Crustal source of the Late Cretaceous Satansarı monzonite stock (central Anatolia – Turkey) and its significance for the Alpine geodynamic evolution

Journal of Geodynamics 65 (2013) 82–93

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Crustal source of the Late Cretaceous Satansarı monzonite stock (central Anatolia – Turkey) and its significance for the Alpine geodynamic evolution Serhat Köksal a,∗, Fatma Toksoy-Köksal b, M. Cemal Göncüo˘glu b, Andreas Möller c, Axel Gerdes d, Dirk Frei e a Middle East Technical University, Central Laboratory, R&D Research and Training Center, Radiogenic Isotope Laboratory, Universiteler Mah., Dumlupinar Blv. No. 1, TR-06800 C¸ankaya, Ankara, Turkey b Middle East Technical University, Department of Geological Engineering, Universiteler Mah., Dumlupinar Blv. No. 1, TR-06800 C¸ankaya, Ankara, Turkey c University of Kansas, Department of Geology, 1475 Jayhawk Boulevard, 120 Lindley Hall, Lawrence, KS 66045-7613, USA d Johann Wolfgang Goethe University, Institut für Geowissenschaften, Altenhöferallee 1, D-60438 Frankfurt Am Main, Germany e Stellenbosch University, Department of Earth Sciences, Private Bag X1, Matieland 7602, South Africa

a r t i c l e

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Article history: Available online 12 June 2012 Keywords: Satansarı monzonite stock Central Anatolia Zircon U–Pb age Lu–Hf isotopes

a b s t r a c t The Late Cretaceous granitic rocks within central Anatolia (Turkey) not only date and show the magmatic aspects of the Alpine realm, but also give clues about its geodynamic character. Among them, the Satansarı monzonite stock (SMS), part of the Terlemez pluton (Aksaray), characterizing the inception of an extensional tectonic regime in central Anatolia, has a subalkaline, metaluminous and magnesian geochemical nature with depletion in Ba, Nb, P and Ti, and with enrichment of Th, U, K and Pb relative to primitive mantle. The SMS has LREE enriched patterns ([La/Yb]N = 18.45–21.21) with moderately negative Eu-anomalies ([Eu/Eu*]N = 0.65–0.73). The geochemical data infer a crustal source with an inherited subduction-related component, and fractionation of plagioclase and amphibole. A crustal signature for the SMS is also inferred from high 87 Sr/86 Sr(t) ratios (0.70826–0.70917), and low εNd(t) values (−6.9 to −7.6). Zircon crystals from the SMS typically have magmatic rims overgrowing inherited cores that are reworked, resorbed and overgrown. Completely new zircon crystals grown in a single magmatic episode have also been identified. Laser ablation ICP-MS U–Pb zircon analyses yield a mean 206 Pb/238 U age of 74.4 ± 0.6 Ma (2) for the intrusion of the SMS. Rare discordant analyses range from the Devonian to the Proterozoic (i.e., 207 Pb/206 Pb ages between 364 Ma and 1263 Ma). In situ zircon Hf isotope analyses reveal low 176 Lu/177 Hf ratios and negative εHf(t) values, which is consistent with a predominantly crustal source of the SMS. We suggest that the water-rich magmas were generated in a hot zone within the crust produced by residual melts from basalt crystallization and partial melts of pre-existing metamorphic and igneous rocks within the lower crust of central Anatolia. The SMS likely formed by episodic injections of these hybrid monzonite melts by adiabatic ascent to shallow crust where they crystallized. This interpretation may be useful in interpreting the involvement of crustal sources for other monzonitic rocks in central Anatolia and granitic magmatism in other similar tectonic environments. © 2012 Elsevier Ltd. All rights reserved.

1. Introduction The Late Cretaceous in the Turkish part of the Alpine-Himalayan orogeny was characterized by the closure of the Neotethyan

∗ Corresponding author at: Middle East Technical University, Central Laboratory, R&D Research and Training Center, Radiogenic Isotope Laboratory, Universiteler Mah., Dumlupinar Blv. No. 1, TR-06800 C¸ankaya, Ankara, Turkey. Tel.: +90 312 2106481, fax: +90 312 2106425. E-mail addresses: [email protected] (S. Köksal), [email protected] (F. Toksoy-Köksal), [email protected] (M.C. Göncüo˘glu), [email protected] (A. Möller), [email protected] (A. Gerdes), [email protected] (D. Frei). 0264-3707/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jog.2012.06.003

oceanic branches and its geodynamic consequences (e.g., Sengör and Yilmaz, 1981). The geological events in this tectonic realm resulted in extensive granitic activity especially within central Anatolia. The petrogenesis of the Central Anatolian Granitoids (CAG) remains an unresolved problem so far, despite numerous studies (e.g., Akiman et al., 1993; Göncüoglu and Türeli, 1994; Boztug, 1998, 2000; Düzgören-Aydin et al., 2001; Ilbeyli et al., 2004, 2009; Ilbeyli, 2005; Kadioglu et al., 2003, 2006; Koc¸ak, 2006; Kadioglu and Dilek, 2010; Köksal et al., 2004, 2012; Boztug et al., 2007a,b,c, 2009a,b). This is mainly due to complexities in the geology of the region, as is the case in other tectonically active systems. Therefore, new approaches to this problem are needed, making use

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Fig. 1. Geological map of the study area (after Yaliniz et al., 1999). CACC, Central Anatolian Crystalline Complex; M, Menderes Massif; IAESZ, Izmir-Ankara-Erzincan suture zone; NAFZ, North Anatolian Fault zone; EAFZ, East Anatolian Fault zone.

of additional and combined analytical data sets. There is already a large geochemical database on the CAG including mineral and whole-rock element chemical data, with limited Nd, Sr, Pb and O isotope data. This study contributes to the research effort on the CAG with a detailed investigation of a monzonite stock in the vicinity of Aksaray city within central Anatolia. New, precise and accurate geochronological data, especially zircon U–Pb ages, are important to constrain the time of generation of the granitoids. It is also essential to have more isotope data on crustal evolution in the CAG. Our study covers zircon Lu–Hf isotope analysis, which is a powerful tool for estimating the source characteristics of rocks (e.g., Hawkesworth and Kemp, 2006), zircon U–Pb age data, as well as whole-rock Sr and Nd isotopic and geochemical data from the Satansarı monzonite stock (SMS). 2. Geological setting The geological history of central Anatolia in the Cretaceous was closely related to the closure of the Izmir-Ankara-Erzincan Ocean (IAEO), which is one of the branches of the Alpine Neotethyan Ocean. The basement of the Central Anatolian Crystalline Complex (CACC) is formed from metamorphic rocks comprised of gneisses, schists, calc-schists, phyllites, and marbles of Precambrian-Palaeozoic-Mesozoic age, which are the HT-LP metamorphic equivalents of the less metamorphosed platform margin sequences of the Taurides-Anatolides (e.g., Göncüoglu et al., 1991). In the Late Cretaceous, the intra-oceanic island arc formed within the IAEO collided with the CACC, which is the northern passive margin of the Gondwanan Tauride-Anatolide continental microplate (e.g., Göncüoglu et al., 1997). During that period, the mafic and ultramafic rocks regarded as the dismembered units of the supra-subduction type ophiolites were thrust onto the metamorphic basement of the CACC (e.g., Göncüoglu et al., 1997; Yaliniz et al., 1999; Toksoy-Köksal et al., 2009). This collision resulted in

