Geochemistry and K-Ar cooling ages of the Ilıca, Çataldağ (Balıkesir) and Kozak (İzmir) granitoids, west Anatolia, Turkey

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1 GEOLOGICAL JOURNAL Geol. J. 44: (2009) Published online 17 July 2008 in Wiley InterScience ( Geochemistry and K-Ar cooling ages of the Ilıca, Çataldağ (Balıkesir) and Kozak (İzmir) granitoids, west Anatolia, Turkey D. BOZTUG 1*, Y. HARLAVAN 2, R. JONCKHEERE 3,İ. CAN 4 and R. SARI 4 1 Department of Geological Engineering, Cumhuriyet University, Sivas, Turkey 2 Geological Survey of Israel, Jerusalem, Israel 3 Geologisches Institut, TU Bergakademie Freiberg, Freiberg (Sachsen), Germany 4 MTA Kuzeybatı Anadolu Bölge Müdürlüğü, Balıkesir, Turkey The Ilıca, Çataldağ and Kozak granitoids, cropping out in the northern part of the İzmir-Ankara (İA) suture zone in west Anatolia, Turkey, intrude metamorphic rocks of the Sakarya continent (SC) and Karakaya complex, and are unconformably overlain by Miocene volcanic and sedimentary rocks. The Ilıca and Kozak granitoids comprised granodioritic and granitic rocks and include mafic microgranular enclaves. The Çataldağ granitoid massif is subdivided into three lithological units: the Bozenköy granodiorite, Çataltepe biotite granite and Turfaldağ biotite granodiorite. Hornblende separates from the Ilıca granitoid yield K-Ar cooling ages that range from Oligocene (29 Ma) to Early Miocene (21 Ma). Biotite separates from subunits of the Çataldağ granitoid massif yield K-Ar cooling ages of Ma. The Kozak granitoid possesses hornblende and biotite K- Ar cooling ages ranging from 17 to 21 Ma. Fractional crystallization (FC), assimilation-combined FC, magma mixing and crustal contamination were the main processes which modified the compositions of magmas during crystallization. The Ilıca, Çataldağ and Kozak granitoids were derived from different magma sources generated by the partial melting of various sources such as metasomatized mantle and crustal material in a post-collisional extensional setting following continent continent collision between the SC and Taurus-Menderes Massif along the İA suture zone in west Anatolia, Turkey. Oligo Miocene K-Ar hornblende/biotite cooling ages seem to be driven with a rapid cooling and fast exhumation of a mid-crustal section that can be resulted from a regional extensional geodynamic setting related to the subduction roll-back of the present-day Mediterranean oceanic lithosphere in the Aegean region in west and northwest Anatolia, Turkey. Copyright # 2008 John Wiley & Sons, Ltd. Received 10 January 2008; accepted 30 May 2008 KEY WORDS K-Ar cooling age; geochemistry; granitoid; geodynamics; west Anatolia; Turkey 1. INTRODUCTION 1.1. Regional tectonic setting The İzmir-Ankara (İA) ocean is one of the northern Neo-Tethyan strands in Anatolia. Its closure during Palaeogene time caused the collision between the Sakarya continent (SC) and the Taurus-Menderes platform (TMP) along the İzmir-Ankara suture zone (İAS, Figure 1; Şengör and Yılmaz 1981; Bozkurt and Mittwede 2001). This collision resulted in contractional deformation during the Palaeogene which was succeeded by Oligo Miocene extension in western Anatolia (e.g. Seyitoğlu and Scott 1992, 1996; Işık et al. 2004; Purvis and Robertson 2004; Kaya et al. 2007). The Oligo Miocene extension is thought to be the reason for the emplacement of plutons not only in western Anatolia (e.g. Seyitoğlu and Scott 1992; Okay and Satır 2000; Köprübaşı and Aldanmaz 2004; Bozkurt 2004; Ring and Collins 2005; Altunkaynak and Dilek 2006), but also in Northern Greece (e.g. Pe-Piper and * Correspondence to: D. Boztuğ, Department of Geological Engineering, Cumhuriyet University, TR Sivas, Turkey. boztug@cumhuriyet.edu.tr Copyright # 2008 John Wiley & Sons, Ltd.

2 80 d. boztuğ ET AL. Figure 1. (a) Major tectonic terranes and suture zones in Turkey and surrounding areas (simplified after Okay and Tüysüz 1999). MP, Moesian Platform; B, Balkanides; RSZ, Rhodope-Strandja Zone; VS, Vardar Suture; PZ, Pelagonian Zone; A, Apulia; WBSF, West Black Sea Fault; WCF, West Crimean Fault; İZ, İstanbul Zone; IPS, Intra-Pontide Suture; İAS, İzmir-Ankara Suture; CI, Cycladic Islands; CACC, Central Anatolian Crystalline Complex; PS, Pamphyllian Suture; ITS, Inner Tauride Suture; AES, Ankara-Erzincan Suture; DSFZ, Dead Sea Fault Zone; KB, Kura Basin; LC, Lesser Caucasus; SAS, Sevan-Akera Suture; BZS, Bitlis-Zagros Suture; TAP, Tauride-Anatolide Platform. (b) Simplified regional geology map of the west Anatolia, Turkey (after Bingöl 1989). The letters a, b and c within rectangles refer to the locations of the Ilıca, Çataldağ and Kozak granitoids, respectively. See Table 1 for the explanation of numbers next to granitoid plutons.

3 geochemistry and k-ar cooling ages, turkish granitoids 81 Piper 2001) and in central Aegean region (e.g. Altherr and Siebel 2002). Some studies suggest that the Aegean and western Turkey probably underwent different tectonic evolutions since the Eocene time (e.g. Ring et al. 1999a, b; Gessner et al. 2001a; Ring et al. 2007). Moreover, it is proposed that the shortening related structures and associated high-p deformation in Crete are probably coeval with extensional structures in the Aegean region to the north of Crete (Ring et al. 2001). However, it is not clear whether western Turkey underwent post-collisional extension as suggested by Ring et al. (2003), Thomson and Ring (2006) and Bozkurt (2007), or compression-related as suggested for the genesis of widespread Miocene volcanism and coeval plutonism (e.g. Genç 1998; Karacık and Yılmaz 1998; Altunkaynak and Yılmaz 1998; Yılmaz et al. 2001). Timing of the emplacement and/or cooling of plutons which are thought to be related to the Oligo Miocene extension in Turkey should shed light on the regional geodynamic setting in western Anatolia (Figure 1). In this paper, the whole-rock geochemistry and K-Ar hornblende-biotite cooling ages of three granitoids are investigated with a special emphasis on the spatial and temporal relationships between the rapid cooling and regional geodynamic setting in western Anatolia State-of-the-art on the western Anatolian granitoids Although the granitoid rocks of western Anatolia have been the subject of intense research over the last two decades, the research on Ilıca and Çataldağ granitoids, the subject of the present text, is scarce. Some of the best known granitoids, from north to south, include: (1) the Eocene to Oligocene Karabiga, Kapıdağ and Armutlu granitoids (Köprübaşı and Aldanmaz 2004); (2) Oligo Miocene Kestanbol and Evciler granitoids (Birkle and Satır 1995; Okay and Satır 2000); (3) Early Miocene Eybek granitoid (Krushensky 1976; Delaloye and Bingöl 2000); (4) Eocene Orhaneli, Topuk and Tepeldağ granitoids (Harris et al. 1994; Okay and Satır 2006); (5) Early Miocene Kozak granitoid (Bingöl et al. 1982; Altunkaynak and Yılmaz 1998, 1999; Delaloye and Bingöl 2000; Yılmaz et al. 2001); (6) Early Miocene Eğrigöz granitoid (Bingöl et al. 1982; Işık et al. 2004; Ring and Collins 2005; Özgenç andilbeyli 2008) and (7) Baklan granitoid (Aydoğan et al. 2008) (Figure 1, Table 1). Most of the above-mentioned researches are concerned with the geochemistry, geochronology and petrogenesis of some western Anatolian granitoids (Table 1). There are also similar studies on the petrogenesis and regional geodynamic significance of the Cenozoic intrusive-volcanic rocks in the region (e.g. Aldanmaz 2006; Altunkaynak and Dilek 2006; Altunkaynak 2007; Dilek and Altunkaynak 2007; Ersoy and Helvacı 2007; Karacık et al. 2007a) and in the south Marmara region (Karacık et al. 2007b). The genesis of Late Cenozoic volcanic and plutonic rocks throughout the Aegean Sea region was formerly ascribed to southward migration of Aegean subduction (e.g. Fytikas et al. 1984), but most are now considered as resulting from regional extension and derived mainly from a hybrid magma formed by mixing of coeval mafic and felsic melts. The source of mafic magma is usually attributed to sub-continental lithospheric mantle (Seyitoğlu and Scott 1992; Pe-Piper et al. 1995; Aldanmaz et al. 2000; Okay and Satır 2000; Pe-Piper and Piper 2001) or mafic lower crust (Aydoğan et al. 2008; Özgenç and İlbeyli 2008). Altunkaynak and Dilek (2006), Altunkaynak (2007) and Dilek and Altunkaynak (2007) have studied in detail the chrono-spatial evolution of the Cenozoic postcollisional magmatism in western Anatolia and concluded that the magmatism has occurred in three distinct pulses and become younger from north to south. The first magmatic episode occurred during Eocene and Oligo Miocene regional compression and is attributed to an enriched subcontinental lithospheric mantle and crustal material which was also affected by an influx of asthenospheric heat and melts provided by lithospheric slab break-off (Dilek and Altunkaynak 2007). The second magmatic episode is ascribed to subduction-modified lithospheric mantle, crustal material and asthenospheric mantle during the Middle Miocene extensional regime as a result of delamination of the lowermost part of the lithospheric mantle and/or partial convective removal of the sub-continental lithospheric mantle (Dilek and Altunkaynak 2007). The third magmatic episode was generated by decompressional melting of asthenospheric mantle which has commenced around 12 Ma and continued through the Late Quaternary under the extensional tectonic regime (Dilek and Altunkaynak 2007); the continental extension is the current tectonic regime of the western Anatolia (e.g. Seyitoğlu and Scott 1992, 1996; Bozkurt and Oberhänsli 2001; Bozkurt 2003; Bozkurt and Sözbilir 2004; Işık et al. 2004; Bozkurt and Mittwede 2005; Okay and Altıner 2006; Koçyiğit and Deveci 2007; Emre and Sözbilir 2007).

4 82 d. boztuğ ET AL. Table 1. Geothermochronology data on the western Anatolian granitoids, Turkey Map Geological unit Mineral Age (Ma) Method Ref. 1 Şevketiye muscovite K-Ar (1) 2 Karabiga biotite K-Ar (1) 3 Avşa island biotite K-Ar (2) 4 Kapıdağ N biotite K-Ar (1) hornblende K-Ar (1) biotite Rb-Sr (3) 5 Kapıdağ S biotite K-Ar (1) biotite Rb-Sr (3) 6 Sarıoluk hornblende K-Ar (2) 7 Ilıca hornblende K-Ar (4) wr-biotite Rb-Sr (5) orthoclase K-Ar (4) biotite K-Ar (2) 8 Danişment biotite K-Ar (2) 9 Kızıldam biotite K-Ar (2) 10 Yenice biotite K-Ar (2) 11 Evciler wr-bio-cpx Rb-Sr (6) wr-bio-hbl Rb-Sr (6) 12 Kestanbol wr- biotite Rb-Sr (7) 13 Eybek biotite K-Ar (8) hornblende K-Ar (8) biotite K-Ar (1) hornblende K-Ar (1) biotite K-Ar (9) phlogopite K-Ar (9) muscovite K-Ar (9) 14 Orhaneli biotite Ar-Ar (10) 15 Topuk bio hbl Ar-Ar (10) 16 Tepeldağ zircon U-Pb (3) biotite Rb-Sr (3) 17 Alaçam biotite K-Ar (4) orthoclase K-Ar (4) biotite K-Ar (1) 18 Eğrigöz biotite K-Ar (4) biotite Ar-Ar (11) zircon U-Pb (12) 19 Koyunoba zircon U-Pb (12) 20 Baklan biotite K-Ar (4) whole-rock K-Ar (13) whole-rock Rb-Sr (13) 21 Turgutlu monazite U-Pb (14) 22 Salihli allanite U-Pb (14) Map refers to the number of geological units in Figure 1: wr, wholerock; bio, biotite; cpx, clinopyroxene and hbl, hornblende. Ref. is the reference as follows: (1) Delaloye and Bingöl (2000); (2) Karacık et al. (2007b); (3) Okay and Satır (2006); (4) Bingöl et al. (1982); (5)Ataman (1974); (6) Okay and Satır (2000); (7) Birkle and Satır (1995); (8) Krushensky (1976); (9) Murakami et al. (2005); (10) Harris et al. (1994); (11) Işık et al. (2004); (12) Ring and Collins (2005); (13) Aydoğan et al. (2008) and (14) Glodny and Hetzel (2007) Geological setting of the Ilıca, Çataldağ and Kozak granitoids In this study three granitoids, located to the north of the Neo-Tethyan İAS zone (Figure 1), were studied in order to determine the hornblende/biotite K-Ar cooling ages and whole-rock geochemistry. Among these three granite outcrops, only the Kozak granitoid has previously been dated (K-Ar) and studied in detail (Bingöl et al. 1982; Altunkaynak and Yılmaz 1998, 1999; Delaloye and Bingöl 2000). The other two Ilıca and Çataldağ granitoids were mapped during the course of this study. The geological setting of the three granitoids is as follows:

5 geochemistry and k-ar cooling ages, turkish granitoids 83 (1) The Ilıca granitoid intrudes the metamorphic rocks of the Sakarya continent (Fazlıkonağı Formation; Ergül et al. 1980) and the Karakaya complex which is interpreted to represent a Paleo-Tethyan marginal basin or subduction-accretion complex (e.g. Okay and Göncüoğlu 2004 and references therein). It also intrudes a Neo- Tethyan ophiolitic mélange (Ergül et al. 1980) and is unconformably overlain by Neogene volcanic lavas and sediments (Figure 2). The Ilıca granitoid and its country rocks are cut by NE SW-, NW SE- and N Strending young oblique-slip normal faults (Figure 2). Figure 2. Geology map of the Ilıca granitoid.

6 84 d. boztuğ ET AL. (2) The Çataldağ granitoid is subdivided into three mappable subunits: the Bozenköy granodiorite, Çataltepe biotite granite and Turfaldağ biotite granodiorite. The contact between the Çataltepe biotite granite and the Turfaldağ biotite granodiorite is sharp, whereas that of the Bozenköy granodiorite and the Çataltepe biotite granite is gradational (Figure 3). All intrude the Fazlıkonağı Formation and are unconformably overlain by Neogene volcanic lava flows and sediments (Figure 3). The Çataldağ granitoid is intensely deformed by WNW ESE- and NW SE-trending post-miocene normal faults (Figure 3). In addition, the Turfaldağ biotite granodiorite displays well-developed foliation, particularly in the south of Sünlük village and to the northeastern part of the granitoid body. The foliation planes appear to parallel the major fault between granitic rocks and the Fazlıkonağı Formation (Figure 3). (3) The Kozak granitoid is similar to most granitoids in west and northwest Turkey; it intrudes the Karakaya complex (Altunkaynak and Yilmaz 1998, 1999) and is unconformably overlain by Miocene volcanic and sedimentary rocks. For more detailed information about the geological and stratigraphical setting of the Kozak granitoid the readers are referred to Altunkaynak and Yılmaz (1998, 1999). 2. ANALYTICAL METHODS A total of 77 whole-rock samples were analysed for major, trace and rare earth element (REE) chemical composition in ACME-Analytical Laboratories, British Columbia, Canada (Electronic Supplementary Materials 1, 2). Approximatly 0.2 g of rock powder was fused using lithium metaborate flux, and major and trace-rare earth Figure 3. Geology map of the Ilıca granitoid.

7 geochemistry and k-ar cooling ages, turkish granitoids 85 elements were analysed by ICP-ES, and ICP-MS, respectively; standard sample SO-17 was used for quality assurance. In addition, 0.50 g of rock powder were leached with 3 ml HCl-HNO 3 -H 2 Oat958C for 1 hour, and analysed by ICP-MS for Mo, Cu, Pb, Zn, Ni, As, Cd, Sb, Bi, Ag, Au, Hg and Tl. The DS-4 standard was used for quality assurance. A total of 29 mafic mineral separates (among which 6, 10 and 13 of them comprise pure hornblende, pure biotite and biotitehornblende, respectively) were analysed for their K-Ar age at the Geochronology Laboratory of the Geological Survey of Israel-Jerusalem (Table 2). For K analysis, two aliquots, sometimes three, of ca g each were taken from a sample and dissolved using LiBO 2. Potassium concentrations were measured on an ICP-AES (Perkin Elmer OPTIMA 3300) along with repeated determinations of three of the international standards SO-3, BE- N, BHVO-1, SCo-1, NIM-L and NIM-G. The 1 s value for the K concentration of duplicates was less than 3%. The argon analysis for K-Ar determination was performed using standard isotope dilution procedures routinely used in the Geochronological Laboratory (Steinitz et al. 1983; Kotlarsky et al. 1992). About 0.03 g of samples were loaded into the glass arm of a metal extraction line and heated overnight at 1208C. Argon was extracted in a molybdenum crucible using RF induction heating. Gases were scrubbed through a liquid nitrogen trap and ZrAl getters. Argon was measured on a VG MM-1200 mass spectrometer. Measured intensities were corrected for linear extrapolation of the 40 Ar peak and then i Ar/ 39 Ar ratios were adjusted accordingly (i ¼ other isotopes). Argon was measured in duplicate and uncertainties are reported at the 1 s level. Table 2. K-Ar age determination data of the Çataldağ, Ilıca and Kozak granitoids, W Anatolia, Turkey Sample Granitoid Mineral N Age (Ma) 1 s error (Ma) 40 Ar rad (cc STP/g) K (%) 40 Ar rad (%) 36 Ar (cc STP/g) CT-9 Çataltepe bio E E-09 CT-11 Çataltepe bio E E-09 CT-19 Turfaldağ bio E E-09 CT-28 Turfaldağ bio E E-09 CT-29 Turfaldağ bio E E-09 CT-30 Turfaldağ bio E E-09 CT-31 Çataltepe bio E E-09 CT-32 Çataltepe bio E E-09 CT-33 Turfaldağ bio E E-09 CT-35 Turfaldağ bio E E-09 CT-37 Bozenköy bio hb E E-09 CT-38 Bozenköy bio hb E E-09 IL-3 Ilıca hb E E-09 IL-4 Ilıca hb E E-09 IL-7 Ilıca hb E E-09 IL-11 Ilıca hb E E-09 IL-13 Ilıca hb E E-09 KZ-1 Kozak hb E E-09 KZ-5 Kozak bio hb E E-09 KZ-6 Kozak bio hb E E-09 KZ-7 Kozak bio hb E E-09 KZ-9 Kozak bio hb E E-09 KZ-12 Kozak bio hb E E-09 KZ-13 Kozak bio hb E E-09 KZ-15 Kozak bio hb E E-09 KZ-16 Kozak bio hb E E-09 KZ-18 Kozak bio hb E E-09 KZ-22 Kozak bio hb E E-09 KZ-23 Kozak bio hb E E-09 N, number of analyzed aliquots for both %K and Ar; 40 Ar rad, 40 Ar radiogenic; bio, biotite and hb, hornblende.

