Jurassic metabasic rocks in the Kızılırmak accretionary complex (Kargı region, Central Pontides, Northern Turkey)

    Jurassic metabasic rocks in the Kızılırmak accretionary complex (Kargı region, Central Pontides, Northern Turkey) ¨ ¨ Omer Faruk C¸elik, Massimo Chiaradia, Andrea Marzoli, Mutlu Ozkan, Zeki Billor, G¨ultekin Topuz PII: DOI: Reference:

S0040-1951(16)00095-0 doi: 10.1016/j.tecto.2016.01.043 TECTO 126941

To appear in:

Tectonophysics

Received date: Revised date: Accepted date:

14 October 2015 11 January 2016 29 January 2016

¨ Please cite this article as: C ¸ elik, Omer Faruk, Chiaradia, Massimo, Marzoli, Andrea, ¨ Ozkan, Mutlu, Billor, Zeki, Topuz, G¨ ultekin, Jurassic metabasic rocks in the Kızılırmak accretionary complex (Kargı region, Central Pontides, Northern Turkey), Tectonophysics (2016), doi: 10.1016/j.tecto.2016.01.043

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ACCEPTED MANUSCRIPT Jurassic metabasic rocks in the Kızılırmak accretionary complex (Kargı region, Central

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Pontides, Northern Turkey)

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Ömer Faruk Çelika,*, Massimo Chiaradiab, Andrea Marzolic, Mutlu Özkana, Zeki Billord,

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Gültekin Topuze a

Kocaeli Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği Bölümü, 41380 Kocaeli / Türkiye

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University of Geneva, Section des Sciences de la Terre et de l’Environnement, CH-1205 Geneva, Switzerland

Dipartimento di Geoscienze, Università di Padova, and IGG-CNR, 35100-Padova, Italy

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University of Auburn, Department of Geology and Geography 117 Petrie Hall, Auburn, Alabama, USA

İstanbul Teknik Üniversitesi, Avrasya Yer Bilimleri Enstitüsü, 34469 Maslak, İstanbul, Turkey

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c

* Corresponding author: Ömer Faruk Çelik, Kocaeli Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği

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Bölümü, 41380 Kocaeli / Türkiye Tel: 00902623033131 e-mail: [email protected]

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ABSTRACT

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The Kızılırmak accretionary complex near Kargı is tectonically bounded by the Jurassic and Early Cretaceous metamorphic massives of the Central Pontides. It consists mainly of serpentinite, serpentinized peridotite, gabbro, basalt, metabasite and deep-marine sedimentary

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rocks. The metabasites in the Kızılırmak accretionary complex are tectonically located within a serpentinite, radiolarian chert, spilitized basalt, gabbro association and commonly display a steep contact with serpentinites. Amphiboles from metabasites yielded robust

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Ar/39Ar

plateau ages ranging between 159.4±0.4 Ma and 163.5±0.8 Ma. These are interpreted as cooling ages of the metabasites. The metabasites have 87Sr/86Sr(i) between 0.7035 and 0.7044 and

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Pb/204Pb(i) ranging between 18.18 and 18.92. The gabbros have higher

between 0.7044 and 0.7060 and

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87

Sr/86Sr(i)

Pb/204Pb(i) ranging between 17.98 and 18.43. Three basalt

samples display 87Sr/86Sr(i) between 0.7040 and 0.7059. Their

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Pb/204Pb(i) are unrealistically

low (15.42 and 15.62), suggesting, most likely, Pb loss which results in over-corrected values for decay through time. Pb-Sr-Nd isotopic compositions for all samples consistently plot 1

ACCEPTED MANUSCRIPT between the fields of MORB or the Depleted MORB Mantle reservoirs and enriched mantle reservoirs (EMII rather than EMI). All the samples (except one dolerite dike) have negative

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ɛ NdDM(t=160 Ma) values, suggesting derivation from a reservoir more enriched than the depleted

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mantle. The protoliths of metabasites correspond to diverse sources (N-MORB, E-MORB,

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OIB and IAT) based on whole rock major and trace element composition. An IAT-like protolith for the metabasites indicates that the İzmir-Ankara-Erzincan ocean domain was subducting and the tectonic regime was compressional during Late Jurassic and before. The

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protoliths of these rocks were metamorphosed during the subduction/accretion processes, as

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observed in the metamorphic rocks located along the Balkan, Northern Turkey and Armenia/Iran ophiolites and/or accretionary complexes. IAT-like geochemistry for the gabbro/dolerites indicates that the non-metamorphosed basaltic

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rocks occurred in a supra-subduction tectonomagmatic environment and is in agreement with

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their radiogenic isotope compositions.

Keywords: Tethys; Mélange; Ophiolite; Suture belts; İzmir-Ankara-Erzincan ocean; Central

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Pontides

1. Introduction

Turkey is one of the key areas to understand the geological evolution of the Tethys ocean which was located between the Gondwana and Laurasia supercontinents during the end of the Paleozoic and much of the Mesozoic time (e.g. Stampfli and Borel, 2002; Topuz et al., 2013a). Remnants of the Tethyan oceanic lithosphere and of accretionary complexes in Turkey are observed along the suture zones (e.g. the İzmir-Ankara-Erzincan suture zone) and also within the tectonic blocks (e.g. Anatolide-Tauride, Pontide) constituting the Turkish land.

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ACCEPTED MANUSCRIPT Ophiolites along the İzmir-Ankara-Erzincan (İAE) suture zone have been previously interpreted as Cretaceous ophiolites and accretionary complexes from the northern branch of

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the Neotethyan ocean (e.g. Juteau, 1980; Göncüoğlu et al., 2006; Sarıfakıoğlu et al., 2009;

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Parlak et al., 2013). However, recent studies have shown that the İAE suture zone comprises

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not only of Cretaceous ophiolitic rocks but also of Jurassic ophiolite and metamorphic rocks (Dilek and Thy, 2006; Çelik et al., 2011, 2013; Topuz et al. 2013a, b). According to previous studies, oceanization and opening of the İAE ocean domain have been constrained to occur

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between the Early–Late Triassic and the Upper Cretaceous, based mostly on radiolarian cherts intercalated within basalts (e.g. Göncüoğlu et al., 2006; 2010; Tüysüz and Tekin, 2007;

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Yalınız et al. 2000, references therein). However, Çelik et al. (2011) indicated that the subduction in the İAE ocean was ongoing in the Early–Middle Jurassic time and therefore the

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tectonic regime in some parts of the İAE ocean was contractionary at that time. The İAE suture zone, outcropping in an east – west direction over 1200 km in northern

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Turkey, bears geological records of the former ocean. In this respect, the accretionary complexes and ophiolites located in different parts of the İAE suture zone should be studied in

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much more detail to clarify the geological evolution of the Tethys ocean. The accretionary complex, including ophiolite rocks, can be observed for example around Kargı (Northern Turkey) and is tectonically located within the metamorphic massifs of the Central Pontides (Fig. 1). In this study we have investigated the metamorphic and magmatic rocks within the the Late Cretaceous Kızılırmak accretionary complex (Fig. 2). The main objective of this study is to present geological, geochemical, isotopic and geochronological characteristics of these metamorphic and magmatic rocks in order to shed light on their protoliths and tectonic significance and possible implications for the origin, evolution, and fate of the Tethys ocean.

2. Geological Framework

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The accretionary complexes located in the Central Pontides are tectonically delimited by

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metamorphic complexes (Fig. 1), which have been variously defined and named in previous

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studies (Tüysüz, 1990; Ustaömer and Robertson, 1997; Yılmaz et al. 1997; Altherr et al.

(107.0±4.6 Ma - 114.1±3.3 Ma)

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2004; Okay et al. 2006, 2013). Okay et al. (2013) have recently reported Early Cretaceous Ar/39Ar radio-isotopic ages from greenschist facies

metamorphic rocks of the Domuzdağ Complex. The eclogite facies metamorphic rocks in the

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Domuzdağ Complex consist mainly of metabasite (eclogite, garnet-blueschist), phyllite,

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micaschist, marble, metachert, serpentinite and metagabbro (e.g., Okay et al. 2013). The cooling age of the eclogite facies rocks is Cretaceous (105 ± 5 Ma) based on

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Ar/39Ar and

Rb-Sr geochronology and is similar to ages of greenschist facies rocks of the Domuzdağ

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Complex (Okay et al. 2006, 2013). Okay et al. (2013) recently described the Jurassic Saka complex, located to the North of Kargı and also to the West of Kastamonu, which was

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metamorphosed in the upper amphibolite facies (Fig. 1). The Saka complex is tectonically delimited by an accretionary complex (near Araç and Kastamonu) and the Martin complex to

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the west of Kastamonu and by the Kızılırmak accretionary complex (dashed rectangle area in Fig. 1) and the Domuzdağ complex to the east of Kastamonu (Fig. 1). On the other hand the accretionary complexes in the Central Pontides have been mapped and described as ophiolite (e.g., the Kızılırmak ophiolite) and ophiolitic mélange (the Kirazbaşı Complex) in previous studies (see e.g. Tüysüz, 1990; Yılmaz et al. 1997; Ustaömer and Robertson, 1997). The Kirazbaşı complex in the Central Pontides (the Kirazbaşı mélange of, e.g., Tüysüz, 1990 and Ustaömer and Robertson, 1997) has been described outside of our study area, around Kirazbaşı (Fig. 1; Tüysüz and Tekin 2007). It consists mainly of deepmarine sedimentary rocks, ophiolitic fragments and metamorphic rocks derived from the metamorphic rock units of the Central Pontides (Yılmaz et al. 1997; Tüysüz and Tekin, 2007).

