Mineral Res. Exp., Bull., 133, 1-29, 2006

A CRITICAL REVIEW OF THE ANATOLIAN GEOLOGY: A DIALECTIC TO SUTURES AND EVOLUTION OF THE ANATOLIAN TETHYS AND NEOTETHYS

Metin ÞENGÜN*

ABSTRACT.- A progressively improving hypothesis of evolution for the Anatolian Tethys and Neotethys will be presented in this paper. The Tethyan, the Western (Bursa-Ýzmir-Antalya zone) and the southern Neotethyan sutures will be substantiated after a discussion on the controversial aspects of the Anatolian geology. The initia- tion of the Tethys in Cambrian is supported on the basis of continous Palaeozoic sedimentation on north-facing Gondwanian and south-facing Eurasian platforms. A thin continental sliver, the Apula-Anatolia, started to rift off northern Gondwana in the Early Triassic coevally with the onset of the northward Tethyan subduction. The mar- ginal ophiolites have obducted onto the Pontian active margin by the Middle Triassic as the consequence of the dextral rotation of Western Pontides. The compressional and dilatational fields have shifted oceanward due to a recess (?) of the subduction zone. The positive area covering most of the central and northern Sakarya has col- lapsed progressively and has been onlapped peripherically from the Liassic onwards. The Anatolian microconti- nent detached off Africa in the Upper Triassic-Liassic and drifted northward during the Jurassic and the Cretaceous and collided incipiently with the Eurasian margin (Pontides) in the Upper Cretaceous. Unsubducted pockets of ocean floor have closed with consequent syn-collisional magmas in the Paleogene. The Salt Lake pocket, the East Anatolia and the Western Neotethys, the Intra-Gondwanian rift separating the Anatolia from Apulia-Greece, have survived until the Late Miocene.

Key words: Controversial aspects of the Anatolian geology; sutures of Anatolia; geological and geophysical con- straints; possible evolutionary frames; geologic evolution.

INTRODUCTION Bursa-Antalya zone has later been designated as the Intra-Gondwanian zone separating the Ae- The stratigraphy of Anatolia is characterized gean plate from the Anatolian. This has been the by many Paleozoic - Mesozoic sections overlying most important revision on the sutures of unconformably overlying the Precambrian base- Anatolia. ment of the Pangea. Had there been no Alpine events, Anatolia would present sceneries similar The Tethyan frames, based essentially on the to the grand canyon of USA. There are many Atlantic Ocean data (Smith, 1971; Pitmann and sections implying such a stratigraphy. Southern Talwani, 1972 and Dewey et al., 1973), agree on Menderes Massif, Central Taurids (Cambrian- the theory that slivers of continental crust have Miocene) and Bitlis yield examples of this stratig- rifted off northern Gondwana and drifted north to raphy. collide with Eurasia (Stocklin, 1974, 1977; Ada- mia et al., 1977; Biju-Duval et al., 1977 and Der- The sutures of Anatolia, based essentially on the teachings of Brinkmann (1972) and of many court et al., 1986). The essence of this theory is others, has first been published by Sengun et al applicable also to the Anatolian segment of the (1990), when the East Anatolia was suggested to Tethyan belt in agreement and in liaison with the be a continental fragment, in the sense that it is neighbouring areas (Stocklin, 1977 and Biju- not an accretionary prism, and the Tethyan su- Duval et al., 1977). The post-Liassic part of the ture was suggested to tie to the Sevan-Akerra evolutionary frame presented in this paper is al- considering the Munzur-Taurus connection. The most world-wide accepted.

* The author unfortunately has passed away during the processing of the manuscript. The corrections and the changes were carried out by his colleagues and very close friends who know him very well in a way to be con- sistent with his thoughts and beliefs . The author has completed his work span in MTA and performed invalu- able scientific performances in Geology. We remember him with a great mercy. 2 Metin ÞENGÜN

On the other hand, the very diverse disputes the origin of 'Antalya nappes'. It has been sug- on Anatolia will be discussed in this paper gested that the Eastern Mediterranean has not towards a plate tectonic model for the Anatolian rifted until the Cretaceous and the 'Antalya nap- Tethys/Neotethys by mounting the discussed evi- pes' have originated from northern Anatolia, the dence on a basic and generalised frame of evo- northern margin of the Gondwanaland (Ricou et lution. Unfortunately, what has been published al., 1974-1986; Dercourt et al., 1986). This theo- about the Anatolian geology is an intermingled ry is in debate with the theory of Triassic age of and living bundle of imaginary hypotheses. rifting of the Eastern Mediterranean and southern Many quests have naturally arisen on the exist- origin of Antalya nappes (Robertson and Wood- ing theories/interpretations with consequential cock, 1981; Robertson and Dixon, 1984; Pois- revisions and corrections as the field evidence son, 1984; Özgül, 1984 and Yýlmaz, 1984). St- has progressed. Some of the controversies will ructural and stratigraphic evidence is in full com- be discussed in this paper, hoping that a step will pliance with the Early Triassic rifting and the be taken towards the final solutions. author is in full agreement with those who defend the Antalya complex to consist of Tertiary imbri- A CRITICAL REVIEW OF MAJOR DISPUTES cations of the continental margin and the margin- al Neotethyan ocean floor of the Antalya region. The Eastern Mediterranean and the Tethyan disputes will be discussed below with some of The Anatolia fragment must have rifted off the entailed arguments, which are crucially relat- northern Gondwana harmoniously with what has ed to Tethyan/Neotethyan evolution of Anatolia. been suggested by Stocklin (1974, 1977) and Biju-Duval et al (1977) respectively for Central The Eastern Mediterranean dispute Iran and Apulia-Greece. It is tied to Central Iran in the east and bounded by the Menderes massif The main controversial issues have been the in the west while the Karaburun-Biga must be the age of rifting of the Eastern Mediterranean and eastern margin of Apulia-Greece. The Western

Figure 1- Sutures of Anatolia (Revised after Þengün et al,1990). ANATOLIAN SUTURE BELTS 3

Neotethys or the Bursa-Ýzmir-Antalya zone com- 1984; Özgül, 1984) disputing the northern origin prises Triassic sediments as the base of a Meso- defended by Ricou et al., (1974-1986). zoic sequence (the Antalya nappes). This shows that the rifting is not directional but scattered in The Alanya debate northern Gondwana with the implication that initi- ation of rifting of Apulia and Anatolia is contem- Özgül's (1976) structural analysis, a widely paraneous although the detachment may be not. accepted tectonic model for the Taurids, defends The rifting of the southern Neotethys has been allochtonous entities or tectono-stratigraphic u- ascribed to the drag caused by the northward nits that are piled up on one another. These are diving Tethys (Robertson, 1990). This is agree- Geyikdað, Bozkýr, Bolkardað, Antalya, Alanya able and seems an effective factor in addition to and Aladað. The structural setting of the Alanya the essential control, rifting of the Atlantic. with respect to the Antalya unit will be discussed below for description of the ongoing dispute. The Antalya complex is the prototype of An- Evidence will be presented to defend that the talya nappes and is well studied (Lefevre, 1968; Antalya and Alanya units are in situ, versus Robertson and Woodcock, 1981; Poisson, 1984; floatation of Alanya on an also allochtonous Özgül, 1984 and Yýlmaz, 1984). Unfortunately, Antalya (Ricou et al., 1974; Özgül, 1976-1984; rifting margins of northern Gondwana have also Ulu, 1983). A northeast section (Figure 2) from been defined as Antalya nappes as in the cases Demirtaþ to the flyschcorridore (the Antalya unit) of the central and eastern Alanya massif, Biga, is described below essentially through the Karaburun-Ýzmir or Kütahya. The Mesozoic fi- author's window with occasional reference to and ning-upward sediments of these areas are un- discussion on the views of the contraveners. conformable/gradational on the Palaeozoic, with the implication that a continental crust bases Carbonates and slates, in the southern part of them. The Palaeozoic sequences of the rifting the section (Point 1 in Figure 2), dated respecti- margins are similar to that elsewhere in the vely as Cambrian and Ordovician (Özturk et al., Taurids, while the Mesozoic sections reflect 1995), constitute the overturned southern flank of unstable conditions caused by the neighbouring an asymetric anticline in the core of which gar- rifting. The Lower Palaeozoic is represented by netiferous micaschists are exposed. The micas- an alternating series of carbonates, quartzites chist has the following generalised paragenesis: and pelites while thick carbonate sections are Quartz+Muscovite+Garnet+Mg-chlorite+Albite/ encountered in the Devonian and the Permo- Oligoclase±Biotite. The physical conditions of al- Carboniferous. There is generally a sharp facies mandine-amphibolite facies or of the medium change into turbiditic sediments in Schytian grade (Winkler, 1974) implied by this paragene- along rifting margins. The Antalya nappes are sis are certainly incomparable with those of the characterised by a flyschoid sequence with inter- overlying incipiently deformed Palaeozoic rocks mittent basic volcanism during Carnian-Norian that are exposed in rest of the section. The (Antalya and Karaburun) followed by deep ma- Cambrian carbonates have been locally sheared rine carbonates of Jurassic-Cretaceous age. out in the northern flank, whereupon the garnetif- erous micaschist has come into tectonic contact The allochtoneity of the Antalya nappes, inc- with the Ordovician-Silurian shales/slates. The luding the rifting margins of the Neotethys, has sheared contact zone between the micaschist almost been unquestioned and the discussions and the overlying shales/slates displays a confor- have been focused on where they had come mable fabric. However, the compositional chan- from (Brunn et al., 1975). Southern origins have ge is very sharp, implying the impossibility of a been defended for Alanya and Antalya (Poisson, gradation in physical conditions of metamor- 4 Metin ÞENGÜN

Figure 2- A tentative sketch map and cross-section from Alanya to the Hadim nappe via the flysch corridore, to show the relations between the tectonic (?) units of Alanya and Antalya. The westernmost Alanya, until the town of Gündoðmuþ, is the stratigraphicand the structural continuation of the Antalya complex, the present morphology of the Antalya gulf being the result of the 30° sinistral rotation of the Beydaðlarý (Robertson, 1990) and dextral rotation (?) of the eastern side. phism. Therefore, an unconformity, in analogy to acceptable for eclogites. It is customary to define other Precambrian basements, seems to be the these rocks as garnetiferous amphibolites. plausible relation. However, the more important question is The micaschist comprises lenses of amphibo- whether or not the micaschist-amphibolite as- lites consisting essentially of pyroxene, amphi- semblage is part of a basement underlying un- bole and pyrope-almandine rich garnets. Block conformably a Palaeozoic-Mesozoic sequence. formation is presumably due to the extreme An analysis is attempted below on the relations incompetency of the micaschist. The amphibolite of pseudo-tectonic units, Alanya and Antalya, in lenses have been interpreted as alpine eclogites search of an answer to this question. on the basis of the omphacitic (very close to diopsitic augite) composition (Okay and Özgül, A vertical fault on the Demirtaþ road juxtapos- 1982) of the pyroxene. However, lenses with the es the Triassic sandstones of the Antalya unit to assemblage of pyroxene+amphibole+almandine the Lower Palaeozoic rocks of the Alanya unit of are well known and commonly encountered in Özgül (1976), a few km northeast of the micas- the Precambrian basements of Anatolia. They chists (point 2 in Figure 2). This fault has been are also peculiar to Eurasian-Gondwanian Pre- evaluated as the base of the Alanya unit of Özgül cambrian basements in Europe as well as Africa (1976), while it is a normal (vertical) fault of minor or Arabia. These rocks are hydrous and have a importance to the author. The downthrow is not high plagioclase-amphibole content, which is not more than a few meters. The Ordovician shales- ANATOLIAN SUTURE BELTS 5

slates appear randomly below the soil cover on 1984) as an upthrow of Antalya onto the Alanya the downthrown side. The Triassic sandstones of versus the earliest interpretation of a sedimen- the tectonic window lie horizontally on these tary contact (Blumenthal, 1951). The deformation rocks. These observations show that the Triassic in this region is almost nil and hardly different sandstones overlie the Lower Palaeozoic slates from that of the tectonic window. Furthermore, unconformably and this fault causes the juxtapo- there are other exposures (Öztürk et al., 1995), sition of these rock units. The base of this section Middle and Upper Triassic in age, sitting on Pa- comprises Cambro-Ordovician rocks (Öztürk et laeozoic sediments in the northwesternmost al., 1995), overlying the garnetiferous mica- Alanya, incompatible with the stratigraphy de- schists. These cannot be included in the Antalya fended (Özgül, 1976 -1984) for the Alanya unit. unit, which is devoid of Palaeozoic sediments by definition. This section is not significantly differ- The examination of the northern boundary of ent from the Geyikdað or Aladað unit of Özgül the Alanya massif (Figure 2) yields crucial evi- (1976) except that it has a Precambrian base. dence. The Alanya massif has been thrusted im- The deformations are restricted to Alpine shear bricately onto the Cretaceous-Eocene section of zones. The Palaeozoic sequence is almost the the flysch corridore or the Antalya unit of Özgül same as that of any other location in the Taurids. (1976) in the westernmost segment. The bound- ary is a thrust trending E-W until the town of The Alanya unit of Özgül (1976) has been Gündoðmuþ where it assumes a southward suggested to float on an entirely undeformed trend. Although the southward turn has been sequence. The Upper Permian pelmicrites, with recognised informally by some, the boundary well-preserved fossils, display a broad and between the Alanya and the flysch corridore con- symetric anticline in the suggested tectonic win- tinues to be accepted as the previously defined dow, with a clear gradation to variegated shales EW trending thrust. This boundary continues of Schytian age as the base of a continous from Gündoðmuþ eastward, to the author, with- Mesozoic sequence (Ulu, 1983). This sequence out any thrusting but with discontinuous normal is unconformable on Ordovician shales/slates faults with the northern blocks downthrown (Point that sit on the garnetiferous micaschists. The described sequence proves very clearly that the 3 in Figure 2). There is Upper Paleocene-deposi- Antalya unit of the pseudo-tectonic window has a tion throughout the eastern half of the northern continental character. boundary covering mutually the Alanya, the flysch corridore and the northern zone of De- The northern boundary of the tectonic window mirtaþlý (1984). On the other hand, the western- is a thrust fault dipping 30 to the north on the most part of Alanya, as the eastern continuation road exposure. This fault dies out on both sides of the Antalya Complex, has been thrusted imbri- according to observations of the author and is cately onto the flysch corridore after Eocene. one of the several northward dipping ecailles of There has been no objection to this evidence, the Alanya. It dissects a gradational and conti- which shows very clearly that the central/eastern nous Permian- Lower-Middle Triassic sequence. part of the Alanya is in situation. Being more The Alanya massif (Palaeozoic rocks with incipi- elaborate, it proves that: ent deformation) is overlain by the Triassic rocks of the tectonic window a few kms north of the 1- The Alanya could not have been transpor- northern boundary of the tectonic window. This ted relative to the flysch corridore (Antalya unit) outcrop has been defended as evidence against after Paleocene with Paleocene-Eocene clastics the allochtonous nature of this sequence. How- on its back, because the cover is mutual on the ever, the contraveners interpreted it (Özgül, Alanya and the northern zone (Geyikdað unit). 6 Metin ÞENGÜN

2- The Antalya nappes of the tectonic window 1- An allochtonous entity that has been defor- cannot be connected to that of the flysch corri- med at northernmost Gondwana (Ricou et al., dore because of emplacement ages of pre and 1974). post Upper Paleocene. This means that the Alan- ya needs to have been emplaced after the youn- 2- An autochtonous asemblage with an alpine gest sedimentation of the pseudo-tectonic win- HP/LT deformation of the westernmost part (Þen- dow, which is Upper Cretaceous in age (Ulu, gün et. al. 1978). 1983), and prior to the Upper Paleocene deposi- 3- An allochtonous assemblage of southern tion. However, there is no evidence, a reason or origin, a deformed active continental margin with an implication for a pre-Upper Paleocene event. glucophane bearing assemblages (Okay and Öz- 3- The absence of the Antalya unit between gül, 1982) the Alanya and the northern zone of Demirtaþlý 4- An allochtonous entity metamorphosed in (1984) and the gradation between the Alanya the island arc setting in the vicinity of Cyprus and the Geyikdað tectonic units is indicative of a (Özgül, 1984). normal stratigraphic order rather than piled up tectonic units. 5- An autochtonous mass in the central/east- ern segment while the western part, suffering a On a rough asessment of the temporal dimen- HP/LT alpine metamorphism, is the eastern part sion, the argument presented above excludes all of the Antalya nappes (Figure 2). but the Uppermost Cretaceous-Upper Paleocene interval for a possible allochtony. However, the The author's perspective for the Alpine meta- Upper Cretaceous cap in northernmost part of morphism is as follows. The Central Taurids, ro- central Alanya brings on a further constraint. The tated dextrally by the Ecemis fault (Figure 1), conglomeratic base is horizontal and has been compressed the marginal ophiolites in the vicini- interpreted as a faulted contact (Ulu, 1983), while ty of the Antalya gulf during the Paleogene. This it is a sedimentary one to the author. Whatever has resulted in northward thrusting of the margin- the relation is, the presence of Upper Cretaceous al ophiolites of the Antalya gulf onto the sedimentation on Alanya indicates dilatation in Beydaðlarý and the westernmost Alanya. The the Upper Cretaceous, quite incompatible with northern margin of the Antalya basin has been an overthrusting phenomenon. In fact, it marks imbricated with these thrust sheets in the area the onset of a grabenization (the flysch corri- lying west of the town of Gündoðmuþ. On the dore). This location needs to be observed by a other hand, there is a gradual twist, from Gün- third party for the crucial conclusion that the doðmuþ eastward, of north vergent folds to the Alanya cannot be transported after the Upper south vergent of the central and eastern Alanya. Cretaceous, implying there is no interval for This observation implies a dextral torsion that transportation. has been caused by the southward push of the western block of the Ecemis fault versus the The idea of allochtonous Alanya is a hyphoth- northward thrusting of the western Alanya. It has esis asserted in search of an answer to how folded and twisted the central Alanya so as to Alanya has been metamorphosed. A chronologi- expose the Precambrian basement in the vicinity cal sequence of the theories for Alpine metamor- of the Alanya town. The post-Eocene obduction phism of the Alanya massif is listed below to con- of ophiolites and imbricate northward thrusting of tribute to a further understanding of the Alanya westernmost Alanya have caused a very-low debate. The Alanya unit is: grade (sensu Winkler, 1974) metamorphism ANATOLIAN SUTURE BELTS 7