8 86 d. boztuğ ET AL. 3. RESULTS 3.1. Texture and petrography The Ilıca and Kozak granitoids show many similarities in their texture, mineralogy and geochemical composition (Electronic Supplementary Material 2). They are homogeneous and represented mainly by medium-grained granodiorites with equigranular texture. The rocks are composed mainly of quartz, plagioclase, brownish-green hornblende and reddish-brown to greenish-brown biotite and K-feldspar minerals. The accessory phases are apatite, titanite, zircon, allanite and opaque oxides. Plagioclases show special microtextures such as dissolution/melting and spongy-cellular texture (Figure 4a), sieve texture due to mafic inclusions (Figure 4b) and complex zoning in addition to polysynthetic albite twinning; they are interpreted as thermal re-equilibrium conditions during crystallization (cf. Hibbard 1991) in both the Ilıca and Kozak granitoids. The mafic microgranular enclaves (MMEs) in both granitoid bodies occur as ovoidal to ellipsoidal in shapes ranging from several cm to 1 2 dmin size; they are very similar not only in terms of the mode of occurrence in the field, but also in mineralogical composition. The enclaves consist mainly of plagioclase and rarely K-feldspar phenocrysts, up to 1 cm in length, set in a fine-grained groundmass of long-prismatic hornblende, plagioclase and acicular apatite. Some K-feldspar and plagioclase phenocrysts from the MMEs represent a poikilitic texture with small mafic mineral inclusions (Figure 4c). Some plagioclase phenocrysts of the MMEs typically show a dissolution/melting and spongy-cellular texture enveloped by later albite occurrences; they indicate equilibrated hybrid system crystallization similar to those of felsic host granitoids that result from thermal-chemical re-equilibration processes during magma mixing (cf. Hibbard 1991) (Figure 4d). The acicular apatite minerals (Figure 4e) indicate rapid cooling, i.e. quenching during mingling type interaction between MME and host felsic granitoid magma (cf. Barbarin and Didier 1992). The Çataldağ granitoid consists of three granitoid bodies, namely Bozenköy granodiorite, Çataltepe biotite granite and the Turfaldağ biotite granodiorite. Bozenköy granodiorite shows a porphyritic texture characterized by large K-feldspar megacrysts set in a medium- to coarse-grained groundmass of quartz, plagioclase, orthoclase, brownish-green hornblende and reddish-brown biotite. Accessory minerals are apatite, titanite, zircon, allanite and opaque oxides; abundant apatites occur as large euhedral to anhedral crystals, with stubby-prismatic shapes and are bigger than 300 mm in size. K-feldspar megacrysts show well-developed poikilitic-sieve texture with randomly distributed small rounded-corroded plagioclase crystals; in some samples plagioclases are concentrated along the margins of the K-feldspar megacrystals (Figure 4f). The Çataltepe biotite granite is very similar to Bozenköy granodiorite in terms of mineral composition and texture. The absence of amphiboles but abundance of biotites together with the lack of inclusions in K-feldspar megacrysts in the Çataltepe granite can be encountered as the main differences between the two bodies. Turfaldağ biotite granodiorite shows an equigranular texture with a medium-grain size. The major rock-forming minerals are quartz, plagioclase, orthoclase and reddish-brown to greenish-brown biotite where allanite, apatite, titanite and zircon form the accessories. Euhedral to anhedral, stubby-prismatic and rounded apatites and reddish-brown allanites are more abundant accessories and they relatively occur as larger crystals. The size of apatites and allanites may reach up to mm. Some samples (samples CT-15, 18, 21) also contain secondary muscovite flakes that have been formed by muscovitization of feldspars Geochemistry Major element characteristics Chemical nomenclature diagram (Debon and Le Fort 1983) reveals that the majority of rock samples are of granodiorite, and adamellite or IUGS monzogranite (Streckeisen 1976; Figure 5a). All rock samples represent a subalkaline composition and the calc-alkaline crystallization trend (Figure 5b and c). The SiO 2 versus K 2 O plot and Shand index diagram yield an apparent high-k, metaluminous composition for the Ilıca and Kozak granitoids and MMEs (Figure 5d and e). The various units of the Çataldağ granitoid show different characteristics: (1) the Bozenköy granodiorite possesses a medium-k metaluminous composition, (2) the Çataltepe biotite granite

9 geochemistry and k-ar cooling ages, turkish granitoids 87 Figure 4. Photomicrographs showing dissolution/melting and spongy-cellular textures in plagioclase from the Ilica granitoid (a), sieve texture formed by mafic mineral inclusions in plagioclase from the Kozak granitoid (b), poikilitic (c), dissolution/melting and spongy-cellular (d), textures in plagioclases and acicular apatite (e) and the mafic microgranular enclaves (MMEs) from the Ilıca granitoid, plagioclase inclusions oriented within K-feldspar megacryst (f) in the Bozenköy granodiorite of the Çataldağ granitoid massif. represents a high-k peraluminous composition and (3) the Turfaldağ biotite granodiorite reveals a medium- to high-k peraluminous composition (Figure 5d and e). All samples show I-type characteristics (Chappell and White 1974; White and Chappell 1988) (Figure 5f). However, three samples from Turfaldağ (CT-15, 18, 28), one sample from Bozenköy (CT-6) and one sample from

10 88 d. boztuğ ET AL. Figure 5. Major element geochemical discrimination diagrams of the Ilıca, Çataldağ and Kozak granitoids. (a) Q-P chemical nomenclature diagram (after Debon and Le Fort 1983); (b) total alkalis versus silica; (c) AFM triangular diagram (after Irvine and Baragar 1971); (d) K 2 O versus silica (after Le Maitre et al. 1989); (e) Shand index and (f) frequency distribution of aluminium saturation index dividing line between I- and S-type granites (ASI, Chappell and White 1974, 1988).

