suture belts Neo-Tethys The İzmir-Ankara-Erzincan suture zone near Çankırı comprises an ophiolite-related rock suite of amphibolite, pyroxene-amphibolite and epidote-amphibolite. The geochemical data reveal that the basaltic protoliths of the Çankırı amphibolite suite are derived from different mantle sources. Amphibolites showing a LREE enrichment in chondrite-normalized REE pattern, relatively high La N /Yb N (8.5–13.1), Sm/Yb (2.8–3.7), Ce/Sm (8.8–9.8), Nb/Yb (14.4–20.5), Th/Nb (1.1–2.6) originate from an OIB-like (Type I amphibolites) mantle source. Those with flat chondrite-normalized REE pattern, low La N /Yb N (~ 0.6), Sm/Yb (~ 1.0), Ce/Sm (~ 2.7) Nb/Yb (~ 0.6), suggest derivation from a depleted MORB-like (Type II amphibolites) mantle source. A third type of amphibolite is characterized by La N /Yb N (1.54), Sm/Yb (1.1), Ce/Sm (4.5), Nb/Yb (1.1) and Th/Nb (0.3). It is derived from an enriched MORB source and shows characteristics similar to island arc basalts. Amphiboles from these rocks yielded 40 Ar/ 39 Ar plateau ages between 177.08 ± 0.96 Ma and 166.9 ± 1.1 Ma. These dates are interpreted as metamorphic ages of the amphibolitic rocks. They differ significantly from previous ages of amphibolitic rocks (the metamorphic sole rocks) related to Turkish ophiolites. However, similar metamorphic ages have been reported for metamorphic sole rocks of the Hellenic-Dinaric ophiolites further west. The metamorphic sole rocks have been generated in intra-oceanic environments via intra-oceanic subduction/ thrusting events. The new age data of the Çankırı amphibolite suite suggest that the İzmir-Ankara-Erzincan ocean was subducted around Early–Middle Jurassic times, i.e. roughly coeval with the oceanic basin(s) generating the Hellenic-Dinaric ophiolites. In the Early–Middle Jurassic time, the tectonic regime in the İzmir- Ankara-Erzincan ocean was compressional and the ocean was closing at that time. The new age data presented here could imply that Jurassic granites which cross-cut basement rocks of the Pontides are related to the northward subduction of the İzmir-Ankara-Erzincan ocean during Jurassic time. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Suture zones defined by ophiolite belts and ophiolitic mélanges are the relics of former ocean basins, which existed between continental blocks (e.g. Moores, 1981). They bear information on the evolution of ancient oceans, which is relevant for paleogeographic reconstructions and for unraveling mantle–crust dynamics. Turkey is a key region for understanding the geologic evolution of the Tethyan Ocean, which was located between the Gondwana and Laurasia supercontinents (e.g. Okay and Tüysüz, 1999; Şengör and Yılmaz, 1981; Stampfli, 2000). The ophiolitic rocks in Turkey define three main belts (i) the Northern Ophiolite Belt, (ii) the Median or Tauride Ophiolite Belt and (iii) the Southern or Peri-Arabic Ophiolitic Belt (Juteau, 1980). The Northern Ophiolite Belt is defining the İzmir-Ankara-Erzincan (İAE) Suture Zone, and represents the northern branch of the Neo-Tethys (İAE Ocean Domain), which was located between the Pontide (Sakarya) and the Anatolide-Tauride blocks (Okay and Tüysüz, 1999; Fig. 1). Ophiolite belts similar to those in Turkey occur in the Balkan region to the east and west of the Pelagonian microcontinent which was separating the Vardar and Pindos oceanic basins during much of the Mesozoic (e.g. Dilek et al., 2007; Robertson, 2002; Stampfli and Borel, 2004). East of Pelagonia, ophiolites of the Vardar Zone (e.g. the Guevgueli ophiolites), also referred to as the Eastern Hellenic Ophiolites, are Jurassic–Early Cretaceous in age (e.g. Robertson, 2002). The ophiolites west of Pelagonia are those of the Pindos Zone (e.g. Othris, Pindos and Vourinos ophiolites), also termed as the Western Hellenic Ophiolites. They are Middle Jurassic in age and are correlated with the Dinaric Ophiolites to the northwest (e.g. Zlatibor ophiolite; e.g. Tectonophysics 509 (2011) 120–134 ⁎ Corresponding author. Tel.: + 90 2623033131. E-mail address: farukclk@yahoo.com (Ö.F. Çelik). 0040-1951/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2011.06.007 Contents lists available at ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto