Spatial, temporal and geochemical evolution of Oligo–Miocene granitoid magmatism in western Anatolia, Turkey

Gondwana Research 21 (2012) 961–986

Contents lists available at SciVerse ScienceDirect

Gondwana Research journal homepage: www.elsevier.com/locate/gr

GR focus review

Spatial, temporal and geochemical evolution of Oligo–Miocene granitoid magmatism in western Anatolia, Turkey Şafak Altunkaynak a,⁎, Yıldırım Dilek b, Can Ş. Genç a, Gürsel Sunal a, Ralf Gertisser c, Harald Furnes d, Kenneth A. Foland e, Jingsui Yang f a

Department of Geology Engineering, Istanbul Technical University, Maslak 34469, Istanbul, Turkey Department of Geology, 116 Shideler Hall, Miami University, Oxford, OH 45056, USA School of Physical and Geographical Sciences, Earth Sciences and Geography, Keele University, Keele, Staffordshire, ST5 5BG, United Kingdom d Department of Earth Science and Centre for Geobiology, University of Bergen, Allegt. 41, 5007 Bergen, Norway e School of Earth Sciences, Ohio State University,125 South Oval Mall, Columbus, OH 43210, USA f State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825,Beijing 100029, China b c

a r t i c l e

i n f o

Article history: Received 15 June 2011 Received in revised form 10 October 2011 Accepted 26 October 2011 Available online 7 November 2011 Handling Editor: M. Santosh Keywords: Oligo–Miocene granitoids Western Anatolia Post-collisional magmatism Open system processes Thermal weakening and synconvergent extension

a b s t r a c t Western Anatolia (Turkey) experienced widespread Cenozoic magmatism after the collision between the Sakarya (SC) and Anatolide–Tauride continental blocks (ATP) in the pre-middle Eocene. Voluminous granitic magmas were generated and emplaced into the crystalline basement rocks of the Rhodope (RM) and Sakarya continent to the north and Anatolide–Tauride Platform to the south of the ~ E–W-trending Izmir–Ankara suture zone (IASZ) during the late Oligocene–middle Miocene. We report here a comprehensive geochronological (combined zircon U–Pb and 40Ar–39Ar dating) and geochemical (major and trace element geochemistry, and Sr–Nd isotopes) dataset from the Oligo–Miocene granitoids in order to evaluate the nature and the spatial–temporal distribution of the Cenozoic magmatism in the Aegean extensional province. Zircon SHRIMP U–Pb dating of these plutons yields ages between 19.48 ± 0.29 and 23.94 ± 0.31 Ma as the timing of their emplacement, whereas 39Ar/40Ar dating of biotite separates from these plutons reveals cooling ages of 18.9 ± 0.1–24.8 ± 0.1 Ma. Regardless of the lithological make-up of the collided blocks, the RMG, SCG and NATPG granitoids that were emplaced into the RM, SC and ATP, respectively, show similar major and trace element and Sr–Nd isotopic compositions, indicating common mantle melt sources and magmatic evolutionary trends. The isotopic signatures and trace element characteristics of these granitoids indicate that both lithospheric and asthenospheric mantle melts appear to have contributed to source region of the RMG, SCG and NATPG magmas. The compositional variations observed in these granitoids are interpreted as a result of opensystem processes (AFC and/or MASH) rather than a reflection of different compositions of crustal lithologies through which RMG and SCG, ATPG magmas migrated. On the other hand, the SATPG with crustal signatures stronger than the other groups may have been produced by crustal melting or significant contributions from the ATP crystalline basement. The isotopic compositions and cooling age relationships of western Anatolian granitoids indicate an increasing crustal signature from 24 to 18 Ma coinciding with crustal exhumation (Kazdag and Menderes core complexes) and extension in western Anatolia. Asthenospheric upwelling caused by partial delamination or convective thinning of lithosphere led to underplating of mantle-derived magmas that provided melts and heat to induce partial melting of sub-continental lithospheric mantle. Stalling of mantle-derived melts in the crust triggered open system processes in separate magma chambers, resulting in the production of granitic magmas. This inferred melt source and magma evolution readily explains the Itype granitoid nature of most late Oligocene to middle Miocene plutons in western Anatolia regardless of their temporal and spatial position. The widespread early to middle Cenozoic magmatism caused thermal weakening and played a significant role for the initiation of synconvergent extension, exhumation and thinning in the hinterland of a young Tethyan orogen in western Anatolia and the broader Aegean region. © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

⁎ Corresponding author. Tel.: + 90 212 2856272; fax: + 90 212 2856080. E-mail address: [email protected] (Ş. Altunkaynak). 1342-937X/$ – see front matter © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2011.10.010

962

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

Contents 1. 2. 3. 4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . Regional geology . . . . . . . . . . . . . . . . . . . . . Synopsis of Cenozoic plutonism in western Anatolia . . . . Analytical techniques . . . . . . . . . . . . . . . . . . . 4.1. SHRIMP dating. . . . . . . . . . . . . . . . . . . 40 Ar/39Ar dating . . . . . . . . . . . . . . . . . . 4.2. 4.3. Major, trace elements and Sr–Nd isotope analyses . . 5. Geochronology . . . . . . . . . . . . . . . . . . . . . . 5.1. U–Pb zircon ages. . . . . . . . . . . . . . . . . . 40 Ar/39Ar dates . . . . . . . . . . . . . . . . . . 5.2. 6. Geochemistry . . . . . . . . . . . . . . . . . . . . . . 6.1. Major and trace element characteristics . . . . . . . 6.2. Sr and Nd isotopic signatures and Nd model ages . . 7. Petrogenesis . . . . . . . . . . . . . . . . . . . . . . . 7.1. Source characteristics . . . . . . . . . . . . . . . 7.2. Magma evolution . . . . . . . . . . . . . . . . . 7.3. Petrogenetic modeling . . . . . . . . . . . . . . . 8. Interplay between syn-convergent extension and magmatism 9. Conclusions . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . in western Anatolia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction Western Anatolia is one of the best natural laboratories in the broader Alpine–Himalayan orogenic system to investigate in fourdimensions the nature and distribution of post-collisional magmatism, the interplay between tectonic and magmatic processes, and the crust–mantle interactions in a young mountain belt. The consumption of a Neo-Tethyan oceanic lithosphere at a subduction zone dipping northwards beneath the Sakarya continent during the late Cretaceous resulted in a continent–continent collision between the Sakarya and Anatolide–Tauride continental fragments in the eastern Mediterranean region (Şengör and Yılmaz, 1981). The timing of this collision has been well established in the literature as pre-middle Eocene (Harris et al., 1994; Okay and Tüysüz, 1999). The widespread magmatic activity in NW Anatolia postdates this continental collisional event in the region (Yılmaz, 1989, 1990; Güleç, 1991; Şengör et al., 1993; Harris et al., 1994; Seyitoğlu and Scott, 1996). The first products of post-collisional magmatism are the middle Eocene granitic plutons and andesitic extrusive rocks (Harris et al., 1994; Genç and Yılmaz, 1997; Delaloye and Bingöl, 2000; Köprübaşı and Aldanmaz, 2004; Altunkaynak and Dilek, 2006; Okay and Satır, 2006; Altunkaynak, 2007). The following magmatic episode during the Oligocene and Early Miocene is known to have produced the widespread granitic plutons (i.e., Kozak, Evciler, Cataldag, Kestanbol, Ilica-Samli, Eybek, Egrigoz, Koyunoba) and associated volcanic rocks in western Anatolia (Yılmaz, 1989; Altunkaynak and Yılmaz, 1998, 1999; Genç, 1998; Yılmaz et al., 2001; Özgenç and İlbeyli, 2008; Akay, 2009). The relationships between tectonics and magmatism and their variation in time and space since the beginning of the Neogene remain some of the most fundamental questions in the geodynamic evolution of western Turkey and the broader Aegean extensional province. Although some geochemical data exist from this region (Harris et al., 1994; Genç and Yılmaz 1997; Altunkaynak and Yılmaz, 1998, 1999; Genç, 1998; Karacık and Yılmaz, 1998; Delaloye and Bingöl, 2000; Köprübaşı and Aldanmaz, 2004; Okay and Satır, 2006; Altunkaynak, 2007; Altunkaynak and Genç, 2008; Özgenç and İlbeyli, 2008; Akay, 2009; Altunkaynak et al., 2010; Hasözbek et al., 2010; Mackintosh and Robertson, 2011), it is not systematic and it does not contain sufficient isotopic and geochronological information to develop a regionally coherent and viable geochemical and geodynamic model for the postcollisional magmatic evolution of NW Anatolia.

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

962 962 965 965 965 965 965 967 968 969 969 972 974 975 975 979 980 980 982 983 974 983

We have investigated the geochronology, geochemistry and petrogenesis (magma sources, magma genesis and crust–magma interaction) of post-collisional granitic plutons and stocks emplaced into the Anatolide–Tauride and Sakarya continental blocks on both sides of the Izmir–Ankara suture zone (Fig. 1). Straddling one of the major continental collision zones in the eastern Mediterranean region, the granitoids we have investigated provide us with an opportunity to evaluate the geochemical fingerprint and melt evolution of post-collisional magmatism in and across a suture zone, and to document, for the first time, the different isotopic domains beneath the early Tertiary western Anatolia. In this paper, we present our new geochemical data, Sr–Nd isotope compositions, 40Ar– 39Ar and zircon Shrimp ages from the late Oligocene to middle Miocene granitoid plutons, and the petrogenesis of thirteen granitoids to constrain the magmatic evolution and melt sources of the post-collisional magmatism in the region. We then discuss the mantle dynamics and the melt evolution beneath western Anatolia as a case study of alpine-style collision zone magmatism. 2. Regional geology The crustal architecture of western Anatolia and the broader Aegean region is formed from a collage of continental blocks, separated by ophiolites and suture zones that are nearly parallel to each other (IPSZ, VS_IASZ, PS in Fig. 1). The basement geology of NW Anatolia includes five tectonic units. These are, from north to south, the Rhodope massif (RM), the Intra-Pontide Suture zone (IPSZ), the Sakarya continent (SC), the Izmir_Ankara suture zone (IASZ) and the Anatolide– Tauride platform (ATP) (Şengör and Yılmaz, 1981; Okay and Satır, 2000 and references therein). The Çamlıca micaschist which is a part of the Rhodope massif (Okay and Satır, 2000) is exposed around the Ezine and Karabiga (Fig. 2) in northwestern areas. The Sakarya continent (Şengör and Yılmaz, 1981) consists of two types of rock associations; a) Palaeozoic continental metamorphic rocks (i.e. the Uludağ and Kazdağ metamorphic massifs and the Söğüt basement) and b) Triassic metamorphic rocks (mainly the Karakaya complex, Bingöl et al., 1975; Okay et al., 1990; Genç, 2004). The Çamlıca micaschist and the Sakarya continent are separated by a high-angle fault zone, marked by ophiolitic fragments of IPSZ (Okay and Satır, 2000, 2006). The Anatolide–Tauride platform farther south is composed of carbonates and intercalated

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

963

30°E

E U R A S I A N P L AT E P

BLACK SEA

e

VS

RRhhooddooppee

IPS SC

28°

Samo Samontraki

pe

o od Rh Kazdag M.

g

u

o

p

Limnos

2

1

4

EB

i a

a l i

n

Psathoura

Evia

Skyros Lesbos

Cylades

40°N

10

13 1

ATP

Chios

AEGEAN Athens ns n s SEA

?

Aegean Sea

PS

A

l a

Istanbul Zone

Sea of Marmara

IAS

20°E

Anatolia

Samos S

Menderes M.

Study area

T iinoss Tinos

Patm tm Patmos

Milos Santorini

Bodrum

Kos

36°N Crete Massif

HELLENIC SUBDUCTION ZONE

32°N

Neogene granitoids Suture zones

AFRICAN

P L AT E

Fig. 1. Generalized map of the Aegean region showing the distribution of Neogene granitoids, metamorphic massifs and major structural elements (modified from Pe-Piper and Piper, 2001, 2006).

volcanosedimentary and epiclastic rocks ranging in age from CambroOrdovician (and older?) to Lower Cretaceous (Ricou et al., 1975; Demirtasli et al., 1984), and is tectonically overlain by Cretaceous ophiolite nappes derived from a Tethyan seaway to the north (Juteau, 1980; Şengör and Yılmaz, 1981; Dilek and Moores, 1990; Dilek et al., 1999). The Kazdag and Menderes metamorphic massifs representing core complexes of western Anatolia (Bozkurt and Park, 1994; Hetzel et al., 1995; Hetzel and Reischmann, 1996; Bozkurt and Satır, 2000) consist of high-grade lower crustal rocks that were exhumed during the postcollisional extensional tectonic evolution of the region. They are overlain by relatively unmetamorphosed cover sequences and are intruded by granitoids (Hetzel and Reischmann 1996; Bozkurt and Park, 1994; Okay and Satır, 2000; Gessner et al. 2004). The Menderes metamorphic massif (i.e. Şengör et al., 1984) was formed mainly from

continent-type metamorphic rocks (micaschists and gneisses) and separated from the Sakarya continent by the Izmir–Ankara suture zone (Şengör and Yılmaz, 1981; Okay and Tüysüz, 1999) (Fig. 2). The IPSZ marks the collision zone between the RM (to the north) and SC (to the south) in northern Turkey (Okay and Tüysüz, 1999; Okay and Satır, 2006). These continental blocks collided as the Intra-Pontide ocean was consumed at a north-dipping subduction zone throughout the Cretaceous (Şengör and Yılmaz, 1981). All these tectonic entities juxtaposed to form a tectonic mosaic prior to the deposition of the Upper Campanian–Maastrichtian successions that form the first common non-metamorphic cover (Yılmaz et al., 1995). Following this event, a new sedimentation phase accompanied by rigorous andesitic volcanism and co-eval granitic plutonism started at the beginning of the middle Eocene (Lutetian, 48–39 Ma; Gulmez and Genc, 2009; Genc et al., unpublished age data). These

964

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

granitic rocks and the volcano-sedimentary succession were described as “post-collisional” magmatic activity (Genç and Yılmaz, 1997; Yılmaz et al., 1997). The Izmir–Ankara suture zone in western Anatolia represents the collision zone between the Sakarya continent and Anatolide– Tauride platform (Şengör and Yılmaz, 1981). The Izmir–Ankara suture zone includes two different tectonostratigraphic units. In its northwestern and western parts, it consists of a wild-flysch sequence (Bornova flysch of Okay and Siyako, 1993), which contains abundant platform type carbonate olistholiths and olistostromes together with the ophiolitic slices and blocks embedded in finegrained flysch-type sediments. In the northern and eastern areas (i.e. south of Uludağ, near the Orhaneli and its east continuation) the Izmir–Ankara suture zone is represented mainly by the dismembered and tectonically mixed ophiolitic rocks. These tectonic units were juxtaposed with each other as a consequence of the collision between the Sakarya continent to the north and the Anatolide–Tauride Platform to the south during the late Cretaceous– Paleocene (Şengör and Yılmaz, 1981; Okay and Tüysüz, 1999). The northern branch of the Neo-Tethyan ocean, located between the Sakarya continent and the Anatolide–Tauride Platform, was totally consumed at the beginning of the pre-middle Eocene at a subduction zone dipping northwards beneath the Sakarya continent (Harris et al., 1994; Okay and Tüysüz, 1999). Following the collision, the units of the Sakarya continent and the Bornova flysch were covered unconformably by continental to shallow marine

sedimentary rocks (Baslamis Formation; Akdeniz, 1980 and Gebeler Formation; Akyurek and Soysal, 1983) during middle Eocene. This stratigraphic relationship indicates that the timing of the collision in NW Anatolia was earlier than the middle Eocene. After the continental collision, two major magmatic episodes occurred in the region. The first was developed during the middle–late Eocene, and produced extensive plutonic and volcanic associations in different parts of NW Anatolia. The middle Eocene magmatic associations have been studied in detail previously (Genç and Yılmaz, 1997; Köprübaşı and Aldanmaz, 2004; Altunkaynak, 2007; Dilek and Altunkaynak, 2007). The second magmatic phase occurred during the late Oligocene–middle Miocene. It is represented by granitic plutons and co-eval volcanic rocks, similar to those of the middle Eocene magmatic associations. Our study focuses mainly on the Late Oligocene–middle Miocene granitic rocks. We studied thirteen granitic bodies (Fig. 2), including, from northwest to southeast, the Kestanbol, Evciler, Karakoy, Katrandag, Yenice, Hıdırlar, Ilica-Samlı, Kozak, Çataldag, Eybek, Çamlık, Eğrigöz and Salihli granitoids. The Katrandağ, Yenice, Hıdırlar and Salihli granites are represented by stocks, whereas the others are large plutons. The Kestanbol granite was emplaced into the Sakarya basement rocks (Karacık and Yılmaz, 1998), which are imbricated with the Çamlıca micaschists of the Rhodope belt. The Kozak, Evciler, Ilıca-Şamlı, Eybek, Çataldağ, Hıdırlar and Katrandağ granites were emplaced into the metamorphic basement rocks of the

Fig. 2. Simplified geological map of W Anatolia showing the distribution of granitoids (Modified from Yılmaz et al., 2000; Okay and Satir, 2006). IAESZ; Izmir–Ankara–Erzincan suture zone, RM: Rhodope Massif, SC: Sakarya Continent, and ATP—Anatolide–Tauride platform). E1 to 7: Eocene granitoids, 1-Kestanbol, 2-Evciler, 3-Hıdırlar-Katrandag 4-Eybek, 5-Yenice, 6-Danisment, 7-Sarıoluk, 8-Kozak 9-Uludag, 10- Ilica-Samli 11-Davutlar, 12-Çataldag, 13-Egrigoz, 14-Koyunaoba, 15-Çamlik, 16-Turgutlu, 17-Salihli granitoids. Data for radiometric ages: This study; Bingol et al., 1982; Hetzel et al., 1995; Delaloye and Bingöl, 2000; Işık et al., 2004; Ring and Collins 2005; Glodny and Hetzel 2007; Karacik et al., 2008; Boztuğ et al., 2009.