11 geochemistry and k-ar cooling ages, turkish granitoids 89 Çataltepe (CT-9) are plotted in the S-type subfields with Al 2 O 3 contents increased due to secondary sericitization of some feldspars in the Bozenköy and Çataltepe granites, and even muscovitization of some feldspars in the Turfaldağ granite. For all samples, major elements correlate well with SiO 2, except Na and K for the Bozenköy, Çataltepe and Turfaldağ granites (Figure 6). They also show almost constant alkali content against increasing silica content. The Bozenköy and Çataltepe granites have more Na than K, but the Turfaldağ granite has more K in Na 2 O versus K 2 O variation diagram (Figure 6) Trace and REE geochemistry The elemental composition is presented in the Electronic Supplementary Material 2 and is plotted in Figure 7. Chondrite-normalized (Sun and McDonough 1989) rare earth element (REE) distribution patterns (denote N) of the Ilıca and Kozak granitoids are very similar and cannot be distinguished (Figure 7a). REE N patterns of both units exhibit a very tight concave-upward pattern with a slight negative Eu anomaly (Figure 7a). The La N /Yb N ratio values, which quantify the fractionation pattern, and the Eu N /Eu N ratio, where Eu N ¼ Eu N /(Sm N.Gd N ) 0.5 is a measure for the Eu anomaly, differ between samples. The La N /Yb N ratio for the Ilıca and Kozak granitoids are similar ( and , respectively) and the Eu N /Eu N ratio ranges from 0.5 to 1.0 (Figure 7a). Nonetheless, two granitoids differ in their REE N distribution patterns; the Ilıca MMEs samples differ from their felsic host rocks and are enriched in almost all REE contents (Figure 7a). On the other hand, the REE N pattern of an aplitic vein (IL-6) from the Ilıca granitoid is considerably depleted in REE content but shows REE fractionation similar to that of the Ilıca granitoid (Figure 7a). Similarly, the PRIM-normalized trace element spider diagrams for both the Ilıca and Kozak granitoids are similar and characterized by pronounced negative Nb, Ta and Ti but positive Th, K and Pb anomalies (Figure 7b). The Bozenköy, Çataltepe and Turfaldağ granodiorites show different REE N distribution patterns (Figure 7c). In general, the Turfaldağ biotite granodiorite has a concave-upward shape, the Bozenköy granodiorite shows a very tight upward-concave shape and the Çataltepe biotite granite shows a relatively broad upward-concave shape. In addition, the Turfaldağ has a wide range of La N /Yb N ratios (7 54) compare with the intermediate values of the Bozenköy (19 29) and the low values of the Çataltepe (3 20). The Turfaldağ has similar Eu anomaly to the Bozenköy (Eu/Eu ¼ , and , respectively) while the Çataltepe granodiorite exhibits a pronounced negative Eu anomaly (Eu/Eu ¼ ). In PRIM-normalized trace element spider diagram, the Çataltepe granitoid represents a pronounced depletion in Ba, Sr and Ti relative to those of Bozenköy and Turfaldağ granitoids (Figure 7d). On the other hand, the Bozenköy granitoid shows a characteristic positive Sr anomaly which seems to be a diagnostic feature for these subunits among all the studied granitoids (Figure 7d) K-Ar data All the separates of the Çataltepe biotite granite and Turfaldağ biotite granodiorite consist of pure biotite, whereas the two mineral separates of the Bozenköy granodiorite consist of biotite and hornblende (CT-37, 38) (Table 2). Mineral separates from the Ilıca granitoid are hornblendes. Only one of the Kozak mineral separate is pure hornblende (KZ-1), while all the others are composed essentially of hornblende and biotite. For the mixed biotite and hornblende separates the biotite percentage is estimated using the following equation as follows: K 2 O total ¼ wt% biotite K 2 O biotite þ wt% hornblende K 2 O hornblende. The average K 2 O contents of biotite and hornblende are derived from the pure mineral separates (6.75% and 1.30%, respectively, Table 2). These calculations yield 70% biotite in the Bozenköy and 25 35% biotite in the Kozak separates. Thus the biotite þ hornblende mixtures of the Bozenköy samples are considered to be very nearly equivalent to pure biotite K-Ar ages, whereas those of the Kozak samples seem to indicate mostly biotite K-Ar ages. The percent radiogenic 40 Ar varies between 70 and 95%, and only two separates have radiogenic 40 Ar less than 70% (KZ-18 and IL-11, Table 2). The hornblende K-Ar ages of the Ilıca granitoid range from ca. 21 to 29 Ma, except for one sample, IL-13, which yields ca. 39 Ma; it is attributed to an excess Ar (Table 2). The biotite K-Ar cooling ages of the Bozenköy, Çataltepe and Turfaldağ granitoids yield ca Ma which are indistinguishable

12 90 d. boztuğ ET AL. Figure 6. Major element oxides versus silica and K 2 O versus Na 2 O variograms of the Ilıca, Çataldağ and Kozak granitoids. Symbols are as in Figure 5.

13 geochemistry and k-ar cooling ages, turkish granitoids 91 Figure 7. Chondrite-normalized REE and Prim (primordial mantle)-normalized trace element spider diagrams of the llica granitoid (host granitoid, MME and aplitic vein) and Kozak granitoid (a, b) and Çataltepe biotite granite, Bozenköy granodiorite and granite Turfaldağ biotite (c, d); Normalization values after Sun and McDonough (1989). at 1 s error, except for sample CT-37 from Bozenköy which gives an age of ca. 26 Ma (Table 2). As for the Kozak granitoid, indeed the hornblende (KZ-1) and biotite hornblende K-Ar ages are very similar (ca Ma); they are also very similar to those of the Çataldağ granitoids (Table 2). However, there are some younger ages ranging from ca. 14 to 18 Ma in the Kozak granitoid samples (e.g. samples KZ-5, 9, 13, 15 and 16; Table 2). 4. DISCUSSION 4.1. Fractional crystallization Samples from the Kozak and Ilıca plutons show similar behaviours for most of the incompatible trace elements. The slight negative correlation in the Sr versus SiO 2 diagram may suggest plagioclase fractionation in these suites (Figure 8a). However, because of their low SiO 2, high Sr concentrations and lack of strong negative Eu anomalies (Eu/Eu ¼ ; Figure 7a) this process is of minor significance and is not the main process of compositional modification for these intrusive suites. The negative correlation between Yand SiO 2, and depletion in Y in Ilıca and Kozak granitoids (Figure 8b), can be interpreted as hornblende fractionation, which has significantly high partition coefficient values for Y in granitic melts ( Y Kd amph/melt ¼6.0; Pearce and Norry 1979). Moreover, these samples from these granitoid suites also display moderate concave upward REE patterns and a relative depletion of MREE with respect to HREE, which is consistent with fractionation of hornblende (Figure 7a). The major element versus silica variation diagrams (Figure 6) of the Çataldağ granitoid show that the different bodies seem to have derived from a single magma source via a fractional crystallization (FC) process in which the