(blue schist facies) in that region. The contempo- has been dated unquestionably as Jurassic- rary deformation appears as northward dipping Cretaceous in the Ankara-Ilgaz part of the Ýzmir- shear zones in the central and eastern Alanya. Ankara zone of Brinkmann (1972) and the adja- The convertion of the Palaeozoic pelites to slates cent Triassic deformation has been covered by or phyllites are restricted to these shear zones. an undeformed sedimentary wedge of Liassic- The alpine deformation on the Precambrian Lutetian age along the southern Sakarya. micaschists appears as imprints of shear planes, Þengör and Yýlmaz (1981) have challenged the which intersect mutually the Ordovician shales/ previous models accordingly, with a radically dif- slates. They appear as quartz-chlorite veins, ferent plate tectonic model. They have presumed which have a discordant relation to the Pre- a two-stranded Tethys, the consecutive Palaeo- cambrian paragenesis in thin sections of the mi- tethys and the Neotethys, with respective posi- caschists. Pseudomorphs of chlorite after garnet tions of north and south of the Cimmerian tec- may also be considered as a frequently encoun- tonites. This model has been a benchmark in the tered symptom of the alpine imprint. history of plate tectonic interpretations for the Anatolian segment. It complies with the following The westernmost Alanya is tectonically and chain of reasoning made up with evaluation of stratigraphically similar to the western side of the today's knowledge. Antalya gulf. On the other hand, the central and eastern part of the Alanya is not different strati- 1- There is an ocean along the Ankara-Ilgaz graphically from the other tectonic units of Özgül zone, the rift separating the Western and Eastern (1976), which differ from one another by facies Pontides, during the Jurassic-Cretaceous, and a changes and deformational variations only. In continous Mesozoic on the Gondwanian side in conclusion, the central and eastern Alanya is in the vicinity of Kütahya (Özcan et al., 1988), imp- situation. lying the Palaeotethys to be located north of the Cimmerian tectonites. The alpine metamorphism of the Tauric belt is in close relation to rotational processes. The 2- The Palaeotethys must have had a south- related strike-slip faults of the western Taurids ward polarity for compliance with the Paleo- have not yet been recognised formally although tethyan / Neotethyan evolution of Pontides. many scientists have declared that rotations have played a very important role (personal com- 3- When the southward polarity is accepted, munication with Dr. Robert Hall) in the structural the Pontian magmatism, being on the passive evolution and the present configuration of the margin, cannot be of the IA type. Thus, it has to Neotethyan ophiolites. They have created dilata- be ascribed to crustal thickening or some other tion on one side while causing thrusting and phenomenon. deformation on the other, resulting in appearance of deformed and undeformed rocks side by side 4- A passive margin cannot suture with entire throughout the western Taurids. undeformation so that the European margin has to consist of allochtonous entities to hide the THE TETHYAN DISPUTE Paleotethyan suture and comply with the crustal thickening. The evidence that the Upper Jurassic con- glomerates of Central Pontides contain serpenti- The kinematics of evolution, as suggested by nite pebbles (Yýlmaz, 1979) triggered another Þengör and Yýlmaz (1981), seems readily accep- major dispute, a very complex one, on the evolu- table once one accepts the need or the obligation tion of the Anatolian Tethys. The oceanic crust for an ocean responsible for the Cimmerian de- 8 Metin ÞENGÜN

formation. However, there has to be something European basin in the Early Mesozoic (Ustaömer wrong with this chain, which is, to the author, the and Robertson, 1992). The latest proposal (Gön- negligence of the possibility of marginal ophiolite cüoðlu, et al, 2000), with an evolutionary sce- obduction onto the active European margin with- nario similar to that of Þengör and Yýlmaz (1981), out a continent-to-continent collision. The model defends a Triassic-Tertiary Ýzmir-Ankara Ocean of Þengör and Yýlmaz (1981 was confronted with geographically coincident with the Ýzmir-Ankara several other objections immediately (Bergoug- zone of Brinkmann (1972) instead of the Liassic nan and Fourquin, 1982; Robertson and Dixon, northern Neotethys. 1984) and after the work in the 1980's (Üþümez- soy, 1987). GEOLOGICAL AND GEOPHYSICAL CON- STRAINTS OF THE TETHYAN EVOLUTION Þengün et al., (1990) have objected by claim- ing that the northern branch of Neotethys is actu- The dialectic analysis of the Tethyan conver- ally the Tethys and has been consumed under gence can only be complete after assesment of the Pontides through northward subduction. The the existing evidence and arguments. marginal ophiolites have been emplaced onto the 1- There is no crustal thickening in the Sa- active margin in the initial stage of convergence, karya fragment. in Lower-Middle Triassic. The obduction is ascri- bed to the dextral rotation of Western Pontides The Bougeur anomaly maps of Turkey, pre- during the Lower-Middle Triassic, as implied by pared by the geophysical department of the the marked southward offset of the Eastern Turkish Geological Survey (MTA), display con- Sakarya. This is in analogy with what has hap- tours that run very smoothly through the entire pened in the case of the Antalya gulf. The Western Pontides. A uniform continental crust, obducted ophiolites on both sides of the Antalya 35 km. thick, has been estimated for western gulf are covered by unfolded sediments of Pontides. This evidence justifies the objections Miocene age, although the Eastern Mediter- (Bergougnan and Fourquin, 1982) to the hypoth- ranean has pockets of unsubducted ocean floor esis of Liassic crustal thickening (Þengör et al., south of Cyprus and Crete, implying that ophio- 1980). lites can be emplaced onto active margins before completion of a continent-to-continent collision. 2- Sakarya fragment has a Palaeozoic sed- A recessed (?) subduction, ascribed to a high imentation unconformably capped by the rate of Tethyan convergence, occurred in the south-facing Karakaya formation. Early Upper Triassic. The consequence of the recess has been dilatation on the upwarped con- Paleozoic sedimentation in northern seg- tinental margin, when an island arc was set up in ments (Ýstanbul and Zonguldak Palaeozoic) of the Upper Triassic. The upwarped continental Western Pontides is of the shallow marine type margin or the island arc has become a progres- covered by the Kocaeli Triassic comprising of sively collapsing terrain, being onlapped by the continental and shallow marine sediments. The Tethys and the Black Sea. Carboniferous is only partly shallow marine in northern Western Pontides, and generally con- On the other hand, most of the tectonic mod- sists of coal bearing sediments. Red sandstones, els dealing with the pre-Liassic events accept possibly fluviatile, were mapped to represent the generally the closure of a marginal ocean to Permian of this region. Towards the south, the explain the Cimmerian deformation. One of these Permo-Carboniferous rocks are represented by is the idea of closure of a local (Küre) marginal shallow marine carbonates and are the grada- ANATOLIAN SUTURE BELTS 9