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(1990)

reported

Cretaceous

(Campanian–Maastrichtian)

pelagic

limestones

interbedded with basaltic pillow lavas. Tüysüz and Tekin (2007) report that the Kirazbaşı

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Complex is non-metamorphic and includes Middle Jurassic and Early–Late Cretaceous

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radiolarites. The Kızılırmak accretionary complex includes also Jurassic to Cretaceous pelagic

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limestones and it is covered by Paleocene and Eocene clastic sedimentary rocks (Tüysüz, 1985). Okay et al. (2006) reported in their map that all ophiolitic rocks in the Central Pontides

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belong to the Upper Cretaceous accretionary complex.

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2.1. Sampling And Field Observations

For this study, we accomplished a detailed sampling on both sides of the Kızılırmak river,

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even though the outcrops are largely obscured due to dense vegetation. A detailed geological map of the study area is presented in Figure 2. The ophiolite rocks occur as coherent tectonic

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slices in the accretionary complexes. A dismembered ophiolitic body in the Kızılırmak accretionary complex, observed to the east of Kargı, is composed mainly of peridotites,

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cumulate and isotropic gabbros, isolated dolerite dikes, sheeted dikes, basalts, spilite and epiophiolitic sedimentary rocks. Pyroxenite rarely found in this area (except for the area with coordinates; 34°57’40.39’’ East - 41°12’34.87’’ North) and only observed as dike in the serpentinized peridotites. Dolerite dikes crosscut serpentinized peridotites as well as gabbros and basalts (Fig. 3a). They have thickness up to 5 - 6 m and show chilled margins indicating that the country rocks were relatively cold during dike injection. Brittle and ductile deformation structures are commonly observed. Intensive deformation was especially observed at the contact zone between serpentinite and gabbros (e.g., at Yalmansaray; 34°50’52.32’’ East - 41°12’20.38’’ North) and in the volcanic rocks. In some places breccia zones with a 50º-60º south dip were observed in gabbros. Pillow lavas occur in the

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ACCEPTED MANUSCRIPT accretionary complex and show a sheared structure in some place (e.g. 34°56’31.98’’ East 41°10’57.42’’ North; Fig. 3c). The metabasites, occurring as tectonic slices in the Kızılırmak

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accretionary complex, have commonly banded and massive textures in the field (Fig. 3d).

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They are observed together with serpentinite, radioliarian cherts, mudstone, gabbro and

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volcanic rock assemblages. In the study area, these different rock units sometimes occur together over very short distances and their contact relationship in the Kızılırmak accretionary complex is tectonic (Fig. 3e). Metabasites are in contact (moderately or steeply dipping) with

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serpentinites (Fig. 3f), supporting their original occurrence in an oceanic environment.

3. Analytical Methods

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Samples for whole-rock geochemical analyses were carefully selected and all altered parts of the samples were removed before grinding into powders in an agate mortar.

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Major and trace element contents of sample FEM-145, FEM-192, FEM-195, FEM-200 and FEM-202 were measured by XRF (Johnson et al., 1999) and quadruple ICP-MS,

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respectively, at the GeoAnalytical Center at the Washington State University. Some of the samples (FEM-128, 130, 135, 137, 140, 141, 143 and 144) were analysed at the ACME (Acme Analytical Laboratories, Vancouver, Canada). About 0.2 grams of rock-powder were fused with 1.5 g LiBO2 and dissolved in 100 ml 5% HNO3 for the whole rock chemical analyses. Samples FEM-134, FEM-193, FEM-198, FEM-210, FEM-211 and FEM-219 were analysed by means of the 4Lithoresearch custom package at ACTLABS (Activation Laboratories Ltd., Ancaster Ontario Canada) after lithium metaborate/tetraborate fusion. Chemical analyses of the ACME and the ACTLABS were performed by ICP-ES for major oxides, whereas trace elements and rare earth elements (REE) were analyzed by ICP-MS (Table 1).

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ACCEPTED MANUSCRIPT Whole rock Sr, Nd and Pb isotopic compositions were investigated at the Department of Earth Sciences, University of Geneva, Switzerland (Table 2). Analytical procedure for the

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isotope chemistry is the same as outlined in Çelik et al. (2013).

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Mineral compositions were determined at the IGG-CNR Padova (Italy) on a Cameca

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SX50 electron microprobe (EMP) using ZAF on-line data reduction and matrix correction procedures. At constant accelerating voltage, 15 kV, the beam current was set at 15 nA for analysing amphibole and plagioclase whereas pyroxenes and oxides were analyzed with a

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beam current of 20 nA. Repeated analyses of standards indicate relative analytical uncertainties of about 1% for major and 5% for minor elements. Ar/39Ar analyses (except sample FEM-198) were carried out at the Auburn Noble

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Isotope Mass Analysis Laboratory (ANIMAL) at Auburn University. Handpicked hornblende

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grains (250–180 mm) from amphibolite samples were irradiated at the McMaster nuclear reactor facility in Hamilton, Ontario, Canada. Crystals were placed in aluminum disks with

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the Fish Canyon sanidine monitor FC-2 (age = 28.305 ± 0.036 Ma, Renne et al., 2010) along with reagent grade K2SO4 and CaF2 as flux monitors. Following irradiation, argon extraction

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was done using laser incremental heating, with a 50 W Synrad CO2 laser. Measurements were made with a 10-cm sector instrument with extended geometry fitted with a Nier-type source (operated at 2 kV), and electron multiplier operated in analog mode at −1.3 kV with a 10–11 ohm preamp. All

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Ar/39Ar ages in this study (weighted means, plateau, or isochron) are

quoted at the 2σ confidence level, whereas errors in individual measurements of single heating steps are quoted at one standard deviation. Data reduction and assessment of statistical ages were accomplished with Isoplot (Ludwig, 2003). Plateau ages were defined such that: the plateau increments constituted more than 70% of the total volume of

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ArK

released in three or more contiguous heating steps with indistinguishable (1σ) apparent ages. The decay constants of Steiger and Jäger (1977) were used. We note that about 1% older ages

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ACCEPTED MANUSCRIPT would be obtained if the revised decay constant of Renne et al. (2010) was considered. 40

Ar/39Ar analysis of sample FEM-198 was carried out at the ARGONAUT Laboratory at the

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University of Salzburg. Analytical procedure for sample FEM-198 is the same as outlined in

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Çelik et al. (2011). 40Ar/39Ar analytical data are given in Supplementary Data-Table 5.

4. Petrography and Mineral Chemistry

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Metabasites in the Kızılırmak accretionary complex have massive or banded appearance

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and present commonly granoblastic and nematoblastic textures. They consist of amphibole + plagioclase ± pyroxene ± prehnite ± pumpellyite ± epidote ± chlorite ± biotite ± phengite/muscovite ± ilmenite ± sphene ± apatite ± opaque minerals (Table 3). A well-

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developed lineation is defined by the alignment of amphiboles in the metabasites. Plagioclases show variable degrees of alteration. Biotite was observed as secondary mineral replacing

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amphibole (e.g. sample FEM-194). Phengite and muscovite (< 1 vol. %) were observed in metabasite samples (FEM-192 and FEM-201). Prehnite, pumpellyite, chlorite and epidote

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were observed mostly in veinlets but also as replacement of plagioclase of the rock (e.g., sample FEM-195). Apatite and opaque minerals are commonly parallel to the lineation defined by the alignment of plagioclase and amphibole grains. Apatite is an abundant mineral in some metabasites (e.g., samples FEM-198, FEM-200). Sample FEM-144 collected near Darıçay is a metabasite dike cross-cutting serpentinite. Plagioclases of this sample have been almost totally transformed to prehnite, pumpellyite and calcite. Calcite from a metabasite sample (FEM-145) in the same area was commonly observed along the contact boundary between plagioclase and amphibole. Pyroxene in metabasites was observed as relict mineral in the mineral association.