14 92 d. boztuğ ET AL. Figure 8. Rb, Ba, Sr, and Y versus SiO 2 semi-logarithmic variation diagrams of the Ilıca, Çataldağ and Kozak granitoids. Arrows indicate theoretical Rayleigh fractionation vectors modelled for crystallization of individual mineral phases. Theoretical vectors for the likely crystallizing phases are for 50% fractionation of single phases. Partition coefficients used for the modelling are from the compilation of Rollinson (1993). Key to abbreviations amp: amphibole, plg: plagioclase, K-feld: K-feldspar, bio: biotite, cpx: clinopyroxene and opx: orthopyroxene. Symbols are as in Figure 5. Bozenköy granitoid crystallized first and the two others crystallized later. However, Na and Mg show no correlation with silica under FC process of a single magma source. Because, in such a FC process, the Turfaldağ biotite granodiorite would yield higher Na and lower Mg contents than those of the Bozenköy and Çataltepe granitoids. Similarly, a FC process would have resulted in a considerable negative Eu anomaly in the Turfaldağ biotite granodiorite. Thus, a different magma source for the Turfaldağ biotite granodiorite could not be ruled out. The Bozenköy and Çataltepe granodiorites form a coherent fractionation trend in element variation diagrams such as Sr and Ba versus SiO 2, and are interpreted as a result of increasing fractionation of plagioclase and K- feldspar, accompanied possibly by amphibole, biotite, and accessory phases (such as titanite, apatite, zircon and allanite) (Figure 8a and c). In particular, strong depletion in Ba and Sr concentrations with increasing silica in relatively high silica granitic rocks of the Çataltepe granodiorite are associated with negative Eu anomalies (Eu/ Eu ¼ ; Figure 7c), indicating evolution by fractional crystallization of plagioclase and alkali feldspar. Fractionation of these major phases is also consistent with negative correlations of CaO and Al 2 O 3 with SiO 2 (Figure 6). In contrast, fractionation of plagioclase does not seem to have played an important role in the genesis of the Bozenköy suite, as indicated by extremely high Sr, contents, small or no negative anomalies of Eu, Ba, Sr and also by the lack of a negative correlation between Sr and SiO 2 (Figures 7d, 8a). Such characteristics indicate that compositional variations in the Bozenköy granodiorite may be due to simple fractional crystallization, but may also be result of assimilation assisted fractional crystallization (AFC) or magma mixing, or even combined effect of both processes (see below) Magma mixing, crustal contamination During the formation of the Kozak and Ilıca plutons, in particular, some fractional crystallization clearly occurred and might have modified the composition of the melts. However, features such as the lack of pronounced Eu

15 geochemistry and k-ar cooling ages, turkish granitoids 93 anomalies and the absence of correlation of Sr, Ba and Rb with SiO 2 (Figure 8a, c, d) suggest that fractional crystallization was not only the most important compositional modification process, and that chemical variations may have been largely distorted by the accumulation and mixing of melts. For these rocks, the most important process in generating much of the geochemical variation appears to be a consequence of variation in partial melting and degree of relative mixing between mafic and felsic melts. The FC derivation of the Bozenköy and Çataltepe granitoids seems to be unlikely a pure FC process, because if it was a pure FC process during the crystallization of magma, the LREE contents of the later product, i.e. the Çataltepe biotite granite, would have been higher than those of the earlier product, and the HREE would have been an inverse. However, this is just the opposite in the Bozenköy and Çataltepe granitoids which, therefore, can be resulted from an assimilation coupled FC process (AFC) or magma mixing. In Figure 9a, the plots of Rb/Sr versus Rb/Ba are shown to facilitate the effects of variations in crustal contamination of a mantle-derived basaltic magma. The data from the western Anatolian granitic rocks form a linear array of increasing Rb/Sr with Rb/Ba (Köprübaşı and Aldanmaz 2004). The Kozak, Ilıca and Bozenköy granitoids with CaO/Na 2 O ratios greater than 0.5 tend to have lower ratios of both Rb/Sr and Rb/Ba than do those Figure 9. (a) Rb/Ba versus Rb/Sr ratios for post-collisional granitoids from WAnatolia. The data mostly define a mixing curve between mantlederived mafic (M) and crust-derived felsic (F) melts. End-member compositions for mafic and felsic melt are from Köprübaşı and Aldanmaz (2004). The inset diagram shows the variations of CaO/Na 2 O with changing Al 2 O 3 /TiO 2 ratios of the rocks. (b) Plot of Eu/Eu (Eu/Eu [¼Eu CN / (Sm CN.Gd CN ) 0.5 ]; chondrite normalizing values were taken after Sun and McDonough (1989) against silica showing the possible effects of plagioclase fractionation or contamination from plagioclase fractionated crustal material. The mixing line is for simple mixing between a nonfractionated basaltic melt (with 48% SiO 2 ) and the most felsic granitic composition from the W Anatolian suite. Thick marks on the line indicate the percentage of the most mafic member used in the modelled mixture. The AFC line is representative for r (the ratio of the rate of assimilation to fractional crystallization) ¼ 0.4 and is drawn for a mineral assemblage of plagioclase 60 þ K-feldspar 20 þ amphibole 20. Symbols are as in Figure 5.

