Figure 1. Granitoids in Turkey and the Balkan Peninsula. Map is modified from Bingöl (1989), Baltatzis et al. (1992) and Ercan and Türkecan (1984).

In spite of copious geological, geochemical, and the isotopical researches in Turkey and the Balkans, there are still problematic features in our understanding of the geological evolution of granitoids rocks in this region. The present study is aimed towards gaining an understanding of the geological and petrological characteristics of the granitoids of Turkey and of the Balkans, and present a complementary data which may form basis for discussion of tectonic evolution. Data from these researches should be evaluated in a standard manner to reach considerable results. Therefore, in this study geochemical data are discussed and correlated depending on the worldwide accepted discrimination schemes.

These discrimination schemes include Irvine and Baragar (1971), Chappel and White (1974) and Pearce et al. (1984)'s classifications. Irvine and Baragar (1971) proposed a discrimination scheme which depends on SiO₂, Na₂O, K₂O, FeO+Fe₂O₃ and MgO contents of igneous rocks. They discriminate igneous rocks as alkali (high Na₂O+K₂O content) and subalkali (low Na₂O+K₂O content) in Na₂O+K₂O versus SiO₂ diagram, then as calc-alkali and tholeiitic in A (Na₂O+K₂O) - F (FeO+Fe₂O₃) - M (MgO) diagram. In AFM diagram of Irvine and Baragar (1971) typical tholeeitic and calc-alkaline trends are also represented.

The second discrimination scheme used in this study is Chappel and White (1974)'s. This scheme depends on the relationships of some major elements (K, Na, Ca, and Al) which reflects the characteristics of the melting source. According to Chappel and White (1974) granitoids formed by the partial melting of the igneous rocks are defined as I-type, that formed by partial melting of sedimentary rocks are defined as S-type granitoids. Addition to Chappel and White (1974) classification, Loiselle and Wones (1979) defined alkaline, anorogenic and anhydrous granitoids as A-type granitoids. A-type granitoids are differed from I-type granitoids depending on their high Na₂O+K₂O, Nb, Ga, Y, Ce, Zn and Zr contents according to Collins et al. (1982).

The third discrimination scheme is Pearce et al. (1984)'s classification. This classification depends on the trace element chemistry. They used Y, Yb, Rb, Ta, Nb and SiO₂ for discriminating the granitoids as VAG (Volcanic Arc Granite), WPG (Within Plate Granite), ORG (Ocean Ridge Granite) and syn- and post-Collisional (syn-COLG and post-COLG) types. Classification of Pearce et al. (1984) is the one presenting the most tectonic approach among these discrimination schemes.

In this study granitoids of Turkey and the Balkans are studied in three different zones as;

1. Eastern Pontides, Eastern and Southeastern Anatolia,

2. Central Anatolia and Central Pontides,

3. Western Anatolia and the Balkans.

Available data are presented depending on the above discrimination schemes, then common characteristics and formation conditions of granitods are discussed and tectonic evolution of the study area is tried to be evaluated.

II.1. GRANITOIDS IN EASTERN PONTIDES, EASTERN AND SOUTHEASTERN ANATOLIA

Granitoids in Eastern Pontides

Yalçınalp (1995) stated that the granitoids cropping out in the Eastern Pontides are of Upper Cretaceous-Eocene in age and generally have quartz diorite-granodiorite-granite and tonalite composition in the northern parts. The granitoid occurences in Gümüşhane, Güzelyayla, İkizdere, Çamlıhemşin, and Balcılı are of I-type with calc-alkaline affinity. In addition they indicate an environment of island arc which is becoming mature (Yalçınalp, 1995).

Köprübaşı (1993) indicate that the Harşit Granitoid has I-type, peraluminous, calc-alkaline features and characterize an island arc environment that is getting mature.

According to Tokel (1995) the Early Alpine granitoid chain which extends from Srednogerie to Lesser Caucasus can be considered as a marker of northern Tethys subduction system. In Pontide, granitoid intrusions and associated dacitic volcanics of Upper Cretaceous age indicate the main calc-alkaline stage of subduction. Major element characteristics, moderate concentrations of LIL, HFS, LREE elements and low HFS/LIL ratios indicate mantle derived magma with subduction-related enrichment. Trace element discrimination diagrams are particularly indicative of normal arc setting for the granitoids (Tokel, 1995). In the Eastern Pontides, except Gümüşhane granitoids, all granitoid outcrops cut the Lower basic comlex of Jurassic age according to Tokel (1995). Multi element chondrite-normalized spectra yields a pattern similar to those of normal subduction related granites reported by Brown et al. (1984). Rb, Rb/Sr, Ba and LREE (La, Ce) values are generally moderate and span the compositional spectrum of I-type volcanic-arc granites (Pearce et al., 1984). The HFS elements Zr, Y and particularly Nb are generally depleted, consequently LIL/HFS ratios are low and similar to those of subduction related I-type granitoids (Brown et al., 1984) indicating the volcanic arc origin on the Rb-(Y+Nb) plot of Pearce et al. (1984) according to Tokel (1995).