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

Sakarya continent. The Çamlık, Eğrigöz and Salihli granitoids are the representatives of the granites that were emplaced into the Anatolide–Tauride Platform (i.e. the metamorphic rocks of the Menderes Massif). The late Oligocene–middle Miocene plutons are magmatic bodies that were emplaced at shallow depths in the crust. They crosscut the metamorphic country rocks and have well developed contact aureoles around their periphery. Along the border zone, the plutons contain numerous metamorphic xenoliths and mafic microgranular enclaves. Many of the late Oligocene–middle Miocene granites have been described as caldera type, sub-volcanic plutons showing close relationships with their co-genetic volcanic rocks in time and space (Yılmaz, 1989; Altunkaynak and Yılmaz, 1998, 1999; Genç, 1998; Yılmaz et al., 2001). 3. Synopsis of Cenozoic plutonism in western Anatolia Cenozoic plutonism in western Anatolia has been the subject of many studies. The models and interpretations derived from these studies support different and often conflicting views about the nature, origin and evolution of Cenozoic magmatism in the region. Borsi et al. (1972), Fytikas et al. (1976) and Delaloye and Bingöl (2000) have argued that the western Anatolian plutons originated from the Paleocene and younger magmatism associated with the Hellenic subduction zone. The Kozak, Kestanbol, Evciler and Karaköy plutons are post-collisional in character and are likely to have been derived from the mantle and contaminated by thickened orogenic crust, and may have evolved from a mixed magma source under a compressional regime (Altunkaynak and Yılmaz, 1998, 1999; Genç, 1998; Karacık and Yılmaz, 1998; Yılmaz et al., 2001; Yılmaz-Şahin et al., 2010). The Ilıca, Cataldag and Kozak granitoids were derived from different magma sources generated by partial melting of various sources including metasomatized mantle and crustal material in a post-collisional extensional setting as a result of slab break-off event following the collision between the SC and the ATP (Boztuğ et al., 2009). Işık et al. (2004) reported that the syn-extensional Egrigöz and Koyunoba plutons in the footwall of the Simav Detachment were emplaced in the early stages of continental extension in the Aegean province. These granitoids are hybrid in nature with dominantly upper crustal compositions similar to the coeval Oligo–Miocene granitoids in the central Aegean Sea region. For the same granitoids, Akay (2009) and Hasözbek et al. (2010) argued for a hybrid magma source produced under a compressional regime. Özgenç and İlbeyli (2008) proposed that the Egrigöz pluton formed by partial melting of mafic, lower crustal rocks during post-collisional extensional tectonics in the region. Catlos et al. (2008) suggested that the trace-element geochemical features of the Salihli and Turgutlu granitoids are consistent with a continental arc origin and that the magmas were generated under a compressional regime above the north-dipping Hellenic subduction zone. Dilek et al. (2009) and Öner et al. (2010) proposed that the Salihli and Turgutlu granitoids represent syn-extensional intrusions and formed by partial melting of the subductionmetasomatized lithospheric mantle and the overlying lower–middle crust. Altunkaynak and Dilek (2006), Altunkaynak (2007) and Dilek and Altunkaynak (2007, 2009) suggested that partial melting of enriched, subcontinental lithospheric mantle-derived melts and subsequent fractional crystallization, accompanied by crustal assimilation, were important processes in the genesis and evolution of the magmas. They demonstrated that mantle-derived melts experienced decreasing subduction influence and increasing crustal contamination during the evolution of the Eocene and Oligo–Miocene volcanoplutonic associations. They further argued that collision-induced slab break-off allowed an influx of asthenospheric heat that resulted in partial melting of the orogenic lithospheric mantle, which was previously metasomatized by slab-derived fluids beneath the Izmir–

965

Ankara suture zone, producing the Eocene and Oligo–Miocene igneous suites. 4. Analytical techniques 4.1. SHRIMP dating Zircons were extracted from 5 to 10 kg of rock samples by standard mineral separation techniques, mainly grinding, sieving, Frantz isodynamic separator and heavy liquids. Separated zircons were handpicked under a binocular microscope, and then a fraction with grain sizes of 63–200 μm was selected and sorted according to their crystal properties (i.e. euhedral morphology, lack of overgrowth and visible inclusions). Zircons were mounted in epoxy resin and polished down to expose grain interiors for cathodoluminescence (CL) and SHRIMP studies. Zircons were dated on the SHRIMP II ion microprobe at the Beijing SHRIMP Centre, Institute of Geology, Chinese Academy of Geological Sciences. The analytical procedures were similar to those described by Williams (1998). Mass resolution during the analytical sessions was ~5000 (1% definition), and the intensity of the primary ion beam was 5–8 nA. Primary beam size was 25–30 μm, and each site was rastered for 120–200 s prior to analysis. Five scans through the mass stations were made for each age determination. U abundance was calibrated using the standard SL13 (U = 238 ppm, Williams, 1998) and 206Pb/ 238U was calibrated using the standard TEMORA ( 206Pb/ 238U age = 417 Ma; Black et al., 2003). The decay constants used for age calculation are those recommended by the Subcommission on Geochronology of IUGS (Steiger and Jager, 1977). Measured 204Pb was applied for the common lead correction, and data processing was carried out using the Squid and Isoplot programs (Ludwig, 2001). The uncertainties for individual analyses are quoted at the 1 sigma confidence level, whereas errors for weighted mean ages are quoted at 95% confidence. 4.2.

40

Ar/ 39Ar dating

Incremental step-heating 40Ar/ 39Ar age measurements were performed on amphibole and biotite mineral separates from the western Anatolian Oligo–Miocene granitoids. The analyses were performed in the Radiogenic Isotopes Laboratory at Ohio State University. The general procedures have been described by Foland et al. (1993) and references therein, except for the use of a new noble-gas mass analysis system. Sized aliquots (~ 1–15 mg) of biotite or amphibole were irradiated in the L-67 position of Ford Nuclear Reactor, Phoenix Memorial Laboratory, at the University of Michigan for 36 h. They were subsequently heated incrementally to successively higher temperatures using a custom-built, resistance-heating, high-vacuum, low-blank furnace. The step heating was continuous with ramp times from one temperature to another of about 1 min and with dwell times of about 30 min at each temperature. These incremental-heating fractions were analyzed by static gas mass analysis with a MAP 215-50 mass spectrometer. Corrections for interfering reactions producing Ar from K, Ca, and Cl were made using factors determined. The monitor used was an intra-laboratory muscovite standard (“PM-1”) with an 40Ar/ 39Ar age of 165.3 Ma; an uncertainty of ±1% is assigned to this age in order to allow for uncertainties in the standards against which PM-1 was calibrated. The age for this monitor was determined by simultaneous cross calibration with several monitors including the Fish Canyon Tuff biotite standard (FCT-3) with an age of 27.84 Ma. 4.3. Major, trace elements and Sr–Nd isotope analyses Major and trace-element (V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr) analyses were carried out using a Philips PW 1140 X-ray fluorescence spectrometry (XRF), and inductively-coupled plasma source mass

966

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

Fig. 3. CL images of dated zircon crystals from; a—the Çataldağ, b—the Eybek, c—the Çamlık, and d—Eğrigöz plutons. SHRIMP sites are marked by circles. The numbers refer to analytical data in Tables 1, 2, 3 and 4. The size of the scale bars is 100 μm.

spectrometry (ICP-MS) was used for the analysis of Sc, Cs, Ba, REEs, Hf, Ta, Nb, U, Pb, Th and U at the Department of Earth Science, University of Bergen, Norway. The glass-bead technique of Padfield and Gray (1971) was used for major elements and pressed-powder pellets for trace elements, utilizing international standards and the recommended or certified concentrations of Govindaraju (1994) for calibration. The USGS standards BCR2 and W2 were run regularly to establish reproducibility. For the major elements it is generally b2%, but for Na2O, K2O and P2O5 around 4%. For the XRF-analyzed trace elements the reproducibility is generally b10%. The ICP-MS analyses were performed on a Thermo Fisher Scientific ELEMENT2 HR-ICP-MS. 100 mg of dry sample powders were digested in a microwave sample container using a mixture of concentrated HNO3 (4 ml), HF (1 ml) and HCL (5Ml). After digestion, the samples were transferred to 30 ml Savillex beakers and evaporated to dryness at 90 °C overnight. The residue was dissolved in 2 N HNO3, transferred to 50 ml volumetric flasks and diluted to volume with pure water. Before analysis the samples were diluted further and Indium (In) was used as an internal standard. For Nb, Cs, Ba, Hf, Ta, Pb, Th, U, and REE the reproducibility is ~ 5%, and ~9–13% for Pr, Tb, Ba, Th and U. Rb/Sr and Sm/Nd ratios were determined using a Finnegan 262 mass spectrometer and isotope dilution techniques at UoB. The chemical processing was carried out in a clean-room environment with

reagents purified in two-bottle Teflon stills. Samples were dissolved in a mixture of HF and HNO3. Rb–Sr and REE were separated by specific extraction chromatography using the method described by Pin et al. (1994). Sm and Nd were subsequently separated using a modified version of the method described by Richard et al. (1976). Sm, Nd, Rb and Sr were loaded on a double filament, and Sm, Rb and Sr were analyzed in static mode and Nd in multi-collector dynamic mode.

Table 1 Summary chart of Ar–Ar and U–Pb Shrimp ages obtained from Oligo–Miocene granitoids of the western Anatolia. Ar–Ar ages are given as plateau ages. Unit

Group

Evciler

SCG

Ilıca Eybek Hıdırlar Çataldağ Kestanbol Eğrigöz Çamlık

SCG SCG SCG SCG RMG NATPG NATPG

40 Ar/39Ar (Ma)

238 U–206 Pb Shrimp (Ma)

Hornblende

Biotite

28.0 ± 0.1 27.7 ± 0.1 22.3 ± 0.1

24.8 ± 0.1 24.8 ± 0.1 21.9 ± 0.1

23.5 ± 0.2

23.0 ± 0.1 20.4 ± 0.1 22.3 ± 0.2 18.9 ± 0.1 20.3 ± 0.1

K-Feldspar

Zircon

23.94 ± 0.31

22.8 ± 0.2 19.0 ± 0.1

20.6 ± 0.1

21.91 ± 0.33 19.48 ± 0.29 22.60 ± 0.77

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

967

Table 2 Zircon U–Pb Shrimp data of the Çataldağ pluton. Spot 1–1.1 1–2.1 1–3.1 1–4.1 1–5.1 1–6.1 1–7.1 1–8.1 1–9.1 1–10.1 2–1.1 2–2.1 2–3.1 2–4.1 2–5.1 2–6.1

U Th Th/U 206Pb* %206 (1) ±% (1) ±% Total ±% Total ±% (1) 206Pb/ 207 207 238 238 (ppm) (ppm) (ppm) Pbc 206Pb*/238U Pb*/235U Pb/206Pb U/206Pb U age 567 662 2835 1413 1912 4276 2192 1997 2215 3849 1611 1008 614 2809 909 736

419 171 1057 353 563 6678 756 663 726 5887 374 771 1094 609 1046 597

0.76 1.77 0.27 1.94 0.39 8.80 0.26 4.21 0.30 5.62 1.61 12.3 0.36 6.09 0.34 6.08 0.34 6.53 1.58 14.2 0.24 4.39 0.79 2.79 1.84 1.84 0.22 8.50 1.19 2.59 0.84 2.22

6.38 3.01 1.02 1.51 2.00 – 0.93 2.68 1.04 2.36 1.60 1.60 1.30 0.37 1.39 6.90

0.003380 0.003303 0.003567 0.003465 0.003294 0.003327 0.003219 0.003480 0.003405 0.004220 0.003116 0.003183 0.003409 0.003499 0.003279 0.003337

3.1 2.4 2.1 2.2 2.3 2.1 2.2 2.2 2.1 5.7 2.3 2.3 2.4 2.2 2.4 2.5

0.0223 0.0227 0.0217 0.02753 0.0133 0.0201 0.02319 0.0232 0.0266 0.0305 0.0204 0.0235 0.0195 0.02278 0.0243 0.0251

38 16 7.5 3.5 26 5.2 3.9 11 4.2 9.3 13 6.6 14 3.4 12 16

0.1019 0.0769 0.0544 0.0576 0.0594 0.04879 0.0552 0.0633 0.0623 0.0682 0.0618 0.0633 0.0608 0.0527 0.0624 0.0935

7.3 5.7 2.3 2.7 2.9 1.8 2.4 2.2 2.2 3.4 4.8 3.6 7.1 2.2 3.8 3.3

275.7 292.3 276.7 288.6 292.3 298.7 309.4 282.0 291.5 232 315.1 310.3 286.2 283.8 301.6 284.7

2.3 2.3 2.1 2.2 2.1 2.1 2.2 2.1 2.1 5.7 2.2 2.3 2.4 2.2 2.3 2.3

21.74 21.26 22.96 22.30 21.20 21.41 20.72 22.39 21.91 27.1 20.06 20.49 21.94 22.52 21.11 21.48

(2) 206Pb/ U age

(3) 206Pb/ U age

238

± 0.68 ± 0.52 ± 0.49 ± 0.48 ± 0.49 ± 0.45 ± 0.45 ± 0.49 ± 0.46 ± 1.5 ± 0.45 ± 0.47 ± 0.53 ± 0.49 ± 0.51 ± 0.54

21.71 21.17 23.02 21.99 21.66 21.48 20.57 22.34 21.63 26.9 20.03 20.30 22.08 22.49 20.91 21.26

238

±0.55 ±0.50 ±0.48 ±0.47 ±0.46 ±0.45 ±0.44 ±0.48 ±0.46 ±1.5 ±0.44 ±0.46 ±0.54 ±0.49 ±0.49 ±0.50

21.85 21.35 23.02 21.96 21.58 21.58 20.60 22.21 21.84 27.0 20.10 20.41 22.19 22.59 21.05 21.05

± 0.70 ± 0.55 ± 0.52 ± 0.51 ± 0.50 ± 0.62 ± 0.48 ± 0.52 ± 0.49 ± 2.2 ± 0.47 ± 0.55 ± 0.82 ± 0.51 ± 0.63 ± 0.65

Errors are 1-sigma; Pbc and Pb* indicate the common and radiogenic portions, respectively. Error in standard calibration was 0.54% (not included in above errors but required when comparing data from different mounts). (1) Common Pb corrected using measured 204Pb. (2) Common Pb corrected by assuming 206Pb/238U–207Pb/235U age-concordance. (3) Common Pb corrected by assuming 206Pb/238U–208Pb/232Th age-concordance.

Repeated measurements of the La Jolla standard (Nd-isotopes) and the NIST SRM 987 standard (Sr-isotopes) yielded average ratios of 0.511669 ± 5 (2 SE) for 143Nd/ 144Nd, and 0.710254 ± 5 (2 SE) for 87Sr/ 86Sr, respectively. 0.10

5. Geochronology We dated seven plutons (Evciler, Ilıca, Hıdırlar, Kestanbol, Eğrigöz, Çamlık, and Çataldağ) using the 39Ar/ 40Ar method, and four plutons 0.10

a

Mean = 21.91 ± 0.33 Ma [1.5%] 2s 12 spots,MSWD = 1.11 spots 1.7.1, 1.10.1, 2.1.1, and 2.2.1 were excluded

0.09

Mean = 23.94 ± 0.31 Ma [1.3%] 2s 11 spots, MSWD = 1.6 spots 1.4.1, 2.1.1, and 2.4.1 were excluded

0.09

0.08

0.08 207Pb/206Pb

207Pb/206Pb

b

0.07

0.07

0.06

0.06

0.05

0.05

25

24

0.04 250

23

270

22 290

21

20

310

30

19 330

0.04 210

350

28

26

230

250

270

238U/206Pb

c

0.064

22

24

20

290

310

330

238U/206Pb

d

Mean = 22.60 ± 0.77Ma [3.4%] 2s 16 spots, MSWD = 13

Mean = 19.48 ± 0.29 Ma [1.5%] 2s 16 spots, MSWD = 0.93

0.12

0.060 207Pb/206Pb

207Pb/206Pb

0.10 0.056 0.052

0.08

0.048

28

26

24

22

20

0.06

18

0.044

0.040 220

260

300 238U/206Pb

340

380

0.04 280

22

21 300

20 320

19 340

18 360

17 380

238U/206Pb

Fig. 4. Tera-Wasserburg 206Pb/238U versus 207Pb/206Pb diagrams with errors depicted at the 1-sigma level. a—the Çataldağ, b—the Eybek, c—the Çamlık, and d—Eğrigöz plutons. Uncertainties on all weighted average age calculations are 2-sigma confidence levels.

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

968 Table 3 Zircon U–Pb Shrimp data of the Eybek pluton. Spot

U Th Th/U 206Pb* %206Pbc (1) ±% (1) ±% 206 207 (ppm) (ppm) (ppm) Pb*/238U Pb*/235U

1–1.1 479 1–2.1 417 1–3.1 619 1–4.1 1046 1–5.1 547 1–6.1 290 1–6.2 700 1–7.1 711 1–8.1 956 2–1.1 1775 2–2.1 539 2–3.1 611 2–4.1 811 2–5.1 816

293 237 386 768 351 173 448 444 1600 1214 337 427 602 563

0.63 0.59 0.64 0.76 0.66 0.62 0.66 0.64 1.73 0.71 0.65 0.72 0.77 0.71

1.68 1.50 2.16 3.61 1.86 1.11 2.37 2.39 3.16 6.54 1.73 1.95 2.11 2.44

8.14 4.58 6.59 2.16 4.56 16.07 5.01 5.29 1.76 1.49 1.40 2.19 – 4.13

0.00369 0.00387 0.003774 0.003865 0.003814 0.00353 0.003701 0.003579 0.003739 0.004199 0.003681 0.003490 0.002862 0.00340

3.2 3.1 2.2 1.6 1.9 4.8 2.0 2.7 1.4 1.4 1.3 2.4 3.3 3.4

0.018 0.014 0.0222 0.0195 0.0289 0.0239 0.011 0.0214 0.0224 0.0224 0.0071 0.0219

Total ±% Pb/206Pb

207

67 76 43 28 23

0.1101 0.084 0.097 0.0667 0.0845 0.173 29 0.0936 97 0.0900 17 0.0645 13 0.0555 8.5 0.0570 100 0.0639 0.0408 23 0.0653

7.7 12 12 5.4 7.8 11 6.4 8.9 3.3 3.0 4.5 4.0 9.5 14

Total ±% (1) 206Pb/ 238 238 U/206Pb U age 245.8 239.6 246.8 249.0 252.3 225.3 254.2 256.1 259.7 233.1 267.3 269.4 330.3 287.4

1.7 2.4 1.4 1.1 1.4 1.9 1.3 1.3 1.1 1.3 1.3 1.6 2.9 3.3

23.72 24.91 24.28 24.87 24.54 22.7 23.81 23.03 24.06 27.01 23.68 22.46 18.42 21.87

±0.75 ±0.78 ±0.53 ±0.40 ±0.48 ±1.1 ±0.47 ±0.62 ±0.34 ±0.38 ±0.32 ±0.53 ±0.60 ±0.74

(2) 206Pb/ U age

238

24.08 25.56 24.40 25.18 24.28 24.00 23.80 23.74 24.21 27.28 23.75 23.36 19.63 21.86

± 0.50 ± 0.71 ± 0.50 ± 0.30 ± 0.41 ± 0.83 ± 0.37 ± 0.40 ± 0.29 ± 0.35 ± 0.32 ± 0.37 ± 0.57 ± 0.78

(3) 206Pb/ U age

238

24.05 25.62 24.35 25.28 24.34 24.0 24.04 23.80 24.34 27.18 23.74 23.36 20.13 21.46

± 0.67 ± 0.77 ± 0.57 ± 0.34 ± 0.48 ± 1.0 ± 0.44 ± 0.44 ± 0.47 ± 0.44 ± 0.37 ± 0.44 ± 0.66 ± 0.90

Errors are 1-sigma; Pbc and Pb* indicate the common and radiogenic portions, respectively. Error in standard calibration was 0.21% (not included in above errors but required when comparing data from different mounts). (1) Common Pb corrected using measured 204Pb. (2) Common Pb corrected by assuming 206Pb/238U–207Pb/235U age-concordance. (3) Common Pb corrected by assuming 206Pb/238U–208Pb/232Th age-concordance.