16 94 d. boztuğ ET AL. from the higher silica Çataltepe suite, which is characterized by lower CaO/Na 2 O ratios (<0.5). Such a distinction is difficult to explain solely by variations in fractionation assemblages of these plutons, because, as is shown in Figure 9a, the increases in ratios of Rb/Sr and Rb/Ba in the low-silica granitic rocks do not correlate with a decrease in Sr and Ba contents. This is inconsistent with the general trend of differentiation towards higher silica compositions and, therefore, can best be explained in terms of variable proportions of mixing between mantlederived basaltic melt and crust-derived felsic melts (e.g. Köprübaşı and Aldanmaz 2004). In terms of Rb-Sr-Ba, the progressive addition of crustal compositions to an average basalt composition will increase both the Rb/Sr and Rb/ Ba ratios of the resulting melts to levels typical of most low-cao/na 2 O granites from the Çataltepe biotite granite. The reason for this is that both the Rb/Sr and Rb/Ba ratios of the crustal rocks are much higher than those of mantlederived basaltic melts. The model calculations show that the addition of less than 15% of crustal contaminant to the basaltic melt would be sufficient to produce a composition with lower Rb/Sr and Rb/Ba ratios (i.e. the least fractionated sample). The effect of adding crustal material to a more mafic magma can also be observed in variations of the Eu/Eu ratio versus silica contents (Figure 9b). The presence of negative Eu anomalies should generally result from either plagioclase fractionation or mixing of mafic magmas with components formed by crustal melting with a plagioclase-rich residue (see Köprübaşı and Aldanmaz 2004 for details). These alternatives are shown in Figure 9b where the calculated Eu negative anomalies are plotted against the silica content of the rocks. It is notable that the Eu anomalies for some of the samples are not related to an increase in silica content. The theoretically calculated, plagioclase fractionation-dominated AFC line and the bulk mixing line between mafic (with 48 wt% SiO 2 ; Eu/Eu ¼ 1) and felsic components follow similar trends and do not provide a definitive answer to whether they reflect plagioclase fractionation or crustal contamination. However, the lack of negative correlation of Eu anomalies with silica content in most of the granitic rocks from the Kozak, Ilıca and Bozenkoy suites may imply that fractionation can not be the sole explanation towards more silicic compositions, and that crustal components have modified the granitic magmas to some extent Source characteristics Almost all of the samples plot above the Th/Nb ¼ 1 line in the Th/Y versus Nb/Y diagram (Figure 10a), except for three samples of the Kozak granitoid, two MMEs from the Ilıca granitoid, one sample from the Ilıca granitoid and one sample from the Turfaldağ biotite granodiorite. The Th enrichment can be attributed to assimilation combined with fractional crystallization (AFC) or partial melting. The studied granitoids cluster around the trends of both AFC and FC trends in a HFSE ratio/ratio diagram of Th/Yb versus Ta/Yb (Figure 10b); a diagram which is used in igneous petrogenesis (e.g. Pearce 1982; Pearce et al. 1990). The Rb/Y versus Nb/Y plot indicates a weak signature of subduction zone enrichment in the source material of these granitoid rocks; this is especially pronounced in the Turfaldağ biotite granodiorite (Figure 10c). The subduction zone-related geochemical fingerprint is particularly remarkable in all subunits of the Çataldağ granitoids in the La/Nb versus Ti (ppm) diagram where the granitoids are plotted next to the subfield of subduction zone metasomatism (Figure 10d). The diagram also indicates that mixingtype interaction between different magma sources is a dominant process both in the Ilıca and Kozak granitoids and Ilıca MME samples (Figure 10d). In light of the above-mentioned considerations, it can be concluded that there are different source materials involved in the genesis of magma sources of the Ilıca, Bozenköy, Çataltepe, Turfaldağ and Kozak granitoid units in western Anatolia. For example, Ilıca and Kozak granitoids seem to be derived from a hybrid magma generated by mingling- and mixing-type interactions between coeval mantle-derived more mafic (underplated mafic magma) and upper crustal-derived more felsic magma. The Bozenköy granodiorite and Çataltepe biotite granite from the Çataldağ granitoids appear to be derived from a single hybrid magma via AFC-combined magma-mixing processes. The crustal material is more dominant than the mantle contribution in the genesis of the Bozenköy and Çataltepe granitoids. The subduction-related geochemical signature of the Bozenköy and Çataltepe granitoids might have been inherited from this small mantle contribution which was metasomatized by earlier Neo-Tethyan subductionderived fluids, and then accreted into the collision zone during the closure of the İzmir-Ankara ocean. The partial

17 geochemistry and k-ar cooling ages, turkish granitoids 95 Figure 10. Th/Y versus Nb/Y (a), Th/Yb versus Ta/Yb (b), Rb/Y versus Nb/Y (c) and La/Nb versus Ti (ppm) (d) plots (Pearce 1982; Pearce et al. 1990) for the Ilıca, Çataldağ and Kozak granitoids. The compositions of MORB (mid-ocean ridge basalts), OIB (oceanic island basalts) and UCC (upper continental crust) were taken after Taylor and McLennan (1985) in (a). The vectors of SZE, FC and AFC stand for possible subduction zone enrichment, fractional crystallization and assimilation-fractional crystallization, respectively, in (b). The compositions of the lower-, bulk-, and upper crusts are after Taylor and McLennan (1985); the vectors for the subduction zone enrichment or crustal contamination and within-plate enrichment are based on the data of Pearce et al. (1990) in (c). The compositions of MORB and OIB were taken after Sun and McDonough (1989), subduction melt (SM), subduction zone metasomatism (SZM) and mixing subfields were taken after Schiano et al. (1995), and Yogodzinski et al. (1995) in (d). Symbols are as in Figure 5. melting of such a metasomatized mantle layer can retain the subduction signature in a post-collisional extensionrelated setting Geodynamic interpretation of K-Ar cooling ages The published geothermochronology of the western Anatolian granitoids (Table 1) are mostly medium-t geothermochronometry on hornblende and biotite (K-Ar and Rb-Sr cooling ages) with U-Pb zircon (two), one monazite and one allanite ages (Table 1). The cooling ages are consistent with two distinct periods of cooling during Eocene and Oligocene to Miocene times. The rapid cooling of granitoid rocks is attributed to exhumation of lower/ middle crustal rocks in an extensional tectonic setting. The origin and cause of continental extension in the central Aegean and western Turkey has been the subject of debate over the last two decades (see Table 3 for detailed information and relevant references). The Eocene post-collisional extension was ascribed to continent continent driven slab break-off subsequent to the collision between (i) the Taurus-Menderes platform and Sakarya continent along the İzmir-Ankara suture zone in western Anatolia (Altunkaynak and Dilek 2006; Boztuğ et al. 2006; Altunkaynak 2007), (ii) the Pelagonia and Rhodope continental blocks along the Vardar suture zone in NW Greece