the formation of collisional to post-collisional granitoids intruding both the metamorphic and ophiolitic rocks (Fig. 1) (e.g., Yaliniz et al., 1999, 2000). These rocks were then covered by a succession of Late Maastrichtian and younger sedimentary rocks (e.g., Göncüoglu et al., 1997; Köksal et al., 2001) (Fig. 1). Exhumation of the country rocks of the CACC occurred in two main stages, first by rapid exhumation between the peak metamorphism and late granitic activity (ca. from 84 to 74 Ma), and then during the Paleocene by brittle upper crustal tectonics associated with erosional activity (Lefebvre et al., 2011).

3. Materials and methods Zircon crystals, used for LA-ICP-MS, scanning electron microscope (SEM) and cathodoluminescence (CL) studies, were selected under a binocular microscope after enrichment by routine heavy mineral separation methods. SEM and CL studies were conducted at the GeoForschungsZentrum (GFZ)-Potsdam with a DSM 962/Zeiss equipped with a polychromatic Zeiss CL detector, using a 15 kV accelerating potential. Zircon U–Pb age analyses were carried out on a ThermoFinnigan Element2 high resolution magnetic sector field ICP-MS coupled with a Merchantek New Wave 213 nm UV laser ablation system at the Geological Survey of Denmark and Greenland (GEUS), after obtaining back-scattered electron (BSE) images by using a Philips XL 40 SEM at GEUS. The methods applied are explained in detail by Frei and Gerdes (2009) and Gerdes and Zeh (2006). A spot size of 40 ␮m was used for all U–Pb analyses. Lutetium–Hafnium isotopes were determined using a Thermo-Finnigan Neptune multi-collector ICP-MS by laser ablation (LA-MC-ICP-MS) at Goethe-University Frankfurt on selected zircon crystals that were previously dated by U–Pb. Details of the methods are described in Gerdes and Zeh (2006, 2009). Data were collected in static mode during 60 s of ablation using a spot size of 40 ␮m.

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Whole-rock geochemical analyses were performed at ACME Analytical Laboratories Ltd. (Canada). Major elements were determined by ICP-AES after fusion with LiBO2 /Li2 B4 O7 . Trace and rare-earth elements were determined by ICP-MS after acid decomposition (HNO3 of 5%). Whole rock Sr and Nd isotope analyses were made at the Radiogenic Isotope Laboratory of Middle East Technical University Central Laboratory by using the standard cation-exchange techniques described in Köksal and Göncüoglu (2008). Sr and Nd isotope data were obtained by using a Thermo Finnigan Triton thermal ionization mass spectrometer (TIMS) in static multi-collection mode. 87 Sr/86 Sr and 143 Nd/144 Nd data are normalized to 86 Sr/88 Sr = 0.1194 and 146 Nd/144 Nd = 0.7219, respectively. Sr NIST SRM 987 and Nd LaJolla standards were measured as 0.710242 ± 10 (n = 3) and 0.511849 ± 10 (n = 2), respectively. No corrections were applied to Nd and Sr isotopic compositions for instrumental bias. Analytical uncertainties are given at 2бm level. During the course of the analyses the AGV-1 USGS standard gave 87 Sr/86 Sr = 0.703985 ± 10 (n = 2) and 143 Nd/144 Nd = 0.512776 ± 10 (n = 2). 4. Results 4.1. Geological, petrographical and geochemical features Intrusive rocks in the study area were named the Terlemez quartz-monzonite by Yaliniz et al. (1999). Field occurrence and some distinct petrographical and geochemical properties of a small stock of monzonitic composition at the northern edge of the Terlemez quartz-monzonite led us to describe it as a distinct body, the Satansarı monzonite stock (SMS). The SMS, having gradational contacts with the quartz-monzonites, intruded the supra-subduction zone ophiolitic rocks (e.g., Yaliniz et al., 1999). The Middle Turonian-Lower Santonian pelagic cherty limestones of the epiophiolitic cover are also cut by these granitoids (Yaliniz et al., 1999). A lower age limit is provided by the uppermost Maastrichtianlowermost Paleocene sedimentary sequences that disconformably cover these granitic and ophiolitic rocks (e.g., Göncüoglu et al., 1991). As a consequence, the age of the monzonites concerned can be constrained as post-Santonian to pre-Maastrichtian, between 83.5 and 70.6 Ma. In the field, monzonites from the Satansarı area clearly differ from the Terlemez quartz-monzonite samples by their fine to medium grained texture and dark greenish gray color. Unlike the Terlemez quartz-monzonite, the SMS does not show a flow texture. The SMS is well-characterized by holocrystalline, microphaneritic and porphyritic textures. Plagioclase, K-feldspar, hornblende, and biotite are the essential minerals, while quartz is a minor phase in the SMS. Both feldspar and mafic phases are found as euhedral and subhedral phenocrysts within a finer-grained groundmass composed mainly of plagioclase. Accessory phases of the SMS are zircon, titanite, apatite and opaque minerals. Epidote, sericite and kaolinite are the alteration products. Plagioclase exists as large, zoned crystals or micro-laths. Bands of melt inclusions are present at the margins of some plagioclase phenocrysts. Plagioclase phenocrysts with melt inclusions are mostly characterized by sericitized centers. Moreover, some of the highly sericitized plagioclase crystals are enveloped by thin rims of unaltered plagioclase. Unaltered plagioclase micro-crystals form poikilitic inclusions in hornblende phenocrysts, while some feldspar minerals are poikilitic, enclosing hornblende, biotite and quartz crystals. Moreover, fine-grained crystals of plagioclase are surrounded by clusters of hornblende micro-crystals. K-feldspar phenocrysts generally show embayments filled with finer grained groundmass together with phenocrysts of hornblende and plagioclase clusters. The SMS contains angular or sub-rounded microgranular mafic enclaves in some places (but fewer than the Terlemez

Fig. 2. Geochemical data of the SMS in comparison to the Terlemez quartzmonzonite [Terlemez q-monzonite (1): data from Yaliniz et al., 1999; Terlemez q-monzonite (2): data from Kadioglu et al., 2006] on the (a) Na2 O + K2 O vs. SiO2 diagram [Fields; I-monzodiorite, II-monzonite, III-syenite, IV-quartz-monzonite, Vdiorite, VI-granodiorite) (after Middlemost, 1994). Alkaline-subalkaline boundary is from Irvine and Baragar (1971)], (b) FeOtot /(FeOtot + MgO) vs. SiO2 diagram (after Frost et al., 2001).