(Eğrigöz, Çamlık, Çataldağ and Eybek) using the Shrimp U–Pb method. Cathodoluminescence (CL) images and summary of the age data are presented in Fig. 3 and Table 1, respectively.

5.1. U–Pb zircon ages The zircons separated from the Çataldağ pluton have mostly euhedral and transparent grains with aspect ratios ranging from 1:1.5 to 1:3.5 (Fig. 3a). The majority of these zircons show magmatic growth zoning with patchy recrystallization zones and local cores. Some grains are represented by faint oscillatory and sector zoning (e.g. Grains 1–6.1 and 2–1.1, Fig. 3a). Recrystallization zones in some of the grains truncate the previously formed oscillatory zones (Grains 1–7.1, 1–8.1, 2–2.1, 2–3.1, and 2–6.1). Grains 1–3.1 and 1–8.1 have xenocrystic cores with weakly developed Cl intensity. Laser spots were concentrated on thin oscillatory zoned parts. All of the spots (16 measurements) yielded ages between 20 and 23 Ma, except Spot 1–10.1 that provided an age of ~27 Ma (Table 2). A coherent group of 12 measurements has been used to calculate a mean age of

21.91 ± 0.33 Ma (Fig. 4a) for the emplacement age of the Çataldağ pluton. Zircons grains from the Eybek pluton are idiomorphic and transparent. Their aspect ratio ranges between 1:2 and 1:4 (Fig. 3b). Most zircon grains exhibit clear oscillatory and sector zoning, indicating a magmatic origin. Some of the grains such as 1–1.1, 1–2.1, 1–3.1, 1–4.1, 2–2.1, and 2–3.1 have apparent inner cores. Laser spots are located on the oscillatory zoned parts (Fig. 3b). Except for one spot (2–1.1), all results from the Eybek zircons gave ages between 20 and 26 Ma (Table 3; Fig. 4b). Spot 2–1.1 yielded an age of 27.18 ± 0.44 Ma. This particular age and the age obtained from Spot 1 to 4.1 were excluded from the mean age calculation because of their high U and Th values (Table 3). The corrected ages obtained from Spot 2 to 4.1 are highly discordant, and hence this measurement was not included in the mean age calculation either. The rest of the measurements that represent a coherent age group were used to calculate a mean age of 23.94 ± 0.31 Ma for the timing of the emplacement of the Eybek pluton (Fig. 4b). Zircon grains from the Çamlık pluton have long prismatic or stubby, idiomorphic crystals (Fig. 3c). The outer rims of these grains display

Table 4 Zircon U–Pb Shrimp data of the Çamlık pluton. Spot 1–1.1 1–2.1 1–3.1 1–4.1 1–5.1 1–6.1 1–7.1 1–8.1 1–9.1 1–10.1 1–11.1 2–1.1 2–2.1 2–3.1 2–4.1 2–5.1

U Th Th/U 206Pb* %206Pbc (1) 206Pb*/ ±% (1) 207Pb*/ 238 235 (ppm) (ppm) (ppm) U U

±%

4458 3151 1497 3375 4510 997 5046 2797 2324 3484 3130 2020 2546 3519 1142 2462

3.6 3.1 11 9.0 2.4 12 3.6 4.4 4.5 3.8 4.1 9.9 3.7 5.6 14 3.8

2433 1887 832 1584 3232 362 1621 1729 625 1469 935 498 638 1364 434 799

0.56 0.62 0.57 0.48 0.74 0.38 0.33 0.64 0.28 0.44 0.31 0.25 0.26 0.40 0.39 0.34

14.0 10.5 4.44 9.47 15.0 2.68 16.5 7.85 7.08 10.4 9.65 5.63 7.85 11.1 3.22 7.44

0.40 1.91 1.85 0.71 1.12 0.24 1.15 0.34 0.40 0.39 0.69 0.33 0.21 1.25 0.71

0.003650 0.003870 0.003410 0.003229 0.003857 0.00308 0.003790 0.003247 0.003516 0.003461 0.003574 0.003220 0.003571 0.003644 0.003221 0.003492

1.5 1.5 1.7 1.9 1.5 6.0 1.5 1.6 1.6 1.5 1.5 1.7 1.6 1.5 2.0 1.6

0.02408 0.02573 0.0204 0.0177 0.02532 0.0195 0.02409 0.02111 0.02119 0.02216 0.02191 0.0202 0.02258 0.0243 0.0208 0.02373

Total ±% Total ±% (1) 206Pb/ 238 238 Pb/206Pb U/206Pb U age

207

0.05054 0.0499 0.0538 0.0490 0.04890 0.0592 0.04868 0.0516 0.0499 0.0481 0.0473 0.0510 0.0496 0.0532 0.0618 0.0545

1.9 2.1 5.1 4.5 1.7 7.1 1.7 2.8 2.6 2.2 2.3 4.5 2.6 4.1 3.8 2.7

273.0 257.8 289.5 306.1 258.8 320 263.0 306.3 282.2 288.3 278.8 308.4 278.7 272.8 304.6 284.5

1.5 1.5 1.7 1.8 1.5 6.0 1.5 1.6 1.6 1.5 1.5 1.7 1.6 1.5 1.8 1.6

23.49 24.90 21.94 20.78 24.82 19.8 24.38 20.89 22.63 22.27 23.00 20.72 22.98 23.45 20.73 22.47

Errors are 1-sigma; Pbc and Pb* indicate the common and radiogenic portions, respectively. Error in standard calibration was 0.26% (not included in above errors but required when comparing data from different mounts). (1) Common Pb corrected using measured 204Pb. (2) Common Pb corrected by assuming 206Pb/238U–207Pb/235U age-concordance. (3) Common Pb corrected by assuming 206Pb/238U–208Pb/232Th age-concordance.

± 0.35 ± 0.37 ± 0.38 ± 0.39 ± 0.36 ± 1.2 ± 0.36 ± 0.33 ± 0.35 ± 0.34 ± 0.35 ± 0.36 ± 0.36 ± 0.36 ± 0.40 ± 0.36

(2) 206Pb/ U age

238

23.45 24.85 22.03 20.96 24.78 19.8 24.40 20.88 22.71 22.27 23.06 20.75 23.00 23.39 20.72 22.39

±0.35 ±0.37 ±0.37 ±0.39 ±0.36 ±1.2 ±0.36 ±0.33 ±0.36 ±0.34 ±0.35 ±0.35 ±0.36 ±0.36 ±0.38 ±0.36

(3) 206Pb/ U age

238

23.48 25.16 21.81 20.64 24.68 19.9 24.41 20.77 22.73 22.23 23.00 20.72 23.01 23.54 20.86 22.46

± 0.38 ± 0.42 ± 0.41 ± 0.43 ± 0.41 ± 1.3 ± 0.38 ± 0.37 ± 0.37 ± 0.36 ± 0.37 ± 0.37 ± 0.38 ± 0.39 ± 0.41 ± 0.38

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

969

Table 5 Zircon U–Pb Shrimp data of the Eğrigöz pluton. U Th Th/U 206Pb* %206Pbc (1) 206Pb*/ ±% (1) 207Pb*/ ±% 238 235 (ppm) (ppm) (ppm) U U

Spot

1–1.1 608 1–2.1 1225 1–3.1 918 1–4.1 629 1–5.1 459 1–6.1 278 1–7.1 318 1–8.1 1025 1–9.1 511 1–10.1 951 1–11.1 559 1–12.1 676 1–13.1 527 1–14.1 807 1–15.1 674 1–16.1 940

375 739 448 326 300 140 191 489 214 599 322 294 276 350 312 418

0.64 0.62 0.50 0.54 0.68 0.52 0.62 0.49 0.43 0.65 0.60 0.45 0.54 0.45 0.48 0.46

1.61 3.42 2.46 1.66 1.25 0.756 0.865 2.71 1.49 2.55 1.58 1.84 1.39 2.19 1.79 2.49

4.93 1.44 3.55 4.16 5.53 7.86 6.82 2.81 6.76 3.52 8.99 5.25 5.02 1.50 2.18 0.93

0.002848 0.003201 0.002988 0.002973 0.00292 0.00293 0.00286 0.002957 0.00310 0.00304 0.00292 0.00296 0.00297 0.003089 0.003017 0.00302

3.2 2.0 2.5 2.5 3.5 3.8 5.9 2.4 3.9 3.4 4.7 3.6 3.8 2.1 2.4 3.3

0.0246 0.0131 0.0221 0.0105 0.0221

9.5 40 18 86 43

0.0178 0.017 0.0202

25 62 13

0.0146 0.0274 0.0225 0.0157 0.0173

68 22 11 26 22

Total 207Pb/ ±% Pb

206

0.0779 0.0668 0.0668 0.0807 0.0893 0.115 0.1040 0.0745 0.107 0.0665 0.118 0.0883 0.0914 0.0686 0.0587 0.0587

8.1 3.4 7.0 5.4 8.5 9.8 5.8 6.1 11 5.5 14 8.9 9.5 5.9 6.3 4.3

Total 238U/ ±% (1) 206Pb/ 238 Pb U age

206

325.0 307.9 320.1 324.9 315.5 315.4 315.6 325.0 295.6 321 303.8 315.6 326 317.2 322.8 324

2.3 1.9 2.1 2.3 2.4 2.9 2.8 2.1 2.9 3.3 3.0 2.3 3.6 2.1 2.1 3.1

18.33 20.60 19.23 19.14 18.81 18.83 18.4 19.03 19.95 19.59 18.78 19.06 19.13 19.88 19.42 19.46

± 0.59 ± 0.41 ± 0.49 ± 0.48 ± 0.66 ± 0.72 ± 1.1 ± 0.46 ± 0.78 ± 0.66 ± 0.89 ± 0.69 ± 0.73 ± 0.43 ± 0.47 ± 0.65

(2) 206Pb/ U age

238

19.02 20.36 19.59 18.96 19.29 18.64 18.91 19.10 20.11 19.55 19.26 19.31 18.63 19.73 19.63 19.58

±0.47 ±0.39 ±0.42 ±0.44 ±0.50 ±0.61 ±0.54 ±0.41 ±0.66 ±0.66 ±0.72 ±0.48 ±0.70 ±0.42 ±0.43 ±0.62

(3) 206Pb/ U age

238

18.83 20.60 19.39 18.99 19.27 18.80 19.00 19.25 20.30 19.35 19.28 19.32 18.76 19.99 19.50 19.71

± 0.57 ± 0.45 ± 0.48 ± 0.53 ± 0.62 ± 0.70 ± 0.76 ± 0.45 ± 0.70 ± 0.76 ± 0.84 ± 0.54 ± 0.79 ± 0.46 ± 0.48 ± 0.68

Errors are 1-sigma; Pbc and Pb* indicate the common and radiogenic portions, respectively. Error in standard calibration was 0.52% (not included in above errors but required when comparing data from different mounts). (1) Common Pb corrected using measured 204Pb. (2) Common Pb corrected by assuming 206Pb/238U–207Pb/235U age-concordance. (3) Common Pb corrected by assuming 206Pb/238U–208Pb/232Th age-concordance.

magmatic oscillatory zoning and locally developed irregular recrystallization zones with low CL (Grains 1–5.1, 1–11.1, 2–3.1 and 2–4.1; Fig. 3c). The inner parts of the grains show xenocrystic cores (e.g. Grains 1–6.1, 1–7.1, and 2–5.1) and some recrystallization zones (e.g. Grains 1–2.1 and 2–2.1). Grains 1–10.1 and 2–1.1 exhibit convoluted and curved zoning. The obtained ages range from 19 to 25 Ma (Table 4). The calculated mean age from the whole data set is 22.60 ± 0.77 Ma (Fig. 4c), representing the emplacement age of the pluton. Zircons from the Eğrigöz pluton have idiomorphic and transparent crystals with aspect ratios between 1:1.1 and 1:2.5. The CL images of the dated zircons commonly show magmatic oscillatory zoning with locally developed sector zoning (Fig. 3d). The majority of the zircon grains display ordinary magmatic growth zoning, and some growth zoning around the inclusion boundaries (Grains 1.9.1 and 1.12.1; Fig. 2d). A total of 16 measurements, taken from the outer oscillatory zones (Fig. 3d), have revealed ages ranging from 18 Ma to 21 Ma (Table 5). The calculated mean age of the Egrigöz pluton is 19.48 ± 0.29 Ma (Fig. 4d).

5.2.

40

Ar/ 39Ar dates

The 40Ar/ 39Ar ages of the plutons, obtained from hornblende, biotite, and K-feldspar separates, are given in Table 1, and the age spectrum plots are shown in Fig. 5. The two biotite separates from the Evciler granitoid display plateau age of 24.8 ± 0.1 Ma (Fig. 5a and b), whereas the two hornblende separates yield plateau ages of 28.0 ± 0.1 Ma and 27.7 ± 0.1 Ma (Fig. 5c and d). The younger biotite ages likely represent the cooling ages, while the slightly older amphibole ages are close to the emplacement age of the Evciler pluton. We obtained hornblende and biotite plateau ages of 22.3 ± 0.1 Ma and 21.9 ± 0.1 Ma (respectively, Fig. 5e–f) from the Ilıca granitoid, and of 23.5 ± 0.2 Ma and 23.0 ± 0.1 Ma (respectively, Fig. 5g–h) from Hıdırlar granitoid. The plateau ages of hornblende and biotite separates from the Kestanbol granitoid are 22.8 ± 0.2 and 22.3 ± 0.2 Ma, respectively (Fig. 5i–j). The hornblende and biotite separates from the Eğrigöz pluton yielded plateau ages of 19.0 ± 0.1 Ma and 18.9 ± 0.1 Ma (respectively, Fig. 5k–l), and the biotite and K-feldspar separates from the Çataldağ pluton gave plateau ages of 20.4 ± 0.1 and 20.6 ± 0.1 Ma (respectively,

Fig. 5m–n). The biotite separates from the Çamlık pluton yielded a plateau age of 20.3 ± 0.1 Ma (Fig. 5o). 6. Geochemistry We have studied a total of thirteen plutons in NW Anatolia and have categorized them into three groups based on the nature and distribution of the tectonic units into which they were intruded. These groups include the granitoids of the 1—Rhodope metamorphic massif (RMG), 2—Sakarya continent (SCG) and 3—Anatolide–Tauride platform (ATP). The RMG group is represented by the Kestanbol pluton, while the SCG includes the Eybek, Evciler, Karakoy, Kozak, and IlicaSamli plutons and the Hidirlar, Katrandag and Yenice stocks (Fig. 1). All these granitoids of the RMG and SCG occur north of the Izmir–Ankara–Erzincan suture zone. To the south of this suture zone, the granitoids of the ATPG are further subdivided into the Northern (NATPG) and Southern (SATPG) sub-groups. The Camlik and Egrigoz plutons are part of the NATPG, whereas the Salihli and Turgutlu granitoids in the Menderes metamorphic massif occur in the SATPG (Fig. 2). The major and trace element compositions and Sr–Nd isotopic concentrations of representative samples from the RMG, SCG and ATPG are listed in Table 6. We also analyzed the major and trace element compositions and Sr–Nd isotopic concentrations of representative metamorphic basement rocks from the Sakarya continent (Kazdağ core complex and cover rocks; Altunkaynak et al., unpublished data) and the Anatolide–Tauride platform (Menderes core complex and cover rocks; Altunkaynak et al., unpublished data) to better evaluate the nature and extent of continental crust–magma interaction. In addition, we evaluated metamorphic rocks of the Pelagonian zone in Greece (Brique et al., 1986; Pe-Piper et al., 2002; Anders, 2005), the central Pontides of northern Turkey (Nzegge et al., 2006) and the Istranca massif in northwestern Turkey (G. Sunal, unpublished data) as possible analogs for the rocks in which the different groups of granitoids, north and south of the IASZ were emplaced. Kula alkaline basalts representing the depleted mantle-derived melts (Aldanmaz et al., 2000, Alıcı et al., 2002, Dilek and Altunkaynak 2010), dioritic enclaves and lavas representing enriched mantle melts (EMM) from China and western Anatolia (Yang et al., 2004; Altunkaynak et al., 2010) and granitoids emplaced into other metamorphic core complexes in the northern (Rhodope massif) and central (Cyclades) Aegean province are also

970

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

Fig. 5. 39Ar/40Ar plateau age spectrums of western Anatolian granitoids. Summary of the ages are listed in Table 1. Plateau steps are shown as white color whereas rejected ones are black. Box heights are 1 sigma errors.

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

Fig. 5 (continued).

971

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

972

Fig. 6. a—Total alkali vs. SiO2 classification diagram (Cox et al., 1979) and b—AFM diagram of western Anatolian granitoids (Irvine and Baragar, 1971).

The SiO2 contents of the RMG and SCG groups vary between 52.74 and 66.77 wt.%, whereas those of the ATPG group ranges from 65.78 to 72.13 wt.%. The SiO2 contents of magmatic enclave from the ATPG contains only 58.91 wt.% SiO2. The RMG and SCG plutons are hence represented mainly by intermediate and silicic rocks based on their SiO2 contents, whereas the ATPG plutons are mostly silicic in composition. On a TAS diagram (Fig. 6a; Cox et al., 1979), the RMG plutons range from granodiorite, monzonite to syenite. Samples from the SCG plutons span a wide range of rock types, extending from syenodiorite, monzonite and diorite to granodiorite. The ATPG plutons plot in the granodiorite and granite fields. One of the magmatic enclaves analyzed from the ATPG is classified as monzodiorite.

The majority of the samples are subalkaline in nature and display a calc-alkaline trend (Irvine and Baragar, 1971; Fig. 6b), except for the two alkaline samples from the RMG and one sample from a SCG pluton (Katrandağ granite) (Fig. 6a). On the K2O vs. SiO2 classification diagram of Peccerillo and Taylor (1976), all pluton samples from the RMG, some samples from the SCG plutons (Evciler, Karakoy, and Yenice granitoids), and one sample from the ATPG pluton (Çamlik granitoid) are classified as shoshonitic, while the others are high-K calc-alkaline in character. Two samples from the Katrandağ and Yenice granitoids (SCG) are medium-K in character (Fig. 7). The A/CNK [Al2O3/(CaO + Na2O + K2O) molecular ratio] values of the analyzed granitoids range between 0.70 and 1.0. All samples of the RMG and SCG plutons are metaluminous (Fig. 8; Shand 1927). The least evolved members of the ATPG plutons and their enclave are predominantly metaluminous, although some more evolved samples exhibit slightly peraluminous signatures with A/CNK ratios ranging from 1.1 to 1.2. In the same diagram,

Fig. 7. K2O vs. SiO2 diagram of western Anatolian granitoids using the classification scheme of Peccerillo and Taylor (1976). See Fig. 6 for the symbols.

Fig. 8. A/CNK vs. A/NK plot of western Anatolian granitoids (Shand, 1927).

used for comparison (Fig. 1; Christofides et al., 1998; Pe-Piper and Piper, 2001; Pe-Piper et al., 2002). 6.1. Major and trace element characteristics

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

a 1000

973

RMG SCG Av. Lower crust Av. Middle crust

RBROM-N/KCO

Av. Upper crust

100

Av. Kula basalt

10

1

0.1 Cs RbBa Th U Nb Ta K La CePb Pr Sr P Nd Zr SmEu Ti Dy Y Yb Lu

b 1000

SATPG NATPG Av. Lower crust Av. Middle crust

ROCK/N-MORB

Av. Upper crust

100

Av. Kula basalt

10

1

0.1 Cs Rb Ba Th U Nb Ta K La Ce Pb Pr Sr P Nd Zr SmEu Ti Dy Y Yb Lu Fig. 10. N-MORB normalized multi-element patterns for the RMG and SCG (a) and ATPG (b). N-MORB normalizing values are from Sun and McDonough (1989).