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ACCEPTED MANUSCRIPT Basalts and spilitic basalts in the accretionary complex have intergranular, amygdaloidal, microlitic, microlitic-porphyric and quenched textures. They consist of plagioclase ±

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pyroxene ± olivine ± amphibole ± epidote ± chlorite ± calcite ± prehnite ± opaque minerals.

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Gabbroic rocks have a similar mineral association as that of basalts (Table 3). Pyroxene in

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basalts was observed both as microlites and porphyrocrysts in the mineral association. Sample FEM-220 is composed of tiny plagioclase microlites and chlorite which is a secondary product of the mafic minerals (e.g., pyroxene). Epitaxial growth of amphibole on the

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pyroxene was observed in some dolerites and gabbros. Because of the intensive tectonism,

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some rocks show a cataclastic texture as observed in a dolerite dike cross-cutting serpentinites (Fig. 3b). Chlorite, prehnite, calcite and epidote occurrences and uralitization suggest the presence of aqueous fluids of either metamorphic or late magmatic origin.

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The chemical compositions of representative minerals are listed in Supplementary DataTables 1, 2, 3 and 4. Amphiboles from the metabasites are calcic amphiboles based on the

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classification diagram of Leake et al. (1997). They are represented by tschermakite, magnesio-hornblende, magnesio-hastingsite, pargasite, tremolite and actinolite (Fig. 4a).

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Plagioclases from metabasites show a relatively large compositional range between labradorite and albite (Ab40-98) (Fig. 4b). Plagioclases from a basalt sample (FEM-134) have albite and oligoclase (Ab87-97) compositions. Clinopyroxenes from a basalt sample (FEM-134) have augite compositions (Wo25.6-42.1 En33-55.2 Fs6.9-15.2). The Mg# of the clinopyroxenes ranges between 61.9 and 88.7. Prehnites from the metabasites (e.g. FEM-195) and a basalt sample (FEM-134) have similar Si values ranging from 5.7 to 6.2 atoms per formula unit (apfu). Al values of prehnites are between 3.4 and 4.0 apfu. Ca values in the same minerals are between 3.5 and 4.3 apfu. Phengite in a metabasite sample (FEM-201) is characterized by Si contents of 3.40–3.45 apfu. Muscovite from metabasite (FEM-192) has a low content of Si (3.06 apfu) and Mg (0.01 apfu). Al content of muscovite is 2.9 apfu and is higher than those of phengite

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ACCEPTED MANUSCRIPT (2.1-2.2 apfu). Chlorite from metabasite samples (FEM-198 and FEM-201) has Si content between 2.7 and 3.0 apfu and Mg / (Mg + Fe2+ + Mn) ratio ranging from 0.48 to 0.70.

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Ilmenite in metabasite samples (FEM-192, 196 and 198) has TiO2 values ranging from 48.9 to

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51.6 wt.% with low MnO (0.42-1.24 wt.%), Cr2O3 (up to 0.07 wt.%) and CaO (up to 1.3

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wt.%). FeO values of the ilmenite show a narrow variability between 45.4 and 48.3 wt.%. Sphene in metabasite samples (FEM-192-FEM-198) exhibits Al2O3 and FeO contents of

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0.99–1.41 and 0.56–0.84 wt.%, respectively.

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5. Whole Rock Geochemistry

Secondary mineral phases resulting from hydration (e.g., chlorite, serpentine) and

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carbonatization (e.g., calcite), commonly occur in magmatic and metamorphic rocks of the accretionary complex (Çelik et al. 2013 and references therein). Petrographic observations

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and whole-rock geochemical compositions reveal that the investigated rocks reflect variable degrees of alteration. For example, the loss on ignition (LOI) values of the samples (except

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sample FEM-128; 13.90 wt.%) range between 1.04 wt.% and 5.50 wt.% (Table 1). Therefore, for our interpretation we relied mainly on High-Field-Strength Elements (HFSE) and, partially, also REE data, which are considered to be largely immobile during the type of alteration affecting the investigated rocks (e.g. Beccaluva 1979; Pearce 1982; Thompson 1991). In this sense, Nd isotopic compositions yield the most reliable isotopic values.

5.1. Major, trace and REE geochemistry

In the Ti/Y vs. Nb/Y diagram (Pearce, 1982), non-metamorphosed basalts and gabbro/dolerite dikes (the basaltic rocks) fall in the tholeiitic field, whereas the metabasites

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ACCEPTED MANUSCRIPT fall in the tholeiitic and transitional fields (Fig. 5a). In the Nb/Y vs. Zr/Ti discriminant diagram of Pearce (1996), while the basaltic rocks fall in the field of gabbro/basalt, the

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metabasites plot within the gabbro/basalt field extending to the boundary with the alkali basalt

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field (Fig. 5c). In the Nb-Y-Zr diagram (Meschede, 1986), the basaltic rocks plot in the

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normal mid-ocean ridge basalt (N-MORB) or in the volcanic arc basalt (VAB) fields, whereas the metabasites fall in the enriched mid-ocean ridge basalt (E-MORB), within plate alkali basalt (WPAB), N-MORB or VAB fields (Fig. 5d). Chondrite-normalized (cn) rare earth

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element (REE) values of the metabasites display different distribution patterns (Fig. 6).

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Lacn/Ybcn values for one group of metabasite samples (FEM-192, FEM-195, FEM-198, FEM200) range from 5.92 to 13.80 similar to the within plate basalts (WPB) or seamounts (Fig. 6a, Table 1). Protoliths of these samples are alkali basalts, based on the Nb/Y vs. Zr/(P 2O5*104)

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diagram of Floyd and Winchester (1975) (Fig. 5b) and their high TiO2 (0.54 – 5.07 wt.%), high Nb/Y (0.53–0.78) and low Zr/Nb (2.6–4.5) values. The Eu/Eu* values of these rocks

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range between 1.03–1.81 (Table 1). The OIB origin of these samples is confirmed also by Th/Yb vs. Nb/Yb and Hf-Th-Nb diagrams (Fig. 7a,b). On the N-MORB normalized spider

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diagram, these samples exhibit multi-element patterns more enriched than N-MORB and are similar to OIB basalts (Fig. 6b). On the other hand, a metabasite sample (FEM-202) displays a depleted chondrite-normalized LREE pattern [(La/Sm)N= 0.42] with nearly flat HREE [(Dy/Yb)N= 1.24] (Fig. 6a). This sample has also a flat pattern in the N-MORB normalized spider diagram (Fig. 6b), indicating clearly a MORB source for its protolith. Metabasite samples FEM-144 and FEM-145 show depleted chondrite-normalized REE patterns compared to the other metabasite samples (Fig. 6c). They have flat and parallel chondrite-normalized REE spectra [(La/Yb)N= 0.98–1.04]. They show positive Eu anomalies (Eu/Eu*= 1.46 – 2.98), suggesting plagioclase accumulation. On the N-MORB normalized spider diagram (Fig. 6d), these samples display HFSE (e.g. Nb, Zr) depletion relative to LILE (e.g., K, Rb,

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ACCEPTED MANUSCRIPT Ba) and LREE. The Th/Yb vs. Nb/Yb diagram highlights the subduction influence for these samples (Fig. 7a). Chondrite-normalized REE values of the other geochemical group for

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metabasite samples (FEM-193, FEM-210 and FEM-211) show roughly flat [(La/Yb)cn ratio;

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0.88-1.67] patterns (Fig. 6c). The same samples exhibit some LILE enrichment on the N-

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MORB normalized spider diagram but there is no clear depletion in HFSE to suggest a subduction influence (Fig. 6d). According to Hf-Th-Nb and Th/Yb vs. Nb/Yb discrimination diagrams, samples FEM-210 and FEM-211 have an E-MORB character (Fig. 7a,b). However,

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sample FEM-193 in the same diagrams is characterized by a subduction-related signature.