quartz-monzonite), which is interpreted as evidence for magma mingling (e.g., Didier and Barbarin, 1991). These enclaves of hornblende and minor amounts of plagioclase are up to a few tens of centimeters in diameter. In addition to the presence of these mafic enclaves, textural features observed in the SMS (e.g., melt inclusions in zoned plagioclase, fresh rims of plagioclase around altered parts, penetration of groundmass material into embayments in Kfeldspar) are interpreted here to be indications of magma mingling processes. Five new whole-rock geochemical analyses from the SMS are presented in this study (Table 1). All samples contain more than 60 wt.% SiO2 , with a sub-alkaline composition based on Irvine and Baragar’s (1971) classification (Fig. 2a). The SMS samples plot into the monzonite, quartz-monzonite, diorite and granodiorite fields of Middlemost (1994) diagram (Fig. 2a). Petrographically, the SMS is monzonitic, where quartz is found in minor amount (less than 5%) therefore we describe these rocks as monzonite rather than quartzmonzonite. The distribution of the Terlemez quartz-monzonite samples (Yaliniz et al., 1999; Kadioglu et al., 2006) is also shown in this diagram. We infer from Fig. 2a that the geochemical character of the intrusive rocks is not uniform throughout the Terlemez and Satansarı areas, including the alkaline samples. The SMS samples are metaluminous based on Shand (1943) index, with molar A/CNK values below 1.1 (not shown). The SMS and the Terlemez quartz-monzonite samples are mainly magnesian based on Frost et al.’s (2001) classification, although few samples gave ferroan character (Fig. 2b). In general, petrographical (i.e., presence of hornblende and absence of muscovite) and

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Table 1 Whole-rock major and trace element, and Sr and Nd isotope data from the Satansarı monzonite stock. Whole-rock dataa

Sample no. 1

2

3

4

5

SiO2 TiO2 Al2 O3 Fe2 O3 (T) MnO MgO CaO Na2 O K2 O P2 O5 Cr2 O3 LOI

63.19 0.52 16.20 4.39 0.16 1.89 6.76 2.47 2.32 0.125 0.037 1.6

62.69 0.58 15.84 4.69 0.13 1.76 5.77 2.79 4.33 0.146 0.039 0.9

60.35 0.67 16.02 5.87 0.10 1.49 5.64 2.92 4.39 0.267 0.027 1.8

62.6 0.58 15.96 4.70 0.13 1.58 6.08 2.26 4.13 0.155 0.031 1.5

64.36 0.47 15.07 5.13 0.11 1.51 4.47 2.59 4.98 0.14 0.030 1.3

Total

99.66

99.67

99.54

99.71

100.26

Rb Sr Nb Co Cs Ta Sc Pb U Th Cu Ga Mo Ba Zr Zn Hf V Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

114.6 706.3 19.9 9.0 8.6 1.50 8 145.3 8.2 29.8 12.7 21.7 4.2 830 227.3 74 6.3 69 19.8 57.7 100.1 11.27 37.1 5.87 1.11 4.59 0.67 3.55 0.67 1.94 0.31 1.97 0.30

164.0 789.5 20.9 9.2 5.6 1.15 8 72.9 6.5 28.3 8.1 20.2 4.3 788 231.7 68 6.6 58 20.6 59.4 101.2 11.61 40.0 6.07 1.15 4.81 0.69 3.88 0.72 2.06 0.33 2.08 0.31

146.6 1155.0 20.4 9.5 3.8 1.20 6 17.4 7.8 30.8 14.8 18.1 3.2 1383 262.8 19 6.7 93 22.3 66.2 115.2 13.54 49.0 7.47 1.54 5.58 0.81 4.22 0.76 2.21 0.34 2.12 0.32

126.3 698.7 20.2 7.3 5.5 1.50 7 33.7 6.8 27.4 5.4 19.5 3.1 805 234.2 106 6.4 55 19.6 58.9 99.9 11.2 38.2 6.04 1.12 4.55 0.68 3.83 0.72 1.91 0.33 1.96 0.30

217.7 611.7 20.4 8.3 5.9 1.40 6 11.5 9.3 35.5 25.7 20.9 4.8 863 212.7 30 6.3 62 25.7 67.9 122.8 10.84 42.6 7.30 1.33 5.24 0.78 4.19 0.78 2.24 0.33 2.50 0.38

(Eu/Eu*)N (La/Yb)N

0.65 19.90

0.65 19.40

0.73 21.21

0.65 20.41

0.66 18.45

87

0.708757 ± 5 0.70826 0.512204 ± 3 0.512157 −7.51 1.49

0.709570 ± 5 0.70894 0.512203 ± 3 0.512158 −7.50 1.49

0.708929 ± 5 0.70854 0.512236 ± 3 0.512191 −6.86 1.44

0.709496 ± 5 0.70894 0.512200 ± 3 0.512153 −7.59 1.50

0.710254 ± 8 0.70917 0.512215 ± 3 0.512164 −7.37 1.48

Sr/86 Sr Sr/86 Sr(t) b 143 Nd/144 Nd 143 Nd/144 Nd(t) εNd(t) TDM (Ga)c 87

a Major element detection limits are 0.01 wt.% for SiO2 , Al2 O3 , MgO, CaO, Na2 O, K2 O, MnO, TiO2 , 0.04 wt.% for Fe2 O3 , 0.001–0.002 wt.% for P2 O5 and Cr2 O3 and 0.10 wt.% for LOI. Trace elements and REE detection limits are as follows; 8 ppm for V, 1 ppm for Ba and Sn, 0.5 ppm for Sr, Gd and W, 0.3 ppm in Nd, 0.2 ppm in Co, 0.1 ppm for Cs, Hf, Nb, Rb, Ta, U, Y, Zr, Th, La and Ce, 0.05 ppm in Sm, Dy, Yb, 0.03 ppm in Er, 0.02 ppm in Pr, Eu and Ho, 0.01 in Tb, Tm, Lu. Analytical precision is about 0.05–0.15% for major elements and 0.5–1.5% for trace and REE. b t = 74.4 Ma as determined from the U–Pb zircon geochronology. c TDM is the two stage crustal age after Liew and Hofmann (1988).

chemical (e.g., A/CNK < 1.1) features suggest that the SMS is a typical hornblende-bearing I-type granitoid based on the classification of Chappell and White (1974). The SMS shows depletion in Ba, Nb, P and Ti and enrichment of Th, U, K and Pb on primitive mantle-normalized spider diagrams (Fig. 3) and its pattern generally coincides with that of the Terlemez quartz-monzonite, with slightly different enrichment levels, especially in the REE.

On a chondrite-normalized REE diagram (Fig. 4), the SMS samples display LREE enriched patterns ([La/Yb]N = 18.45–21.21) with moderate negative Eu-anomalies ([Eu/Eu*]N = 0.65–0.73). These REE patterns infer some plagioclase and amphibole fractionation for crystallization of the SMS (Fig. 4). On this diagram, the Terlemez quartz-monzonite differs from those of the SMS by its lower LREE enrichment levels, lack of Eu-anomalies, and HREE patterns.