Fig. 9. Major and trace element versus SiO2 variation diagrams for western Anatolian granitoids. See Fig. 6 for the symbols.

the metamorphic basement rocks of the Sakarya continent and the ATP are predominantly peraluminous (A/CNK = 1.1–1.9), with the exception of three samples from the SC basement that are metaluminous (A/CNK = 0.9–1.0) (Fig. 8). Both the basement and granitic rocks have similar A/NK (Al2O3/Na2O + K2O) ratios between 1.1 and 2.5. All of the granitoid samples display I-type granite affinity, although two haplogranite sample of the ATPG pluton shows S-type affinity (Fig. 8). In the SiO2 variation diagrams (Fig. 9), the TiO2 (0.37–0.79 and 0.21–0.62 wt.%, respectively), Al2O3 (15.27–17.58 and 14.35– 16.66 wt.%), FeO* (3.49–7.09 and 1.86–3.83 wt.%), MgO (1.60–3.38 and 0.42–1.50 wt.%), CaO (3.67–7.08 and 1.04–4.56 wt.%) and P2O5 (0.12–0.75 and 0.08–0.25 wt.%) contents of the SCG and ATPG pluton samples decrease with increasing SiO2 (52.74–66.77and 65.20– 72.13 wt.%, respectively). In these diagrams, the RMG samples display

trends that differ from those of the other groups. For example, the TiO2 (0.44–0.48 wt.%), FeO*(3.85–4.50 wt.%) and CaO (3.44–3.95 wt.%) contents of the RMG pluton samples remain nearly constant with increasing SiO2 (57.09–65.51 wt.%) contents, and these rocks display two separate trends in the diagrams of K2O (5.09–6.99 wt.%), MgO (1.38–1.71 wt.%) and Al2O3 (15.42–18.55 wt.%) against SiO2. The SCG samples (Katrandag and Yenice granitoids) and the magmatic enclave from the ATPG are the least evolved samples with the highest MgO (2.70 wt.%), TiO2 (1.19 wt.%) and FeO* (7.89 wt.%) contents. The ATPG contains the most silicic compositions. The Sr (695–1573 ppm and 163–671 ppm, respectively) and Zr (235–391 ppm and 114–224 ppm, respectively) contents of the RMG and ATPG plutons decrease whereas the SCG samples (Sr: 421–785 ppm, Zr: 95–164 ppm) stay almost constant (or slightly decrease) with increasing SiO2 contents. The Rb contents (38–160 ppm, 178–268 ppm and 75–155 ppm, respectively) of the SCG, RMG and ATPG display a positive correlation with SiO2 (Fig. 9). On N-MORB normalized spider diagrams (Fig. 10a and b), all groups (RMG, SCG and ATPG) display similar patterns with enrichment in the most incompatible elements (e.g., Rb, Ba, Th, U, K, La and Ce) and depletion in Nb, Ta, Ti, P and Zr. All of the granitoid groups are strongly enriched in LILE and LREE compared to the average lower crust, and display trace element compositions similar to average middle and upper

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

5

Hidirlar Kozak Evciler Katrandag

Nd(20)

0

100

OIB

Ave. EMM

-5 -10 Dy Ho

Er

Tm Yb

100

Ave. Kula Basalt Ave. Lower Crust Ave. Middle Crust Ave. Upper Crust

Eybek Yenice Karaköy

SCG

SC basement

0.710

0.715

0.720

0.725

87Sr/ 86Sr(20)

Fig. 12. εNd(20) vs. 87Sr/86Sr(20) diagram for western Anatolian granitoids. Data source: ATP (Menderes core and cover rocks) and SC (Kazdağ core and cover rocks) middle– upper crustal compositions: Altunkaynak (unpub. data), Pelagonian Upper Crust : Anders (2005), Santorini UC: Briqueu et al. (1986), Rhodope granites: Christofides et al. (1998), Cyclades granitoids and Hercinian protoliths: Pe-Piper and Piper (2001, 2006), Kula basalts: Dilek and Altunkaynak (2010), average EMM (enriched mantle melts: Yang et al. (2004) and Altunkaynak et al. (2010)), lithospheric mantle melting array: Davis and von Blanckenburg (1995), Aegean Sea sediments: Altherr et al. (1988) and Global River Average: Goldstein and Jacobsen (1988).

on the basis of their Eu anomalies (Fig. 11a and b), whereas the syenitic samples show positive Eu anomalies. 10

6.2. Sr and Nd isotopic signatures and Nd model ages

1

b La

Ce

Pr

Nd Pm Sm Eu Gd Tb

Dy Ho

Er

Tm Yb

Lu

Fig. 11. Chondrite-normalized REE patterns for the RMG and SCG (a), and ATPG (b). Chondrite normalizing values are from Boynton (1984).

crustal values. They also display a significant positive Pb anomaly, which is not shown by the Kula basalts. Compared to N-MORB, the ATPG samples and the SCG and RMG samples show a ~300 times and a ~100 times enrichment in Pb, respectively. The granitoid groups have variable Ce/Pb ratios ranging from 1.1 to 4.4 that are similar to the Ce/Pb ratios of the average middle continental crust (Ce: 43 ppm, Pb: 11 ppm; Ce/Pb = 3.9) and average upper crustal values (Ce: 63 ppm, Pb: 17 ppm, Ce/Pb = 3.7; Rudnick and Gao, 2003). On chondrite-normalized spider diagrams (Fig. 11a and b), the REE distributions of the SCG samples display considerable LREE enrichments with respect to MREE and HREE (Lan/Ybn = 10.5–24.8) with some minor depletions in MREE (Gdn/Ybn =1.2–2.4; Fig. 10a). Their HREE patterns show nearly flat trends. The overall REE concentrations of these samples fall between those of the Kula basalts and the average middle–upper continental crust. The SCG group is characterized by either minor negative or slightly positive Eu anomalies. (Eu/Eu*= 0.80–1.25). Only three samples from the SCG intrusions (Ilıca-Şamlı granite, one sample from Hidirlar) display pronounced negative Eu anomalies (Eu/ Eu*= 0.51–0.61). In contrast, the ATPG samples show REE patterns similar to those of the average upper crust with significant negative Eu anomalies (Eu/Eu* =0.30–0.60). The granodioritic samples of the RMG group are transitional between those of the SCG and the ATPG groups

Sr and Nd isotopic data for the analyzed samples are shown in Table 6. The initial Sr and Nd isotopic ratios ( 87Sr/ 86Sr(i); 143Nd/ 144 Nd(i)) were calculated for the RMG, SCG and ATPG groups assuming a mean magma crystallization age of 20 Ma. The 87Sr/ 86Sr(i) ratios vary from 0.705248 to 0.711428, and 143Nd/ 144Nd(i) values range from 0.512619 to 0.512184. The Karakoy granitoid of the SCG group is characterized by the lowest 87Sr/ 86Sr(i) = 705248–0.706106 and the highest 143Nd/ 144Nd(i) = 0.512619–0.512548 values. The samples 8 6

RMG SCG NATPG SATPG

Kula basalts

4 2

Ave. EMM

0

Nd

ROCK/CHONDRITE

0.705

Lu

ATPG

ATPG

Global river average

Cyclades Granites

1

Nd Pm Sm Eu Gd Tb

1000

Pr

NATPG (SATPG)

ATP basement

Aegean Sea Sediments

0.700 Ce

RMG

SCLM melting array

Rhodope granites (N. Greece)

a La

Kestanbol Camlik Egrigoz Salihli

Kula Basalts

RMG SCG Ave. Kula Basalt Ave. Lower Crust Ave. Middle Crust Ave. Upper Crust

10

ROCK/CHONDRITE

1000

974

-2 -4

NATPG ATP basement

Rhodope granites (Greece)

-6 -8

Cyclades granitoids

-10

Hercynian protoliths

-12

SATPG SC basement

-14 0

0.5

1

1.5

2

TDM (Ga) Fig. 13. εNd(i) vs. TDM (Nd-model ages) diagram of the RMG, SCG and ATPG. See Fig. 12 for data source.

975

Kestanbol Camlik Egrigoz Salihli

(SATPG)

Hidirlar Kozak Evciler Katrandag

Eybek Ilıca Yenice Karaköy

RMG NATPG

0.2

Nb/Zr0.1

ATPG

SCG

Kula Basalts Pa rti al m el tin g

30 20

La /Yb(n)

40

Pa rtia lm elt ing

50

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

MMA

10

FC 0.0

FC

MMA Kula Basalts

20 Nb (ppm)30

40

0

10

20

40

60

80

100

120

La (ppm) Fig. 14. La/Yb versus La (ppm) diagram illustrating the effects of partial melting in comparison to fractional crystallization. The inset diagram shows the variations of Nb/Zr with changing Nb contents of the rocks. Vectors for FC and PM are from Thirlwall et al. (1994).

from the southern sub-group (SATPG) of the ATPG display higher 87 Sr/ 86Sr(i) ( 87Sr/ 86Sr(i) = 0.711428–0.71080) and lower 143Nd/ 144 Nd(i) ( 143Nd/ 144Nd(i) = 0.51227–0.512184) ratios compared to those of the RMG samples ( 87Sr/ 86Sr(i) = 0.707966–0.708799, 143Nd/ 144 Nd(i) = 0.512408–0.512335) and SCG (average: 87Sr/ 86Sr(i) = 0.707540, 143Nd/ 144Nd(i) = 0.512450). The samples from the northern sub-group (NATPG) of the ATPG have initial Sr and Nd isotopic ratios of 0.708001–0.709039 and 0.512370–0.512348, respectively, which are similar to those of the RMG and SCG samples (Table 6). The calculated εNd(i) values for the western Anatolian granites range from − 0.2 to − 8.35, with one sample from the SCG (Karakoy pluton) showing a value of +0.12. The SATPG samples have the lowest εNd(i) values varying from − 8.4 to − 7.6, whereas the SCG samples have the relatively highest εNd(i) values between +0.12 to −6.3. The RMG and NATPG groups have values intermediate between these other two groups (Fig. 12). The Kula basalts from western Anatolia have εNd(i) values varying from + 5.2 to +6.5 (average: 6.1). The RMG, SCG and NATPG samples lie on an array between the Kula basalt field, representative of the partial melts of depleted Aegean mantle (Aldanmaz et al., 2000; Alıcı et al., 2002), and the metamorphic basement rocks occurring to the north (SC) and the south (ATP) of the Izmir–Ankara–Erzincan suture zone (Fig. 12), which are similar to the Rhodope granites from northern Greece–Bulgaria. In contrast, the Cyclades granitoids from the Aegean Sea, as well as the SATPG samples from our study area plot in the field of the ATP basement rocks. The ATP crystalline basement rocks have εNd(i) values ranging from − 11.5 to −6.3 (average: −7.5). The SC crystalline basement rocks have more restricted values of εNd(i) ranging from −11.3 to − 7.1 (average: −8.8) (Fig. 12). The Nd depleted mantle model (TDM) and the εNd values of the late Oligocene–middle Miocene granitoids are plotted together in Fig. 13. The RMG and SCG plutons, which were emplaced into the metamorphic basement rocks to the north of the suture zone (IASZ) have younger TDM ages in comparison to those of the ATPG plutons that were emplaced into the basement rocks in the ATP south of the suture zone. The TDM of RMG and SCG plutons range from 0.6 to 1.2 Ga, corresponding to a Proterozoic age, similar to the Rhodope

granites from northern Greece–Bulgaria. This time constraint is consistent with the inferred extraction age of the K-enriched subcontinental lithospheric mantle source of the post-collisional lavas in western Anatolia (0.9–1.0 Ga; Altunkaynak, 2007) and of the Rhodope granites in northern Greece (Christofides et al., 1998; Pe-Piper and Piper, 2001; Pe-Piper et al., 2002). The TDM ages of the ATPG plutons range from 1.2 to 1.6 Ga and constrain the residence age of their source in the continental crust as the middle Proterozoic. This model age is consistent with those of the Cyclades granitoids and the ATP, representative of the Pan-African crust (Fig. 13) (Pe-Piper and Piper, 2001, 2006; Pe-Piper et al., 2002).

7. Petrogenesis 7.1. Source characteristics All pluton groups are subalkaline in nature, as revealed by their major and trace element characteristics (Fig. 6a). Only two syenitic samples from the RMG plutons and one sample from the SCG are alkaline. All groups are also potassic in character (high K-calcalkaline to shoshonitic), resembling the compositions of those granitoids commonly known as post-collisional in origin. The granitoids have moderately to highly evolved compositions, as shown by their Mgnumbers (Fig. 8, average Mg# = 50 and 35, respectively) and silica contents. All of the granitoid groups are represented by metaluminous to slightly peraluminous, I-type granitoids, whereas two haplogranite samples representing the most evolved members of the NATPG are slightly to moderately peraluminous, S-Type granitoid (Fig. 8). The RMG, SCG, and NATPG plutons, which were emplaced into different tectonostratigraphic units, show similar major and trace element characteristics and overlapping Sr–Nd isotopic ratios. These observations may be attributed to similar evolutionary trends and/or common melt sources. The SATPG plutons show higher Sr and lower Nd isotopic compositions than those of the other groups. Given the geochemical affinities among the RMG, SCG and NATPG plutons (Figs. 12 and 13) and their distinctive isotopic differences

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

0.711

Kula basalts (Ave. Nb/La:2.3 Ave. Ba/Rb: 12)

0.709

Open System

0.708

/ 86Sr 10

0.706

a

100

0.705

0.2 0.0

1.0

0.707

Crustal contamination

Ave. EMM

UC

0.1

87Sr

0.8

Subduction zone enrichment

0.4

0.6

Nb/La

1.0

0.710

1.2

1.4

976

1000

Closed system

b 0.002

0

0.004

0.006

0.008

0.010

1/Sr

Ave. Kula Basalt (Ce/Pb=20)

40

Ave. Kula Basalt

30

c

d

0

Ave. SC basement

10

2

20

4

Zr/Sm

Ce/Pb

6

8

Ba/Rb

0.705

0.710

0.705

0.715

0.710

87Sr/86Sr(i)

0.715

87Sr/86Sr(i)

Fig. 15. a—Nb/La versus Ba/Rb diagram illustrating the effects of crustal contamination and subduction metasomatism during evolution of the MEG. CC (Average Continental Crust): McLennan (2001), EMM (average enriched mantle melts): Yang et al. (2004) and Altunkaynak et al. (2010), Kula basalts: Dilek and Altunkaynak (2010). b—87Sr/86Sr vs. 1/Sr diagram, c—Ce/Pb vs. 87Sr/86Sr(i) diagram and d—Zr/Sm vs. 87Sr/86Sr(i) diagram for RMG, SCG and ATPG.

1

Calc-alkaline volcanism associated with plutonism

KESTANBOL (RMG)

-5 -6 -7

re ls ig

na

tu

ILICA

SCG

us ta

EYBEK

g

cr

YENICE HIDIRLAR

in

-4

KOZAK

as

εNdi

-3

KARAKOY

cr e

-2

EVCILER

In

-1

Initiation of mildly alkaline volcanism

Initiation of alkaline volcanism

0

SALIHLI (SATPG) CAMLIK EGRIGOZ

-8

NATPG

Exhumation of MM and KD core complexes

-9 10

12

14

16

18

20

22

24

26

28

Average age (Ma) Fig. 16. εNd(i) vs. average age diagram for western Anatolian granitoids. MM: Menderes core complex, KD: Kazdağ core complex. See Fig. 2 for data source.

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

977

Ave. Kula basalt EMM

Ave. upper crust (Nzegge et al., 2006)

RMG

Ave. upper crust (Sunal, unpub. data)

0.73

0.74

a

SC basement

SCG

(20 Ma)

G

Ave. gneiss; Kazdag Massif

0.72

H

(H)

(G)

(H)

0.71

(G)

J

I

45

0.72

H

A

0.70 50

55

60

65

70

75

J

I B

(J)

(I)

A

0.70

G

0.71

(J)

(I)

B

c

0.73

Ave. amphibolite, Kazdag Massif

87Sr/86Sr

87Sr/86Sr

(20 Ma)

0.74

45

80

50

55

SiO2 (wt%) 0.5134

b (20 Ma)

A

0.5130

(I)

I B

0.5126

(J)

(I) (J)

(G)

J 0.5122

H

65

70

75

80

SiO2 (wt%)

G

(G)

(H)

143Nd/144Nd

143Nd/144Nd

(20 Ma)

0.5134

60

d A

0.5130

I 0.5126

J

B

G 0.5122

H 0.5118

0.5118 45

50

55

60

65

70

75

80

SiO2 (wt%)

45

50

55

60

65

70

75

80

SiO2 (wt%)

Fig.17. Plots of 87Sr/86Sr(i) and 143Nd/144Nd(i), calculated at 20 Ma, versus SiO2 (wt.%), showing the results of AFC and bulk mixing modeling for the SCG and RMG. For the AFC models (a–b), an average Kula basalt (A), representative of a depleted mantle-derived melt, and a melt derived from an enriched mantle source (EMM; B) were used as starting magmas and different crustal compositions as contaminants: average upper crust (Nzegge et al., 2006) (G); average upper crust (Sunal, unpub. data) (H), average amphibolite from the Kazdag Massif (Altunkaynak, unpub. data) (I), and average gneiss from the Kazdag Massif (Altunkaynak, unpub. data) (J). AFC model input parameters were: r = 0.8, DSiO2 = 0.9, DSr = 1.1, DNd = 1.2. The dots along the AFC curves represent F (fraction of melt remaining) values decreasing in steps of 0.1 from left to right. The crustal contaminant for each AFC curve is indicated in brackets. Bulk mixing arrays between the same endmembers with the dots along the lines at 20% intervals are shown in c–d.