Radiometric age determination analysis carried out in the granitoids of the Eastern Pontides, proposed the 62.4± 4.2 my (K/Ar method on hornblende, Moore et al., 1980) for Balcılı, 30, 32 and 47 my (K/Ar method, Çoğulu, 1975) for Çamlıhemşin, 80.7± 0.6 - 39.9± 0.3 my (K/Ar method on mineral+whole rock, Taner, 1977) for İkizdere, 72± 3.6 my (JICA, 1986) for Güzelyayla granitoids.

Granitoids in Eastern and Southeastern Anatolia

There are few granitoid occurrences in Eastern and Southeastern Anatolia, and researches are also limited. In this section general characteristics of the granitoids in Şebinkarahisar, Kösedağ, Murmano, Kızılağıç, Baskil and Afşin are presented.

Oyman et al. (1995) stated that the granitoids of Şebinkarahisar Region (Giresun) show an evolution starting from monzodiorites passes through monzonite and quartz syenite field and reach granite field. The development of granitoids from metaluminous monzodiorite to peraluminous granites with a negative slope is a typical indicator of alumino-cafemic magma. Either VAG, and syn-COLG or WPG characters of these plutons emphasise the geological complexity of the region aaccording to Oyman et al. (1995). They also stated that K/Ar ages of separated orthoclase, biotite and hornblende indicate a Senonien to Upper Paleocene (82.4 to 58.3 Ma), and relatively wide age interval implies that the intrusions were cooled relatively slow after their emplacement.

Boztuğ et al (1994) studied the eastern part of Kösedağ Pluton which is on the northeast of Sivas. According to them, the Upper Eocene Kösedağ Pluton which exhibits mainly syenitic and monzonitic compositions, shows cafemic, metaluminous and silica saturated alkaline character. They suggested that the Kösedağ Pluton derived from a magma which was generated from the upper mantle by the tensional regime in the passive margin towards the final stages of the crustal thickening which results from the collision related to the northward subduction of the northern branch of Neotethys. Crustal contamination must have been also effective according to Boztuğ et al. (1994).

According to Zeck and Ünlü (1987). the Murmano pluton, NNW of the town of Divriği, province of Sivas, has a composite character, ranging in a composition from quartz-syenitic to dioritic. The area is located within the Inner Tauride suture zone, a zone between the Kırşehir block and the East Tauride block, which contains many ophiolite complexes. The ophiolites represent obducted and reworked remnants of ocean floor complexes and thought by many aouthors to indicate plate tectonic suture zones. In the area investigated the ophiolite complex appears dismembered, consisting mainly of serpentinites. It shows thrust contacts towards a formation of marbles. Murmano pluton is intrusive into the serpentinites and possibly also into the marbles. The age of intrusion is given as 110±5 Ma based on the Rb-Sr whole rock isochron (Zeck and Ünlü, 1987).

Asutay (1986), indicated that the Baskil granite contains dioritic, monzonitic and tonalitic kind of magmatic rocks which are mostly observed as transitional. Baskil granite is of calc-alkaline type, trace element distribution is quite regular. Baskil granite is determined as of I-type, and generally rich in hornblende but poor in muscovite and biotite. It shows the features of continental margin magmatism and is an example of systematic differentiation according to Asutay (1986). Asutay (1986) also stated that considering their features and under the light of plate tectonic concept, Baskil magmatics may be said to be a product of continental margin magmatism, and are presumably the products of an oceanic lithosphere existing between Keban microplate and Arabian platform which later on subducted under Keban microplate.

Göncüoğlu (1984) studied the Kızılağıç (Muş) metagranite, and determine the intrusion age as Middle Devonian-Late Permian. According to him, the Kızılağıç granite which is leucogranite in composition intruded into Bitlis metamorphic rocks, and cataclastically metamorphosed by regional metamorphism in Lower Turronian (95 my) following the compression of the continental crust within which it occurs. The emplacement of an ophiolite nappe over the Bitlis metamorphics in Upper Campanian (75 my) caused reheating of the metagranite through burial according to Göncüoğlu (1984).

According to Tarhan (1986), granitoids cutting the sheeted dyke complex (Göksun metaophiolite), the Elbistan ensimatic island arc volcanoclastic sequence of Neocomian age and the Kabaktepe metamorphics (Bitlis/Pötürge metamorphics) of Paleozoic-Lower Triassic age respectively, outcrop around Afşin-Elbistan-Göksun. The granitoids of Afşin Magmatism have not been developed during island arc eruptions. These granitoids according to Tarhan (1986), took place on the collision belts of the subduction zone formed by the N-S directed compressionla forces of Late-Cretaceous started in Lower Cretaceous and increased after Neocomian. Their development is due to the increasing crustal thickness and sinking of the islan arc deposits and its basement which is oceanic crust during Conacian-Upper Santonian. Tarhan (1986) indicated that the granitoids are the differentiated products of anatectic magma. Tarhan (1986) also stated that there are some granitoids don't show any intrusive features and magmatic phase, and they formed by recrystallization from metamorphic rocks, island arc deposits and ophiolites insitu, and granitoids were subjected the low grade regional metamorphism in Upper Santonian-Campanian (Tarhan, 1986).