18 96 d. boztuğ ET AL. Table 3. Summary of available literature data for the Eocene to Oligo Miocene deformation and extension-related geodynamic framework in the west Anatolia and Aegean region Mechanism/geodynamic framework Relevant geological record 1 Tectonic escape model: westward escape of Anatolia along its boundary structures, the dextral North Anatolian and sinistral East Anatolian fault zones, commenced by the late Serravalian (12 Ma) (e.g. Dewey and Şengör 1979; Şengör et al. 1985; Şengör 1987) 2 Late orogenic collapse model: spreading and thinning of overthickened crust, immediately following cessation of latest Palaeogene collision between the Sakarya continent in the north and the Anatolian-Tauride platform in the south, along the İzmir-Ankara suture 3 Back-arc extension model: subduction roll-back of the presently subducting Mediterranean oceanic lithosphere beneath Eurasia (e.g. Le Pichon et al. 1979, 1981; Meulenkamp et al. 1988, 1994; Thomson et al. 1998) 4 Episodic, two-stage graben model (e.g. Koçyiğit et al. 1999; Bozkurt 2001b; Bozkurt and Sözbilir 2004; Purvis and Robertson 2004, 2005a, b; Purvis et al. 2005; Bozkurt and Rojay 2005; Emre and Sözbilir 2007) 5 Differential rates of convergence between northeastward-directed subduction of the African plate relative to the hanging-wall Anatolian plate Tortonian age of apparently extension-related sediments in the Büyük Menderes and Gediz grabens (1) The age of sediments and intercalated volcanic rocks both in the NE SW-trending basins and E W-trending grabens (e.g. Seyitoğlu and Scott 1991, 1992, 1994, 1996; Seyitoğlu et al. 1992; Seyitoğlu 1997); (2) Syn-extensional granitic rocks (e.g. Bingöl et al. 1982; Seyitoğlu et al. 1992; Hetzel et al. 1995a; Ring and Collins 2005; Bozkurt 2004; Bozkurt et al. 2006; Thomson and Ring 2006; Glodny and Hetzel 2007); (3) Geochronological data from mylonitic rocks (Işık and Tekeli 2001; Ring et al. 2003; Işık et al. 2004; Catlos and Çemen 2005); (4) Latest Oligocene Early Miocene exhumation of the Menderes Massif in the footwall of the now low-angle normal faults and extensional shear zones (e.g. Bozkurt and Park 1994; Hetzel et al. 1995a, b; Bozkurt 2001a, 2004; Gessner et al. 2001b; Lips et al. 2001; Seyitoğlu et al. 2004; Bozkurt 2007) (1) Emplacement of the Cycladic plutons in a back-arc rifting setting (Altherr and Siebel 2002); (2) Greenschist- to amphibolite-facies overprint in the Eocene eclogite and blueschist-facies rocks during Oligo Miocene in the central Aegean region (Pe-Piper and Piper 2001; Altherr and Siebel 2002); (3) Core-complex development and accompanying granite emplacement in the Kazdağ Massif in NW Anatolia during Oligocene (Okay and Satır 2000) (1) Early Middle Miocene phase of core-complex formation; (2) Subsequent modern phase of Plio Quaternary normal faulting and graben formation; (3) Intervening short-time of N S crustal shortening and/or tectonic quiescence Relatively rapid southwestward movement of Greece relative to Cyprus and Anatolia (Doglioni et al. 2002) 6 Flat subduction combined with erosion Rapid cooling of the Menderes Massif during mid to Late Cenozoic (Westaway 2006) 7 Southward translation of Lycian nappes over the Menderes Massif and Alpine nappe stacking during the Eocene collision between the Sakarya continent and the Tauride-Menderes platform and burial of the Massif area (1) Medium pressure high temperature Barrovian-type main Menderes metamorphism (e.g. Şengör et al. 1984; Satır and Friedrichsen 1986; Bozkurt and Park 1994; Bozkurt and Satır 2000; Bozkurt and Oberhänsli 2001; Whitney and Bozkurt 2002; Regnier et al. 2003, 2007; Bozkurt 2007); (Continues)

19 geochemistry and k-ar cooling ages, turkish granitoids 97 Table 3. (Continued) Mechanism/geodynamic framework 8 Continent-continent collision driven slab break-off following the closure of İzmir-Ankara Ocean and the Pindus-Cyclades Ocean 9 Lithospheric delamination following the closure of northern Neo-Tethys Relevant geological record (2) Relic HP fabrics in the Lycian nappes and in the Menderes Massif (Oberhänsli et al. 2001; Rimmelé et al. 2003a, b; Whitney et al. 2008) (1) Formation of the Attic-Cycladic blueschist belt during the Eocene (e.g. Davies and Von Blanckenburg 1995); (2) Emplacement of Eocene to Oligo Miocene granitoids in west Anatolia (Altunkaynak and Dilek 2006; Boztuğ et al. 2006; Altunkaynak 2007; Dilek and Altunkaynak 2007); (3) Extensive Early to Middle Miocene granitoid magmatism in the central Aegean region (e.g. Davies and Von Blanckenburg 1995) Emplacement of the Eocene granitoid in NW Anatolia (e.g. Köprübaşı and Aldanmaz 2004) (Pe-Piper and Piper 2001) and (iii) the continental Peleponnesan-south Aegean (micro-plates of Apulia, a promontory of Africa) and the Pelagonian microplate (a part of Europe) in the central Aegean region (Davies and von Blanckenburg 1995 and references therein). The second phase of extension commenced by the latest Oligocene Early Miocene time due to the combined effect of orogenic collapse and subduction roll-back Aegean arc (Table 3). Pe-Piper and Piper (2001) reported that the subduction of the Mediterranean ocean crust has been synchronous with extension, since at least Oligocene time, which has been induced by the decreasing rates of convergence between Africa and Eurasia in the Oligocene that resulted in the roll-back of the subducting plate of the present-day Mediterranean oceanic lithosphere and extension of the Aegean region. This subduction roll-back is also known to be the reason for the genesis of the widespread Miocene (e.g. between 22 and 9 Ma) granitoid rocks of the Cyclades in the central Aegean region (Altherr and Siebel 2002). The subduction roll-back related extension has also been cited as the cause of Late Oligocene core complex formation and granitic magmatism in the Kazdağ Massif, NW Anatolia (Okay and Satır 2000). Furthermore, regionally significant Late Oligocene to Early Miocene rapid cooling events, associated with extensional tectonics, were identified in different parts of western Turkey. For example, Ring et al. (2003) reported a Late Oligocene to Early Miocene rapid cooling event, with a cooling rate of ca.308c/ma, in northern (Gördes) Menderes Massif exhumed in the footwall of top-to-the-nne Simav detachment to the north and in the southern (Çine) Menderes Massif exhumed in the immediate footwall of top-to-the-south southern Menderes shear zone (also known as south Çine, Kayabükü or Selimiye shear zone; see Bozkurt 2007 and references therein) and extensionally reactivated basal thrust of the structurally overlying Lycian nappes. Similarly, Ring and Collins (2005) reported very rapid cooling (>ca. 2008C/Ma) in the Eğrigöz and Koyunoba granitoids during core-complex formation in the northern Anatolide belt of western Turkey during time interval between 24 and 19 Ma (Late Oligocene to Early Miocene). Another Late Oligocene to Early Miocene rapid cooling event has been described by Thomson and Ring (2006) in the light of zircon and apatite fission-track and apatite (U/Th)- He geothermochronology in the footwall rocks of the Simav detachment fault which is known to be the earliest developed major extensional structure in western Anatolia. The biotite K-Ar ages of the Bozenköy granodiorite, Çataltepe biotite granite and Turfaldağ biotite granodiorite are ca Ma. The hornblende and biotite K-Ar cooling ages of the Kozak granitoid appear to be very similar to biotite K-Ar cooling ages of the Çataldağ granitoids and hornblende K-Ar ages of the Ilıca granitoid (Table 2). There is only one sample in the Ilıca granitoid (sample IL-13) with older hornblende K-Ar cooling age (ca. 39 Ma) is not consistent with the new age data and this is attributed to excess Ar.