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Fig. 3. Primitive mantle-normalized (after Sun and McDonough, 1989) traceelement patterns for the Satansarı monzonite stock and the Terlemez quartzmonzonite (Data source Table 1, Yaliniz et al. (1999) (Terlemez q-monzonite [1]) and Kadioglu et al. (2006) (Terlemez q-monzonite [2]).

Petrological variation within the Terlemez pluton can be explained by assimilation and fractional crystallization processes, but the available geochemical data are not comprehensive enough to check the validity of these processes for the study area. 4.2. Strontium and neodymium isotopes Results of the whole-rock Sr and Nd isotopic analyses from the SMS are shown in Table 1. 87 Sr/86 Sr(t) ratios range from 0.70826 to 0.70917, while εNd(t) values range from −6.86 to −7.59. Moreover, mean crustal residence ages (TDM model ages) are between 1.44 and 1.50 Ga. Accordingly, similar Sr and Nd isotope data, i.e. high 87 Sr/86 Sr(t) ratios and low εNd(t) values were documented from the other Late Cretaceous granitoids within central Anatolia (e.g., Ataman, 1972; Göncüoglu, 1986; Türeli et al., 1993; Gülec¸, 1994; Ilbeyli et al., 2004; Ilbeyli, 2005; Köksal and Göncüoglu, 2008; Koc¸ak, 2008). 4.3. Zircon structures Zircon populations of the SMS are generally characterized by Jtype (J2 , J3 , J4 , and J5 ), and rarely S-type (S19 , S22 , S23 , S24 , and S25 ) zircon crystals based on the classification of Pupin (1980). Zircon crystals of the SMS mainly show high T-indices (i.e., 700–800), and abundant J-types, which are rarely observed in calc-alkaline granitoids, but the typological evolution trend of the SMS (not shown)

Fig. 5. SEM and CL images of some selected zircon crystals from the Satansarı monzonite stock. Osc: oscillatory zoning, C: core, r: resorption zone, s: sector zoning, i: inclusion.

Fig. 4. Chondrite-normalized (after McDonough and Sun, 1995) rare earth element patterns for the Satansarı monzonite stock (Data source Table 1). Fields correspond to the rare earth element patterns for the Terlemez quartz-monzonite (data from Yaliniz et al., 1999).

is similar to that of group 4-c of Pupin classification (1980). Group 4-c rocks, according to Pupin (1980), are calc-alkaline with crust and mantle sources, and include mafic microgranular enclaves. Fig. 5 shows J2 , J3 , and J4 type zircon crystals from the SMS and their internal structures. Zircon crystals of the SMS have usually oscillatory and occasionally sector zoning (Fig. 5). Inherited cores are rarely observed, while resorption zones (characterized by lowcathodoluminescence signals) covering small cores and/or broken and dissolved parts of a crystal are typical in Satansarı zircons (Fig. 5). Inclusions of apatite and titanite and intermittent resorption zones interrupting the oscillatory zoning occur in some zircons (Fig. 5). Zircon structures show crystals with inherited cores that

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Fig. 6. BSE images and LA-ICP-MS 206 Pb/238 U ages (in Ma) of some selected zircon crystals from the Satansarı monzonite stock. Circles indicating the locations of the LA-ICP-MS are ca. 40 ␮m in diameter. Circles with numbers indicate locations of the LA-MC-ICP-MS Lu-Hf isotope analyses.

are reworked, resorbed and covered by igneous zoning as well as completely new zircon crystals interpreted to have grown during a single magmatic episode.

Fig. 7. (a) U–Pb concordia diagram of the Satansarı monzonite stock (source Table 2), blue (dashed) circles indicate discordant analyses. (b) Six-point U–Pb concordia age of the Satansarı monzonite stock (source Table 2).

4.4. U–Pb zircon ages

4.5. Lu–Hf isotopes

Selected zircon crystals from the SMS were U–Pb dated by LAICP-MS. Table 2 shows the 45 U–Pb ages obtained from the SMS zircon, from which 35 were used to calculate the mean 206 Pb/238 U age of the SMS. BSE images of some zircon grains with analyses points of U–Pb ages are presented in Fig. 6. All concordant analyses reveal Late Cretaceous ages between 71 ± 2 Ma and 78 ± 3 Ma with a mean 206 Pb/238 U age of 74.4 ± 0.6 Ma (2) (Fig. 7a). The 6point U–Pb concordia age is 75.4 ± 1.1 Ma (2), overlapping the mean age within analytical error (Fig. 7b). Yaliniz et al. (1999) documented K–Ar hornblende and K-feldspar ages of 81.5 ± 1.9 Ma and 67.1 ± 1.3 Ma, which they interpreted as intrusion and cooling ages, respectively. The age of the SMS, on the other hand, is similar to that of our unpublished LA-ICP-MS U–Pb isotopic data from the Terlemez quartz-monzonite (75.0 ± 1.3 Ma; e.g., Köksal et al., 2008) regarding the errors. Discordant analyses, mostly from the inherited cores, gave 207 Pb/206 Pb ages ranging from the Devonian to the Proterozoic (i.e., 364 ± 32 Ma to 1263 ± 115 Ma). Similar old zircon core ages have been documented for other granitic rocks within central Anatolia (e.g., Whitney et al., 2003; Köksal et al., 2007, 2012).

Results of Lu–Hf in situ LA-MC-ICP-MS zircon analyses from the SMS are presented in Table 3 and Fig. 8. Locations of the points of analyses are shown in Fig. 6 (analyses spots are numbered from 1 to 12). Zircons from the SMS do not show large variation in Hf isotopic compositions. Initial 176 Hf/177 Hf ratios range from 0.282435 to 0.282517, which correspond to εHf(t) values between −7.4 and −10.2 (Table 3). These low Hf isotopic values of the analyzed zircons of the SMS indicate their crustal character (e.g., Kinny and Maas, 2003). Calculated TDM Hf ages are between 1.40 and 1.56 Ga, covering a similar range as the whole rock TDM Nd ages (i.e., 1.44–1.50 Ga, Table 1). The overall variation of ±1.5 epsilon units for Hf is only slightly larger than the typical reproducibility (±0.8–1.0; n = 11) of the GJ-1 standard zircon. Zircon U–Pb ages, both from cores and rims, corresponding to spots analyzed for Lu–Hf, show only very minor variation within the given age range (Fig. 8a). The narrow range for U–Pb and Lu–Hf data indicate that the non-inherited zircon cores and rims crystallized during a single magmatic event (e.g., Zeh et al., 2007). The nature of the discordant inherited cores, which can only be approximated by 207 Pb/206 Pb ages, cannot be further resolved here because there are no concordant U–Pb ages with

88

Table 2 LA-ICP-MS zircon U–Pb ages of zircons from the Satansarı monzonite stock. Analysis Nr.