II.2. GRANITOIDS IN CENTRAL ANATOLIA AND CENTRAL PONTIDES

Granitoids in Central Anatolia

The assemblage of magmatic and metamorphic rocks, cropping out in Central Anatolia, to the east and southeast of Ankara, between Sulakyurt, Yozgat, Sivas, Kayseri, Ulukışla, Aksaray and Şereflikoçhisar, in an area of roughly triangular shape with corners at Sulakyurt, Ulukışla and Sivas, is called Central Anatolian Crsytalline Complex - CACC (Göncüoğlu et al., 1991, 1992, 1993), and the rocks of granitoid composition in this complex are called Central Anatolian Granitoids (Göncüoğlu et al., 1991, 1992). The complex has boundaries with the Ankara and Çorum ophiolitic melanges of Cretaceous age at northwest and north, the Tertiary sediments of the Tuzgölü basin at west and southwest, the Tertiary volcanics at south and southeast, and the Tertiary sediments of the Sivas basin at east. The outcrops of the Central Anatolian Granitoids may be subdivided into three groups as (1) at the western edge, a wide belt with large outcrops, extending from Sulkayurt at north to Aksaray at south, trending NE-SW at north and changing to NW-SE at south, (2) at the eastern edge, a narrow belt with small outcrops in metamorphic rocks, extending from Sivas at north to Ulukışla at south, trending NE-SW, and (3) at the northern edge, outcrops of batholitic dimensions between Yerköy, Yozgat, Sorgun, Sarıkaya, Osmanpaşa, and Şefaatli. The granitoids are (1) generally of monzogranitic, quartz-monzonitic and granodioritic composition and of calcalkaline trend, (2) display characteristics of both I- and S-type granites and may be classified as H-type (hybrid), (3) plot in island arc granitoids, within plate granitoids and collision granitoids fields on trace element discrimination diagrams (Erler and Bayhan, 1995).

The oldest units of the Central Anatolian Crystalline Complex are metamorphic rocks which are overlied by parts of ophiolite and ophiolitic melange, and are cut by granitoids and alkaline plutons (Seymen, 1981). Parts of ophiolite and ophiolitic melange are cut by granitoids and alkaline plutons and observed as roof-pendants within them (Erler et al., 1991; Göncüoğlu et al., 1992). Granitoids are cut by alkali plutonics and dykes (Göncüoğlu et al., 1992). Alkaline plutonics are quartz-syenitic and foid-syenitic in composition while dykes are aplitic textured alkali-feldspar granitic and porphyritic textured leucite syenitic in composition (Göncüoğlu et al., 1993). Felsic volcanics are cover all the units and also observed as dykes cutting other units (Göncüoğlu et al., 1993).

Erler and Göncüoğlu (1996) stated that the granitoids of the Yozgat Batholith which lies along the northern edge of CACC are principally metaluminous monzogranites, of subalkaline-calc-alkaline character, except for the peraluminous leucogranitoids of the Yozgat subunit. They also stated that the granitoids were derived by thickening of the continental crust and related partial melting; the thickening was caused by emplacement of ophiolitic nappes during collisional events. They discriminated the granitoids of the Yozgat Batholith as the post-collisional granitoids depending on the Pearce et al. (1984)'s diagrams.

Tatar and Boztuğ (1997) indicated that the Yozgat Batholith includes both of the syn-collisional S-type, two-mica granites; post-collisional I-type, calc-alkaline monzonitic association and post-collisional, M-type, tholeitiic gabbroic/dioritic association. According to them, the monzonitic association can be subdivided into five units which represent good evidences of the fractional crystallization and magma mingling/mixing processes by means of field, mineralogical-petrographical and geochemical characteristics. In the Akdağmadeni region, based on major and trace element trends Akakışla Granite and rhyodacitic-dacitic Akakışla lava flows are genetically related according to Gençalioğlu Kuşçu (1997).

The Halaçlı monzogranite in Çiçekdağ region characterizes the post-collisional, high-K calc-alkaline, hybrid type magmatism, intrudes the Central Anatolian ophiolite according to Yılmaz and Boztuğ (1998). The Eğrialan Syenite in the Çiçekdağ region on the other hand typically exhibits alkaline composition. The Halaçlı Monzogranite and the Eğrialan Syenite are spatially and temporally considered to be members of post-collisional Central Anatolian plutonism in which they are regarded to belong to the post-colisional, I-type, calc-alkaline association and post-collisional, A-type, alkaline association, respectively (Yılmaz and Boztuğ, 1998).