from the SATPG plutons, we focus the remaining discussion on these two distinct magmatic groups. The RMG–SCG–NATPG plutons are isotopically depleted (εNd(i) = +0.12 to −6.3, 87Sr/86Sr(i) =0.705248–0.709900), with respect to the samples from the SATPG (87Sr/86Sr(i) =0.711428–0.71080, εNd(i) = −8.4 to −7.6). These isotopic features imply either different source materials or different degrees of crustal contamination. The RMG, SCG and NATPG samples have low εNd values and relatively high 87Sr/86Sr(i) compositions and display relatively high Mg-numbers and high abundances of many incompatible elements, suggesting derivation of their melt from a mantle source (Figs. 12 and 13). In Fig. 12, RMG–SCG–NATPG exhibit systematic co-variations within the lithospheric mantle array which lies between the Kula basalts and the metamorphic basement rocks and look similar to those of Rhodope granites in northern Greece and enriched lithospheric mantle melts (EMM) from China and Turkey (Yang et al., 2004, Altunkaynak et al., 2010). These features indicate that melting of an enriched lithospheric mantle was involved in the evolution of RMG– SCG–NATPG magmas. However, some of these granitoids have lower 87 Sr/86Sr ratios and higher εNd(i) values (+0.12 to −1.50) compared to the enriched mantle melts (EMM). Hence, they display transitional values between the depleted and enriched mantle melts. Similarly, it can be inferred from Fig. 13 that the RMG–SCG and some NATPG plutons have isotopic compositions and TDM ages (TDM =0.6–1.2 Ga) transitional between those of the Kula basalts (TDM =0.3 Ga), EMM (TDM =0.9–1.1 Ga) and

the crystalline basement rocks (TDM =1.2 to 2 Ga). Therefore, these model ages may indicate mixed model ages between the two endmembers rather than crustal extraction ages for each end-member. Based on these lines of evidence, we deduce that melting of enriched lithospheric mantle and/or depleted mantle melts (at least partly) have contributed to the RMG–SCG–NATPG source region. The systematic covariation between mantle and crustal components and the large range of the TDM ages is also consistent with the evolution of the RMG–SCG– NATPG granitoid magmas through various degrees of crustal assimilation or mixing of mantle melt with an evolved crustal component in different proportions (McCulloch and Chappell, 1982; Arndt and Goldstein, 1987; Chappell, 1996; Jwa, 2004, Sun et al., 2010). It is also apparent from Fig. 12, for the genesis of the RMG–SCG–NATPG magmas, a potential contribution of crustal materials would have been lower in comparison to those of the SATPG magmas. On the other hand, the SATPG samples with crust-like geochemical signatures may have been produced by crustal melting or significant contributions from the ATP crystalline basement. (Figs. 12 and 13) Both the SC and ATP metamorphic basement rocks have higher A/ CNK values and lower Mg-numbers in comparison to the granitoid samples from the RMG–SCG. As the SC and ATP metamorphic basement rocks are dominantly peraluminous (Fig. 8), crustal melting or a large degree of crustal contamination of the magmas would further increase their A/CNK ratios and cause the formation of strongly peraluminous S-

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

978

0.74

D

ATP basement

(20 Ma)

ATPG (D)

Ave. upper crust (Anders, 2005) Ave. amphibolite, Menderes Massif

0.72

87Sr/86Sr

Ave. gneiss; Menderes Massif

C

F

(C)

87

(F)

0.71

E

0.73

0.72

F C

0.71

B

E

(E)

A

0.70

c

D

EMM

0.73

Sr/86Sr (20 Ma)

0.74

a

Ave. Kula basalt

45

B A

0.70 50

55

60

65

70

75

45

80

50

55

SiO2 (wt%)

75

80

75

80

A (E)

B

(C) (E) (C)

E

(F)

(F)

0.5122

F

C D

(20 Ma)

d 0.5130

143Nd/144Nd

(20 Ma) 143Nd/144Nd

70

0.5134

b

0.5126

65

SiO2 (wt%)

0.5134

0.5130

60

0.5126

A

B E

0.5122

F

(D)

C

D 0.5118

0.5118 45

50

55

60

65

70

75

80

SiO2 (wt%)

45

50

55

60

65

70

SiO2 (wt%)

Fig. 18. Plots of (87Sr/86Sr)i and (143Nd/144Nd)i, calculated at 20 Ma, versus SiO2 (wt%), showing the results of AFC and bulk mixing modeling for the ATPG. As in Fig. 17, an average Kula basalt (A), representative of a depleted mantle-derived melt, and a melt derived from an enriched mantle source (EMM; B) were used as starting magmas in the AFC models (a–b), alongside amphibolite from the Menderes Massif (E). Chosen crustal contaminants are: average upper crust (Anders, 2005) (C), upper crustal composition (UC9 from Anders, 2005) (D), average amphibolite from the Menderes Massif (Altunkaynak, unpub. data) (E), and average gneiss from the Menderes Massif (Altunkaynak, unpub. data) (F). AFC model input parameters and explanations as in Fig. 17. Bulk mixing arrays between the same endmembers with the dots along the lines at 20% intervals are shown in c–d.

type granitoids. Therefore, we infer that none of the analyzed granitoids could have been produced solely by these basement units. The metaluminous to slightly peraluminous I-type character of the RMG–SCG– NATPG plutons precludes metapelitic rocks of the RM-SC and ATP basement as suitable source materials. Instead, it points to an igneous protolith such as metabasalt, juvenile K-rich basaltic underplate magma, and/ or mantle rocks (Roberts and Clemens, 1993; Tepper et al., 1993; Pearce, 1996; Patiño Douce and McCarthy, 1998; Von Blanckenburg et al., 1998; Altherr and Siebel, 2002; Ashwall et al., 2002). On the other hand, the geochemical and isotopic compositions and TDM ages of SATPG samples overlap with those of the middle to upper crustal rocks of the ATP basement indicating a significant crustal contribution from the ATP crystalline basement (Figs. 8, 12 and 13). Experimental studies report that hydrous melting of amphibolites or basalts could produce tonalitic magmas and subsequent magma– crust interaction and/or fractional crystallization of these magmas yields granodioritic to granitic compositions. (Rapp and Watson, 1995Patiño Douce, 1996, 1999; Patiño Douce and McCarthy, 1998). These studies also demonstrate that, regardless of the degree of partial melting, partial melts of metabasalts are characterized by relatively high Na2O (>4 wt.%) and low Mg numbers . The low Na2O contents (b4) and relatively high Mg numbers of RMG–SCG–NATPG samples eliminates metabasalts as a suitable source material. Besides that, some researchers have argued that metabasaltic rocks are not suitable source rocks for the generation of high-K calc-alkaline, Itype granitoids as metabasalts contain low-K2O and insufficient

incompatible trace elements to form appreciable volumes of granitic melts (Roberts and Clemens, 1993; Ashwall et al., 2002). Therefore, the high-K calc-alkaline, and incompatible element-enriched nature of the RMG–SCG–NATPG and SATPG suggest that a purely metabasalt source is not suitable for their magmas. The REE patterns of all granitoid groups are parallel to each other and define a trend between Kula basalts and middle–upper crustal rocks. The majority of the plutons display concave-upward patterns with only minor or no negative Eu anomalies, indicating a plagioclase- and garnet-poor and amphibole-, clinopyroxene- and titanite-rich residual source (Altherr and Siebel, 2002) (Fig. 11a, b). Although some samples from NATPG display weakly to moderately peraluminous S-type affinity, isotopic compositions of these samples overlap with those of I-type granitoid samples from NATPG and SCG (Fig. 12). The REE patterns of these samples display more pronounced negative Eu anomalies in comparison to other granitoids groups. Using the REE patterns of the ATPG samples, we can infer that these rocks show evidence for amphibole and feldspar fractionation during magma evolution, rather than a garnet bearing mantle source. Partial melting models show that steep partial melting trajectories observed in Nb/Zr vs. Nb and La/Yb vs. La plots (Fig. 14) can only be produced by partial melting of a residual garnet-bearing mantle source (Thirwall et al., 1994), and that the effect of partial melting was more important than the sole influence of fractional crystallization in controlling the compositional variations in both RMG–SCG and ATPG plutons.

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

979

Fig. 19. Schematic model for the spatial, temporal and geochemical evolution of late Oligocene to middle Miocene magmatism in western Anatolia and the Aegean region.

7.2. Magma evolution The RMG–SCG–NATPG and SATPG samples display LILE enrichment and negative Nb, Ta, Ti, and P anomalies (Fig. 10a, b). These features are consistent with derivation of their magmas from an incompatible element enriched source similar to those of rocks that form at convergent margin settings (Pearce, 1982; McDonough, 1990; Pearce et al., 1990; Thirlwall et al., 1994; Pearce and Peate, 1995; Eyuboglu et al., 2011) and/or post-collisional granitoids (von Blanckenburg and Davies, 1995). The subduction-related enrichment of the mantle source may have been a result of either arc-derived magmas or a subduction component inherited from earlier convergent margin events. Source enrichment through previous subduction events in the region has been suggested for the western Anatolian plutons and related volcanism by some authors (Yılmaz and Polat, 1998; Aldanmaz et al., 2000; Yılmaz et al., 2000; Dilek and Altunkaynak, 2007). Although subduction-induced mantle metasomatism can account for enriched source characteristics of the studied granitoids, it can be argued that the multi-element patterns and isotopic compositions shown by the Oligo–Miocene granitoids could have also been inherited from crustal contamination (Figs. 10–13). The analyzed samples display similar trace-element patterns, comparable to those of the middle–upper continental crust (Fig. 10), which might have been inherited from crustal melts of variable magma sources

and source compositions. In the Nb/La vs. Ba/Rb plot (Fig. 15a), observed in these samples cannot be explained solely by this mechanism. The vertical trend between continental crust and mantle derived melts (Kula basalts and EMM) suggests mixing or AFC of a mantle derived magma with a crustal component, rather than the sole influence of subduction generated fluids (Tatsumi et al., 1986; Pecerillo, 1999; Wang et al., 1999; Marchev et al., 2004). Therefore, a critical evaluation of possible contamination by crustal material is crucial to understand granitoid magma generation in western Anatolia. The relatively constant 1/Sr ratios, increasing Zr/Sm and decreasing Ce/Pb ratios with increasing 87Sr/ 86Sr(i) suggest that opensystem evolutionary processes played an important role in the generation of these granitoids (Fig. 15a–d). Individually, each granitoid group displays isotopically uniform signatures but dispersed variation patterns in the Rb, Sr, Zr and Mg-number vs. SiO2 diagrams (Fig. 9). This may have been caused by heterogeneity in the source and/or different compositions of the overlying crust, through which the RMG, SCG, and ATPG granitoid magmas migrated. Therefore, the observed geochemical features of the late Oligocene–middle Miocene granitoids may indicate that both varying degrees of crustal contamination of mafic parental magmas and/or different compositions of the overlying crust were in part responsible for the geochemical differences between these granitoid suites. In order to test these alternative

980

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

processes, we evaluated εNd(i) vs. TDM (depleted mantle model age) relationships (Fig. 13). On the εNd(i) vs. TDM diagram, the RMG and SCG granitoids plot on an array between the fields of the Kula basalts and the metamorphic basement rocks of the SC (north of the suture zone) which overlaps with the fields of the Hercynian protoliths and the Pelagonian upper crust and the crystalline basement of the ATP (south of the suture). The RMG and SCG granitoids have generally younger TDM values (0.6–1.2 Ga) compared to the SC basement and ATPG granitoids (1.2–1.6 Ga). The RMG and SCG granitoids with the youngest TDM values are characterized by a high amount of mantle-derived protoliths in the mixed source, and the extraction age of their mantle material is younger than 1.2 Ga. Based on the patterns observed in Figs. 12 and 13, we conclude that the samples from the RMG and SCG granitoids have isotopic compositions and TDM ages similar to those of the Rhodope granites in Bulgaria–Greece. Christofides et al. (1998), Pe-Piper and Piper (2001) and Pe-Piper et al. (2002) suggested that fractionation of mafic magmas and/or their mixing with felsic crustal material, some of which was derived by crustal anatexis could produce the granitoid plutons of the Rhodope massif. The distribution of the TDM values of the NATPG samples shows a slight overlap with those of the RMG and SCG plutons, and they generally have older TDM values (>1.2 Ga) that are similar to those of ATP basement. On the same diagrams, it can be inferred that the NATPG samples have a higher amount of crustal and a minor mantle component in the mixed source in comparison to the RMG–SCG samples. It is also apparent from Fig. 13 that the SATPG samples plot in the field of the metamorphic basement rocks from the ATP and the Hercynian protoliths, and show close similarities to the Cyclades granites from the central Aegean Sea. We can deduce that the extraction age of crustal source rocks might be slightly older than 1.2 Ga, which is consistent with the TDM model ages of the crystalline basement rocks representing those occurring south of the suture zone (IASZ). This inferred age is consistent with that of the Pan-African crustal rocks and indicates that the both the NATPG and SATPG magmas were strongly affected by the ATP basement units. Alternatively, as the isotopic compositions and TDM ages of the SATPG samples overlap with those of middle–upper crustal rocks of ATP basement rocks an origin as a middle crustal melt cannot be discarded. Some authors suggested a metasedimentary crustal source for the generation of the I- and Stype granitoid plutons in the Cyclades, which shows similar geochemical and isotopic features to those of the ATPG samples (Altherr and Siebel, 2002; Stouraiti et al., 2010). The isotopic compositions vs. average cooling ages of the RMG, SCG and NATPG granitoids as reported by previous workers and in this study (Table 1) suggest an increasing crustal signature (crustal contamination) with time (Fig. 16). The youngest granitoid group in northwestern Anatolia, SATPG (16 Ma; Catlos et al. ., 2008), displays a strong crustal signature, and the timing of its formation corresponds to the time interval between the initiation of mildly alkaline and strongly alkaline volcanism in western Anatolia (Altunkaynak and Dilek, 2006). 7.3. Petrogenetic modeling In order to test quantitatively whether open-system processes can explain the geochemical and isotopic variations and magmatic evolution of the western Anatolian granitoids, we conducted assimilation and fractional crystallization (AFC) and simple bulk mixing modeling (Figs. 17 and 18) and evaluate these contrasting models for the SCG– RMG and the ATPG, respectively. In the AFC models (Figs. 17a–b and 18a–b), calculated using the equations of DePaolo (1981), it is assumed that a primary magma with an isotopic composition similar to an average Kula basalt (representative of a melt derived from depleted mantle) and a melt derived from an enriched mantle source (EMM) evolved by crystal fractionation to give rise to a series of derivative magmas, which subsequently assimilated different amounts

of crustal material, thus increasing the effects of crustal contamination with the degree of differentiation. To account for the variable composition of the crustal basement in western Turkey and for the different rock types into which the granitoids were emplaced, we used different crustal lithologies and compositions as potential contaminants in the models (Figs. 17a–b and 18a–b). For the ATPG, a lower crustal amphibolite from the Menderes Massif (Altunkaynak, unpub. data) was also used as a starting composition in the AFC models. Bulk mixing arrays (Figs. 17c–d and 18c–d) were calculated between the same endmembers. The AFC models for the SCG–RMG presented in the 87Sr/ 86Sri and 143 Nd/ 144Ndi vs. SiO2 plots (Fig. 17a–b) show that the variations within these granitoids can be modeled successfully, using both depleted and enriched mantle melts as starting compositions, although the models critically depend on the contaminant chosen. Suitable crustal contaminants include the gneisses from the Kazdag Massif and the middle and upper crustal rocks from Altunkaynak (unpub. data) and Sunal (unpub. data) (Fig. 17a–b). Lower crust amphibolite can be ruled out as a potential contaminant, based on the models presented. Realistic models indicate relatively high rates of assimilation to fractional crystallization (r; all AFC models were calculated with r = 0.8). High values for r suggest a comparatively minor role for fractional crystallization; however, as all r values are b1.0, fractional crystallization still dominates over assimilation of crustal rocks. In all AFC models, the extent of differentiation that the parental magmas underwent to reach the values similar to those of the SCG–RMG depends largely on the chosen contaminant. Fractions of original melt remaining (F) are ~ 0.6 for the most contaminated samples of the SCG–RMG, although higher values of “F” (or less crystallization) may be required for particular potential contaminants. Bulk mixing trends between depleted or enriched mantle melts and most of the crustal compositions chosen for the AFC models mostly fail to reproduce the observed compositional variations (in 87Sr/ 86Sr(i) and 143Nd/ 144Nd(i) vs. SiO2 space) of the SCG–RMG, although multi-component mixtures between mantle melts (both depleted and enriched) and/or amphibolites and silicic crustal lithologies remain a possibility (Fig. 17c–d). AFC and bulk mixing models for the ATPG are illustrated in 87Sr/ 86 Sr(i) and 143Nd/ 144Nd(i) vs. SiO2 plots (Fig. 18a–d). Using the same depleted and enriched mantle melts as above as well as a lower crustal amphibolite from the Menderes Massif as starting compositions and several crustal lithologies as potential contaminants in the AFC calculations (Fig. 18a–b), the best-fit models for the observed compositional variations of the ATPG are obtained with the same high rates of assimilation versus fractionation (r = 0.8). Models using a depleted mantle melt or lower mafic crust (amphibolites) as starting compositions and upper crustal values and the Menderes Massif gneisses as contaminants reproduce best the observed compositional variations of the ATPG (with fractions of original melt remaining (F) of ~0.6 (or higher)), although derivation of the ATPG magmas from an enriched mantle source and subsequent AFC processes are also feasible. As for the SCG–RMG, lower crust amphibolite can be ruled out as a potential contaminant of any mantle-derived melt, based on the models presented. Bulk mixing models between depleted and enriched mantle-derived melts and crustal rocks (Fig. 18c–d) largely fail to reproduce the observed compositional variations of the relatively silicic ATPG, although these models do not exclude the possibility of mixtures of mantle-derived melts (or Menderes Massif amphibolite) with more SiO2-rich partial crustal melts. 8. Interplay between syn-convergent extension and magmatism in western Anatolia Convergence between the Eurasian and African plates played an important role in shaping the crustal architecture of the western Anatolia and broader Aegean region during the late Mesozoic–Cenozoic (e.g., Kalvoda and Babek, 2010). This crustal architecture formed from

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

a collage of continental blocks, separated by suture zones (IPS, VS_IASZ, PS in Fig. 1). The continental fragments (RM, SC, ATP) were amalgamated through collisional events starting in the Cretaceous (Şengör and Yılmaz 1981; Dilek and Moores, 1990; Okay et al., 1996; Okay and Tüysüz, 1999). The multiple episodes of continental collision in the Aegean region caused orogen-wide burial metamorphism in the late Paleocene– early Eocene. This regional metamorphism was responsible for the development of high-grade metamorphic rocks in the Rhodope, Kazdağ and Menderes massifs. Continental collision events also produced thick orogenic crust and heterogeneous mantle that affected the mode and nature of syn- to post collisional magmatism and extension in the Aegean region (Seyitoğlu and Scott, 1996; Aldanmaz et al., 2000; Yılmaz et al., 2001; Altunkaynak and Dilek, 2006). In western Anatolia, magmatism occurred in distinct episodes since the early Eocene and appears to have changed in nature from calc-alkaline to alkaline over time. The interpretations explaining the mode and nature of multiple episodes of Cenozoic magmatism through time are subject to discussions and further testing. The current models are; a) active subduction zone magmatism, b) regionwide extension and magmatism caused by orogenic collapse and c) syn-convergent extension and magma generation driven by slab break-off, delamination or convective removal of the lithosphere. The variations in tectonic regimes were a result of feedback mechanisms between the tectonically driven crustal processes and mantle dynamics in the late-stage evolution of the western Anatolian orogenic belt. Current subduction zone models suggest that the Cenozoic magmatism was either a product of the north-dipping subduction of a Tethyan ocean floor (Borsi et al., 1972; Fytikas et al., 1984; Pe-Piper and Piper, 1989; Gülen, 1990; Delaloye and Bingöl, 2000; Okay and Satır, 2000; 2006) or that the Cretaceous subduction along the Izmir–Ankara–Erzincan suture zone and the Miocene subduction along the Hellenic trench could have been related in space and time through slab retreat (Spakman, 1990; van Hinsbergen et al., 2005; Pe-Piper and Piper, 2006). Although magmatic rocks of western Anatolia display a geochemical subduction fingerprint, there is no convincing geological evidence for a subduction event such as the formation of an ophiolithic melange, accretionary prism or blueschist facies metamorphic rocks synchronous with Cenozoic magmatic activity in the region during the middle Eocene through middle Miocene (Harris et al., 1994; Genç and Yılmaz, 1997; Yılmaz et al., 2000, 2001 and references therein). Cretaceous subduction of the Tethyan seafloor beneath the Sakarya continent was halted and terminated by the partial subduction of the Anatolide–Tauride continental margin, following the emplacement of the Cretaceous ophiolites exposed along the Izmir–Ankara–Erzincan suture zone (Harris et al., 1994; Okay et al., 1998; Sherlock et al., 1999; Dilek et al., 2007). The isostatic rebound of this partially subducted continental material in the lower plate was the driving force for the uplift and exhumation of the blueschist rocks in the Paleogene (Sherlock et al., 1999). Time constraints on the obduction of the ophiolite fragments exposed along the collision zone and accretionary processes (Harris et al., 1994; Okay and Tüysüz, 1999; Sherlock et al., 1999; Önen and Hall, 2000) indicate that the timing of collision SC and ATP in NW Anatolia was preearly Eocene. Following the collision, the units of the SC and the suture zone units were covered unconformably by a continental to shallow marine sedimentary rocks of Baslamis (Akdeniz, 1980) and Gebeler Formations (Akyurek and Soysal, 1983) during middle Eocene. This stratigraphic relationship also supports the timing of collision in NW Anatolia was earlier than the middle Eocene. This continental collision resulted in the development of the western Anatolian orogenic belt (Şengör et al., 1985; Dilek and Whitney, 2000). As subduction of African lithosphere beneath Eurasia along the Hellenic trench south of the Anatolide–Tauride and Cyclades belts started around ~ 12 Ma (Meulenkamp et al., 1988), the Eocene to middle