207

Pb (cps)

U (ppm)

Pb (ppm)

Th U

207 235

238

Pb U

1 (%)

rho

207 206

Pb Pb

1 (%)

207 235

Pb U

2 (Ma)

206 238

Pb U

2 (Ma)

207 206

Pb Pb

2 (Ma)

2.0 2.6 2.1 2.8 2.5 2.0 2.9 2.4 2.2 2.7 2.8 2.1 2.4 2.2 2.1 1.9 2.5 2.0 2.0 2.0 2.3 3.8 2.2 2.7 2.1 2.2 2.9 2.2 2.5 2.3 2.7 2.7 3.0 4.4 2.8

0.0119 0.0115 0.0114 0.0120 0.0113 0.0114 0.0116 0.0116 0.0120 0.0117 0.0110 0.0113 0.0118 0.0122 0.0117 0.0118 0.0114 0.0118 0.0116 0.0116 0.0117 0.0115 0.0119 0.0114 0.0113 0.0117 0.0118 0.0115 0.0114 0.0115 0.0116 0.0115 0.0115 0.0121 0.0114

1.5 1.8 1.5 2.0 2.0 1.6 2.3 1.7 1.7 1.9 1.7 1.8 1.8 1.7 1.7 1.7 1.8 1.6 1.4 1.7 1.7 1.9 1.7 1.7 1.7 1.7 1.8 1.7 1.5 1.6 1.7 1.6 1.6 1.5 1.7

0.72 0.69 0.74 0.70 0.80 0.83 0.81 0.70 0.79 0.71 0.61 0.83 0.77 0.77 0.82 0.88 0.71 0.82 0.71 0.82 0.77 0.50 0.76 0.62 0.80 0.76 0.63 0.76 0.59 0.69 0.63 0.58 0.52 0.34 0.61

0.0500 0.0510 0.0500 0.0495 0.0497 0.0492 0.0473 0.0500 0.0486 0.0520 0.0527 0.0532 0.0472 0.0476 0.0478 0.0481 0.0486 0.0488 0.0488 0.0490 0.0501 0.0501 0.0502 0.0503 0.0504 0.0505 0.0506 0.0509 0.0511 0.0513 0.0514 0.0516 0.0521 0.0524 0.0527

1.4 1.9 1.4 2.0 1.5 1.1 1.7 1.7 1.4 1.9 2.2 1.2 1.5 1.4 1.2 0.9 1.8 1.1 1.4 1.2 1.4 3.3 1.4 2.1 1.2 1.4 2.2 1.4 2.1 1.7 2.1 2.2 2.6 4.1 2.2

80 79 77 80 76 76 74 78 78 82 78 81 75 78 76 76 75 78 76 77 79 78 80 77 77 79 81 79 79 79 80 80 81 85 81

3 4 3 4 4 3 4 4 3 4 4 3 4 3 3 3 4 3 3 3 4 6 3 4 3 3 5 3 4 4 4 4 5 7 4

76 74 73 77 72 73 74 75 77 75 71 73 75 78 75 76 73 76 75 75 75 74 76 73 73 75 76 74 73 74 74 74 74 77 73

2 3 2 3 3 2 3 3 3 3 2 3 3 3 3 3 3 2 2 3 3 3 3 2 2 2 3 2 2 2 3 2 2 2 2

194 239 195 172 183 159 65 193 129 287 318 336 62 79 92 104 130 137 137 147 198 198 204 208 214 217 224 237 247 252 259 268 289 304 316

33 44 32 47 35 26 40 41 32 44 51 27 37 33 29 22 42 26 32 27 33 76 32 49 29 33 52 32 47 39 49 51 59 94 50

95 93 95 96 96 97 100 95 98 92 90 90 101 100 99 99 98 98 97 97 95 95 95 95 94 94 94 94 93 93 93 92 91 91 90

Discordant analyses not used for calculation of the mean age 17,670 1037 14 0.14 Zircon 16 13,731 550 8 0.74 Zircon 81 9447 343 5 0.78 Zircon 85 10,422 230 4 1.85 Zircon 176 10,518 263 4 0.99 Zircon 77 12,804 609 9 0.98 Zircon 157 12,051 352 6 1.12 Zircon 76 6266 119 2 1.75 Zircon 165 10,166 195 4 Zircon 172 1.61 13,312 449 7 0.50 Zircon 177

0.082 0.099 0.102 0.108 0.107 0.119 0.092 0.091 0.105 0.137

2.8 2.2 1.9 7.2 6.7 3.7 2.2 3.3 3.6 6.2

0.0108 0.0119 0.0120 0.0115 0.0113 0.0121 0.0125 0.0115 0.0127 0.0120

1.4 1.7 1.6 1.4 2.2 1.9 1.6 1.7 2.5 1.8

0.51 0.76 0.84 0.19 0.33 0.51 0.75 0.52 0.69 0.29

0.0547 0.0602 0.0617 0.0683 0.0687 0.0713 0.0538 0.0576 0.0604 0.0827

2.4 1.4 1.0 7.0 6.3 3.2 1.4 2.9 2.6 5.9

80 96 99 104 103 114 90 89 102 130

4 4 4 15 14 8 4 6 7 16

69 76 77 73 72 78 80 74 81 77

2 3 2 2 3 3 3 3 4 3

399 612 663 879 890 966 364 516 618 1263

53 31 22 145 130 64 32 63 56 115

87 80 78 71 70 68 89 83 80 59

c

3 2 4 3 3 4 4 4 4 4 5 5 2 6 4 5 3 3 4 4 5 2 4 4 5 5 2 5 3 2 3 2 2 5 2

206

0.082 0.081 0.079 0.082 0.078 0.077 0.076 0.080 0.080 0.084 0.080 0.083 0.077 0.080 0.077 0.078 0.077 0.080 0.078 0.079 0.081 0.079 0.082 0.079 0.079 0.081 0.083 0.081 0.081 0.081 0.082 0.082 0.083 0.087 0.083

a

191 118 243 178 212 265 199 304 222 214 300 325 142 391 230 342 197 203 300 234 325 104 253 220 390 321 86 391 129 115 192 115 91 347 109

1 (%)

1.52 2.00 2.04 1.69 1.35 1.43 2.31 1.02 1.72 1.85 1.50 1.22 1.57 1.21 1.62 1.34 1.36 1.75 1.02 1.44 1.09 2.55 1.11 1.39 0.94 0.97 2.12 0.91 1.98 1.85 1.45 1.54 2.27 1.21 1.75

b

7500 8628 7067 8275 7001 8222 8485 9434 6123 6792 10,231 8029 7889 7520 9739 8029 7930 8283 10,802 9334 10,550 8301 7909 8820 8836 9546 7604 10,815 8363 7703 7182 6627 6255 10,978 5395

Pb U

Conc (%)

Zircons on which Lu–Hf isotope analyses were performed. Italicized ages are apparent or preferred ages. Zircons used for U–Pb concordia age.