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Various discrimination diagrams (not all shown here) support diverse sources (N-MORB, EMORB, OIB and IAT) for the protoliths of the metabasites. In the chondrite-normalized REE diagram (Fig. 8a), non-metamorphosed gabbro/dolerite

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dikes have REE spectra which range from slightly depleted to nearly flat [(La/Yb)cn= 0.75– 1.38]. The Eu/Eu* values of these rocks range between 0.83 and 1.11, suggesting limited

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plagioclase fractionation or accumulation. On the N-MORB normalized spider diagram (Fig. 8b), gabbro/dolerite dikes display slight enrichments in LILE (e.g. K, Rb, Ba), strong

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depletion in Nb and moderate depletion in Zr and Ti, indicating that they were generated in a subduction-related environment (Pearce et al. 1984; Saunders and Tarnery 1979, 1984). The subduction-related nature of these rocks can be also observed in their low TiO2 (<1.7 wt.%), low Nb/Y (<0.15) and high Zr/Nb values (48 – 127). One gabbro (FEM-128) and one dolerite (FEM-219) sample, on the other hand, display 25-30 times chondritic values and have slightly depleted patterns with respect to LREE [(La/Sm)N= 0.68-0.91] but a flat HREE [(Dy/Yb)N= 1.01-1.13] (Fig. 8c). On the N-MORB normalized spider diagram, these samples present rather MORB-like patterns (Fig. 8d). According to the Hf-Th-Nb and Th/Yb vs. Nb/Yb discrimination diagrams, gabbro/dolerite dikes fall in the arc basalts and N-MORB fields (Figs. 7a,b).

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ACCEPTED MANUSCRIPT In the chondrite-normalized REE diagram, the basalts display flat REE spectra [(La/Yb)cn= 1.06–1.19]. They have high Nb/Y (0.15-0.18) and low Zr/Nb values (15 – 17),

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compared to the subduction-related gabbro/dolerite samples (Fig. 8c). On the N-MORB

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normalized spider diagram, they show a slight enrichment in some LILE (e.g. K, Rb, Ba) and

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show a flat pattern for the other elements, suggesting an N-MORB or E-MORB origin (Fig. 8d). An E-MORB signature of the basalt samples is favored based on the Th/Yb vs. Nb/Yb

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and Hf-Th-Nb diagrams (Figs. 7a,b).

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5.2. Radiogenic isotope (Nd, Sr, Pb) geochemistry

As indicated above, the investigated rocks display variable degrees of alteration. This

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may represent a problem for the meaning of the isotope data as for any geochemical data. The problem with radiogenic isotope data of altered magmatic rocks like those here investigated is

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twofold: (i) the isotopic signatures of the magmatic rocks may have been altered by introduction after their crystallization of external Pb, Sr and Nd during the alteration process.

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In such a case the isotopic signature that we measure would be a mixture between the pristine signature and the signature introduced during the alteration process. Divergence from the pristine isotopic signature will depend on the amount of the Pb, Sr, Nd introduced and on the isotopic difference of the introduced Pb, Sr, Nd with respect to the isotopic signatures of the pristine magmatic rocks; (ii) since the investigated rocks have Jurassic ages, in order to know the isotopic compositions at the time of their formation we need to perform an age correction, which is based on knowledge of parent (U, Th, Rb, Sm) and daughter (Pb, Sr, Nd) concentrations in the rocks (measurable by an independent method, e.g., ICP-MS) and of rock ages. If during the alteration process parent and daughter elements are removed differentially (which is likely, due to the different fluid solubilities of, e.g., parent HFSE Th and U and

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ACCEPTED MANUSCRIPT daughter LILE Pb) the age-corrected values will not provide any longer the correct initial isotopic composition at the time of magmatic crystallization because the system has behaved

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as open. Addition of external radiogenic elements (Pb, Sr, Nd) discussed in the point above

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will result in a double complication, one associated with the introduction of exogenous

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radiogenic elements with a different isotopic signatures from the pristine rock, and the other with the wrong age-correction that this addition will imply.

Usually it is considered that the Sm-Nd system is the most refractory to alteration,

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because Sm and Nd are REE elements with low solubility in aqueous fluids. Çelik et al.

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(2013) have coped with a similar problem investigating similar rocks as those analysed here and have primarily based their interpretations on Nd isotope signatures, using Sr and Pb only as a support, should their interpretation be compatible with the indications of Nd isotopes.

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They showed that, surprisingly, Sr and Pb isotopes gave meaningful results also in altered mafic rocks, supporting previous conclusions of Chiaradia (2009).

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In this work we will take a similar approach to that of Çelik et al. (2013). For the reasons discussed above, in Figure 9 we plot both age-corrected (to an age of 160 Ma, consistent with Ar/39Ar geochronology, see below) and age-uncorrected isotopic compositions of Pb, Sr and

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40

Nd. This should provide us with a range of variability within which the “real” isotopic compositions of the pristine rocks should fall, should the latter have undergone preferential leaching of parent or daughter nuclides. The results show that the difference between agecorrected and age-uncorrected values is virtually insignificant for Sr isotope compositions. This is due to the low Rb/Sr values of mafic rocks in general and, specifically, of those here investigated (see Table 1). Potentially anomalous Sr isotope compositions in the investigated rocks therefore should result only from exogenous Sr introduction during the alteration process (e.g., high-temperature seawater alteration). Also the changes of Nd isotopic compositions are relatively minor (<0.05%). In contrast, changes of Pb isotope compositions

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ACCEPTED MANUSCRIPT are more significant due to the overall low amounts of Pb, U and Th in the rocks. An additional problem with the U-Th-Pb isotope system of the investigated rocks is that several

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samples had U, Th and/or Pb contents below the detection limit of ICP-MS analysis, which

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precludes the possibility to age-correct the measured present-day Pb isotope compositions.

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Two samples (FEM-140, FEM-141) return age-corrected Pb isotope compositions that are unrealistic (corresponding to Proterozoic model ages) and have certainly undergone a preferential Pb loss with respect to U and Th during the alteration process. The effect of age

Pb/204Pb ratio because the parent of 207

Pb/204Pb ratio than for the

Pb (238U) is ~138 times more abundant than the

Pb (235U), which is almost extinct. This means that the variability of the

parent of 207

206

206

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207

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correction in the U-Pb system is much stronger for the

Pb/204Pb values along Mesozoic isochron lines is relatively small and that therefore

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imprecise age-corrections due to differential mobility of parent/daughter nuclides will not have a significant effect as that due to the introduction of exogenous Pb.

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Given this background, the rock data plotted in Figure 9 still provide some consistent information. In fact, in all plots coupling Pb-Sr-Nd isotope systems our rock data consistently

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plot between the fields of MORB or Depleted MORB Mantle (DMM) reservoirs and enriched mantle reservoirs (EMII rather than EMI). Three samples display more radiogenic Sr isotope compositions for similarly radiogenic

143

Nd/144Nd isotope compositions as those of samples

with less radiogenic Sr. These samples might have been affected by seawater alteration. Alternatively, but less likely, in the age corrected plot they could fit a mixing line with the EMII reservoir different from the mixing line defined by the other samples. In the 207Pb/204Pb versus

206

Pb/204Pb plot, independently from the variability of

investigated rocks plot above the NHRL (at high

207

206

Pb/204Pb values, most of the

Pb/204Pb values) and within the fields of

typical island arc systems developed upon oceanic crust. In this plot there is no clear evidence for involvement of a HIMU reservoir in the genesis of the investigated rocks.

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ACCEPTED MANUSCRIPT Except for one sample (FEM-219) the investigated rocks have negative NdDM values where the suffix DM denotes normalization to the depleted mantle, (after De Paolo, 1981),

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suggesting derivation from a reservoir more enriched than the DM. Consequently they also

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have DM model ages (between 0.099-3.864 Ga) that are in average significantly older than

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the Jurassic age of their formation.

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5. 40Ar/39Ar Geochronology

were dated by the

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Hornblendes from four metabasite samples (FEM-193, FEM-197, FEM-198, FEM-200) Ar/39Ar method. They yield robust plateau ages indicating Late Jurassic

39

Ar released; Fig. 10). Amphiboles from sample FEM-197

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161.6±0.4 Ma (88.4% of the

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metamorphic cooling ages (Fig. 10). Data of sample FEM-193 define a plateau age of

yielded a plateau age of 161.7±0.4 Ma (84.2% of the

39

Ar released; Fig. 10). Multigrain

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concentrates of amphiboles from sample FEM-198 yielded a plateau age of 163.5±0.8 Ma defined by 6 adjacent steps representing more than 98% of the total

39

Ar released (Fig. 10).

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Multigrain concentrates of amphiboles from sample FEM-200 yielded a plateau age of 159.4±0.4 Ma (72.7% of the 39Ar released; Fig. 10).