tional base of the south facing Triassic flysch. location that may be considered as the base of Thus, the Permo-Carboniferous of Western Pon- the proposed nappes comprising the Palaeozoic tides, or the Eurasian Karakaya formation is rocks of the northern Western Pontides is the south-facing. There are two sections one bet- Devrekani charriage, which is 400 and 600 km ween Daday and Azdavay (Þengün et al, 1990) respectively to the Ýstanbul Palaeozoic and the and the other in the Ankara region where the Strandjha. Furthermore, the age of this charriage Karakaya is unconformable on the Palaeozoic is not Liassic as suggested by Yýlmaz (1979) and (Figure 3). Þengör et al., (1980), but is post Upper Creta- ceous as it captures globotruncana bearing sed- 3- Detachment of the Anatolian fragment iments on its front (Þengün et al., 1990). This was not complete prior to the Liassic. overthrust comprises of the Precambrian- Mesozoic sequence as the overriding block, cap- Rifting in northern Gondwana started in Late turing on its front, many ophiolite outcrops with Permian/Early Triassic on the basis of strati- unconformable Cretaceous sediments. It contin- graphic and sedimentologic evidence. However, ues not only to the Ankara region southwards, the Anatolian microcontinent has been suggest- but is also continuous in the north causing forma- ed (Þengün, 1993) to detach off Africa not in the tion of the ridge (Zonenshain and Le Pichon, Early Triassic but in the Late Triassic- Liassic. 1986) that separates the Eastern and the Because, time is needed for crustal thinning and Western Black Sea. the related Carnian-Norian volcanism must have occurred prior to the detachment. This sugges- 5- Northern branch of Neotethys has been tion is to point out that there is no discrepancy annulled. between the kinematic (Westphall et al., 1986) and the structural/ stratigraphic/sequential evi- Northern strand of Neotethys of Þengör and dence. Yýlmaz (1981) has never existed. Instead, there existed an ocean, the Ýzmir-Ankara zone of 4- The allochtoneity of the Pontian Palaeo- Brinkmann (1972) whose suture is of the Tethys zoic is hyphothetical. from Ilgaz to the city of Bursa where it splits to Ýstanbul Palaeozoic is the term commonly Ýzmir as the Western Neotethys (Figure 1) and used to denote a vaguely defined area essential- continues to the Vardar zone via the Sea of ly on the eastern side of the Ýstanbul strait in Marmara. The Tethyan suture connnects to the northwesternmost Western Pontides. The active Sevan Akerra through the Eastern Pontides- margin of the Tethys in Thrace is the Strandjha Eastern Anatolia boundary. The following are massif, the domed westward continuity of the some of the reasons for annulment of the north- Ýstanbul Palaeozoic (Caðlayan and Yurtsever, ern Neotethys. 1999). The suggestion of the allochteneity of the 'Ýstanbul Palaeozoic' is a means of elimination of There is a continuous Lower Triassic- the contradiction that this domain is of European Cretaceous fining upward sequence, Kütahya, origin but located south of the Palaeotethyan south of the northern strand of Neotethys (Özcan suture of Þengör and Yýlmaz (1981). The sug- et al., 1988). This evidence shows on its own that gested thrust (Þengör et al., 1980, 1984) and this suture belongs to an ocean that existed at strike-slip faults, which revise the former theories least for the entire Mesozoic (Þengün, 1990; of thrusting (Okay et al., 1994), have been nei- Göncüoðlu, et al., 1994), in fact, to the Palaeo- ther substantiated nor there has been a hint zoic- Mesozoic Tethys on the basis of north fac- pointing to a locality where the thrusting or the ing Gondwanian and south facing Eurasian Pa- strike-slip faulting has been observed. The only laeozoic platforms. 10 Metin ÞENGÜN

Figure 3- Figure to show various features of the eastern-Central Pontides. Cross-sections AB and CD illustrate the routes along which the type sections of the Karakaya formations ,can be seen. The deformation augments towards the south where a type of melange is encountered representing the shallow seg- ments of shear zones. The type sections are oversimplified to emphasise the fact that rocks and strati- graphic relations are well preserved because of being carried on the back of the uppermost slice. ANATOLIAN SUTURE BELTS 11

There is extensive geochemical research, all 6- The Mesozoic magmatism of the Western defending the Triassic-Jurassic (?) magmatism Pontides is of the island arc type and is Up- of the Pontides to be of the island arc type per Triassic in age. (Boztuð et al., 1985; Kazmin et al., 1986 and To- kel, 1992). The Upper Triassic basic magmatism of Cent- ral Pontides have been differentiated to yield a On the northern side of the suture, namely in granitic magma, followed by high silica differenti- the Sakarya fragment, there is a post-tectonic ates. The basic magmatism is displayed very sedimentation unconformable on the Cimmerian neatly in Central Pontides hosting the granitic. tectonites. It generally starts in Liassic as a fining The granitic bodies display extremely wide upward sequence (Þengün, 1992). The sequen- aphanitic perypheries, implying that they have ce is continuous from the Liassic to the upper- been very shallow seated and the country rock most Cretaceous in the Eskiþehir (Bingöl and has been very cold. There are many granite Neugebauer, 1992) and Ankara regions. On the batholithes (comprising basic rocks as the host) other hand, a post-tectonic wedge in the range of in Central Pontides dissecting mutually ophio- Portlandian-Lutetian is well established in the lites, the Palaeozoic sediments and the Kara- Central Pontides. North-facing character of the kaya formation. Boztuð et al (1985) state that the latter is readily recognised on the Boyabat-Sinop basic and the granitic magmas of this region belong to the same magmatic suit. The author, and Devrekani-Çatalzeytin roads. The Upper agreeing with this statement, suggests further- Jurassic-Lutetian sections are almost identical more that the granitic magma is the differential with their counterparts in the sections starting product of the basic. The suggestion is based on with the Liassic. This sedimentary wedge is very the basic rocks being the host for the granitic and probably related to the Tethyan onlap in the the striking resemblance of the pleochroism of south while it is definitely a Black Sea sequence the hornblend phenocrystals of the diorites and north of the positive area. The evidence is indica- those of the granitic rocks, crucially implying the tive of a transgression diminishing the positive continuity of crystallisation of hornblend of a spe- area centering the Sakarya fragment. There cific composition. Further petrochemical investi- have been small islands that have not been gations should, hopefully, check up the sugges- transgressed until the end of Eocene as indicat- tion. This proposal has the crucial implication that ed by local columnar sections. the basic and granitic magmatism are of the same age. The Liassic-Lutetian sediments cover uncon- formably the Palaeozoic rocks and the Karakaya On the other hand, the radiometric dating of formation, the latter being restricted to the south- 165±3 my for the granite (Yýlmaz, 1979) cannot ern belt juxtaposed to the Tethyan (or the pseu- be proven wrong for the Central Pontides on the do-Neotethyan) suture. The Karakaya formation, basis of direct evidence. Nevertheless, no gran- Carboniferous-Triassic in age, bears a genetic ite dyke has been reported to dissect any section relation to this suture, which cannot be of the of Liassic age. Secondly, the sedimentary wedge Liassic Neotethys, but the Carboniferous-Tri- covering the Karakaya complex is Upper Ju- assic Tethys. The regressive Triassic of the rassic-Lutetian in age in the northern Central northern Tethyan margin versus the fining up- Pontides, with full stratigraphic correlation of the ward Mesozoic sequence of the southern is not section with those of the Ankara and Eskiþehir compatible with a Liassic extensional basin, but regions (Saner, 1980; Bingöl and Neugebauer, a Mesozoic active margin in the north and a pas- 1992). In other words, the Liassic-Cretaceous sive one in the south. sedimentation of these regions are tied to the 12 Metin ÞENGÜN

Central Pontides, showing very clearly that this wanian sequence is scattered on northern Gond- wedge covers the magmatism and the Triassic wana and is related to dilatation of the Anatolian deformation. In conclusion, the granitic magma- microcontinent. tism has to be Upper Triassic in age to be com- patible with the stratigraphic constraints, and is There is a type section/area between Beytepe not post-collisional but of the island arc type in and Ýmrahor in the vicinity of Ankara. The north- Central Pontides on the basis of extensive geo- ward younging section north of the deformed chemical research. suture is carried on the back of the uppermost slice (Figure 3, sections AB and CD). It compris- 7- The Karakaya enigma es of:

There has been an enigma on the Karakaya 1- A lower Palaeozoic clayey unit exposed in formation caused by the similarities between the the vicinity of Eymir Lake. Triassic sedimentation on Gondwanian and Eurasian margins. The nomenclation (Bingöl, 2- Carboniferous-Permian limestones with a 1968) has been applied to both (Sakarya and conglomeratic base. Biga). 3- High-energy clastics of Lower Triassic age The Gondwanian Karakaya is Mesozoic in gradational to Permian limestones. age while the Eurasian is Carboniferous-Late Triassic. 4- A continous carbonate sedimentation of Ju- rassic-Cretaceous age covering these unconfor- The Gondwanian Triassic (Antalya nappes) mably. grades to deep marine Jurassic-Cretaceous sed- iments while the Eurasian ends up in the Upper 5- Serpentinites juxtaposed to Liassic- Creta- Triassic, being invariably regressive in the Upper ceous carbonates on the Eskiþehir road. Triassic section. Block formation in the Eurasian margin oc- The Gondwanian Permian blocks are covered curs, to the author, mostly in shallow segments of and underlain by continuous layers that converge Upper Cretaceous-Paleocene thrusts, which on both ends. The strata are turbiditic with blocks have dragged the inter/back-arc regions towards of various dimensions. There is no crystallization the Tethyan suture. The deformation diminishes in Permian limestones. The fauna has Gond- going away from the suture so that undisrupted wanian affinities. On the other hand, the Permian sequences, with extremely rich faunas, can be blocks north of the Tethyan suture are of the bro- seen as in the case of Permo-Carboniferous ken type and partly crystallised. Block formation rocks in the vicinity of Ankara. The Cretaceous of the Eurasian Permo-Carboniferous in the deformation appears as rhythmic and southward Triassic sandstones is encountered essentially in narrowing shear planes. The deformations are the shear zones. restricted to these shear planes so that the lithons, when fairly distant to the suture, can dis- The Triassic of the Eurasian Karakaya is play the previous, i.e. the Triassic deformations. restricted to a belt adjacent to north of the Teth- In other words, the belt with intense Cretaceous yan suture and has never been deposited out- deformation grades northward, to the zone with side this narrow belt. Thus, it is genetically relat- pre-Liassic deformations showing rhythmic and ed to the southward-located Triassic Tethys. On progressive northward diminishing of its Creta- the other hand, the deposition of the Gond- ceous imprint. ANATOLIAN SUTURE BELTS 13