S. Köksal et al. / Journal of Geodynamics 65 (2013) 82–93

Zircon 1a Zircon 2a Zircon 3a Zircon 4a Zircon 5a Zircon 6a Zircon 7a , c Zircon 8a Zircon 9a Zircon 10a Zircon 11a Zircon 12a Zircon 183c Zircon 86c Zircon 74c Zircon 67c Zircon 65c Zircon 152 Zircon 153 Zircon 75 Zircon 73 Zircon 196 Zircon 195 Zircon 184 Zircon 68 Zircon 64 Zircon 168 Zircon 80 Zircon 154 Zircon 182 Zircon 166 Zircon 193 Zircon 169 Zircon 178 Zircon 164

Ages( b )

Atomic ratios

Table 3 LA-MC-ICP-MS zircon Lu–Hf isotope data from the Satansarı monzonite stock. Analysis nr.

176

1 2 3 4 5 6 7 8 9 10 11 12

0.0156 0.0139 0.0298 0.0275 0.0358 0.0197 0.0316 0.0168 0.0243 0.0171 0.0200 0.0227

GJ-1f , n = 11

Yb/177 Hf a

0.0104

±2

176

2 5 47 12 17 4 16 4 24 4 2 26

0.00043 0.00043 0.00080 0.00078 0.00097 0.00056 0.00091 0.00051 0.00071 0.00050 0.00058 0.00065

1 1 11 3 5 1 4 1 7 1 1 6

0.00031

8

94

Lu/177 Hf a

±2␴

178

Hf/177 Hf

180

Hf/177 Hf

1.46714 1.46717 1.46717 1.46724 1.46720 1.46717 1.46722 1.46717 1.46720 1.46714 1.46723 1.46726

1.88670 1.88676 1.88678 1.88692 1.88681 1.88684 1.88690 1.88669 1.88682 1.88673 1.88688 1.88688

1.46721

1.88685

␤(Yb)

␤(Yb)

±2

176

0.282436 0.282481 0.282468 0.282462 0.282450 0.282492 0.282507 0.282485 0.282503 0.282498 0.282491 0.282518

17 17 19 19 18 17 20 17 17 18 18 18

0.282435 0.282481 0.282467 0.282461 0.282448 0.282491 0.282506 0.282485 0.282502 0.282497 0.282490 0.282517

−10.2 −8.7 −9.2 −9.3 −9.9 −8.3 −7.8 −8.5 −7.8 −8.1 −8.4 −7.4

0.282005

13

0.282002

−13.8

SigHf b (V)

176

16 14 16 14 15 17 15 17 16 16 17 14 19

Hf/177 Hf

Hf/177 Hf(t)

εHf(t)

c

±2

TDM

0.6 0.6 0.7 0.7 0.6 0.6 0.7 0.6 0.6 0.6 0.7 0.7

1.56 1.47 1.50 1.51 1.53 1.45 1.42 1.46 1.43 1.44 1.45 1.40

0.5

2.19

d

(Ga)

Age e (Ma)

±2 (Ma)

76 74 73 77 72 73 74 75 77 75 71 73

2 3 2 3 3 2 3 3 3 3 2 3

609

9

␤

177

176

177

173

177

176

177

175

177

89

Fig. 8. (a) εHf(t) vs. 206 Pb/238 U age, (b) εHf(t) vs. 176 Lu/177 Hf diagrams for the Satansarı monzonite stock.

corresponding Lu–Hf isotope data available. We have only one zircon crystal with Lu–Hf isotope analyses from both core and rim (analyses 7 and 8), with εHf(t) values of −7.8 and −8.5, respectively, which may be an indication of increasing crustal signature from core to rim.

5. Discussion

Central Anatolia is an important segment of the Alpine geodynamic system. The Late Mesozoic evolution of central Anatolia (Turkey) is characterized by the closure of the northern branch of the Neotethyan Ocean (Sengör and Yilmaz, 1981), which was suggested to be followed by an intraoceanic arc-continent and a subsequent continent–continent collision (e.g. Akiman et al., 1993; Boztug et al., 2007c; Göncüoglu, 2009) (Fig. 9a). The southern component of the collision was the Gondwanan Tauride-Anatolide microplate and its northern passive margin was represented by the CACC (Fig. 9a). Isolated outcrops of the Mesozoic ophiolitic rocks, which are considered to be generated in a supra-subductionzone setting within the Izmir-Ankara-Erzincan Ocean of Neotethys (Fig. 9a), are observed as allochthonous bodies over the metamorphic basement rocks (e.g. Yaliniz et al., 1999, 2000; Toksoy-Köksal et al., 2001, 2009) (Fig. 9b). Alternative geodynamic models on the evolution of the CAG propose the existence of the Inner Tauride Ocean, which is suggested to have separated the CACC from the Tauride-Anatolide micro-plate (e.g., Sengör and Yilmaz, 1981;

S. Köksal et al. / Journal of Geodynamics 65 (2013) 82–93

Yb/ Hf = ( Yb/ Hf)true × ( Yb/ Hf)meas × (M176(Yb) /M173 ) /(M176(Yb) /M177 ) (Hf). Lu/ Hf values were calculated in a similar way by using the measured Lu/ Hf and the Yb . The effect of the inter-element fractionation on the Lu/Hf was estimated to be 4–6%. b Mean Hf signal. c εHf(t) was calculated by using a decay constant of 1.865 × 10−10 (Scherer et al., 2001), a CHUR 176 Lu/177 Lu and 176 Hf/177 Hf ratio of 0.0332 and 0.282772, and the U–Pb zircon ages. d Two stage model age using the measured 176 Lu/177 Lu of each spot (first stage = age of zircon), a value of 0.0113 for the average continental crust (second stage), and a depleted mantle 176 Lu/177 Lu and 176 Hf/177 Hf of 0.0384 and 0.28325, respectively. e U–Pb zircon ages (data source Table 2). f Mean ± 2 standard deviation of 11 spot analyses of GJ-1 reference zircon. a 176

90

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Fig. 9. (a) Proposed geodynamic evolution of the region from >95 Ma to 80 Ma. (b) Proposed geodynamic evolution of the CACC between 80 and 70 Ma. Series of events are numbered from I to VII indicating the magmatic and geodynamic events sequentially during this period.