According to Bayhan (1986), Çelebi Granitoid is in granitic, granidioritic, quartz-monzonitic, quartz-monzodioritic composition and calc-alkaline character, and are divided into two groups as leucocrotic and mesocrotic in character based on their mafic mineral contents.

Tolluoğlu (1993) examined the characteristics of Buzlukdağ Syenitoid and Kötüdağ Volcanite on the north of Kırşehir city in CACC. Buzlukdağ Syenitoid is alkaline in character and consists of quartz syenite, syenite and monzonite. Buzlukdağ Syenitoid is younger than Kötüdağ Volcanite, which indicates the active continental edge volcanism, and Buzlukdağ Syenitoid and Kötüdağ Volcanite are formed from different magmatic sources according to him.

Bayhan (1988), noticed that the syenitoids in the Bayındır-Akpınar area to the northeast of Kaman were formed from different magmas derived from different source materials, and were not fractionated from a single parent magma.

According to Lünel and Akıman (1986), around Hamitköy (Kırşehir) area the syenitic batholith is cut by silica poor microsyenitic dykes containing feldspathoids. They assume that the presence of pseudoleucites as feldspathoids suggests that the source magma is silica poor and volatile rich, and formed at 7 km depth and under 2 kbar pressure.

According to Bayhan (1989), Keskin Pluton is calc-alkaline in character, and formed by the partial melting of the mantle+continental crust source.

According to Bayhan (1987), the Cefalıkdağ and Baranedağ plutons around Kaman (Kırşehir) can be differentiated into subalkaline and alkaline groups of cafemic associations showing meta-aluminous characteristics. The alkaline rocks are of syenitic composition and resemble A-type granitoids, formed by differential partial melting of a source that includes both crust and mantle material. Geven (1995) stated that the Cefalıkdağ granitoid is calcalkaline in character and follows the cafemic trend. According to geochemical data, Cefalıkdağ granitoid has properties of both I- and S-type, and was probably derived from a hybrid magma in which the sialic material is dominant (Geven, 1995). According to Lünel (1985), the Baranedağ Monzonite on the west of Kaman (Kırşehir) is a product of alkaline magmatism, and different compositions were probably developed through crystal differentiation.

Bayhan and Tolluoğlu (1987) determined that the Çayağazı Syenitoid in the northwest of Kırşehir exhibits an alkaline character, and it comprises microcline syenites, felsic dykes and nepheline-bearing syenites. They suggested that the different compositions are formed by partial melting of different source materials.

According to Tarhan (1987), the granitoids in Central Anatolia were derived from the metamorphic rocks by partial melting and show lateral and vertical transition into them. Both the oceanic crust, and volcano-sedimentary units which had been deposited in an extensional forearc basin, developed over the oceanic crust were subjected to high P/T and low P/T metamorphisms, respectively, giving rise to formation of Central Anatolian Granitoids during the time interval ranging from Campanian to Upper Maastrichtian.

Bayhan (1990) has studied the geochemistry of three different intrusions in the Ortaköy (Aksaray) area. First of these intrusions is S-type, and derived from the magma which is formed due to the partial melting of the crustal material. Second and third intrusions are I - type, and derived from hibridic magma which is formed due to the partial melting of crust and mantle materials.

Erler et al. (1991) interpreted the igneous rocks cropping out around Kaman (Kırşehir) area as the products of a magmatic arc and classified them as I - type igneous rocks. The granitoids of Yozgat area, however, are developed by partial melting of the pre-existing metamorphic rocks during the collision of Pontide and Tauride Belts and they belong to S-type granitoids of Chappel and White (1974).

Kadıoğlu (1991), studied the Ağaçören Granitoid which is exposed on the southwest of Kırşehir. According to him, the results of major and Rb/Sr analyses suggest a crustal source for granitoids in the region.

Göncüoğlu and Türeli (1994) stated that the Ekecidağ Granitoid, consisting of genetically related granodiorite-monzogranite, microgranite, porphyritic granite, leucogranite and aplite-granite subtypes, is calc-alkaline in character. The main phase, Borucu subtype, is metaaluminous, whereas the late products are typically peraluminous, corresponding to typical trends of alumina-cafemic type associations. Trace element discrimination diagrams for the tectonic interpretation of Ekecikdağ granitoid suggest post-collision type of origin. Nd and Sr isotope data, as well as geochemical considerations, reveal that Ekecikdağ granitoid was essentially derived from continental crust with minor contamination from lower crust/mantle. Regional geological constraints related to the closure of the İzmir-Ankara branch of Neotethys suggest that the collision of CACC with the Sakarya Continent during Early Upper Cretaceous could be the main triggering for the generation of Ekecikdağ granitoid (Göncüoğlu and Türeli, 1994).

Terlemez quartz monzonite is a calc-alkaline, metaluminous intrusion, typically displays moderately developed negative Ba- and Nb- anomalies, LREE enrichment relative to HREE without any significant Eu-, Sr-and Ti-anomalies, and cuts the ophiolites (Yalınız et al., 1998). Terlemez quartz monzonite was classified as H-type which requires significant input from mantle-derived mafic magma. The intrusion is neither VAG nor syn-COLG, it rather represents advanced stage of the post-collisional magmatism of the CACC according to Yalınız et al. (1998).