The Karakaya formation is a marker of the The Karakaya formation sits, with a sedimen- European margin in the Sakarya where it is tary contact (Þengün et al., 1990), on the Palaeo- unconformable on Palaeozoic sequences of zoic rocks of Eurasian origin in the Daday-Az- European origin. It is of Gondwanian origin in the davay section of the central Pontides. The Car- Biga-Karaburun as will be discussed in the fol- boniferous of the Beytepe- Ýmrahor section of the lowing item. Ankara region sits on the underlying Devonian shales also with a sedimentary contact. Anything 8- The Sakarya fragment is of European European in any part of these sections implies origin while the Biga is of Gondwanian. the European character of the whole. The Eu- ropean character of the Sakarya fragment (Þen- Which continental fragment (Figure 1) be- gün et al 1990) is backed up not only sequential- longs to which major continent? Is there satisfac- ly but also paleontologically. The Liassic sedi- tory evidence for the origins of the Sakarya and mentation of the Sakarya contains European the Biga? These are probably the most signifi- ammonites (Alkaya, 1990) and the Eurasian ori- cant and appropriate questions that should be gin of the Zonguldak Carboniferous is well estab- raised for the Anatolian segment of the Tethyan lished (Kerey, 1982, Toprak, 1984). It has been belt. There is no direct claim based on paleonto- asserted (personal communication with Prof. E. logic evidence that the Biga is European but Ya. Leven of Moscow University) that the Permo- implied to be hypothetically (Okay and Tüysüz, Carboniferous carbonates of the Beytepe 1999). On the other hand, European origin of (Ankara) section (Figure 3) have a very rich Eu- Sakarya (Þengün et al., 1990) receives accept- rasian fauna. ance in the recent years. The present author claims on the basis of sequential evidence that Nevertheless, further investigations will hope- the Sakarya is European while the Biga is of fully complement the sequential evidence and Gondwanian origin. the paleontologic assertion cited, to show that the Sakarya belongs to Europe while the Biga There is a continuous Triassic-Cretaceous peninsula to Gondwana. A consensus on the ori- sequence in the Biga peninsula (Koçyiðit and gin of the Biga will resolve many of the entailing Altýner, 1990) and there are many Mesozoic fin- disputes such as the Intra-Pontide Ocean. ing-upward sequences along the Bursa-Ýzmir Further paleontologic and paleomagnetic works zone (Akdeniz, 1985). The D'orsay group (Brunn on the Permian limestones of Biga may yield evi- et al., 1975; Ricou et al., 1974-1986) has defined dence that will hopefully resolve the ongoing these as the Antalya nappes, the very typical debate. Gondwanian facies. The Triassic sequence of 9- The Intra-Pontide Ocean is hypothetical. the Biga, or the Karakaya formation of Bingöl (1968) has also been defined as the Antalya Okay et al (1994), Okay and Tüysüz (1999) nappes. The Antalya nappes of the Karaburun and Göncüoglu et al. (2000) defend an E-W tren- peninsula, which has been declared as Gond- ding intra-Pontide ocean separating the Sakarya wanian and juxtaposed to the Bursa-Ýzmir zone and northern Pontides. The author's objections (Erdoðan, 1990), are certainly on the continua- to existence of this ocean are outlined below. tion of the Biga Peninsula, the Aegean and the Greece. Bursa-Ýzmir zone comprises other Lo- The sediments, younger than the Liassic, are wer Triassic-Upper Cretaceous sequences (Ak- undeformed on both sides of the suggested Int- deniz, 1985), substantiating the designation of ra-Pontide suture, which is mostly coincident with this zone as intra-Gondwanian. the NAF. 14 Metin ÞENGÜN

The belt of Upper Cretaceous volcanics one Neotethyan suture in Anatolia as shown in trends perpendicular to the suggested strike-slip Figure 1, the southern and the western zones faults and shows no offsets in Central Pontides. being connected (?) through the Eastern Medi- terranean. The western branch possibly con- An unbroken Pontide belt is unacceptable nects to the northern Antalya basin of Robertson (Lauer et al., 1981). The abrupt end up of the (1990) and the loop north of Karaburun towards Intra-Pontide ocean in the middle of the Pontides the Vardar zone is theoretical. The loop is theo- is not only subject to objection as a concept but retically undeletable to maintain the distinction also brings in the necessity to explain the east- between the Tethyan and Ýntra-Pontian sutures. ward ophiolite thrusts onto the Kirsehir massif, In other words, elimination of this loop or accept- which are connected to ophiolites of the Daday. ance of the Biga as Gondwanian would mean coincidence of the Tethyan and the Intra-Pontian The Portlandian-Lutetian sedimentary wedge sutures. However, the suture cannot pass covers the paleo-lineament that causes the offset through north, in disagreement with Okay and of the Daday-Devrekani massif with respect to Tüysüz (1999), of the broadly folded Mesozoic the Ilgaz in northern Central Pontides. On the sediments of the Gondwanian Karaburun (Er- other hand, the Liassic-Lutetian wedge has start- doðan, 1990), but passes through the southwest ed to transgress the northern Pontides in Port- of this peninsula (Gökten et al., 2001) where the landian as a result of the progressive collapse of ophiolites have been ultramylonitised due to the Western Pontides. Therefore, the lineament, imbrication with the continental rocks of the by which the Western Pontides has been dis- Menderes massif (personal observation with Dr. placed southwards relative to the Eastern N. Konak and. Mr. A. Caðlayan). This means that Pontides, must have died out by Portlandian. this suture is in between the Karaburun and the This interpretation is backed up by the hardly Menderes, both of which being of an undoubted detectable offset between the Elekdag (Figure.3) Gondwanian origin. The Menderes massif, the and the westward continuation (Karadere ophio- domed continuation of the Taurids, has a Pa- lites) separated by the Arac-Boyabat graben. laeozoic-Mesozoic cover (Çaglayan et al, 1980) in the southern segment of the Izmir-Ankara Yýlmaz et al (1994) have suggested an Upper zone. The sections exclusively display the se- Cretaceous closure of the Intra-Pontide Ocean quential and palaeontological characteristics of versus the Paleogene collision of Okay and Tuy- the Tauric facies. This evidence backs up the suz (1999). However, the lack of deformation on connection of this zone to the Antalya basin. The the Mesozoic rocks on both sides of the suture suture and the Lycien nappes, the latter being seems to be an important drawback for either of presumably related to the compressive field gen- these theories. The active margin may be unde- erated in relation to closure of this zone, have formed because of being carried on the back of probably been subject to post-collisional config- thrust sheets. However, non-deformation along a ureuration by strike-slip faults. passive margin is unacceptable The southern Neotethyan suture passes THE SUTURES OF ANATOLIA through the immediate north of the Pütürge (Yazgan, 1984) and the Bitlis massifs, and not THE NEOTETHYAN SUTURE through the zone known as the Bitlis suture (Hall, 1976) or the southern branch of Neotethys of The northern branch of the Neotethys Þengör and Yýlmaz (1981), which is referred to (Þengör and Yýlmaz, 1981) seems to be annulled as the Maden-Cungus foredeep in this text. This (Þengün et al, 1990; Okay et al, 1994), leaving assertion is based on detailed regional geologi- ANATOLIAN SUTURE BELTS 15