981

Miocene magmatism was not related to any active subduction processes at that time. Therefore, the Oligo–Miocene granitoids were most likely generated in a post-collisional setting rather than in an active continental margin setting, and subduction-related enrichment of the western Anatolian lithospheric mantle was associated with the previous, late Cretaceous subduction of the Neo-Tethyan oceanic lithosphere beneath the Sakarya continent, as suggested by previous researchers (Yılmaz and Polat, 1998; Yılmaz et al., 2000; Aldanmaz et al., 2000; Altunkaynak and Genç, 2008). The orogenic collapse models suggest that the Late Oligocene– Miocene magmatism in western Anatolia was a consequence of extensional tectonics associated with the collapse of the overthickened western Anatolian orogenic belt (Seyitoğlu and Scott, 1991, 1992, 1996; Seyitoğlu et al., 1997). The inferred catastrophic orogenic collapse caused crustal attenuation and magmatism associated with decompressional melting. This model does not explain the mode and nature of earlier Eocene magmatism in the region and has limited applications to the Cenozoic evolution of western Anatolia. Synconvergent extension and associated magma generation is widely recognized within the interiors of modern convergent orogens (e.g., Dalmayrac and Molnar, 1981; Molnar and Chen, 1983; Molnar and Lyon-Caen, 1988, England and Houseman, 1989; Platt and England, 1994; McCaffrey and Nabelek, 1998; Seghedi and Downes, 2011) and the young Tethyan orogen in Anatolia (Turkey) and the broader Aegean region (Aldanmaz et al., 2000; Keskin, 2003; Köprübaşı and Aldanmaz, 2004; Dilek and Altunkaynak, 2007; Altunkaynak and Genç, 2008). Different driving mechanisms such as slab break-off, extensive delamination, partial delamination or convective removal of lithosphere have all been invoked to explain the interplay between syn-convergent extension and magma generation in the region. Some researchers have suggested that the Cenozoic magmatism in western Anatolia displays compositionally distinct magmatic episodes controlled by slab breakoff (Köprübaşı and Aldanmaz, 2004; Altunkaynak and Dilek, 2006; Altunkaynak 2007; Dilek and Altunkaynak, 2007; Boztuğ et al., 2009). Others have proposed that lithospheric delamination (Aldanmaz et al., 2000) and/or partial convective removal of the subcontinental lithospheric mantle resulting in asthenospheric upwelling and decompressional melting were important processes during the post collisional build up of Cenozoic western Anatolia (Altunkaynak and Genç, 2008). We think that the long-lived Cenozoic magmatism in western Anatolia was spatially and temporally associated with different tectonic events driven by crustal- and mantle-scale processes and their interactions. The first episode of granitoid magmatism and its volcanic equivalents evolved during the early to late Eocene (54–35 Ma) and produced medium to high-K calc-alkaline I type granitoids. The emplacement of localized granitoid plutons along the IASZ and into the Sakarya continent has been interpreted to have resulted from slab breakoff-related asthenospheric upwelling and associated partial melting of the subduction-metasomatized continental lithospheric mantle by previous studies (Köprübaşı and Aldanmaz, 2004; Altunkaynak, 2007; Dilek and Altunkaynak 2007). Partial underplating of the leading edge of the buoyant Anatolide–Tauride platform beneath the Sakarya continent jammed the north-dipping Tethyan subduction temporarily, while the continued sinking of lithospheric mantle resulted in slab breakoff in NW Anatolia. This interpretation is supported by the seismic tomography model of Dilek and Sandvol (2009) demonstrating the existence of a second high-velocity (cold) slab near the 660 km discontinuity in the lower mantle north of the Hellenic slab, which is interpreted as a detached Tethyan slab dipping beneath the western Anatolian orogenic belt. Slab detachment and breakoff is a natural consequence of the gravitational settling of subducted lithosphere in continental collision zones, as a result of a decrease in the subduction rate caused by the positive buoyancy of partially subducted continental lithosphere (Davis and Von Blanckenburg, 1995; Von Blanckenburg and Davies, 1995; Wortel and Spakman, 2000; Gerya et al., 2004).

982

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

The second magmatic episode produced widespread I-type plutonic and associated volcanic rocks in western Anatolia during the late Oligocene to middle Miocene. This time interval coincides with the exhumation of lower to middle crustal rocks in western Anatolia (as in the Menderes and Kazdağ core complexes) and in the Aegean province (Naxos, Cyclades) (Fig. 19). The initial exhumation age of the Kazdağ core complex has been suggested as the latest Oligocene–early Miocene (Okay and Satır, 2000) and that of the Menderes core complex as the earliest Miocene (Işık et al., 2004; Thomson and Ring, 2006; Bozkurt, 2007; Dilek and Altunkaynak, 2007; Altunkaynak and Genç, 2008). In general, tectonic extension also appears to have migrated southward in time. Following the exhumation of the Kazdag and Menderes metamorphic core complexes, the Tauride block in SW Anatolia was uplifted (Dilek et al. 1999b) and the blueschist rocks in Crete and the Cyclades in the South Aegean region (Ring and Layer, 2003) were exhumed in the Miocene and onwards (Fig. 19). Zircon SHRIMP U–Pb dating of NATPG and SCG groups yields ages between 19.48 ± 0.29 and 23.94 ± 0.31 Ma as the timing of their emplacement, whereas 39Ar/ 40Ar dating of hornblende and biotite separates from the SCG, RMG and NATPG groups reveals cooling ages of 18.9 ± 0.1–24.8 ± 0.1. These results are consistent with the radiometric ages (mostly K/Ar ages) obtained in previous studies and indicate that the extensional deformation was spatially and temporally associated with voluminous granitoid magmatism which is represented by metaluminous to slightly peraluminous, I-type granitoids. The Sr–Nd isotopic signatures and trace element characteristics of these granitoids indicate that the melts derived from both lithospheric mantle and depleted mantle (at least for the SCG and RMG magmas) contributed to magma source region of the parental magmas. The asthenospheric melt contribution in addition to lithospheric mantle melts most likely resulted from lithospheric delamination or partial convective removal of the subcontinental lithospheric mantle. Although the extensional tectonic regime was operating fully during the latest Oligocene–Early Miocene, the relationships between the isotopic compositions and cooling ages as documented in this study indicate an increasing crustal signature from 24 to 18 Ma (Fig. 16). We propose that asthenospheric upwelling caused by partial delamination or convective thinning of lithospheric mantle led to underplating of mantle-derived magmas providing melt and heat to induce partial melting of the lithospheric mantle (Fig. 19). Invasion of the crust by melts derived from both asthenospheric (depleted) and enriched lithospheric mantle triggered open system processes (AFC and/or MASH (melting, assimilation, storage, homogenization; Hildreth and Moorbath, 1988)) in separate magma chambers, resulting in the production of mildly to highly evolved Oligo–Miocene granitoid magmas. This inferred melt source and magma evolution readily explains the I-type granitoid nature of most Cenozoic plutons in western Anatolia, regardless of their temporal and spatial position. This widespread early to middle Cenozoic magmatism caused thermal weakening of the young orogenic crust and played a significant role for the initiation of syn-convergent extension and crustal exhumation as early as in the latest Oligocene–early Miocene (Fig. 19). The absence of large volumes of alkaline basaltic lavas in western Anatolia during this period also contradict extensive lithospheric delamination models. Moreover, previous workers suggested that the crustal thickness in the Aegean province ranges from 16 km in the Crete Sea to 25–35 km in the Cyclades and W Turkey (Makris and Stobbe1984; Doglioni et al. 2002; Tirel et al. 2004; Zhu et al. 2006). Variations in crustal thickness may indicate that extensional thinning has not been uniform in western Anatolia and the Aegean region, consistent with the proposed models of convective removal and partial delamination of lithospheric mantle. The effects of convective removal or partial delamination of the cold mantle lithosphere and its replacement by hot asthenosphere are well documented in other orogenic belts and in eastern Anatolia, where the lower–middle crust has been remobilized upwards,

causing exhumation, surface uplift, and overall net extension (Bird, 1979; England and Houseman, 1989; Molnar et al., 1993; Houseman and Molnar, 1997; Keskin 2003; Şengör et al., 2003; Dokuz, 2011). The degree of crustal contribution appears to have increased in plutonic rocks by middle Miocene (Fig. 16). The age of the youngest granitoid group (SATPG; 13–16 Ma; Hetzel et al., 1995), which displays a strong crustal signature, corresponds to the time interval between the initiation of, mildly alkaline (associated with bimodal volcanism) and strongly alkaline volcanism in western Anatolia. Thus, both asthenospheric- and lithospheric mantle and crustal melts were involved in the evolution of magmatism in the middle Miocene and onwards. Therefore, the geochemical variations in the late Cenozoic post-collisional magmatism in western Anatolia reflect the increasing intensity of regional extension through time (Altunkaynak and Dilek 2006, Altunkaynak and Genç 2008, Altunkaynak et al., 2010). This shift in the geochemical affinity of magmatism is interpreted as a result of tectonically driven asthenospheric upwelling beneath this highly extended terrane, following a period of extreme crustal thinning after the exhumation of core complexes in western Anatolia and the Aegean region in response to rapid slab rollback at the Hellenic trench (Meulenkamp et al., 1988; Spakman et al., 1988; Pe-Piper and Piper 2006). Pn velocity and Sn attenuation tomography models indicate that the uppermost mantle is anomalously hot and thin, consistent with the existence of a shallow asthenosphere beneath western Anatolia (Sandvol et al., 2003). The close temporal and spatial relationships between the late Cenozoic tectonic extension and magmatism suggest that the widespread early to middle Cenozoic magmatism caused thermal weakening and played a significant role in the initiation of synconvergent extension, crustal exhumation and thinning in the hinterland of a young Tethyan orogen in western Anatolia and the broader Aegean region. 9. Conclusions The majority of the Oligo–Miocene granitoids are represented by metaluminous to slightly peraluminous, I-type granitoids. Isotopic signatures and major-trace element characteristics of the RMG–SCG and NATPG granitoids which emplaced into different tectonic units of western Anatolia indicate that both lithospheric- and asthenospheric mantle (at least partly for the SCG–RMG magmas) melts appear to have contributed to source region of mafic parental magmas which evolve toward granodioritic to granitic compositions. The compositional variations observed in the RMG, SCG and NATPG granitoids are interpreted as a result of open-system processes during evolution of these granitoids rather than a reflection of different compositions of crustal lithologies through which the RMG and SCG, ATPG magmas migrated. The TDM ages of the RMG and SCG suggest a high amount of mantle-derived protoliths in the mixed source and the extraction age of the mantle material to be younger than 1.2 Ga. The calculated TDM ages of the NATPG samples are consistent with those of the PanAfrican crustal rocks, and indicate that these granitoids, characterized by stronger crustal signatures than the other groups, were affected by the crystalline basement of the Anatolide–Tauride platform. By contrast, the SATPG samples with crust-like geochemical signatures may have been produced by crustal melting or, at least, significant contributions from the ATP crystalline basement. The observed isotopic characteristics and variations with indices of differentiation suggest that the crustal signature within the Oligo–Miocene granitoids developed predominantly through simultaneous assimilation of upper–middle crustal rocks and fractional crystallization (AFC) of mantle derived melts during magma ascent. Assimilation and fractional crystallization models explain the compositions of the Oligo–Miocene granitoids slightly better than bulk mixing between different mantle and crustal components, although mixing between mantle-derived melts and partial crustal melts

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

cannot be entirely ruled out. Thus, the observed range in isotopic variations is not solely a feature of the inferred mantle melt source. Zircon SHRIMP U–Pb dating of the NATPG and SCG groups yields ages between 19.48 and 23.94 Ma as the timing of their emplacement, whereas cooling ages of same granitoids range between 20.6 and 18.9. 39Ar/ 40Ar dating of biotite separates from the SCG, RMG and NATPG groups reveals cooling ages of 18.9–28.0 Ma. The isotopic compositions and cooling ages of the western Anatolian granitoids suggest a progressive increase in the amount of crustal signature (assimilation of crustal rocks) from 24 to 18 Ma, coinciding with the timing of crustal exhumation and core complex formation (Kazdağ and Menderes massifs) in western Anatolia. The heat and basaltic material to induce partial melting, which led to the generation of granitoid magmas, were provided by asthenospheric upwelling caused by partial lithospheric delamination and/or convective thinning beneath western Anatolia. This widespread early to middle Cenozoic magmatism caused thermal weakening of the young orogenic crust and played a significant role for the initiation of syn-convergent extension and crustal exhumation as early as in the latest Oligocene–early Miocene. The age of the youngest granitoid group (SATPG; 13–16 Ma; Hetzel et al., 1995; Glodny and Hetzel 2007), which displays a strong crustal signature, corresponds to the time interval between the initiation of mildly alkaline and strongly alkaline volcanism in western Anatolia. This shift in the geochemical affinity of magmatism is interpreted as a result of tectonically driven asthenospheric upwelling beneath this highly extended terrane, following a period of extreme crustal thinning after the exhumation of core complexes in western Anatolia and the Aegean region. Supplementary materials related to this article can be found online at doi:10.1016/j.gr.2011.10.010. Acknowledgments This study has been funded by grants from the Istanbul Technical University (BAP Project No: 35691) and the Turkish Research Council (TUBITAK-CAYDAG-109Y010) that are gratefully acknowledged. Constructive and insightful comments by P.T. Robinson and Y. Eyupoglu helped us to improve the paper. We would like to thank the Editorin-Chief, Professor M. Santosh, for inviting us to prepare this contribution as a Focus Paper in Gondwana Research. References Akay, E., 2009. Geology and petrology of the Simav Magmatic Complex (NW Anatolia) and its comparison with the Oligo–Miocene granitoids in NW Anatolia: implications on Tertiary tectonic evolution of the region. International Journal of Earth Sciences (GeolRundsch) 98, 1655–1675. doi:10.1007/s00531-008-0325-0. Akdeniz, N., 1980. Başlamış formasyonu. Journal of Geological Engineering 10, 39–47 (in Turkish). Akyurek, B., Soysal, Y., 1983. Biga yarımadası güneyinin (Savastepe-Kırkagac-BergamaAyvalık) temel jeoloji ozellikleri. Bulletin of Mineral Research and Exploration Institute of Turkey 95, 1–12. Aldanmaz, E., Pearce, J., Thirlwall, M.F., Mitchell, J., 2000. Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey. Journal of Volcanology and Geothermal Research 102, 67–95. Alıcı, P., Temel, A., Gourgaud, A., 2002. Pb–Nd–Sr isotope and trace element geochemistry of Quaternary extension-related alkaline volcanism: a case study of Kula region (western Anatolia, Turkey). Journal of Volcanology and Geothermal Research 115, 487–510. Altherr, R., Siebel, W., 2002. I-type plutonism in a continental back-arc setting: Miocene granitoids and monzonites from the central Aegean Sea, Greece. Contributions to Mineralogy and Petrology 143, 397–415. Altherr, R., Henjes-Kunst, F.J., Matthews, A., Friedrichsen, H., Hansen, B.T., 1988. O-Sr isotopic variations in Miocene granitoids from the Aegean: evidence for an origin by combined assimilation and fractional crystallization. Contributions to Mineralogy and Petrology 100, 528–541. Altunkaynak, Ş., 2007. Collision-driven slab breakoff magmatism in northwestern Anatolia, Turkey. Journal of Geology 115, 63–82. Altunkaynak, Ş., Yılmaz, Y., 1998. The Kozak magmatic complex; western Anatolia. Journal of Volcanology and Geothermal Research 85/1–4, 211–231. Altunkaynak, Ş., Yılmaz, Y., 1999. The Kozak Pluton and its emplacement. Geological Journal 34, 257–274.