Aydın (1985) worked in the Gümüşkent (Nevşehir) Town, and described alkaline plutonic rocks in the area. According to her, in the area granitoids and syenitoids at a nearly shallow depth intrude the metamorphic rocks such as marbles, gneissic rocks and amphibolites, and the volcanic rock types in the area were created from almost the same magma.

Lulu (1993) described that in the Gülşehir (Nevşehir) area, there are Paleozoic-Mesozoic Central Anatolian Metamorphic rocks, Cenomanian Üçkapılı Granodiorite which intruded the metamorphics, and Tertiary Elmadere Olistostrome and the younger cover units. According to him, the crystalline rocks have thrust fault contact with the Elmadere Olistostrome and normal fault contacts with cover units.

Göncüoğlu et al. (1993), in discussing the geodynamic setting of Central Anatolian Plutonics, suggested that late-stage alkaline magmatism in CACC (which is mainly represented by syenitoids) should be interpreted as post-collisional and related to thermal relaxation and extension of the thickened crust. According to Göncüoğlu et al. (1997), the İdiş Dağı Syenitoids are a late-stage member of the Central Anatolian Plutonics. They intrude the Central Anatolian Metamorphic basement and were subsequently cut by feldspathoid dykes of the Karahıdır Volcanics. They are unconformably overlain by the latest Cretaceous - early Paleocene Göynük Volcaniclastic Olistostrome. Their emplacement age is assumed to be early Maastrichtian. Discrimination of their tectonic environment based on chemical data indicates that the İdiş Dağı Syenitoids have the character of within-plate A₂-type post-collisional granitoids (Eby, 1992); which includes post-collisional granitoids emplaced after a long period of high heat flow and granitic magmatism. Interpretation of spidergram patterns confirm that the İdiş Dağı Syenitoids are very similar to post-collisional granitoids produced by crustal anatexis. The late orogenic alkaline plutonic rocks of the CACC are thus collectively assumed to be the melt products of a post-collisional uplift and extension event which followed crustal thickening related to the closure of the İzmir-Ankara-Erzincan oceanic strand of Neotethys by Göncüoğlu et al. (1997).

Özkan (1987) studied the alkaline rocks in the Hayriye (Kayseri) area, suggested that the Atdere foid syenite may have formed by partial melting of the residue after the formation of I-type granitoids. In a complementary work, Özkan and Erkan (1994) suggested that the foid syenite probably derived from an originally undersaturated and potassic melt which then fractionated towards a Na-rich sodalite-nepheline syenitic composition.

According to Göncüoğlu (1986) and Göncüoğlu et al. (1991), the Üçkapılı Granitoid in Niğde area, cuts whole Niğde Metamorphics. Göncüoğlu et al. (1991) suggested that the intrusion of granite occurred at a late stage of metamorphism, and it is post-tectonic. Üçkapılı Granitoid is peralkaline in composition and the presence of sillimanite and garnet is an indication of S-type intrusion, and formed by the partial melting of shortened and thickened continental crust.. The intrusion age of the granitoid is Cenomanian and this is approximately the same age for the main metamorphism phase. Göncüoğlu et al. (1991) interpret the Campanian age found by Göncüoğlu (1986) in a different way that during the emplacement of ophiolite, cataclastic deformation affected the radiometric Rb/Sr age of the system, but not radiometric age of whole rock.

According to Çevikbaş et al (1995), Horoz Pluton in the Ulukışla (Niğde) area, comprises medium grained hornblende-biotite granodiorites and fine-medium grained biotite granodiorites which intrude the Permian Bolkardağı Marble. They stated that the Horoz Pluton is the product of the equilibrated hybrid system, and constitutes a homogenous group in geochemistry indicating, alumino-cafemic, felsic I-type and mostly magnesian characters. They also stated that the Horoz Pluton is a post-collisional calc-alkaline pluton Upper Cretaceous-Paleocene in age.

The age of the plutonic rocks in the CACC is another important issue that is in contention. Ayan (1963) made the first geochronological study in the CACC and proposed that the age of intrusion of Baranedağ monzonitic granite was 54 Ma (total Pb method). Later, Ataman (1972) calculated a 71±1 Ma isochron age for the Cefalıkdağ granitic rocks (Rb/Sr method). This age was assumed by Erkan and Ataman (1981), who used K/Ar method, to be an intrusion/cooling age for these intrusive rocks. Göncüoğlu (1986), using both Rb/Sr and K/Ar methods, determined the crystallization age of the Üçkapılı Granitoid to be 95 ± 11 Ma, with a cooling age of 77.8 ± 1.2 Ma. Kuruç (1990) calculated an isochron age of 85.1 ± 3.6 Ma (Rb/Sr whole rock method) for syenitic rocks in the Kaman region, whereas Güleç (1994) obtained an intrusion age of the Ağaçören granitoid of 110 ± 14 Ma (Rb/Sr method).