cal mapping of eastern Bitlis (Caglayan et al., The overall geophysical evidence shows that 1984) and the Puturge massifs (Yazgan, 1984). there has been a collage between the East Ana- tolia and the Bitlis/Puturge in the Upper Creta- The following information is a summary of the ceous. The ophiolites have been obducted onto evidence that show Bitlis to be in situ and the the passive margin (Bitlis/Puturge) from the Ce- uplifted passive margin of the southern Neo- nomanian onwards (Yazgan, 1984; Yazgan and tethys. Chessex, 1991). There is a consensus that the obducted ophiolites imbricated with the crustal The Mesozoic sequence of the southeastern rocks of Bitlis glide gravitationally into this fore- Bitlis (Caðlayan et al., 1983), exactly the same deep. This is a crucial support to the dilatational as that of the border folds, not only shows that regime implied by the sedimentation between the Bitlis and the border folds were on the same Upper Cretaceous and Miocene. north-facing Mesozoic platform of Gondwana but also proves that Bitlis is in situ. It also implies that The closure of the pockets of unsubducted there has been no rifting along the Bitlis suture of ocean floor has resulted in formation of fore- Hall (1976) until the end of the Mesozoic. deeps south of Bitlis and Puturge. This process is reflected in the sedimentation and the mag- Southern branch of Neotethys or the Bitlis matic activity. The initiation of the extensional suture of Hall (1976) is juxtaposed on both sides Maden-Cungus trough is indicated by convertion by undeformed rocks. The Bitlis/Puturge block is of carbonate sedimentation of the southeastern represented by a Precambrian basement capped Bitlis to gradational high-energy clastics of unconformably by incipiently deformed Palaeo- Campanian- Maastrichtian age. The dilatation zoic-Mesozoic (Yýlmaz, 1971) and there is no and sedimentation is continous including the quest for the undeformed nature of the border Miocene along this trough. folds (Þengün, 1990). Can the northern block have a sheared Precambrian basement so that a The rotations generate dilatation causing par- subduction zone is sealed? No, because there is tial melting in the uppermantle-lower crust. A syn- nowhere any sign of such a deformation. Is a collisional magmatism, the Maden formation, Triassic rifting possible south of Bitlis? There is forms and is expelled through diabase dikes no sign of changing sedimentologic parameters along NNE trending paleo-transtensional faults neither in Permian limestones, nor in the Triassic that spread the lavas as flows intercalated in sedimentation, which is exactly the same as coeval sedimentation in the EW trending troughs those of the pseudo-suture and the border folds. extending along both extremities of the Bitlis This means that there has been a Permo-Tri- massif. assic platform extending from northern Bitlis/ Pütürge to the Arabian platform. The thrusting of Bitlis onto this graben took place in the Late Miocene after the collage The intensity of alpine deformation, un- between the East Anatolia/ Pontides and comple- dressed of folding, diminishes towards the south, tion of the Neotethyan closure, with the aid of the showing that the suture lies in the north. NNE push of the Arabian platform (McKenzie, 1972). Detailed mapping has shown that the Bit- Bitlis massif is the uplifted passive margin of lis head-thrust of Altýnlý (1963), which borders the the Neotethys on the basis of the island-arc set- massif in the south, is not a single plane but com- ting in its immediate north (Yazgan and Chessex, prises of many unlinked thrusts (Ozkaya, 1982). 1991) and the southward obducted Gevas ophi- It is possible to cross from the Eastern Bitlis to olite (Caðlayan et al., 1984). the Dodan anticline of the border folds without 16 Metin ÞENGÜN

any thrusting. Thus, the division of the northern THE TETHYAN SUTURE Arabian platform into tectonic slices of Bitlis, oro- genic flysch and the border folds is a false and A Cretaceous-Paleogene (?) Tethyan suture unsubstantiated hypothesis, but is currently between Bursa and the coastal areas of the Sea accepted. of Marmara substantiates itself by the ophiolite slivers that show the same high pressure/low Yazgan (1984) has described the magmatic temperature metamorphism and the same defor- and stratigraphic relations to show that the Neo- mational geometry as the eastern Sakarya. The tethys also lied not in the south but the immedi- Tethyan suture is theoretically connected to the ate north of the Pütürge massif. Vardar zone through the Sea of Marmara also on the basis of the Biga being Gondwanian and the West of the Puturge massif, the suture has a Sakarya of European origin. The Tethyan suture southward displacement of 105 kilometers coincides with the northern strand of the (Freund et al., 1970) by the Dead Sea transform Neotethys of Þengör and Yýlmaz (1981) between Bursa and Ankara. It is also well marked in the so that it passes through the north of well-known segment bounding the Eastern Pontides and the pockets of unsubducted ocean floor south of East Anatolia and is characterised by imbricate Cyprus and Crete in the Eastern Mediterranean. southward thrusting (Yýlmaz, 1985). The Mio- There has been Neotethyan acretions to the cene blocks in emplaced ophiolites juxtaposed to Taurids as in the case of Antalya Complex (Ro- the Tethyan suture shows that the suturing of the bertson and Woodcock, 1981; Yýlmaz, 1984; Tethys in East Anatolia has not been completed Poisson 1984 and Özgül, (1984). It is possible until the Late Miocene. that the Northern Antalya basin may be tied to the Ecemis lineament. However, this issue is left A wide belt of ophiolites thrusted onto the out because of the author's inadequate know- Kirsehir massif marks the Tethyan (+Neoteth- ledge of this region. yan) suture between Ankara and Ilgaz. This ophi- olitic slice is connected to that of the Daday mas- The reason for the misinterpretation (Þengün, sif via the Arac - Boyabat graben. The suturing 1993) about the Bursa-Ýzmir segment of the Ýz- has caused uplift of the passive margin, the mir-Ankara zone of Brinkmann (1972) was the Kirsehir massif with an intense multistage Alpine acceptance of the Biga as Gondwanian followed deformation with southeastward diminishing by the consequential false reasoning that this grade of metamorphism (Erkan, 1975; Seymen, zone could have been a foredeep only. Many 1982 and Tolluoðlu, 1987). have considered ophiolites of the Menderes massif as transported tectonites originating from A DISCUSSION ON POSSIBLE SCENARIOS the north, although the imbrication with the OF PRE-LIASSIC GEOLOGIC EVOLUTION Menderes massif is suggestive of a suture. The The post-Liassic evolution of Dercourt et. al. SSW trend of the Ýzmir-Bursa zone also backs up (1986) is mostly agreeable except the evolution a suture. The author has realized on the basis of of the Eastern Mediterranean. Most of the tecton- the preceding thoughts that this zone is not a ic models accept that closure of a marginal basin Tethyan but an Intra-Gondwanian Neotethyan rift is unavoidable to explain the Triassic deforma- separating the Anatolian microcontinent from tion. The possibilities and selected past hypho- Apulia-Greece. It seems that this rift has to con- theses on the issue will be examined briefly. nect to the Northern Antalya Basin of Robertson (1990) via the west of the Lycien nappes of I. The Paleotethys dives Southward under southwest Anatolia. Gondwana comprising Southern Sakarya and ANATOLIAN SUTURE BELTS 17

the Biga. Northern Neotethys is a Marginal fenders of the possibility. The pre-Liassic evolu- (Back-Arc) Gondwanian Basin (Þengör and tion is the same as that of Þengör and Yýlmaz Yýlmaz, 1981). (1981) except that the Ýzmir-Ankara ocean or the northern strand of Neotethys has opened in the The key point has been that there must have Lower Triassic. The following criticism is addi- been a collage responsible for the Cimmerian tional to the ones enumerated above. orogen in the Sakarya fragment, as there is a Jurassic-Cretaceous ocean floor south of the 1- The Mesozoic dilatation of the southern Cimmerian tectonites in the Sakarya fragment. margin of the Ýzmir-Ankara ocean is not compat- However, the following geological and geophysi- ible with the coeval compressive state of the cal constraints are not consistent with the northern margin in the Triassic. Known const- hyphothesis of Þengör and Yýlmaz (1981). raints back up a passive margin in the south and an active one in the north. 1- The gap between the Taurids and the Pon- 2- The theory has to explain how the Mesozo- tides is more than 4 000 kms in the Liassic ic fining upward sequences of the Bursa-Ýzmir (Westphall, et al, 1986). Thus, a collision by M. zone is replaced on the eastern continuation, the Jurassic is almost impossible. Sakarya, by a weakly deformed Carboniferous- Triassic overlain by the undeformed Liassic- 2- The geophysical evidence is suggestive for Lutetian sedimentary wedge. Can these sequen- a uniform crust with a thickness of about 35 kms ces belong to the same continental margin? The in Pontides, thinning smoothly towards the Black crucial constraint is the Gondwanian and Eu- Sea, justifying the objection of Bergougnan and rasian origins respectively for the Biga and Sa- Fourquin (1982) to the theory of crustal thicken- karya. Both of these fragments have to be of the ing. same origin for consistency of this model. Both have to be of either Gondwanian origin or Eura- 3- The Liassic-Dogger piling of the Palaeo- sian, as the marginal Karakaya Ocean could zoic rocks of the northern Pontides is false also have not possibly extended in both of the major because of the post-Upper Cretaceous age of mainlands. Therefore this model has to defend thrust faults. These have a widening spacing the Gondwanian character of the Biga and south- going away from the Tethyan sutuýre. They cap- ern Sakarya for consistency. However, the ture many bodies of serpentinites with Cretace- European character of the Sakarya is well estab- ous caps in the Sakarya fragment and are cer- lished. tainly related to the Tethyan suturing. 3- The Ýzmir-Ankara ocean, separating the 4- There is concrete evidence for non-exis- Menderes-Taurid block from the Sakarya, cannot tence of the northern strand of Neotethys of Þen- open in the Triassic, because this means that the gör and Yýlmaz (1981). Gondwana and Eurasia had formed a single con- tinental mass in the Triassic, unless a very thin 5- The ascription of the Upper Triassic (Ju- continental fragment of Gondwanian origin is rassic?) magmatism to crustal thickening is ex- separated from the European by an ocean at clusively denied by extensive geochemical re- least 4000 km wide. search (Boztuð et al., 1985, Kazmin et al., 1986 and Tokel, 1992), all defending the IA type. II. There has been a Southward diving the Eu- ropean Marginal Basin Responsible for the Göncüoðlu et al. (2000) have proposed a sim- Triassic deformation (Ustaömer and Ro-bert- ilar scenario representing the latest of the de- son, 1992). 18 Metin ÞENGÜN