983

Altunkaynak, Ş., Dilek, Y., 2006. Timing and nature of post collisional volcanism in Western Anatolia and geodynamic implications. In: Dilek, Y., Pavlides, S. (Eds.), Post-collisional Tectonics and Magmatism of the Eastern Mediterranean Region: Geological Society of America Special Paper, 409, pp. 321–351. Altunkaynak, Ş., Genç, Ş.C., 2008. Petrogenesis and time-progressive evolution of the Cenozoic continental volcanism in the Biga Peninsula, NW Anatolia (Turkey). Lithos 102, 316–340. Altunkaynak, Ş., Rogers, N.W., Kelley, S.P., 2010. Causes and effects of geochemical variations in Late Cenozoic volcanism in the Foca volcanic centre (NW Anatolia, Turkey). International Geology Review 52, 579–607. Anders, B., 2005. The pre-Alpine evolution of the basement of the Pelagonian Zone and the Vardar Zone, Greece. PhD. Thesis, Johannes Gutenberg-Universität Mainz, Germany. Arndt, N.T., Goldstein, S.L., 1987. Use and abuse of crust formation ages. Geology 15, 893-89. Ashwall, L.D., Demaiffe, D., Torsvik, T.H., 2002. Petrogenesis of Neoproterozoic granitoids and related rocks from Seychelles: the case for Andean-type arc origin. Journal of Petrology 43, 45–83. Black, L.P., Kamo, S.L., Allen, C.M., Aleinikoff, J.N., Davis, D.W., Korsch, R.J., Foudoulis, C., 2003. A new zircon standard for Phanerozoic U–Pb geochronology. Chemical Geology 200, 155–170. Bingol, E., Delaloye, M., Ataman, G., 1982. Granitic intrusions in western Anatolia, a contribution to the geodynamic study of this area. Eclogae Geologicae Helvetiae 75, 437–446. Bingöl, E., Akyürek, B., Korkmazer, B., et al., 1975. Biga Yarımadası'nın jeolojisi ve Karakaya formasyonunun bazı özellikleri, Cumhuriyetin 50. yılı Yerbilimleri Kongresi, Proceedings. MTA, pp. 70–75. Bird, P., 1979. Continental delamination and the Colorado Plateau. Journal of Geophysical Research 84, 7561–7571. Borsi, S., Ferrara, G., Innocenti, F., Mazzuoli, R., 1972. Geochronology and petrology of recent volcanics in the Eastern Aegean Sea. Bulletin of Volcanology 36, 473–496. Boynton, W.V., 1984. Geochemistry of the rare-earth elements: meteorite studies. In: Henderson, P. (Ed.), Rare Earth Element Geochemistry. Elsevier, Amsterdam, pp. 63–114. Bozkurt, E., 2007. Extensional vs. contractional origin for the southern Menderes shear zone, SW Turkey: tectonic and metamorphic implications. Geological Magazine 144, 191–210. Bozkurt, E., Park, R.G., 1994. Southern Menderes Massif: an incipient metamorphic core-complex in western Anatolia, Turkey. Journal of the Geological Society of London 151, 213–216. Bozkurt, E., Satır, M., 2000. The southern Menderes Massif (western Turkey): geochronology and exhumation history. Geological Journal 35, 285–296. Boztuğ, D., Harlavan, Y., Jonckheere, R., Can, I., Sarı, R., 2009. Geochemistry and K–Ar cooling ages of the Ilıca, Cataldag (Balıkesir) and Kozak (Izmir) granitoids, west Anatolia, Turkey. Geological Journal 44, 79–103. Briqueu, L., Javoy, M., Lancelot, J.R., Tatsumoto, M., 1986. Isotope geochemistry of recent magmatism in the Aegean arc: Sr, Nd, Hf and O isotopic ratios in the lavas of Milos and Santorini: geodynamic implications. Earth and Planetary Science Letters 80, 41–54. Catlos, E.J., Baker, C., Sorensen, S.S., Çemen, I., Hançer, M., 2008. Monazite geochronology, magmatism and extensional dynamics within the Menderes massif, Western Turkey. Donald Harrington Symposium on the Geology of the Aegean. IOP Conference Series: Earth and Environmental Science, vol. 2, pp. 1–7. Chappel, B.W., 1996. Magma mixing and the production of compositional variation within granite suites: evidence from the granites of southeastern Australia. Journal of Petrology 37, 449–470. Christofides, G., Soltados, T., Eleftheriadis, G., Koroneus, A., 1998. Chemical and isotopic evidence for source contamination and crustal assimilation in the Hellenic Rhodope plutonic rocks. Acta Vulcanologica 10, 305–318. Cox, K.G., Bell, J.D., Pankhurst, R.J., 1979. The Interpretation of Igneous Rocks. Allen and Unwin, London. 450 pp. Dalmayrac, B., Molnar, P., 1981. Parallel thrust and normal faulting in Peru and the constraints on the state of stress. Earth and Planetary Science Letters 55, 473–481. Davis, J.H., Von Blanckenburg, F., 1995. Slab breakoff: a model of lithosphere detachment and its test in the magmatism and deformation of collisional orogens. Earth and Planetary Science Letters 129, 85–102. Delaloye, M., Bingöl, E., 2000. Granitoids from western and northwestern Anatolia: geochemistry and modeling of geodynamic evolution. International Geology Review 42, 241–268. Demirtasli, E., Turhan, N., Bilgin, A.Z., Selim, M., 1984. Geology of the Bolkar Mountains. In: Tekeli, O., Goncuoglu, M.C. (Eds.), Geology of the Taurus Belt, International Symposium Proceedings, 1984, Ankara. Mineral Research & Exploration Institute of Turkey (MTA), Ankara, pp. 125–141. DePaolo, D.J., 1981. Trace element and isotopic effects of combined wallrock assimilation and fractional crystallization. Earth and Planetary Science Letters 53, 189–202. Dilek, Y., Moores, E.M., 1990. Regional tectonics of the Eastern Mediterranean ophiolites. In: Malpas, J., et al. (Ed.), Ophiolites, Oceanic Crustal Analogues: Symposium “Troodos 1987,” Proceedings, Nicosia, Cyprus, pp. 295–309. Dilek, Y., Whitney, D.L., 2000. Cenozoic Crustal Evolution in Central Anatolia: Extension, Magmatism and Landscape Development. Proceedings, Nicosia, Cyprus. pp. 183–192. Dilek, Y., Altunkaynak, Ş., 2007. Cenozoic crustal evolution and mantle dynamics of post-collisional magmatism in western Anatolia. International Geology Review 49 (5), 431–453.

984

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

Dilek, Y., Furnes, H., Shallo, M., 2007. Suprasubduction zone ophiolite formation along the periphery of Mesozoic Gondwana. Gondwana Research 11, 453–475. Dilek, Y., Altunkaynak, Ş., 2009. Geochemical and temporal evolution of Cenozoic magmatism in western Turkey: mantle response to collision, slab breakoff, and lithospheric tearing in an orogenic belt. In: Van Hinsbergen, D.J.J., Edwards, M.A., Govers, R. (Eds.), Geodynamics of Collision and Collapse at the Africa–Arabia–Eurasia Subduction Zone: Geological Society, London: Special Publication, vol. 311, pp. 213–233. doi:10.1144/sp321. Dilek, Y., Whitney, D.L., Tekeli, O., 1999. Links between tectonic processes and landscape morphology in an Alpine collision zone. South-Central Turkey: Annals of Geomorphology 118, 147–164. Dilek, Y., Altunkaynak, Ş., Öner, Z., 2009. Syn-extensional granitoids in the Menderes core complex, and the late Cenozoic extensional tectonics of the Aegean province. In: Ring, U., Wernicke, B. (Eds.), Extending a Continent: Architecture, Rheology and Heat Budget. Geological Society, London: Special Publications, vol. 321, pp. 197–223. Dilek, Y., Sandvol, E., 2009. Seismic structure, crustal architecture and tectonic evolution of the Anatolian–African Plate Boundary and the Cenozoic Orogenic Belts in the Eastern Mediterranean Region. In: Murphy, J.B., Keppie, J.D., Hynes, A.J. (Eds.), Ancient Orogens and Modern Analogues. Geological Society, London: Special Publications, vol. 327, pp. 127–160. doi:10.1144/SP327.8. Dilek, Y., Altunkaynak, Ş., 2010. Geochemistry of Neogene–Quaternary alkaline volcanism in western Anatolia, Turkey, and implications for the Aegean mantle. International Geology Review 52 (4), 631–655. Doglioni, C., Agostini, S., Crespi, M., Innocenti, F., Manetti, P., Riguzzi, F., Savascin, Y., 2002. On the extension in western Anatolia and the Aegean Sea. In: Rosenbaum, G., Lister, G.S. (Eds.), Reconstruction of the Evolution of the Alpine–Himalayan Orogen: Journal of the Virtual Explorer, vol. 8, pp. 169–183. Dokuz, A., 2011. A slab detachment and delamination model for the generation of Carboniferous high-potassium I-type magmatism in the Eastern Pontides, NE Turkey: the Köse composite pluton. Gondwana Research 19, 926–944. England, P., Houseman, G., 1989. Extension during continental convergence, with application to the Tibetan plateau. Journal of Geophysical Research 94, 17561–17579. Eyuboglu, Y., Chung, S.L., Santosh, M., Dudas, F.O., Akaryali, E., 2011. Transition from shoshonitic to adakitic magmatism in the Eastern Pontides, NE Turkey: implications for slab window melting. Gondwana Research 19, 413–429. Foland, K.A., Fleming, T.H., Heimann, A., Elliot, D.H., 1993. Potassium–argon dating of fine-grained basalts with massive Ar loss: application of the 40Ar/39Ar technique to plagioclase and glass from the Kirkpatrick Basalt, Antarctica. Chemical Geology 107, 173–190. Fytikas, M., Giuliani, O., Innocenti, F., Marinelli, G., Mazzuoli, A., 1976. Geochronological data on recent magmatism of the Aegean sea. Tectonophysics 31, T29–T34. Fytikas, M., Innocenti, F., Manetti, P., Mazzuoli, R., Peccerillo, A., Villari, L., 1984. Tertiary to Quaternary evolution of volcanism in the Aegean region. In: Dixon, J.E., Robertson, A.H.F. (Eds.), The Geological Evolution of the Eastern Mediterranean: Special Publication, Geological Society, London, vol. 17, pp. 687–700. Genç, Ş.C., 1998. Evolution of the Bayramiç magmatic complex. Journal of Volcanology and Geothermal Research 85 (1–4), 233–249. Genç, Ş.C., 2004. A Triassic large igneous province in the Pontides, northern Turkey: geochemical data for its tectonic settings. Journal of Asian Earth Sciences 22 (5), 503–516. Genç, Ş.C., Yılmaz, Y., 1997. An example of post-collisional magmatism in northwestern Anatolia: the Kizderbent Volcanics (Armutlu Peninsula, Turkey). Turkish Journal of Earth Sciences 6, 33–42. Gessner, K., Collins, A.S., Ring, U., Gungor, T., 2004. Structural and thermal history of poly-orogenic basement: U–Pb geochronology of granitoid rocks in the southern Menderes Massif, western Turkey. Journal of the Geological Society of London 161, 93–101. Glodny, J., Hetzel, R., 2007. Precise U-Pb ages of syn-extensional Miocene intrusions in the central Menderes Massif, western Turkey. Geological Magazine 144, 1–12. Goldstein, S.J., Jacobsen, S.B., 1988. Nd and Sr isotopic systematics of river-water suspended material: implications for crustal evolution. Earth and Planetary Science Letters 87, 249–265. Govindaraju, K., 1994. Compilations of working values and sample description for 383 geostandards. Geostandards Newsletter 18, 1–158. Gerya, T.V., Yuen, D.A., Maresch, W.V., 2004. Thermomechanical modeling of slab detachment. Earth and Planetary Science Letters 226, 101–116. Güleç, N., 1991. Crust–mantle interaction in western Turkey: implications from Sr and Nd isotope geochemistry of Tertiary and Quaternary volcanics. Geological Magazine 23, 417–435. Gülen, L., 1990. Isotopic characterization of Aegean magmatism and geodynamic evolution of Aegean subduction. In: Savascin, M.Y., Eronat, A.H. (Eds.), International Earth Science Colloquium on the Aegean Region (IESCA). : İzmir. Turkey, Proceedings II, pp. 143–166. Gülmez, F., Genç, Ş.C., 2009. Petrology of the Middle Eocene volcanic rocks of Almacik mountain, NW Turkey. Goldschmidt Conference Abstracts. Geochimica Et Cosmochimica Acta 73/13, A477-A477. Harris, N.B.W., Kelley, S., Okay, A.I., 1994. Post-collisional magmatism and tectonics in northwest Anatolia. Contributions to Mineralogy and Petrology 117, 241–252. Hasözbek, A., Satır, M., Erdoğan, B., Akay, E., Siebel, W., 2010. Early Miocene postcollisional magmatism in NW Turkey: geochemical and geochronological constraints. International Geology Review 1–22. doi:10.1080/00206810903579302. Hetzel, R., Passchier, C.W., Ring, U., Dora, O.Ö., 1995. Bivergent extension in orogenic belts: the Menderes massif (southwestern Turkey). Geology 23, 455–458. Hetzel, R., Reischmann, T., 1996. Intrusion age of Pan-African augen gneisses in the southern Menderes Massif and the age of cooling after Alpine ductile extensional deformation. Geological Magazine 133 (5), 565–572.

Hildreth, W., Moorbath, S., 1988. Crustal contributions to arc magmatism in the Andes of Central Chile. Contributions to Mineralogy and Petrology 98, 455–489. Houseman, G.A., Molnar, P., 1997. Gravitational (Rayleigh–Taylor) instability of a layer with non-linear viscosity and convective thinning of continental lithosphere. Geophysical Journal International 128, 125–150. Irvine, T.N., Baragar, W.R.A., 1971. A guide to the chemical classification of common volcanic rocks. Canadian Journal of Earth Science 8, 523–548. Işık, V., Tekeli, O., Seyitoğlu, G., 2004. The 40Ar/39Ar age of extensional ductile deformation and granitoid intrusion in the northern Menderes core complex: implications for the initiation of extensional tectonics in western Turkey. Journal of Asian Earth Sciences 23, 555–566. Juteau, T., 1980. Ophiolites of Turkey: Ofioliti 2, 199–238. Jwa, Y.J., 2004. Possible source rocks of Mesozoic granites in South Korea: implications for crustal evolution in NE Asia. Transactions of the Royal Society of Edinburgh, Earth Sciences 95, 181–198. Kalvoda, J., Babek, O., 2010. The margins of Laurussia in Central and Southeast Europe and Southwest Asia. Gondwana Research 17, 526–545. Karacık, Z., Yılmaz, Y., Pearce, J.A., Ece, O.I., 2008. Petrochemistry of the south Marmara granitoids, northwest Anatolia, Turkey. International Journal of Earth Sciences 97, 1181–1200. doi:10.1007/s00531-007-0222-y. Karacık, Z., Yılmaz, Y., 1998. Geology of the ignimbrites and the associated volcanoplutonic complex of the Ezine area, northwestern Anatolia. Journal of Volcanology and Geothermal Research 85 (1–4), 251–264. Keskin, M., 2003. Magma generation by slab steepening and breakoff beneath a subduction–accretion complex: an alternative model for collision-related volcanism in Eastern Anatolia. Geophysical Research Letters 30 (24), 8046. doi:10.1029/2003GL018019. Köprübaşı, N., Aldanmaz, E., 2004. Geochemical constraints on the petrogenesis of Cenozoic I-type granitoids in Northwest Anatolia, Turkey: evidence for magma generation by lithospheric delamination in a post-collisional setting. International Geology Review 46, 705–729. Ludwig, 2001. User's Manual for Isoplot/Ex version 2.49. A Geochronological Toolkit for Microsoft Excel. Special Publication, vol. 1A. Berkeley Geochronology Center, Berkeley, CA, USA. 59 pp. Mackintosh, P.W., Robertson, A.F., 2011. Late Devonian–Late Triassic sedimentary development of the central Taurides, S Turkey: implications for the northern margin of Gondwana. Gondwana Research. doi:10.1016/j.gr.2011.07.016. Marchev, P., Raicheva, R., Downes, H., Vaselli, O., Chiaradia, M., Moritz, R., 2004. Compositional diversity of Eocene–Oligocene basaltic magmatism in the Eastern Rhodopes, SE Bulgaria: implications for genesis and tectonic setting. Tectonophysics 393, 301–328. McCulloch, M.T., Chappell, B.W., 1982. Nd isotopic characteristics of S- and I-type granites. Earth and Planetary Science Letters 58, 51–64. McDonough, W.F., 1990. Constrains on the composition of the continental lithospheric mantle. Earth and Planetary Science Letters 101, 1–18. McCaffrey, R., Nabelek, J., 1998. Role of oblique convergence in the active deformation of the Himalayas and southern Tibet plateau. Geology 26, 691–694. McLennan, M.S., 2001. Relationships between the trace element composition of sedimentary rocks and upper continental crust. Geophysics,and Geosystems (G3) 2 Paper number (2000GC00109). Meulenkamp, J.E., Wortel, W.J.R., Van Wamel, W.A., Spakman, W., Hoogerduyn, S.E., 1988. On the Hellenic subduction zone and geodynamic evolution of Crete since the late Middle Miocene. Tectonophysics 146, 203–215. doi:10.1016/00401951(88)90091-1. Molnar, P., Chen, W.P., 1983. Focal depths and fault plane solutions of earthquakes under the Tibetan plateau. Journal of Geophysical Research 88, 1180–1196. Molnar, P., Lyon-Caen, H., 1988. Some simple physical aspects of the support, structure and evolution of mountain belt. In: Clark Jr., S.P. (Ed.), Processes in Continental and Lithospheric Deformation: Geological Society of America Special Paper, vol. 218, pp. 179–207. Molnar, P., England, P., Martinod, J., 1993. Mantle dynamics, uplift of the Tibetan plateau, and the Indian monsoon. Reviews of Geophysics 31, 357–396. Nzegge, O.M., Satır, M., Siebel, W., Taubald, H., 2006. Geochemical and isotopic constraints on the genesis of the Late Paleozoic Deliktaş and Sivrikaya granites from the Kastamonu granitoid belt (Central Pontides, Turkey). Neues Jahrbuch für Mineralogie Abhandlungen 183, 27–40. Okay, A.I., Siyako, M., 1993. The new position of the Izmir–Ankara Neo-Tethyan suture between İzmir and Balıkesir. In: Turgut, S. (Ed.), Tectonics and Hydrocarbon Potential of Anatolia and Surrounding Regions. Ozan Sungurlu Symposium, Proceedings, Ankara, pp. 333–355 (in Turkish with English abstract). Okay, A.I., Tüysüz, O., 1999. Tethyan sutures of Northern Turkey. In: Durand, B., Jolivet, L., Horthváth, F., Séranne, M. (Eds.), The Mediterranean Basin: Tertiary Extension within the Alpine Orogen: Geological Society, London, Special Publication 156, vol. 156, pp. 475–515. Okay, A.I., Satır, M., 2000. Coeval plutonism and metamorphism in a latest Oligocene metamorphic core complex in northwest Turkey. Geological Magazine 137, 495–516. Okay, A.I., Satır, M., 2006. Geochronology of Eocene plutonism and metamorphism in northwest Turkey: evidence for a possible magmatic arc. Geodinamica Acta 19 (5), 251–266. Okay, A.I., Siyako, M., Bürkan, K.A., 1990. Biga Yarımadasının jeolojisi ve tektonik evrimi. Türkiye Petrol Jeologları Derneği Dergisi 2 (1), 83–121 (in Turkish). Okay, A.I., Harris, N.B.W., Kelley, S.P., 1998. Exhumation of blueschists along a Tethyan suture in northwest Turkey. Tectonophysics 285, 275–299. doi:10.1016/S00401951(97)00275-8. Okay, A.I., Satir, M., Maluski, H., Siyako, M., Monie, P., Metzger, R., Akyüz, S., 1996. Paleo- and Neo-Tethyan events in northwest Turkey: geological and geochronological constraints. In: Yin, A., Harrison, M.T. (Eds.), Tectonics of Asia. Cambridge University Press, Cambridge, pp. 420–441.