There are also granitoids besides those in CACC, in Central Anatolia. Among these Orhaniye Syenite which is Mid-Paleocene in age and lkaline to shosonitic character defined as volcanic arc granitoid by Tokay et al. (1988). According to Kadıoğlu (1994), the Kaymaz granite located approximately in the 35 km NW of Sivrihisar (Eskişehir) is biotite granite in composition, and has been mixed with a more basic magma before the crystallization. Beypazarı granites are calc-alkaline in character, and the initial ⁸⁷Sr^/88Sr ratios, ranging between 0.706 and 0.707 indicate that these granitoids were formed by anatexis of older continental crust, and are shallowly intruded to the region probably during Upper Cretaceous time according to Helvacı and Bozkurt (1994). Ataman (1973c) determined the Rb/Sr age for Mihalıççık granitoids as 72 - 77.5 my for biotite samples, Çoğulu et al. (1965) on the other hand determined U+Th/Pb ages for zircons in Mihalıççık granitoid varying from 33-151 my. Çoğulu and Krummenacher (1967) determined 46 and 71 my Rb/Sr (biotite) ages for Sivrihisar Granodiorite.

Granitoids in Central Pontides

Boztuğ (1992), stated that in the Küre region the discrete plutonic bodies from the Kastamonu granitoid belt, are called Karaman, Sallamadağ and Battallar plutons. Sarpunçay pluton are made up of altered gabbro and quartz-diorite and is defined as a part of Küre ophiolite. Sarpunçay pluton represents a tholeiitic and ocean ridge magmatism. The Karaman and Sallamadağ plutons also determine a single assemblage derived from an aluminocafemic magma showing partly I-type, partly S-type origin. The Battallar pluton and vein rocks also form another assocciation solidified from a cafemic and I-type magma (Boztuğ, 1992).

Boztuğ and Yılmaz (1983) studied the Büyükçay-Elmalıçay granitoid outcropped on the northern part of the Daday-Devrekani massif. According to them, the Büyükçay-Elmalıçay granitoid established which has been intruded during Dogger, formed intensive contact metamorphic auroles in the Börümce formation of Liassic age. They suggested that the intrusion formed by the crystal differentiation from a subalkali magma of granite-granodiorite character. The differentiation developed from east (from Büyükçay outcrop) to west (to Elmalıçay outcrop). This subalkali magma has been derived by the partial melting of a metasedimentary source material by means of ultrametamorphism in the deeper parts of earth's crust. However, it received the material from a magma derived from the igneous source material. But there was a contamination by the later autohydrothermal activation processes which caused enrichment in alkali content of the Büyükçay-Elmalıçay granitoid (Boztuğ and Yılmaz, 1983).

III. GRANITOIDS IN WESTERN ANATOLIA AND THE BALKANS

Granitoids in Western Anatolia

The granites of Western Anatolia are numerous, their outcrops ranging in size from a few square kilometers to hundreds of square kilometers. They are geographically situated along many directions, roughly east-west in the north of the region and northeast-soutwest in the northwest. Granitoids in Western Anatolia are mainly calc-alkaline and exhibit generally the volcanic arc character (Bingöl et al., 1982).North of the North Anatolian Fault the granitic intrusions are isotopically dated as Paleozoic in age (e.g. Bürküt, 1966). In the Northern part of Istranca massif Aydın (1974) has described and also dated pre-Triassic metamorphic granites (the Kırklareli metagranites) together with Upper Cretaceous granitic, gabbroic, monzonitic and syenitic intrusions.

Ages of granitic intrusions south of North Anatolian Fault are spread between the Paleozoic and the Tertiary. Bingöl et al. (1982) stated that the granitic massifs of northwestern Anatolia can be classified into three families on the basis of age and petrology:

a) North of the North Anatolian Fault Paleozoic to Late Cretaceous granites are found,

b) Between the North Anatolian Fault and the Eskişehir-Bursa-Edremit line the granites are of pre-Liassic age,

c) South of Eskişehir-Bursa-Edremit line the granites give Miocene radiometric ages. Moreover, it is possible to subdivide the latter family into three groups on the basis of K₂O content: for a fixed SiO2 content the amount of K₂O in these granites increases from north to south according to Bingöl et al. (1982). Bingöl et al. (1982) also stated that on a regional scale the relations between the domains separated by the Eskişehir -Bursa-Edremit line have been reconsidered: the southern domain is thckened by the reverse faults dipping north as a result of collision or by down plunging under itself following the subduction northwards.