The objections to this possibility is summa- the other hand, the Sakarya fragment is charac- rised as follows. terised by the European Karakaya formation of Carboniferous-Triassic age. Thus, these seg- 1. There is no direct evidence showing that a ments are genetically different and are not parts Eurasian sliver has collided with Europe by the of a single continuous margin. Liassic. III. The European (Intra-Pontian) Marginal Ba- 2. A marginal European basin can be possible sin dives Northward. only if it is in the range of Carboniferous-Upper Triassic, coeval with the Karakaya formation, A European marginal basin (in a model anal- because the Karakaya formation is uncon- ogous to that of Adamia et al. (1977), noting that formable on the European Palaeozoic se- the marginal basin in the Caucasus corresponds quences (Þengün et al., 1990). This implies that to the Black Sea) diving north may be considered a southward polarity (Ustaömer and Robertson, possible, only if the Carboniferous-Upper Trias- 1992) is unavoidable with the chain conse- sic sedimentation unconformable on European quence that the granites of Central Pontides, rocks is false or ignored. In that case, the Kure being located north of any European marginal ophiolite needs to have been emplaced on the basin, has to be ascribed to crustal thickening. active margin by rotationary processes of the The theories with a southward polarity are not continental margin so that it can be intruded by compatible not only with the incipient deforma- the island arc magmatism. The mechanism tion of the Palaeozoic sequences underlying the would not be significantly different from that Karakaya formation of northern Pontides, but are defended in this paper for both the Eastern in contradiction with the extensive geochemical Mediterranean and the Tethys. Existence of finite research (Boztug et al., 1985; Kazmin et al., pieces of continental crust that have been 1986 and Tokel, 1992), exclusively suggesting an deformed into an unrecognisable state by the island arc origin for the granitic magmatism. Triassic/Cretaceous events cannot be proven wrong. However, such a theory has to place the 3. Another objection to a southward diving marginal basin in the middle of the accretionary European basin would be that the Cimmerian prism, leaving a remarkably narrow strip of deformation intensifies southward showing the southern margin, which has left no fingerprints cause of deformation is in the south of the accre- behind. tionary prism. IV. There is no Marginal Intra-Pontian Basin. 4. A gradation exists through northward wide- ning tectonic slices in the Western Pontides (Sa- The Triassic deformation is caused by the karya). marginal ophiolite obduction onto the active European margin without a continent-to-conti- 5. The Karakaya formation of the Sakarya nent collision. This is the possibility preferred, so fragment is European and is juxtaposed continu- it will be described and defended below. ously to the northern (the Tethyan) suture, imply- ing that such a marginal basin has to be coinci- GEOLOGIC EVOLUTION dent with the Tethys. PRECAMBRIAN 6. Along the Izmir-Bursa zone, there is a con- tinuous fining-upward Mesozoic sequence, The Precambrian basement is exposed in se- which has been defended as the Gondwanian veral locations in Turkey. Alanya, Menderes, Kýr- Karakaya, also known as the Antalya nappes. On þehir, Bitlis and Puturge are well-known Gond- ANATOLIAN SUTURE BELTS 19

wanian massifs with Precambrian basements. remaining as a positive area until the Late There are several other exposures in northern Jurassic. It was not transgressed completely until Pontides underlying unconformably uniform and the Late Cretaceous or even Eocene. incipiently deformed Palaeozoic sequences. The Precambrian basements comprise essentially of The stratigraphic, sedimentologic and mor- amphibolites and micaschists/paragneisses me- phologic evidence for the formation of the Tethys tamorphosed in physical conditions of alman- can be complemented with the Atlantic Ocean dine-amphibolite facies. Granites have intruded data for the conclusion that the Tethys had a these and have been deformed by the Alpine width of roughly 5000 kms in the vicinity of uplift only. Palaeozoic- Mesozoic sediments Anatolia at the end of Permian as suggested by cover these unconformably in the Central Taurids Westphall et. al., (1986). (Özgül, 1976-1984). The westward narrowing gulf of the Pangea (the Tethys) seems to have MESOZOIC-PALEOGENE initiated with the beginning of the Palaeozoic Era (Figure 4). TRIASSIC

PALEOZOIC There have been marked facies changes in the Taurids with initiation of rifting in northern There has been immense stratigraphic re- Gondwana. Permian limestone deposition has search since the late 1960's in Central and been converted, along the Neotethyan margins, Western Taurids. Detailed mapping in the follow- to high-energy deposition represented essential- ing years resulted in new disputes about the ly by turbiditic sequences with Permian limestone structure. However, there is almost full agree- olistolithes. The crustal attenuation initiated basic ment on the Palaeozoic stratigraphy of the eruptions during the Carnian-Norian. The cessa- Taurids. The continental (coal bearing) to shallow tion of this volcanism presumably marks the marine Permo-Carboniferous sequence of the onset of ocean-floor spreading in Neotethyan Alanya massif and other Lower Palaeozoic sedi- rifts. Facies changes between the rifting margins ments of Western Taurids grade to continuous and the positive areas result in juxtaposition of Palaeozoic marine sedimentation northwards, deep and shallow marine environments. implying a north-facing Tauric platform (Blumen- thal, 1951; Özgül, 1984; Demirtaþlý, 1984). The replacement of carbonate deposition by high-energy clastics in southern Pontides is sug- The stratigraphy and sedimentologic parame- gestive of a Triassic onset of northward subduc- ters of the Palaeozoic fining upward sedimenta- tion of the Tethys. However, the author questions tion in northern Pontides are suggestive of dilata- the deepening environment even for the begin- tion during the Lower Palaeozoic, converted to ning of the Triassic period with the consequent compression during the Permo-Carboniferous. quest on the indispensability of a subduction in There is a continuous Palaeozoic sequence in the Early Triassic. The Triassic sedimentation of the Karadere region west of Daday. If a south- the Karakaya formation is represented by high- facing morphology is acceptable for the energy clastics with rare interbeds of limestones Karakaya formation, the continuous Palaeozoic yielding fossils of Lower, Middle and Upper implies that there has been an ocean south of Triassic age. The section in the Ankara region these sequences during the entire Palaeozoic (Figure 3) represents the proximal part of the era. The Carboniferous and older rocks of the Eurasian continental slope. The Lower Triassic northern Pontides were subject to southward segment comprises blocks of Permian lime- onlap of the Black Sea, the Central Pontides stones. The Upper Cretaceous thrusting as 20 Metin ÞENGÜN

Figure 4- A tentative and unscaled chain of evolutionary cross sections from the Eastern Mediterranean to the Black Sea. ANATOLIAN SUTURE BELTS 21

described in the preceeding sections has broken The Gondwanian sedimentation comprises up the Permian limestones resulting in blocks in essentially of deep marine carbonates in subsid- a Lower Triassic matrix in the Permian-Triassic ing troughs such as Izmir-Bursa zone, Kutahya boundaries. The Triassic sequence of the Kure trough and Karaburun. There are sharp facies region sits on the abyssal clays covering the changes perpendicular to the axes of these sub- sheeted dykes and is the representative of the siding troughs with gradations to relatively shal- marginal ocean floor. It continues as a regressive lower environments and onlaps onto the positive sequence comprising carbonate interbeds that areas. The sedimentologic record is indicative of yield Lower, Middle and Upper Triassic fossils. continuous dilatation during the entire Mesozoic There are small serpentinite wedges in the medi- in the Anatolian microcontinent. Rifting has oc- al part of the section with sheared bottoms and curred in the Eastern Mediterranean south and sedimentary tops, implying that the emplacement north of Cyprus/Crete, the northern strand possi- is coeval with the deposition. bly extending as the Northern Antalya Basin con- necting to the Ýzmir-Bursa zone and the Ecemis JURASSIC (?) lineament in the east.