6. Discussion

6.1. Sources of the rock units

The Jurassic metabasites in the non-metamorphosed Late Cretaceous Kızılırmak accretionary complex which is located in the Central Pontides exhibit a large range of possible protoliths compositions, from N-MORB, E-MORB, OIB to the island arc tholeiite

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ACCEPTED MANUSCRIPT (IAT) based on whole rock geochemistry (Figs. 5,6,7). Similar geochemical affinities were recently reported for Jurassic metamorphic rocks located along different parts of the İAE

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suture zone (e.g. Çelik et al. 2011; Göçmengil et al. 2013) and the Sevan-Akera accretionary

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complex (e.g. Hassig et al. 2013). An IAT-like geochemical affinity, i.e. a supra-subduction

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fingerprint for the ca. 160 Ma metabasites, proves that subduction of the İzmir-AnkaraErzincan ocean domain was active during or before Late Jurassic time. Non-metamorphosed basalts in the Kızılırmak accretionary complex exhibit tholeiitic character with E-MORB

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affinity. Gabbro and dolerite rocks, on the other hand, have N-MORB and IAT geochemical

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characteristics. As non-metamorphosed basaltic rocks are located in the accretionary complex as slices and blocks and we have no age data for these rocks, it is difficult to interpret them in a whole geodynamic context. However, geochemical characteristics of the dolerite dikes

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cross-cutting serpentinized peridotites and gabbro show clearly a subduction influence, suggesting that they occurred in a supra-subduction zone setting.

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Radiogenic isotopes (Nd, Sr, Pb) suggest derivation of the rocks here investigated from mixing between MORB (DMM) and an enriched mantle source, most likely EMII (Fig. 9). In

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particular, in agreement with trace element geochemistry, isotope data (Nd and Pb isotopes, in particular) indicate that non-metamorphosed basalts have homogeneous isotopic signatures close to MORB. In contrast, metabasite and dolerite/gabbro samples, except some samples with a dominant MORB fingerprint, display enriched compositions typical of the EMII endmember. This signature is frequently recognized in island arc mafic rocks developed on oceanic crust and supports the arguments of trace element geochemistry that metabasites and dolerite/gabbro were generated in a supra-subduction setting.

6.2. Implications for regional geology

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ACCEPTED MANUSCRIPT In the Central Pontides (Fig. 1) the non-metamorphosed Kızılırmak accretionary complex is tectonically located in the Jurassic (the Saka Complex) and Early Cretaceous (the

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Domuzdağ, Esenler, Martin complexes) metamorphic rock units. The Esenler complex is

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covered by Maastrichtian and younger sediments (Fig. 1). The Martin complex, on the other

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hand, is tectonically covered by the Lower Cretaceous Çağlayan formation (Hippolyte et al. 2010). The Martin complex near Daday and the Domuzdağ complex around the Kızılırmak accretionary complex were both metamorphosed in the greenschist facies in Albian times

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(Okay et al. 2013). Therefore, we suggest that the root zones of the Martin complex and the Domuzdağ complex are similar and they should not be separated as distinct metamorphic

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complexes. The rock units of the Kızılırmak accretionary complex exhibit well observed repetitions and they have commonly steep contact between them, suggesting that tectonic

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events were responsible for their emplacement. Although the sedimentary cover precludes recognition of the continuity of all the metamorphic complexes along the cross-section from

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A to A’ in Figure 1, the lower Late to Middle Jurassic Saka complex and the Late Cretaceous accretionary complexes show also clear repetition in the region (Figs. 1 and 11a). The

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repetition of these units could be explained by hypothetical huge thrust faults generated during the Early Cretaceous and afterwards (e.g. Okay et al., 2013, references therein). These thrust faults probably occurred in the accretionary wedge of the subduction zone, during closure of the İAE ocean domain (Fig. 11b,c). The Saka complex (Fig. 1) consists of significant amounts of micaschist and small amounts of metabasite, marble, calc-schist and serpentinite slivers (Okay et al. 2013). The metamorphic pressure and temperature for the Saka complex was estimated by Okay et al. (2013) as 620 ± 30 °C and 1 ± 0.2 Gpa indicating upper amphibolite facies conditions. Okay et al. (2013) reported 40Ar/39Ar mica ages ranging between 162 and 170 Ma for micaschists of the Saka Complex. They correlated the Saka Complex with those of the Çankırı (Çelik et al.

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ACCEPTED MANUSCRIPT 2011) and Erzincan areas (Topuz et al., 2013a), which belong to the İAE suture zone and were interpreted as Jurassic subduction or subduction-accretion complexes.

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The mineral paragenesis of the investigated metabasites in the Kızılırmak accretionary

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complex is not suitable to determine P-T metamorphic conditions. The hornblende-

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plagioclase thermometer of Holland and Blundy (1994) for the metabasites yields temperatures higher than 700ºC for 0.5 – 0.6 GPa. The presence of prehnite and pumpellyite in the mineral association of some metabasites indicates a low-grade metamorphic overprint

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following the amphibolite facies metamorphism. Our age data from metabasites of the Kızılırmak accretionary complex, on the other hand, are similar to those of the Saka Complex,

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as well as the Çankırı and the Erzincan (Refahiye) metamorphics. Therefore, the Saka Complex and the metabasites of the investigated area were exhumed and tectonically

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transported together into the Kızılırmak accretionary complex during the Late Cretaceous (Fig. 11).

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Becasue the estimated metamorphic temperature for the metabasites is higher than the closure temperature of amphiboles (~500-550°C: Hanson and Gast, 1967; Harrison, 1981), Ar/39Ar dates represent cooling ages of the metabasites.

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7. Conclusions

Metabasic rocks, tectonically located in the Late Cretaceous non-metamorphosed Kızılırmak accretionary complex, are commonly observed together with serpentinite, suggesting that they occurred in the oceanic environment. The contact between serpentinites and metabasites is commonly steep, suggesting that tectonic events were responsible for their emplacement.

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ACCEPTED MANUSCRIPT Protoliths of metabasic rocks exhibit diverse sources (N-MORB, E-MORB, OIB and IAT) based on both trace element geochemistry and radiogenic isotope compositions. IAT-

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like metabasic rocks indicate that the İAE ocean domain underwent subduction and

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metamorphism during or before Late Jurassic time. Non-metamorphosed basaltic rocks in the

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accretionary complex display N-MORB (gabbro and dolerite), E-MORB (basalt) and IAT (gabbro and dolerite) geochemical characters, suggesting that the ophiolitic rocks were formed in a supra-subduction tectonomagmatic environment.

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Ar/39Ar geochronology

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indicates that protoliths of the metabasic rocks were metamorphosed during and/or before

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Late Jurassic time, as observed in many metamorphic rock units located between the Balkan, and Armenia/Iran ophiolite and/or accretionary complex.

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Acknowledgements

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The research presented in this paper was funded by the TÜBİTAK, the project no: 106Y222. We thank to İsmail Emir Altıntaş, Rahmi Melih Çörtük and Mehmet Hanefi İnce

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for their assistance during field study. Raul Carampin is thanked for assistance during electron microprobe analyses. The Editor Rob Govers and reviewers Nuretdin Kaymakçı and Aral Okay are thanked for their constructive comments on the manuscript.

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Fig. 1. Geological map of the eastern part of the northern Central Pontides (modified after Okay et al. 2013 and references therein). Some ages from the Cretaceous volcanoclastic and sedimentary rocks were modified after Hippolyte et al. (2010, 2015). Inset indicates to the study area and the main Neo-Tethyan sutures and continental blocks in the Eastern Mediterranean area. Abbreviations: İAES, İzmir–Ankara–Erzincan suture; İTS, Inner Tauride suture; BZS, Bitlis–Zagros suture; RO, Refahiye Ophiolite; EO, Eldivan Ophiolite; SO, Sevan ophiolite; KO, Khoy ophiolite; VO, Vorinous ophiolite.

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Fig. 2. (a) Geological map, including the sample locations, of the Kızılırmak accretionary complex. (b) A-A’, B-B’ and C-C’ geological cross sections showing the tectonic alternation of different oceanic rock units.

29

AC

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ACCEPTED MANUSCRIPT

Fig. 3. (a) A dolerite dike crosscutting serpentinized peridotites from Yalmansaray area. (b) tectonized and altered dolerite dike crosscutting serpentinites. (c) sheared pillow structured basalts. (d) a close view of a metabasite. (e) field view of volcanite, radiolarite, serpentinite and metabasite. (f) field view of a steep tectonic contact between metabasite and serpentinite.

30

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ACCEPTED MANUSCRIPT

Fig. 4. (a) Chemical composition of amphiboles in metabasites of the Kızılırmak accretionary complex, after Leake et al. (1997). (b) Feldspar ternary diagram showing plagioclase compositions of metabasites and a basalt sample.

31

CE P

TE

D

MA

NU

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IP

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ACCEPTED MANUSCRIPT

AC

Fig. 5. Tectonomagmatic discrimination diagrams for the metabasite, gabbro/dolerite and basalt rocks of the Kızılırmak accretionary complex. (a) Nb/Y vs. Ti/Y plot (after Pearce, 1982). (b) Zr/(P2O5*1000) vs. Nb/Y plot (after Floyd and Winchester, 1975). (c) Nb/Y vs. Zr/Ti plot (after Pearce, 1996). (d) Nb–Y–Zr triangular diagram after Meschede (1986).