Birkle and Satır (1995), on the other hand stated that the Biga Peninsula experienced a sudden change from a compressional tectonic regime, dominated by NW- oriented subduction of African microplates below the the southern edge of the Eurasian Plate to an extensional oriented regime. According to them, slighlty alkaline affinities of of Kestanbol indicate the final stage of the collision processes. A combination of the geochemical and geochronological data from different igneous complexes on the Biga Peninsula indicate an Early Miocene age for this event. Kestanbol is close in composition to Aegean sea sediments and to some volcanic rocks from Bergama, and Karaköy implies higher portions of mantle derived material with lower crustal components than in the case of Kestanbol (Birkle and Satır, 1995).

According to Üşümezsoy (1989), Istranca Batholith is consisted of the multiple and composite pluton of Late Cretaceous age emplaced in the NE-SW trnding extensional zone within the Istranca metamorphic belt of Triassic-Jurassic age.

The intrusions in southern part (mainly around Bodrum) are correlable with the intrusions in the Cycladic islands, in age and character. Also intrusions in the Istranca massif are correlable with those in the neighboring regions.

Granitoids in the Balkans

Üşümezsoy (1989) suggested that the intrusions in the area comprising Banat-Timok-Srednogora-Istranca are emplaced either within continental margin arc, intra arc basin or back arc basin consequence of the subduction of the Vardar Ocean beneath the Rhodope Belt, or witihn the rift zone opened above the suture belt extending between Moesian platform and Thrace block. According to him, formers suggestions on the developing of this Banat-Timok-Srednogora-Istranca volcano-plutonic belt (S VP B) are agreed on the subduction of the Vardar ocean beneath the Rhodope belt during the Late Cretaceous time whereas the Vardar ocean is considered that was terminally closed in the latest Jurassic time. Disaapearing of the Vardar ocean by the Late Jurassic collision exludes the former suggestions oceanic domain existed between Moesian platform and Rhodope fragment was closed in the Albian time. Post-collisional subduction of oceanic crust and lower continental crust of the Moesian platform beneath the Phodope belt resulted opening of the S VP B rift within the overriding Rhodope block coeval with the northword transporting of the thrust sheet over the northward transporting of the thrust sheet over the underriding Moesian platform. Upwelling of the mantle derived melts underplating beneath the NE-SW strecthed and thinned Rhodope block resulted the generation of the three modal alkaline, basic and acidic volcanic by the partial melting of the crust and asthenospheric segregation. Batholitic magmas which tonalitic and granodioritic, granitic and monzonitic composition were generated by the partial melting of the respectively undepleted lower crustal amphibolites, middle and upper crustal gneissic rocks and depleted lower crustal or subcontinental mantle granulite and eclogites (Üşümezsoy, 1989).

According Baltatzis et al. (1992), various granitic intrusions of Jurassic to Eocene age occur in Greece, especially in Macedonia, Thrace and in some of the islands the Aegean Sea. The Hellenides along with the Dinarides form the Dinaric branch of the Alpine belt. The Hellenides are described in terms of ten "isopic" zones flanked by two others, one to the south-west and the other to the north-east. The term "isopic" zone has been widely used to refer to each successive zone with a distinctive facies succession. Mountrakis (1983 in Baltatzis et al., 1992) distinguished the following isopic zones from east to west:

A. Rhodope massif (RM)

B. Serbomacedonian massif (SMM)

C. Perirhodopic zone (PRZ)

D. Axios (Vardar) zone (AZ)

E. Pelagonian zone (PZ)

F. Attico-Cycladic zone (ACZ)

G. Subpelagonian zone (SPZ)

H. Parnassos-Giona zone (PGZ)

I. Pindos zone (PNZ)

J. Gavrovo-Tripolis zone (GTZ)

K. Ionian zone (IZ)

L. Paxos zone (PXZ).

According to Brunn (1956 in Baltatzis et al., 1992) the above A-G isopic zones, forming the eastern part of the Hellenides, comprise the internal belts, while H-L zones are external ones. It is considered that the internal zones have been formed under "inner arc" geotectonic conditions while the external zones have been formed under "outer arc" geotectonic conditions. Baltatzis et al. (1992) indicated that the major granitic intrusions occur in the internal zones. Baltatzis et al. (1992) stated that the granitoids in Arnea and Sochos are S-type while the others are the I-type. But they proposed that the all granitoids in these zones have the geochemical characteristics of granites generated in a volcanic arc environment, except Arnea granite pluton which plot in WPG field in Pearce et al. (1984) discrimination diagram, due to their high Y and slightly high Nb contents that can be explained by the source material characteristics. The I-type granites from four of the zones, namely the Rhodope Massif, the Serbomacedonian Massif, the Perirhodope Zone and the Atttico-cycladic Zone show some systematic differences in their geochemistry. In particular, the Rb, Y, Nb, K and Ti contents increase in the sequence PRZ, SMM, RM and ACZ. The PRZ granites are of Jurassic age, those of the SMM and RM are Eocene to Oligocene and the ACZ ones are Miocene. The differences between zones are attributed to a combination of differences in partial melting and high-pressure fractionation processes. Geochemical differences within zones are explained by variable degrees of amphibole and apatite fractionation and accumulation (Baltatzis et al., 1992).