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986 Önen, A.P., Hall, R., 2000. Sub-ophiolite metamorphic rocks from northwest Anatolia, Turkey. Journal of Metamorphic Geology 18, 483–495. Öner, Z., Dilek, Y., Kadıoğlu, Y.K., 2010. Geology and geochemistry of the synextensional Salihli granitoid in the Menderes core complex, western Anatolia, Turkey. International Geology Review 52, 336–368. Özgenç, İ., İlbeyli, N., 2008. Petrogenesis of the Late Cenozoic Eğrigöz Pluton in Western Anatolia, Turkey: implications for magma genesis and crustal processes. International Geology Review 50, 375–391. Padfield, T., Gray, A., 1971. Major element analysis by X-ray fluorescence a simple fusion method. Philips Bulletin Analytical Equipment, vol. 35. 4 pp. Patiño Douce, A.E., 1996. Effects of pressure and H2O contents on the composition of primary crustal melts. Transactions of the Royal Society of Edinburgh Earth Sciences 87, 11–21. Patiño Douce, A.E., McCarthy, T.C., 1998. Melting of crustal rocks during continental collision and subduction. In: Hacker, B.R., Liou, J.G. (Eds.), When Continents Collide: Geodynamics and Geochemistry of Ultrahigh-pressure Rock. Kluwer Academic, Dordrecht, pp. 27–55. Patiño Douce, A.E., 1999. What do experiments tell us about the relative contributions of crust and mantle to the origin of granitic magmas? In: Castro, A., Fernandez, C., Vigneresse, J.L. (Eds.), Understanding Granites: Integrating New and Classical Techniques: Geological Society, London, Special Publications, vol. 168, pp. 55–75. Pearce, J.A., Bender, J.F., DeLong, S.E., Kidd, W.S.F., Low, P.J., Guner, Y., Saroğlu, F., Yılmaz, Y., Moorbath, S., Mitchell, J.J., 1990. Genesis of collision volcanism in eastern Anatolia, Turkey. Journal of Volcanology and Geothermal Research 44, 189–229. Pearce, J.A., 1996. Sources and settings of granitic rocks. Episodes 19, 120–125. Pearce, J.A., Peate, D.W., 1995. Tectonic implications of the composition of volcanic arc magmas. Annual Review of Earth and Planetary Sciences 23, 113–134. Peccerillo, A., Taylor, S.R., 1976. Geochemisty of Eocene calc-alkaline volcanic rocks in the Kastamonu area, Northern Turkey. Contributions to Mineralogy and Petrology 58, 63–81. Pecerillo, A., 1999. Multiple mantle metasomatism in central southern Italy: geochemical effects, timing and geodynamic implications. Geology 27, 315–318. Pe-Piper, G., Piper, D.J.W., 1989. Spatial and temporal variations in late Cenozoic backarc volcanic rocks, Aegean Sea region. Tectonophysics 169, 113–134. doi:10.1016/ 0040-1951(89)90186-8. Pe-Piper, G., Piper, D.J.W., 2001. Late Cenozoic, post-collisional Aegean igneous rocks: Nd, Pb, and Sr isotopic constraints on petrogenetic and tectonic models. Geological Magazine 138, 653–668. Pe-Piper, G., Piper, D.J.W., 2006. Unique features of the Cenozoic igneous rocks of Greece. In: Dilek, Y., Pavlides, S. (Eds.), Postcollisional tectonics and magmatism in the Mediterranean region and Asia: Geological Society of America Special Paper, vol. 409, pp. 259–282. Pe-Piper, G., Piper, D.J.W., Maatarangas, D., 2002. Regional implications of geochemistry and style of emplacement of Miocene I-type diorite and granite, Delos, Cyclades, Greece. Lithos 60, 47–66. Pin, C., Briot, D., Bassin, C., Poitrasson, F., 1994. Concomitant separation of strontium and samarium–neodymiumfor isotope analyses in silicate samples, based on specific extraction chromatography. Analytica Chimica Acta 298, 209–217. Platt, J.P., England, P.C., 1994. Convective removal of lithosphere beneath mountain belts: thermal and mechanical consequences. American Journal of Science 293, 307–336. Rapp, R.P., Watson, E.B., 1995. Dehydration melting of metabasalt at 8–32 kbar: implications for continental growth and crust–mantle recycling. Journal of Petrology 36, 1–25. Richard, P., Shimizu, N., Allegre, C., 1976. 143Nd/146Nd a natural tracer: an application to oceanic basalts. Earth and Planetary Science Letters 31, 269–278. Ricou, L.E., Argygiadis, I., Marcoux, J., 1975. L'axecalcaire du Taurus, unalignement de fenetres arabo-africaines sous des nappesradiolaritiques, ophiolitiques et métamorphiques. Bulletin de la Société de Geologie de France 16, 107–111. Ring, U., Collins, A.S., 2005. U-Pb SIMS dating of synkinematic granites: timing of corecomplex formation in the northern Anatolide belt of western Turkey. Journal of the Geological Society, London 162, 289–298. Ring, U., Layer, P.W., 2003. High-pressure metamorphism in the Aegean, eastern Mediterranean: underplating and exhumation from the Late Cretaceous until the Miocene to Recent above the retreating Hellenic subduction zone. Tectonics 22, 1022. doi:10.1029/2001TC001350. Roberts, M.P., Clemens, J.D., 1993. Origin of high potassium, calcalkaline, I-type granitoids. Geology 21, 825–828. Sandvol, E., Turkelli, N., Barazangi, M., 2003. The Eastern Turkey Seismic Experiment: the study of a young continent–continent collision. Geophysical Research Letters 30 (24), 8038. Seghedi, I., Downes, H., 2011. Geochemistry and tectonic development of Cenozoic magmatism in the Carpathian–Pannonian region. Gondwana Research 20, 655–672. Seyitoğlu, G., Scott, B., 1991. Late Cenozoic crustal extension and basin formation in West Turkey. Geological Magazine 128, 155–166. Seyitoğlu, G., Scott, B., 1992. Late Cenozoic volcanic evolution of the northeastern Aegean region. Journal of Volcanology and Geothermal Research 54, 157–176. Seyitoğlu, G., Scott, B., 1996. The cause of N–S extensional tectonics in western Turkey: tectonic escape vs. backarc spreading vs. orogenic collapse. Journal of Geodynamics 22, 145–153. Seyitoğlu, G., Anderson, D., Nowell, G., Scott, B., 1997. The evolution from Miocene potassic to Quaternary sodic magmatism in western Turkey: implications for enrichment processes in the lithospheric mantle. Journal of Volcanology and Geothermal Research 76, 127–147.

985

Şengör, A.M.C., Yılmaz, Y., 1981. Tethyan evolution of Turkey: a plate tectonic approach. Tectonophysics 75, 181–241. Şengör, A.M.C., Satır, M., Akkök, R., 1984. Timing of tectonic events in the Menderes Massif, western Turkey: implications for tectonic evolution and evidence for PanAfrican basement in Turkey. Tectonics 3, 693–707. Şengör, A.M.C., Görür, N., Şaroglu, F., 1985. Strike-slip deformation, basin formation and sedimentation: strike-slip faulting and related basin formation in zones of tectonic escape: Turkey as a case study. Society of Economic Paleontologists and Mineralogists 37, 227–264. Şengör, A.M.C., Natalin, B.A., Burtman, V.S., 1993. Evolution of the Altaid tectonic collage and Paleozoic crustal growth in Eurasia. Nature 364, 299–307. Şengör, A.M.C., Özeren, S., Gena, T., Zor, E., 2003. East Anatolian high plateau as a mantle-supported north–south shortened domal structure. Geophysical Research Letters 30, 8045. doi:10.1029/2003 GL017858. Shand, S.J., 1927. On the relationships between silica, Alumina and the bases in eruptive rocks, considered as a means of classification. Geological Magazine 64, 446–449. Sherlock, S., Kelley, S.P., Inger, S., Harris, N., Okay, A.I., 1999. 40Ar–39Ar and Rb–Sr geochronology of high-pressure metamorphism and exhumation history of the Tavsanli Zone, NW Turkey. Contributions to Mineralogy and Petrology 137, 46–58. Spakman, W., Wortel, M.J.R., Vlaar, N.J., 1988. The Hellenic subduction zone: a tomographic image and its geodynamic implications. Geophysical Research Letters 15, 60–63. Spakman, W., 1990. Images of the upper mantle of central Europe and the Mediterranean. Terra Nova 2, 542–553. Steiger, R.H., Jager, E., 1977. Subcommission on geochronology: convention on the use of decay constants in geo- and cosmochronology. Earth and Planetary Science Letters 36, 359–362. Stouraiti, C., Mitropoulos, P., Tarney, J., Barreiro, B., McGrath, A.M., Baltatzis, E., 2010. Geochemistry and petrogenesis of late Miocene granitoids, Cyclades, southern Aegean: nature of source components. Lithos 114, 337–352. Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders, M.J., Norry, A.D. (Eds.), Magmatism in the Ocean Basins: Geological Society, London, Special Publications, vol. 318, pp. 313–345. Sun, X., Deng, J., Zhao, Z., Zhao, Z., Wang, Q., Yang, L., Gong, Q., Wang, C., 2010. Geochronology, petrogenesis and tectonic implications of granites from the Fuxin area, Western Liaoning, NE China. Gondwana Research 17, 642–652. Tatsumi, I., Hamilton, D.L., Nesbit, R.W., 1986. Chemical characteristics of fluid phase released from a subducted lithosphere and origin of arc magmas: evidence from high-pressure experiments and natural rocks. Journal of Volcanology and Geothermal Research 29, 293–309. Tepper, J.H., Nelson, B.K., Bergantz, G.W., Irving, A.J., 1993. Petrology of the Chilliwack batholith, North Cascades, Washington: generation of calc-alkaline granitoids by melting of mafic lower crust with variable water fugacity. Contributions to Mineralogy and Petrology 113, 333–351. Thirlwall, M.F., Smith, T.E., Graham, A.M., Theodorou, N., Hollings, P., Davidson, J.P., Arculus, R.D., 1994. High field strength element anomalies in arc lavas: source or processes. Journal of Petrology 35, 819–838. Tirel, C., Brun, J.P., Burov, E., 2004. Thermomechanical modeling of extensional gneiss domes. In: Whitney, D.L., et al. (Ed.), Gneiss Domes in Orogeny: Geological Society of America Special Paper, vol. 380, pp. 67–78. Thomson, S.N., Ring, U., 2006. Thermochronologic evaluation of postcollision extension in the Anatolide orogen, western Turkey. Tectonics 25, TC3005. doi:10.1029/ 2005TC001833 20pp. Von Blanckenburg, F., Davies, J.H., 1995. Slab breakoff: a model for syncollisional magmatism and tectonics in the Alps. Tectonics 14, 120–131. Von Blanckenburg, F., Kagami, H., Deutsch, A., Oberli, F., Meier, M., Wiedenbeck, M., Barth, S., Fischer, H., 1998. The origin of Alpine plutons along the Periadriatic Lineament. Schweizerische Mineralogische und Petrographische Mitteilungen 78, 55–66. Van Hinsbergen, D.J.J., Hafkenscheıd, E., Spakman, W., Meulenkamp, J.E., Wortel, R., 2005. Nappe stacking resulting from subduction of oceanic and continental lithosphere below Greece. Geology 33, 325–328. Wang, K.L., Chung, S.L., Chen, C.H., Shinjo, R., Yang, T., Chen, C.H., 1999. Post-collisional magmatism around northern Taiwan and its relation with opening of the Okinawa Trough. Tectonophysics 308, 363–376. Williams, I.S., 1998. U–Th_Pb geochronology by ion-microprobe. In: McKibben, M.A., Shanks II, W.C., Ridley, W.I. (Eds.), Application of Microanalytical Techniques to Understanding Mineralizing Processes: Reviews in Economic Geology, 7, pp. 1–35. Wortel, M.J.R., Spakman, W., 2000. Subduction and slab detachment in the Mediterranean– Carpathian region. Science 290, 1910–1917. doi:10.1126/science.290.5498.1910. Yang, J.H., Wu, F.Y., Chung, S.L., Wilde, S.A., Chu, M.F., 2004. Multiple sources for the origin of granites: geochemical and Nd/Sr isotopic evidence from the Gudaoling granite and its mafic enclaves, northeast China. Geochimica et Cosmochimica Acta 68, 4469–4483. Yılmaz, Y., 1989. An approach to the origin of young volcanic rocks of western Turkey. In: Şengör, A.M.C. (Ed.), Tectonic Evolution of the Tethyan Region: The Hague. Kluwer Academic, pp. 159–189. Yılmaz, Y., 1990. Comparision of young volcanic associations of western and eastern Anatolia under conpressional regime; a review. Journal of Volcanology and Geothermal Research 44, 69–87. Yılmaz, Y., Polat, A., 1998. Geology and evolution of the Thrace volcanism, Turkey. Acta Vulcanologica 10, 293–303. Yılmaz, Y., Genç, Ş.C., Yiğitbaş, E., Bozcu, M., Yılmaz, K., 1995. Geological evolution of the late Mesozoic continental margin of Northwestern Anatolia. Tectonophysics 243, 155–171.

986

Ş. Altunkaynak et al. / Gondwana Research 21 (2012) 961–986

Yılmaz, Y., Tüysüz, O., Yiğitbaş, E., Genç, Ş.C., Şengör, A.M.C., 1997. Geology and tectonic evolution of the Pontides. In: Robinson, A.G. (Ed.), Regional and Petroleum Geology of the Black Sea and Surrounding Region: American Associations of Petroleum Geologists, Memoir, 68, pp. 183–226. Yılmaz, Y., Genç, Ş.C., Gürer, O.F., Bozcu, M., Yılmaz, K., Karacik, Z., Altunkaynak, Ş., Elmas, A., Elmas, A., 2000. When did the western Anatolian grabens begin to develop? In: Bozkurt, E., Winchester, J.A., Piper, J.A.D. (Eds.), Tectonics and Magmatism in Turkey and the Surrounding Area: Geological Society, London, Special Publication, 173, pp. 353–384. Yılmaz, Y., Genç, Ş.C., Karacık, Z., Altunkaynak, Ş., 2001. Two contrasting magmatic associations of NW Anatolia and their tectonic significance. Journal of Geodynamics 31, 243–271. Yılmaz-Şahin, S., Örgün, Y., Güngör, Y., Göker, A.F., Gültekin, A.H., Karacık, Z., 2010. Mineral and whole-rock geochemistry of the Kestanbol Granitoid (Ezine-Çanakkale) and its mafic microgranular enclaves in northwestern Anatolia: evidence of felsic and mafic magma interaction. Turkish Journal of Earth Sciences 19, 101–122. Zhu, L., Mitchell, B.J., Akyol, N., Cemen, I., Kekovali, K., 2006. Crustal thickness variations in the Aegean region and implications for the extension of continental crust. Journal of Geophysical Research 111, B01301 10pp.

Şafak Altunkaynak is an Associate Professor in the Department of Geology at Istanbul Technical University (Turkey). She received her PhD from Istanbul Technical University in 1997. She was a visiting scientist at the Open University (UK) in 2003 and the University of Nevada Las Vegas (USA) in 2009. She has worked on the geology, petrology and geochemistry of post-collisional volcanic and plutonic rocks, volcanic–plutonic connections in Turkey, the Aegean region and the Lesser Caucasus (Azerbaijan). Her current research projects involve Cenozoic crustal evolution and mantle dynamics of post-collisional magmatism in western Anatolia and the Aegean extensional province; thermobarometry and geochronology of magmatic and metamorphic rocks of Çataldağ, Kazdağ and Menderes core complexes; and petrology and geodynamics of adakitic magmatism in NW Turkey. She has published a number of refereed papers on these topics in international journals. Yıldırım Dilek is a Professor of Tectonics in the Department of Geology and a Harrison Scholars Professor at Miami University (USA). He received his PhD from the University of California-Davis (1989), worked as a Senior Research Fellow (1989–90) at the Getty Conservation Institute (Los Angeles, CA), and taught at Vassar College (New York) until 1996. The focus of his research is mostly on the structure, petrology, and tectonics of modern oceanic crust and ophiolites, postcollisional igneous complexes in orogenic belts, and metamorphic core complexes. He has also worked extensively in the western U.S. Cordillera, Northern Appalachians, Norwegian Caledonides, Caucasus Mountains, Arabian–Nubian Shield, and Central Asian orogenic belts. He is an expert scientist for the NATO Science for Peace Programme and a member of the United States Science Advisory Committee. Ş. Can Genç is a Professor of Geology at the Istanbul Technical University, Istanbul (Turkey) since 2004. Genc received his BSc (1981) and MSc (1987) from Istanbul University, and PhD (1993) from the Istanbul Technical University, Turkey. Genc's main research topics include magmatic petrology, petrogenesis, and volcanology. He has published over 20 research papers.

Gürsel Sunal is an Assistant Professor in the Department of Geology at İstanbul Technical University, İstanbul, Turkey, since 2009. Sunal received his BSc (1993) and MSc (1997) from Istanbul Technical University, Turkey, and PhD (2008) from the University of Tübingen, Germany. His main research interests include geochronology of metamorphic and magmatic rocks and exhumation history of tectonically active belts. He has published a number of research papers on these topics.

Ralf Gertisser is a lecturer in Mineralogy and Petrology at Keele University, UK, since 2005. He studied geology at the University of Freiburg, Germany, and the University of Oregon, USA, and received his diploma (M.Sc.) in geology from the University of Freiburg in 1996. In 2001, he was awarded a doctorate (Dr. rer. nat.) “with highest honors” (summa cum laude) in Earth Sciences from the University of Freiburg. Before joining Keele University, he held postdoctoral positions at the University of Freiburg and The Open University, UK. Gertisser's main research interests include magma generation and differentiation in subduction-zone (and other geodynamic) settings, rates and timescales of magmatic processes using short-lived isotopes, magma chamber processes, volatile behavior in volcanic systems, and the generation and emplacement mechanisms of small-volume pyroclastic flows. Study areas have included the Aeolian Islands (Italy), the Azores (Portugal), Santorini (Greece), the Sunda arc in Indonesia and the Chilean Andes.

Harald Furnes is Professor at the Department of Earth Science, University of Bergen, Norway, since 1985. He received his D.Phil. at the University of Oxford, UK, in 1978. His main research interest has been connected to volcanic rocks. This involves physical volcanology, geochemistry and petrology of volcanic rocks, mainly connected to ophiolitic and island arc development of various ages. Another research focus has been related to the alteration of volcanic glass, which again led to a long-term study on the interaction between microorganisms and glassy rocks, and the search for traces of early life. On these topics he has published a number of refereed papers in international journals.

Kenneth A. Foland is Professor Emeritus in the School of Earth Sciences at Ohio State University. He received a B.S. from Bucknell University (1967) and M.S. (1969) and Ph.D. (1972) degrees from Brown University. He joined Geology faculty at the University of Pennsylvania in 1972, leaving in 1980 for Ohio State University in Columbus. There he developed new facilities for high-precision, low-blank measurements of radiogenic isotopes and noble gases. After more than 40 years of research in isotope geochemistry and geochronology, he recently retired from active lab work and teaching. His research includes laboratory, experimental, field, and clinical studies on isotopic compositions of a broad range of natural and modified materials including rock, mineral, water, gas, and blood samples.

Jingsui Yang graduated from Dalhousie University in Canada in 1992 with a PhD in geology. In 1995 he became a Research Professor and now is a chief scientist at the National Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences. He has carried out a number of research projects on the tectonics and petrology of the orogenic zones of the Qinghai-Tibet Plateau. His research work has mainly been focused on the ultra-high pressure metamorphic zones, terrane amalgamation and collision, and deep mantle processes. Yang with collaborators has published 325 research papers and two books and became GSA Fellow in 2011.