32

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ACCEPTED MANUSCRIPT

AC

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D

Fig. 6. Chondrite-normalized REE patterns (a, c) and N-MORBnormalized multi element 2 diagrams (b and d) for metabasites from the Kızılırmak accretionary complex. All 3 normalizing values after Sun and McDonough, 1989.

33

NU

SC R

IP

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ACCEPTED MANUSCRIPT

AC

CE P

TE

D

MA

Fig. 7. Tectonomagmatic discrimination diagrams for the metabasite, gabbro/dolerite and 2 basalt rocks of the Kızılırmak accretionary complex. (a) Th/Yb vs. Nb/Yb diagram (after 3 Pearce, 1982). (b) Th–Hf–Nb triangular plot (after Wood et al., 1979).

34

MA

NU

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IP

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ACCEPTED MANUSCRIPT

AC

CE P

TE

D

Fig. 8. Chondrite-normalized REE patterns (a, c) and N-MORB-normalized multi element diagrams (b and d) for gabbroic and basaltic rocks from the Kızılırmak accretionary complex. All normalizing values after Sun and McDonough, 1989.

35

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D

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ACCEPTED MANUSCRIPT

Fig. 9. Nd-Sr (a), Nd-Pb (b), Sr-Pb (c) and Pb-Pb (d) diagrams of present day and initial (at t=160 Ma) isotopic ratios for gabbros, basalts and metabasites of the Kızılırmak accretionary complex. Mantle end member compositions are from Zindler and Hart (1986). The dashed contour fields of MORB, DMMa and DMMb are corrected to 160 Ma ago using element

36

ACCEPTED MANUSCRIPT

AC

CE P

TE

D

MA

NU

SC R

IP

T

concentrations and isotopic compositions of those reservoirs from Hart et al. (1999) and Workman and Hart (2005).

37

CE P

TE

D

MA

NU

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IP

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ACCEPTED MANUSCRIPT

AC

Fig. 10. 40Ar/39Ar hornblende ages from metabasites of the Kızılırmak accretionary 1 complex.

38

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ACCEPTED MANUSCRIPT

Fig. 11. (a) Geological cross-section from A to A’ (see Fig. 1). (b, c) Hypothetical tectonic model depicting the Jurassic metamorphic rock emplacement in the Late Cretaceous accretionary complex. (i), (ii), (iii) indicate to the order of faulting.

39

ACCEPTED MANUSCRIPT Table 1 Major (wt.%), trace and rare earth element (ppm) analyses from metabasite and basaltic rocks of the Kızılırmak accretionary complex. met aba site (pr oto dik e)

met aba site

met aba site

met aba site

met aba site

met aba site

met aba site

met aba site

met aba site

met aba site (pr oto dik e)

FE M144 43. 15 0.1 6 16. 80

FE M145 44. 20 0.0 5 17. 34

FE M192 41. 84 3.8 6 18. 81

FE M193 48. 01 1.7 6 13. 99

FE M195 45. 66 0.5 4 12. 98

FE M198 40. 06 5.0 7 11. 56

FE M200 46. 71 1.0 0 13. 16

FE M202 43. 30 0.8 9 14. 57

FE M210 47. 94 0.8 2 16. 35

FE M211 49. 51 1.2 4 14. 40

3.9 9 0.0 7 9.7 7 19. 67 0.4 9 0.0 2 0.0 1 5.5 0 99. 79

4.1 7 0.1 1 14. 61 13. 10 1.1 0 0.4 5 0.0 1 4.3 7 95. 13

12. 02 0.1 4 5.7 3 9.6 3 2.6 5 1.6 0 0.8 3 2.5 3 97. 10

13. 09 0.2 2 6.3 3 10. 57 2.4 1 0.5 6 0.1 8 1.8 3 98. 94

10. 56 0.1 8 13. 29 12. 52 1.5 2 0.2 9 0.0 8 1.7 7 97. 63

17. 44 0.2 1 8.2 6 12. 22 1.7 5 0.4 2 1.6 6 1.0 4 99. 68

11. 79 0.2 0 10. 20 10. 91 2.3 8 0.5 3 0.3 1 2.1 0 97. 20

9.3 8 0.1 7 8.8 3 18. 18 0.9 1 0.0 4 0.0 6 3.6 0 96. 32

8.7 5 0.1 5 8.0 2 11. 56 2.3 1 0.3 3 0.0 7 2.9 7 99. 27

10. 12 0.1 4 7.9 3 9.8 0 2.8 9 0.2 1 0.1 5 2.8 8 99. 27

Rb

b.d.

5.5 5

23. 75

17. 00

2.9 4

7.0 0

4.6 1

0.4 0

3.0 0

Ba

2.0 0

Th

b.d.

U Nb

b.d. 0.3 0

Ta

b.d. b.d.

446 .02 0.3 7 0.0 9 8.8 7 0.7 5 2.1 2

121 .00 1.4 4 0.2 8 6.3 0 0.4 9

Pb

172 .45 0.0 3 0.0 1 0.0 9 0.0 1 0.1 0

b.d.

44. 26 1.4 8 0.3 4 4.6 1 0.3 5 0.5 3

179 .00 1.4 4 0.2 4 16. 70 1.6 6 10. 00

149 .64 1.5 8 0.3 7 10. 84 0.7 8 0.6 2

4.9 5 0.0 4 0.0 1 1.4 3 0.0 8 0.1 6

Sr

12. 90

53. 75

488 .29

156 .00

72. 30

381 .00

186 .02

Zn

5.2 0 0.2 0 3.8 0 9.0 0

1.4 2 0.0 5 1.7 2 25. 60

23. 38 0.7 6 11. 32 77. 10

142 .00 3.3 0 39. 90 120 .00

15. 54 0.4 9 6.4 7 80. 50

50. 00 1.6 0 26. 70 110 .00

Cu

71. 50

4.6 0

20. 30

290 .00

9.8 0

111 .10 112 2.0 8

308 .70

50. 70

100 .00

655 .50

35. 60

79. 68. V 00 90 Rare earth elements (ppm)

292 .30

Zr Hf Y

Ni

Cr

ba sal t FE M13 4 49. 13 1.0 1 14. 10

ba sal t FE M14 0 48. 65 1.4 1 14. 37

ba sal t FE M14 1 49. 12 1.2 9 14. 11

12. 22 0.1 9 4.5 3 7.4 4 5.1 6 0.7 1 0.0 6 1.9 0 99. 82

11. 55 0.1 7 4.4 4 6.5 1 5.1 3 1.2 3 0.0 8 1.8 0 99. 78

8.7 1 0.1 4 6.0 3 9.3 5 4.7 8 0.9 7 0.0 4 3.2 0 99. 81

10. 99 0.1 9 6.5 2 8.4 4 4.3 9 0.0 6 0.1 5 2.9 3 99. 69

8.9 3 0.1 6 7.8 2 9.9 0 3.6 7 0.1 8 0.0 9 3.5 3 98. 51

10. 99 0.2 0 8.4 4 7.8 1 3.0 2 0.4 4 0.1 5 4.2 0 99. 71

10. 96 0.1 9 8.7 7 8.0 6 3.0 3 0.3 3 0.1 3 3.7 0 99. 70

2.0 0

1.6 0

2.3 0

3.1 0

b.d.

b.d.

54. 00 0.3 0 0.5 0 3.9 0 0.2 0 1.2 0

109 .00

62. 00

63. 40

28. 00 0.3 9 0.1 1 3.5 0 0.2 4 b.d . 10 8.0 0

87. 00 0.5 0 0.2 0 5.2 0 0.3 0 0.1 0 11 5.2 0

49. 36 1.5 1 20. 07 85. 60

31. 37 1.0 0 18. 91 65. 50

51. 00 1.3 0 20. 20 50. 00

88. 00 2.0 0 26. 90 40. 00

86. 90 2.6 0 33. 90 96. 00

27. 30 0.7 0 11. 80 5.0 0

25. 40 1.2 0 16. 70 49. 00

20. 20 0.7 0 12. 10 57. 00

60. 00 1.5 0 22. 90 80. 00

87. 40 2.4 0 28. 60 57. 00

71. 90 2.0 0 26. 70 64. 00

60. 00

3.7 0

65. 50

90. 00

60. 00

22. 60

0.8 0

23. 10 1.0 0 16. 20 50. 00 15 5.4 0

23. 00 0.3 0 0.0 7 2.6 0 0.2 3 b.d . 11 6.0 0 12 5.0 0 3.0 0 35. 60 50. 00

2.6 0 10 6.0 0 0.4 0 0.2 0 4.5 0 0.3 0 0.1 0

21. 52

27. 00 b.d . b.d . 1.8 0 0.2 0 b.d . 16 1.1 0

15. 40 11 1.0 0 0.3 0 0.1 0 0.4 0 b.d . 2.0 0 40 5.0 0

2.0 0

29. 00 0.6 0 0.1 8 5.8 0 0.4 1

17. 10 18 0.0 0 0.9 0 0.2 0 0.2 0 b.d . 0.4 0 25 3.4 0

b.d .