Since there are not enough detailed studies further correlation of the granitoid occurences through the whole Balkan Peninsula, the geological and tectonic features remain their complexity.
 
 

IV. DISCUSSION AND CONCLUSIONS

There are numerous researches on granitoids in Turkey and the Balkan Peninsula. Geological, geochemical and isotopical features of granitoids reflect the characteristics of the source region, formation conditions, and the tectonic seting of the region. Therefore right evaluation of the present data on granitoids may help to solve some tectonic problems.

In the Eastern Pontides granitoids are mainly I-type and calc-alkaline and exhibit characteristics of the volcanic arc granitoids. Tokel (1995) stated that the Northern Tethys subduction system can be traced as a continuous zone from Carpathians eastwards through the Balkans, Pontides, Lesser Caucasus towards Kohistan. The Eastern Pontides exhibit exceptional natural cross sections through a portion of the composite arc system. Tokel also indicated that the The Early Alpine granitoid chain which has normal arc setting characteristics is a marker of northern Tethys subduction system.

The most problematic region of present study is the Central Anatolia. In Central Anatolia, there are post-collisional granitoids besides arc ones. I-type and calc-alkaline granitoids are dominant, although S- and rarely A-type and alkaline to peralkaline suites are present in Central Anatolia.

Tüysüz et al. (1995) ascribed the formation of granitoids to the Late Cretaceous-Paleocene southward subduction of the İzmir-Ankara oceanic plate beneath the CACC and related arc-type magmatism.

Göncüoğlu et al. (1991, 1992, 1993, 1997), Göncüoğlu and Türeli (1994), Erler and Göncüoğlu (1996) on the other hand defined the Central Anatolian Granitoids as post-collisional type formed due to the crustal thickening and following crustal extension after the ophiolite emplacement on to the units of CACC. According to Göncüoğlu et al. (1993) the CACC forms the northern edge of the Tauride-Anatolide Platform directly opposite to the İzmir-Ankara-Erzincan (IAE) ocean branch during the Mesozoic. The oceanic strand was consumed, not only by early subduction beneath the Pontides, but also along an intraoceanic subduction zone at a later stage (Göncüoğlu et al., 1991). The emplacement of ophiolites formed above this zone (Göncüoğlu and Türeli, 1993; Yalınız et al, 1994, 1996) onto the platformal units and subsequent closure of the IAE ocean eventually lead to the collision of the CACC with an ensimatic arc to the north. This event caused crustal thickening, HT/LP regional metamorphism and the formation of collision related S- and I-type granitoids in CACC.

Kadıoğlu et al. (1998) stated that the gabbroic rocks in the Ağaçören area are not parts of the ophiolitic complex but rather indicate an intrusion coeval with the Ağaçören Granitoid. They interpret the gabbroic rocks have sinuous contacts with the Ağaçören Granitoid and displaying a gradual change in composition and texture. They indicate that the gabbroic rocks in Ağaçören Granitoid are not allochthonous ophiolitic bodies representing the remnants of Neotethyan ocean floor.

According to Boztuğ (1998), the metamorphism and magmatism in this crystalline body show an apparent synchronisation in Upper Cretaceous as revealed by radiometric datations carried out by various authors in different parts of Central Anatolia. Therefore, the metamorphism in Central Anatolia can be suggested to generated by an inverted metamorphism induced by by Anatolide-Pontide collision on the basis of an apparent metamorphism-magmatism synchronization in Upper Creatceous. On the other hand, collision related intrusives within this crystalline body represent some differences in geological setting, mineralogical-chemical composition and associated ore deposits. Boztuğ (1998) stated that the magmatism in CACC can be suggested to be induced in the passive margin of Anatolide by various magmatic pulses such as syn-collisional peraluminous, post-collisonal calcalkaline hybride and post-collisional within-plate episodes.

In Western Turkey calc-alkaline granitoids are again become dominant. They are mainly arc type granitoids. In the Balkans especially in Greece, I-type and S-type, and volcanic arc and post-collisional granitoid types occur. Turkey and the Balkans have some similarities and differences in tectonic setting. The continuation of young magmatism is detectable from Western Turkey to Cycladic islands. But the zones of older magmatism show more complexity.

The principal problems in evaluating the granitoids in Turkey and the Balkan Peninsula are the age and the conditions of formation, and tectonic setting. Although there are some detailed studies including geological, geochemical, isotopical analyses, there is no available standard data to evaluate all granitoids in the study area. Also there is no enough researches to correlate the characteristics of the granitoids of Anatolia and of the Balkan Peninsula. The researches vital to the solution of the problems maybe detailed mapping within outcrop areas of granitoids, systematic sampling, petrographic studies, geochemical, geochronological and isotope geological analysis, publication of similar studies on the other units of the Turkey and the Balkans and deciphering the relationships between all the units, and the investigation of the contact relationships of the granitoids with the other units of the study area.

REFERENCES