Görür et al., 1984, 1998; Whitney and Dilek, 1997; Kadioglu et al., 2003, 2006). Görür et al. (1984, 1998) suggested that the CAG were formed by calc-alkaline arc magmatism during closure of the Inner Tauride Ocean during the Early Paleocene-Eocene by northward subduction beneath the CACC. Kadioglu et al. (2006), on the other hand, suggested a collisional origin for the CAG, but they proposed collision and partial subduction of the front edge of the Tauride micro-plate with a trench within the Inner Tauride Ocean. Kadioglu et al. (2006) explained the evolution of the CAG by slab break-off, followed by rising of hot asthenosphere through an asthenospheric window, beneath the continental lithosphere of the CACC. In their model they then invoked metasomatisation of the lithosphere and generation of the high-K calc-alkaline/shoshonitic magmas of the granitic and monzonitic magmas, and then the highly fractionated alkaline magmas, which had interacted with mantle-derived parental melts of the syenitic rocks of the CACC. These geodynamic models generally include the magmatism in the region as a key

topic. As a consequence, understanding the petrology of the Late Cretaceous granitic rocks within central Anatolia is an important subject because it reflects the nature of tectonic activity in this period. The Satansarı monzonite stock as a member of the CAG reveals important geological information although it is a small exposure. Although it has some unique petrographical features, in general the SMS represents the monzonitic and/or quartz-monzonitic intrusive rocks in the CACC. Based on petrographic and whole-rock elemental data it is a classic I-type hornblende-bearing granite (Chappell and White, 1974), whereas isotopic data on the SMS make the case more complex. Studies in other areas have shown that there is no clear-cut tectono-magmatic distinction between S- and Itype granitoids because mixing and contamination processes (e.g., Collins, 1998; Maas et al., 2001) make simple petrographic or chemical recognition very difficult. This is even the case for the Lachlan Fold Belt granitoids where the S- and I-type granitoid classification

S. Köksal et al. / Journal of Geodynamics 65 (2013) 82–93

was first proposed by various researchers (e.g. Chappell et al., 1987, 1999) based on geological and geochemical data. It has now been recognized that the Lachlan Fold belt granitoids have a complex evolution history that is best revealed by isotopic data (Keay et al., 1997; Kemp et al., 2007). A three source-component mixing model proposed by Keay et al. (1997) suggested interaction of basaltic magmas with the greenstone rocks in the lower crust to form a hybrid magma that was then extensively contaminated by older metasedimentary rocks (e.g., Keay et al., 1997; Collins, 1998). This idea is supported to some extent by zircon O and Hf isotope data of Kemp et al. (2007) who stated that hybrid magma formed from residual liquids of basalt sills, and crustal melts ascended and ponded in the shallow crust where mingling and amalgamation of melt batches occurred. During these events zircons of the I-type hornblende-bearing granitoid record increasing supracrustal character detected by O and Hf isotopes (Kemp et al., 2007). We propose that in a similar fashion, the SMS with its common I-type geochemical features contains zircons whose Hf isotope data imply a crustal source. Trace element patterns from the SMS suggest a crustal source, but with a subduction-related component, which should be related to the earlier events. The Sr and Nd isotopic data are also consistent with a predominantly crustal origin, accordingly the low 176 Lu/177 Hf ratios and negative εHf (t) values (Fig. 8b) reveal that a crustal signature is significant within zircons from this monzonite. Based on the combined U–Pb and Lu–Hf isotope data, along with the other geochemical and isotopic data, we therefore interpret the potential predominant sources for the SMS to be crust-derived melts. The documented Late Cretaceous granitic intrusion ages in central Anatolia mainly fall into two main periods, i.e. 85–80 Ma and ca. 75 Ma, with smaller intrusions between them (e.g., Köksal and Göncüoglu, 2008; Köksal et al., 2012). Granitoids of the older period can be defined as collisional and are found in different areas in the CACC (e.g., the Uc¸kapili granitoid, Göncüoglu, 1986; the Behrekdag batholith, Ilbeyli et al., 2004; the Sinandi granitoid, Köksal et al., 2007; the Danaciobasi granitoid, Boztug et al., 2007c; the Kerkenez granitoid, Isik et al., 2008; the Agac¸ören biotite-muscovite and hornblende-biotite granitoids, Köksal et al., 2012). These granitoids were probably formed by high heat-flux likely to be associated with thermal recovery following the Turonian-Coniacian crustal thickening and coeval regional metamorphism (e.g., Göncüoglu, 1986; Whitney et al., 2003) (Fig. 9a). In order to produce these collisional granitoids the central Anatolian crust must have been considerably thickened before melt generation, similar to models proposed for the Lachlan fold belt (e.g., Collins, 1998). Crustal thickening is likely to be related to the collision of the intra-oceanic island arc formed within the IAEO with the CACC (e.g., Göncüoglu et al., 1997) (Fig. 9a). Granitoids of the second main period at ca. 75 Ma cover larger areas throughout the CACC (e.g., the Cefalikdag granitoid, Ataman, 1972; Kadioglu et al., 2006; the Baranadag granitoid, Köksal et al., 2004; Ilbeyli et al., 2004; Boztug et al., 2007c; Agac¸ören monzonite, Köksal et al., 2012). Moreover, we determined the age of the SMS as 74.4 ± 0.6 Ma, which is in accordance with these ages, and our unpublished LA-ICP-MS zircon U–Pb age from the Terlemez quartz-monzonite (i.e., 75.0 ± 1.3 Ma) (e.g., Köksal et al., 2008). These granitoids are commonly monzonitic and have been interpreted to be the products of post-collisional uplift and extension accompanied by lithospheric delamination and thinning and crustal contamination processes during which the underplating mafic magma supplied heat for melting of the subcontinental lithospheric mantle and minor amounts of lower to middle crustal rocks (e.g., Aydin et al., 1998; Boztug, 1998, 2000; Düzgören-Aydin et al., 2001; Köksal et al., 2004, 2012; Ilbeyli et al., 2004; Ilbeyli, 2005; Boztug et al., 2007a,b,c; Boztug and Arehart, 2007; Boztug and Harlavan, 2008; Boztug et al., 2009a,b). These models, however, are inadequate to explain the crustal isotopic character of the SMS.

91

The Lu–Hf data from zircon cores as well as rims of Late Cretaceous age present a crustal source that requires zircon crystallization completely within the crust. This circumstance is possible through crustal anatexis. However, the multiple resorption zones observed in the zircons are accepted as indications of heat input by mafic mantle melt contribution possibly related to magma mingling/mixing events (e.g., Vavra, 1994; Miller and Wooden, 2004; Köksal et al., 2008, 2012), an interpretation supported by the presence of mafic microgranular enclaves. These multiple zircon resorption zones are interpreted as evidence for episodic injection of mafic magma to the lower or middle crust where the zircons crystallized. The numerical model proposed by Annen et al. (2006) may offer a possible scenario for the evolution of the SMS and its constituent zircons. We propose that a deep crustal hot zone was generated by underplating of a mafic magma possibly coupled with the mantle derived hydrous basalts emplaced as a series of sills into the lower crust of the CACC (e.g., Annen et al., 2006). This event was accompanied with lithospheric delamination and thinning. The hot zone leads to formation of partial melts sourced from residual water-rich melts from crystallization of the basalt sills and from former crustal rocks (Annen et al., 2006), i.e. the Paleozoic-Mesozoic-Cretaceous metamorphic rocks and the products of the first episode of the Late Cretaceous magmatism in the CACC. Low viscosity leads to adiabatic rise of these hybrid melts of mainly dioritic composition to the shallow levels of crust where they pond and crystallize (Annen et al., 2006; Kemp et al., 2007) (Fig. 9b). Monzonites of similar age from other parts of the CACC have been interpreted as shallow level intrusions (e.g., Whitney et al., 2003; Boztug et al., 2009a; Lefebvre et al., 2011). Therefore, evolution of a shallow magma chamber as a source of monzonitic rocks could be suggested (Fig. 9b). The finer grain size of the SMS also implies shallow emplacement of this stock. The hybrid melts resorb pre-existing residual crystals, including zircons, and incorporate country rock xenoliths on their way through the thickened continental crust (Annen et al., 2006). There is continuous granitic magmatism between the collisional period and the second phase of granitic magmatism in the CACC (Köksal et al., 2012), so it is plausible to also expect entraining of partly solidified crustal materials. Episodic injection of hybrid magmas derived from the hot zone (Fig. 9b) via feeder dykes may have triggered the multiple resorption events recorded in the zircon crystals. Extension in the central Anatolian crust due to the postcollisional uplift may have produced such rheologically weak zones of melt migration. The chief component within the resulting granitoid, therefore, is the pre-existing crustal component. Accordingly, while the SMS has I-type granitoid petrography and geochemistry, it shows a predominantly crustal signature in the isotopic data. The SMS and the other monzonitic rocks in central Anatolia, possibly within most of the Alpine realm, represent the latest stages of orogenic activity (e.g., Köksal et al., 2004), which is followed by post-collisional extension (Fig. 9b). Alkaline igneous rocks (e.g., Köksal et al., 2001; Alpaslan et al., 2004, 2006) are the products of extensional period in the region. Consequently, understanding the petrological characteristics of these monzonitic rocks besides their similarities or differences from the preceding and subsequent igneous rocks is very important for developing a model for the complete geodynamic evolution of the region.