34. 00 0.2 7 0.0 7 2.6 0 0.1 5

12. 30 14 2.0 0 0.5 0 0.3 0 0.3 0 b.d . 0.4 0 26 2.3 0

89. 80

33. 20

20. 00

75. 80

67. 50

232 .30

50. 00

145 .10

108 .50

120 .00

110 .00

43. 30

8.9 0

7.9 0

324 .90

b.d.

473 .10

312 .00

310 .00

273 .68

455 .00

112 .70

376 .00

155 .60

267 .80

219 .00

272 .00

68. 42 30 9.0 0

68. 42 34 5.0 0

68. 42 26 3.0 0

32. 70 20 5.2 6 26 6.0 0

60. 00 13 6.8 4 32 7.0 0

55. 70 20 5.2 6 30 2.0 0

47. 20

190 .00

14. 20 27 3.6 8 17 2.0 0

70. 00 12 0.0 0 42 0.0 0 25 0.0 0

IP

SC R

NU

MA 40

T

6.2 4 0.1 2 7.8 5 11. 41 4.0 3 0.1 6 0.0 6 2.4 0 99. 77

D

Mn O Mg O Ca O Na 2O K2 O P2 O5 LO I To tal Trace elements (ppm)

dol erit e (di ke) FE M21 9 51. 50 1.7 7 12. 75

9.8 4 0.1 8 6.8 2 13. 54 3.2 6 0.1 4 0.1 9 13. 90 99. 83

TE

3

ga bb ro (di ke) FE M14 3 51. 75 0.4 5 14. 36

ga bb ro FE M13 0 52. 80 0.5 3 14. 13

CE P

Sa mp le Si O2 Ti O2 Al2 O3 Fe 2O

ga bb ro (di ke) FE M13 7 53. 70 0.5 2 14. 65

ga bb ro FE M12 8 38. 85 1.4 2 11. 68

AC

Ro ck

ga bb ro (di ke) FE M13 5 53. 35 0.5 6 13. 69

71. 80

68. 42 29 9.0 0

ACCEPTED MANUSCRIPT

Dy Ho Er T m Yb Lu (L a/ Yb )N (L a/ S m) N

1.0 5

0.9 8

13. 80

1.6 7

5.9 2

10. 02

7.2 1

0.4 5

0.8 8

1.1 4

1.3 1

1.8 9

1.2 8

1.8 2

1.6 1

1.8 1

0.4 3

1.1 3

3.0 5

1.1 1

2.0 0

2.6 6

1.9 8

2.9 9

1.5 7

0.9 3

1.8 2

1.0 4

1.4 1

(D y/ Yb 1.0 )N 3 Eu /E 1.4 u* 7 b.d: below detection

2.4 7 6.4 9 1.0 3 5.5 4 1.8 6 0.7 6 2.6 7 0.5 2 3.1 8 0.6 7 1.9 9 0.3 2 2.0 1 0.3 1

5.2 0 12. 80 1.9 0 9.4 7 2.8 5 1.0 2 3.7 7 0.7 1 4.3 1 0.9 0 2.6 4 0.4 2 2.6 6 0.4 0

4.7 0 12. 00 2.0 0 10. 10 3.3 4 1.1 0 4.5 0 0.9 3 5.6 2 1.2 3 3.6 4 0.6 0 3.7 3 0.5 8

2.2 0 5.2 0 0.8 0 3.9 0 1.3 6 0.5 7 1.8 0 0.3 5 2.1 4 0.4 5 1.2 2 0.1 9 1.1 4 0.1 8

2.9 0 6.4 0 0.8 9 4.2 0 1.4 3 0.4 9 2.0 2 0.4 0 2.6 4 0.5 9 1.7 3 0.2 9 1.9 3 0.2 9

3.8 0 8.2 0 1.0 9 5.1 0 1.6 1 0.5 1 2.2 0 0.4 4 2.7 1 0.6 5 1.9 3 0.3 0 1.9 7 0.3 1

1.5 0 3.1 0 0.4 7 2.7 0 0.9 4 0.3 6 1.4 1 0.3 0 2.0 1 0.4 8 1.3 9 0.2 5 1.4 3 0.2 3

4.4 7 14. 30 2.3 7 12. 80 4.2 2 1.5 4 5.8 2 1.1 1 7.2 0 1.4 9 4.3 5 0.6 8 4.2 8 0.6 8

3.3 2 8.4 5 1.3 1 6.6 4 2.2 3 0.8 1 3.0 9 0.6 0 3.6 3 0.8 0 2.2 0 0.3 5 2.2 4 0.3 3

5.1 0 12. 90 2.1 2 10. 40 3.1 2 1.1 2 4.2 6 0.8 3 4.8 9 1.0 6 3.0 8 0.4 9 3.0 7 0.4 7

4.4 0 10. 90 1.7 7 9.1 0 2.8 2 0.9 9 3.8 0 0.7 8 4.5 2 1.0 2 3.0 3 0.4 8 2.8 3 0.4 3

1.4 0

0.9 0

1.3 8

1.0 8

1.3 8

0.7 5

0.7 5

1.0 6

1.1 9

1.1 2

0.8 6

1.1 8

0.9 1

1.0 4

1.3 1

1.5 2

1.0 3

0.6 8

0.9 6

1.0 6

1.0 1

1.2 4

1.0 6

1.0 8

1.0 1

1.2 6

0.9 2

0.9 2

0.9 4

1.1 3

1.0 8

1.0 7

1.0 7

0.9 4

1.0 5

0.9 5

0.8 7

1.1 1

0.8 8

0.8 3

0.9 6

0.9 5

0.9 4

0.9 4

0.9 2

41

T

1.2 1 4.2 1 0.7 8 4.5 2 1.8 2 0.6 7 2.6 5 0.5 2 3.5 6 0.7 6 2.1 4 0.3 0 1.9 2 0.3 0

IP

15. 02 35. 78 4.9 9 22. 57 5.3 6 2.4 9 5.4 2 0.8 1 4.4 3 0.8 4 1.9 9 0.2 6 1.5 0 0.2 2

SC R

Tb

24. 30 59. 00 8.5 4 41. 20 9.7 3 3.3 7 10. 10 1.4 1 6.9 1 1.1 3 2.7 1 0.3 2 1.7 4 0.2 3

NU

Gd

4.0 1 8.2 3 1.1 3 5.2 6 1.4 2 0.9 0 1.6 1 0.2 5 1.4 5 0.2 7 0.6 6 0.0 9 0.4 9 0.0 7

MA

Eu

9.1 3 21. 60 3.1 7 15. 40 4.6 1 1.5 7 5.8 4 1.0 8 6.4 9 1.3 5 3.9 1 0.6 1 3.9 3 0.6 0

D

Nd S m

11. 72 26. 04 3.6 0 16. 78 4.0 0 2.1 0 4.1 9 0.5 4 2.7 7 0.4 8 1.0 2 0.1 2 0.6 1 0.0 9

TE

Pr

0.2 6 0.5 5 0.0 7 0.3 4 0.1 3 0.1 6 0.2 1 0.0 4 0.3 2 0.0 7 0.1 9 0.0 3 0.1 9 0.0 3

CE P

Ce

0.6 0 1.3 0 0.2 0 1.0 0 0.3 4 0.2 0 0.5 1 0.1 1 0.6 3 0.1 4 0.4 0 0.0 7 0.4 1 0.0 6

AC

La

ACCEPTED MANUSCRIPT Table 2 Sr-Nd-Pb isotopes ratios.

Initia l (a)

Mea sure d

Initi al

Mea sure d

Initi al

Mea sure d

Initi al

0.70 407 9

n.d.

0.51 297 4

0.5 127 59

18.4 99

n.d .