6. Conclusions The monzonitic rocks of ca. 75 Ma age represent the latest periods of the Alpine orogeny in central Anatolia (e.g., Köksal et al., 2004, 2012). Their enriched trace element and isotopic nature (e.g., Ilbeyli, 2005; Köksal and Göncüoglu, 2008) cannot be fully explained solely by magma mixing and/or AFC processes. The

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monzonitic and quartz-monzonitic intrusive rocks in the CACC commonly reveal significant crustal signature in their whole-rock isotope (e.g., Ilbeyli et al., 2004; Köksal and Göncüoglu, 2008) and zircon Lu–Hf isotope data (Köksal et al., 2012). Consequently, our suggestion is that the monzonites in the Satansarı and other areas in the CACC evolved in a post-collisional tectonic setting by partial melting of pre-existing lower and middle crustal rocks of either meta-sedimentary or igneous origin. The hybrid melts generated in the hot zone within the deep crust carried the mantle component to the middle to upper crust, but the major component of the SMS magma is crust, as determined by Sr and Nd wholerock isotope and zircon Lu–Hf data. The integration of the Annen (2006)’s model into the Alpine geodynamic evolution for this case study of the SMS is proposed as a key to the petrogenesis of most of the I-type granitoids in this part of the Alpine-Himalayan orogen. Acknowledgements We wish to thank Radiogenic Isotope Laboratory of Middle East Technical University Central Laboratory for Sr–Nd isotope analyses, Johann Wolfgang Goethe Universität, Institut für Geowissenschaften for zircon Lu–Hf isotope analyses and German Research Centre for Geosciences (GFZ)-Potsdam for SEM and CL imaging. We thank the Scientific and Technical Research Council of Turkey (TUBITAK; project codes 101Y051 and 106Y066) for supporting the whole rock geochemical and LA-ICP-MS U–Pb analyses. We would like to thank Prof. Dr. Ercan Aldanmaz, and two anonymous reviewers for their constructive and valuable reviews, and comments. We acknowledge Prof. Dr. Erdin Bozkurt for editorial handling and patience with the revision. References Akiman, O., Erler, A., Göncüoglu, M.C., Gülec¸, N., Geven, A., Türeli, K., Kadioglu, Y.K., 1993. Geochemical characteristics of granitoids along the western margin of the Central Anatolian Crystalline Complex and their tectonic implications. Geological Journal 28, 371–382. Alpaslan, M., Boztug, D., Frei, R., Temel, A., Kurt, M.A., 2006. Geochemical and Pb–Sr–Nd isotopic composition of the ultrapotassic volcanics from the extension-related C¸amardi-Ulukisla basin, Nigde province, central Anatolia, Turkey. Journal of Asian Earth Science 27, 613–627. Alpaslan, M., Frei, R., Boztug, D., Kurt, M.A., Temel, A., 2004. Geochemical and Pb–Sr–Nd isotopic constraints indicating an enriched-mantle source for Late Cretaceous to Early Tertiary volcanism, central Anatolia, Turkey. International Geology Review 46, 1022–1041. Annen, C., Bluny, J.D., Sparks, R.S.J., 2006. The genesis of intermediate and silicic magmas in deep hot zones. Journal of Petrology 47, 505–539. Ataman, G., 1972. The preliminary study on the radiometric age of Cefalık Dagi that is one of the granitic-granodioiritic bodies in the SW of Ankara. Journal of Hacettepe Fen ve Mühendislik Bilimleri 2, 44–49 (in Turkish). Aydin, N.S., Göncüoglu, M.C., Erler, A., 1998. Latest cretaceous magmatism in the Central Anatolian Crystalline Complex: review of field, petrographic and geochemical features. Turkish Journal of Earth Science 7, 259–268. Boztug, D., 1998. Post-collisional central Anatolian alkaline plutonism, Turkey. Turkish Journal of Earth Science 7, 145–165. Boztug, D., 2000. S-I-A-type intrusive associations: geodynamic of significance of synchronism between metamorphism and magmatism in central Anatolia, Turkey. In: Bozkurt, E., Winchester, J.A., Piper, J.D.A. (Eds.), Tectonics and Magmatism in Turkey and the Surrounding Area. Geol. Soc. Lond. Spec. Publ. 173, pp. 441–458. Boztug, D., Arehart, G.B., 2007. Oxygen and sulfur isotope geochemistry revealing a significant crustal signature in the genesis of the post-collisional granitoids in central Anatolia, Turkey. Journal of Asian Earth Sciences 30, 403–416. Boztug, D., Arehart, G.B., Platevoet, B., Harlavan, Y., Bonin, B., 2007a. High-K, calcalkaline I-type granitoids from the composite Yozgat batholith generated in a post-collisional setting following continent-oceanic island arc collision in central Anatolia, Turkey. Mineralogy and Petrology 91, 191–223. Boztug, D., Güney, O., Heizler, M., Jonckheere, R.C., Tichomirowa, M., Otlu, N., 2009a. 207 Pb–206 Pb, 40 Ar–39 Ar and fission-track geothermochronology quantifying cooling and exhumation history of the Kaman-Kırsehir region intrusions, central Anatolia, Turkey. Turkish Journal of Earth Sciences 18, 85–108. Boztug, D., Harlavan, Y., 2008. K–Ar ages of granitoids unravel the stages of NeoTethyan convergence in the eastern Pontides and central Anatolia, Turkey. International Journal of Earth Sciences 97, 585–599.

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