15.5 47

0.70 474 8 0.70 439 8 0.70 465 6 0.70 461 6 0.70 461 7 0.70 407 6 0.70 377 3

0.70 442 8 0.70 368 1 0.70 438 8 0.70 449 5 0.70 445 4 0.70 395 4 0.70 359 2

0.51 258 5 0.51 268 9 0.51 263 2 0.51 260 6 0.51 259 4 0.51 300 2 0.51 295 5

0.5 124 35 0.5 125 00 0.5 124 62 0.5 124 57 0.5 124 45 0.5 127 48 0.5 127 43

NU

0.70 378 1

0.70 356 8

0.51 291 5

0.5 127 25

FE M211 FE M128 FE M130 FE M135 FE M137

gabb ro

0.70 618 1 0.70 453 5

0.70 601 5 0.70 444 2

0.51 298 5 0.51 292 5

0.5 127 77 0.5 127 05

gabb ro gabb ro (dike ) gabb ro (dike )

0.70 491 4

0.70 460 5

0.51 284 5

0.70 511 2

0.70 466 8

0.51 281 9

Pb( i)

19.5 68 18.9 68 19.3 57 18.3 06

P b/ 204 P b

Pb / 204

Pb( i)

P b/ 204 P b

Pb / 204

Pb( i)

DM model age

Mea sure d

Initi al

n.d .

38.7 05

n.d .

1.144

SC R

204

15.6 93

15. 68 96

39.4 29

39. 33 7

0.999

n.d .

15.7 02

n.d .

39.6 05

n.d .

1.592

18. 50 42 18. 92 82 18. 37 88 18. 18 82

15.6 33 15.6 19 15.5 62 15.5 55

15. 58 04 15. 61 66 15. 51 4 15. 54 97

41.1 09 39.8 73 40.2 57 38.3 38

39. 59 0 39. 79 6 38. 88 1 38. 20 34

ɛD M( t)

ɛCH UR( t)

1. 64

6.39

Ga

18. 48 74

MA 18.8 64

D

TE

CE P

18.5 59

Pb /

208 208

T

Mea sure d

AC

FE M144 FE M192 FE M193 FE M195 FE M198 FE M200 FE M202 FE M210

Roc k meta basit e (prot odike) meta basit e meta basit e meta basit e meta basit e meta basit e meta basit e meta basit e meta basit e (prot odike)

86

P b/ 204 P b

207 207

N d/ 144 N d

Sr/ 86 Sr

N d/ 144 N d(i)

206

Sr/ Sr( i)

87

87

Sa mpl e

143

IP

206 143

1.212

0.938

0.971 0.522

7. 97 6. 69 7. 43 7. 54 7. 77 1. 87 1. 95

0.05

1.33

0.59

0.48

0.25

6.16

19.1 85

n.d .

15.5 95

n.d .

39.4 83

n.d .

21.8 07

n.d .

15.2 20

n.d .

41.5 87

n.d .

18.8 63

18. 19 5

15.5 84

15. 55 1

38.3 35

38. 20 43

0.682

18.7 18

n.d .

15.6 18

n.d .

39.1 31

n.d .

2.603

0.5 126 30

19.2 02

17. 98 1

15.6 64

15. 60 4

39.1 10

38. 44 48

3.864

4. 16

3.86

0.5 126 20

18.8 45

18. 03 7

15.6 03

15. 56 3

38.9 80

37. 79 12

1.419

4. 36

3.67

42

1.139

0.642

2. 31 1. 30 2. 70

6.07

5.72

6.72

5.33

ACCEPTED MANUSCRIPT

basa lt basa lt

0.51 294 6

0.5 127 27

18.5 19

18. 43 9

15.6 28

15. 62 4

38.5 59

38. 48 06

2.692

2. 27

5.76

0.70 506 6

n.d.

0.51 306 0

0.5 128 52

17.9 58

n.d .

15.2 95

n.d .

37.5 33

n.d .

0.099

0. 16

8.19

0.70 498 4 0.70 424 6 0.70 621 5

0.70 486 2 0.70 406 9 0.70 597 7

0.51 293 3 0.51 295 5 0.51 295 1

0.5 127 21 0.5 127 66 0.5 127 56

18.5 28

n.d .

15.4 13

n.d .

38.4 08

18.6 38 18.8 51

n.d. = not determined because Rb or Pb, U, Th concentrations were below detection limit

AC

CE P

TE

D

MA

(a) initial ratios and DM(t) are calculated for an age of 160 Ma for all samples

15. 42 73 15. 62 3

43

15. 40 93 15. 37 8

T

0.70 596 5

15.5 67 15.5 37

n.d .

IP

basa lt

0.70 621 5

SC R

FE M219 FE M134 FE M140 FE M141

gabb ro (dike ) doler ite (dike )

NU

FE M143

38.7 12 38.9 38

36. 08 93 36. 82 77

1.405

0.467

0.573

2. 39 1. 51 1. 71

5.64

6.52

6.32

ACCEPTED MANUSCRIPT Table 3 Mineral assemblages in the rock units of the Kızılırmak accretionary complex. Lon gitu de

Textur e

Roc k

A P P O m l x l p

41° 12'2 0''N

34° 50'5 2''E

catacla stic

gab bro

X X

41° 13'3 1''N

34° 49'3 0''E

bas alt

X X X

41° 13'3 6''N

34° 49'2 5''E

intergr anular microlit icporphy ric

bas alt

X X

41° 13'2 2''N

34° 49'1 7''E

ophitic

gab bro

X X

X

41° 13'1 3''N

34° 50'1 0''E

ophitic

gab bro

X X

X

41° 12'0 6''N

34° 44'4 3''E

quench ed

41° 12'5 8''N

34° 45'5 7''E

41° 14'2 8''N

34° 57'2 3''E

K C P f Q E B M P h r s z p t s h l h

IP SC R

X *

C S a p l n

O A Il p p m q

X *

X

X *

X *

X

X *

X

X

X *

X *

X *

X *

X

TE

D

MA

NU

X *

CE P

bas alt

X X

gab bro

granobl astic

met aba site

34° 57'1 8''E

granobl astic

met aba site

X

X

41° 11'3 8''N

34° 55'0 1''E

nemato blastic

met aba site

X

X

41° 11'3 8''N

34° 55'0 1''E

granobl astic

met aba site

X

X

41° 11'3 9''N

34° 54'5 8''E

granobl astic

met aba site

X

X

X X *

X *

X *

41° 11'3 9''N 41° 11'3

34° 54'5 8''E 34° 54'5

nemato blastic granobl astic

met aba site met aba

X

X

X *

X

X

X * X *

X * X *

X X

X

X *

X

X *

X *

subophitic

41° 14'3 1''N

P m p

T

Latit ude

AC

Sa mpl e FE M12 8 FE M13 3 FE M13 4 FE M13 5 FE M13 7 FE M14 1 FE M14 3 FE M14 4 FE M14 5 FE M19 2 FE M19 3 FE M19 4 FE M19 5 FE M-

X X X

X

X *

X

X X

X *

X *

X *

X *

X *

X *

X *

X

X

X X X

X

44

X

X *

X

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7''N 6''E 19 site 6 FE 34° 41° Mmet 11'4 54'5 granobl aba 19 X 1''N 3''E astic 8 site X X * X X X X FE 34° 41° Mmet 11'4 54'5 granobl aba 20 1''N 3''E astic 0 site X X X X FE 41° 34° Mmet 11'4 54'5 granobl aba 20 X X 1''N 3''E astic 1 site X X * * FE 41° 34° Mmet 11'4 53'0 granobl aba 20 X X X 5''N 6''E astic 2 site X X X * * * X FE 34° 41° Mmet 12'1 54'3 nemato aba 21 X X X X 3''N 8''E blastic 0 site X X * * * * FE 41° 34° Mmet 12'1 54'3 granobl aba 21 X 3''N 8''E astic 1 site X X X * X FE 41° 34° M11'5 55'4 sub21 dole X X 7''N 8''E ophitic 9 rite X X * * X FE 34° 41° Mmicrocr 11'2 55'4 ystallin bas 22 X 0''N 9''E e 0 alt X * X* indicates to the secondary mineral developments (mostly in veinlets) by the low grade metamorphic overprint or the hydrothermal alteration processes. Abbreviations: Pl, plagioclase; Px, pyroxene; Ol, olivine; Amp, amphibole; Kfs, K-feldspar; Qz, quartz; Ep, epidote; Bt, biotite; Ms, muscovite; Ph, phengite; Chl, chlorite; Prh, prehnite; Pmp, pumpellyite; Cal, calcite; Spn, sphene; Ap, apatite; Ilm, ilmenite; Opq, opaque mineral.

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ACCEPTED MANUSCRIPT Highligts - Amphiboles from metabasites yield Jurassic 40Ar/39Ar plateau ages (159.4±0.4 Ma and

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163.5±0.8 Ma)

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- The new data indicates Late Jurassic subduction-accretion in the Central Pontides.

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- Geochemistry and isotopes of metabasic rocks indicate N-MORB, E-MORB, OIB and IAT sources

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- Ophiolitic rocks were formed in a supra-subduction tectonomagmatic environment

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