The assesment of the kinematic evidence The Liassic initiation of deposition on the (Westphall et al., 1986) implies that the western Pontian arc seems to have occurred in areas of and central Taurids seem to be moving with earlier collapse along the southern coast of the Africa until the Early Jurassic. Therefore, the island arc. The northern part of the Western suggestion of a Liassic age of detachment is Pontide block has persisted as a positive area plausible and is compatible with the geophysical between the Late Carboniferous and the Upper constraints (Figure 5). Cretaceous. The Central Pontides have been

Figure 5- A sketch map to show the relative positions of the main continental and oceanic domains in the Upper Triassic - Liassic. 22 Metin ÞENGÜN

transgressed in Portlandian-Berriasien in liasion with consequent gravitational gliding towards the with the progressive collapse. The time of onlap foredeeps that are suggested to form by rotation- is Albian in the Daday region while it is Upper ary processes of the collisional period. There Cretaceous in areas that are fairly distant from were presumably pockets of unsubducted the suture, such as the Ýstanbul and Zonguldak oceanic crust after the collision (Figure 6), as the Palaeozoic. The times of onlap on two sides of continental fragments are not expected to fit like the same hill are Berriasien and Campanian in jigsaw puzzles. The closure of these pockets the Elekdag region where the basal columnar must have been fulfilled with the aid of strike-slip section is the same, displaying the same rock faulting with the consequence of compression sequence. It must be emphasised again, that the and dilatation, the latter being responsible for Upper Cretaceous transgressions are not related creation of syn-collisional magmas of essentially to initiation of rifting of the Western Black Sea, Paleogene age. The author disagrees with the but to onlap of the existing. Thus, the Western theory that crustal thickening may be the cause Black Sea must have started to rift before the of partial melting of the upper mantle/lower crust. Jurassic, very probably in the Early Triassic to be Because, pressure is hydrostatic in depth and in consistency with the hypothetical dextral rota- rigid displacements are not possible. Marine sed- tion of Western Pontides. imentation stops invariably by the end of Lutetian along the Tethyan suture in Western and Central The Liassic deposition from Ankara region to Anatolia. Bursa, in Western Pontides, is suggestive of the subduction to trend parallel to the Tethyan Suturing along the East Anatolia-Eastern suture. It is not possible to say that there has Pontides has not been completed before Late been coeval subduction in the Ankara-Ilgaz zone Miocene. The Western Neotethys, or the Bursa during the Liassic, and ocean floor spreading Antalya basin, has sutured by the Miocene as could have been dominant, particularly in the indicated by the multistage compressive defor- southern segment of this zone, conformably with mation between Early Eocene- Late Miocene the possible dextral rotation of Western Pontides. (Gökten et al., 2001), although most of this zone has collided by the Late Eocene. But the imbrica- CRETACEOUS-NEOGENE tion of the suture zone has continued until the Miocene. The sedimentation is continuous inc- The Cretaceous was a period of rapid drifting luding Miocene in the vicinity of the Salt Lake. It of the Anatolian microcontinent towards the Pon- seems that there could have been an unsubduct- tides. The deposition has continued in the exten- ed pocket of ocean floor there, which has closed sional basins of the Anatolian microcontinent and with the aid of NW trending strike-slip faults cre- the back-arc basin of northern Pontides. Slicing ating an immense Tertiary magmatism NW of of the active margin must have continued Ankara (Galatya volcanics). throughout the period resulting in a HP/LT meta- morphism along the suture. Ophiolite obduction The northward movement of the Arabian plate onto the passive margins, the Kýrþehir and (McKenzie, 1972) put a brake on rifting of the Menderes massifs, must have started towards Maden-Cungus foredeep, continuing so that the the end of the Cretaceous period. It is observed Bitlis have been pushed onto this basin following that the slicing is imbricate and the lithons widen the collision between Eastern Pontides and East southward. It is suggested to have progressed Anatolia during the Miocene. The compression towards the south, the earlier slices having been has continued to cause uplift and crustal thicken- carried on the back of the following. The thrust- ing of East Anatolia and formation of new plate ing has resulted in uplift of the passive margin margins such as the E-W trending dextral North ANATOLIAN SUTURE BELTS 23

Figure 6- A sketch map showing unsubducted pockets of oceanic crust during the Upper Cretaceous.

Anatolian Fault (NAF) and the NNE-SSW sinis- quakes, which will theoretically migrate east- tral Ecemis, followed by the NE-SW sinistral East ward. There cannot be a strike-slip fault parallel Anatolian (EAF), to push the western part of to the northern coast of the Marmara, for a tech- Turkey onto the ocean floor south of Cyprus and nical reason, which is the principle that such a Crete. It seems that the East Anatolian fault and strike slip fault has to join a plate margin. Thus, several other sinistral faults en echelon with the the threat will be from the NAF. The period of Dead Sea transform enable the push of western time for a new earthquake of the same magni- Anatolia onto the Eastern Mediterranean so that tude along the Marmara segment is not less than the Ecemiþ Fault can be inactive. However, 150 my on consideration of the 1-5m displace- many scientists have questioned this inactivity. ment in the recent earthquakes and on the as- sumption of a slip rate of 1.5 (Kasapoðlu, 1984) The Anatolian plate escapes west not only to 2.5 cm/year. because of the northward push of the Arabian DISCUSSION AND CONCLUSION plate (McKenzie, 1972) but also the southwest- ern drag of the Aegean back-arc basin of the The Tethyan suture is characterised by a Hellenic trench. Otherwise, the movement along HP/LT metamorphism of the active margin and the NAF would have died out as the Marmara imbrication of ophiolites with the continental crust and the Aegean region had squeezed up. in the passive margin. A section from the Black Nevertheless, the North Anatolian tear has oc- Sea to the northern Menderes comprises of very curred because the Pontide plate (The Eurasian) weakly deformed Lower Palaeozoic sediments is rigid and stable, implying the southern block to unconformably capped by the south-facing be mobile with respect to a stationary northern Karakaya formation. This formation grades into block. This is the crucial point on which a deduc- an unrecognizable state towards the suture mar- tive process can be started as to locate the area ked by a fairly wide sliver of ultrabasic rocks ob- of dilatation on the North Anatolian Fault (NAF) ducted onto the passive margin. The passive so that a guess can be projected for future earth- margin displays ecailling with a widening spacing 24 Metin ÞENGÜN

away from the suture. Concrete field and exten- 4- The overthrust planes of the Sakarya run- sive paleontologic evidence back up the Gond- ning paralel to the Tethyan suture are of post- wanian origin of the passive margin, the Taurid- Cretaceous age (Þengün et. al.1990). Menderes and the Biga. The Eurasian origin of the Western Pontides is also well established. THE FIELD EVIDENCE WITH REGARD TO Origins of these continental fragments locate the SUTURES Tethyan suture coinciding with that of Brinkmann (1972) between Ankara and Bursa. The basic Southern branch of Neotethys lied not in the features of the evolutionary frame may be sum- south, but immediate north of the Bitlis/Pütürge marised as: massifs (Yazgan, 1984; Çaðlayan et al, 1984).

a) The basic evidence for the evolutionary 1- There is a continuous Mesozoic sequence frame is certainly the geophysical. exactly the same as the border folds in eastern Bitlis (Çaðlayan et. al, 1984). b) Sutures are not long distance thrusts, but are rotating systems that are not much longer 2- Bitlis suture of Hall (1976) is undeformed than 500 kms as in the case of Western Pon- on both sides. tides. Northern branch of Neotethys has never c) The Ankara Ilgaz Black Sea line needs fur- existed. The Neotethyan suture coincides mostly ther attention, in the sense that separation of with that of the Tethys (Palaeotethys). The Bur- Eastern and Western Pontides is far from being sa-Ýzmir zone, presumably extending to northern thoroughly understood. Antalya basin and emplacing ophiolites onto southwestern Anatolia (Lycien nappes), is here- This paper comprises of not only substantial by proposed as an intra-Gondwanian ocean. It evidence but also assertions based on the has started to rift not in Liassic but in Early author's field observations. Nevertheless, the fol- Triassic. lowing evidence is independent of the author's perspective. Concrete evidence is presented showing that the Intra -Pontide Ocean is also a pseudo-suture. 1- There is a post tectonic sedimentary wed- ge of Liassic Lutetian age, covering most of the 1- There are flat-lying Mesozoic sequences Sa-karya fragment with the implication of dilata- on both sides of this suture. tion from Liassic onwards (Saner, 1980: Bingöl and Neugebauer, 1992; Þengün, 1992a). 2- The controlling strike-slip faulting suggest- ed by Okay et. al, (1994) is unsubstantiated. 2- The Karakaya formation lying adjacent to the Tethyan suture in the Sakarya is European by 3- The deformation coincides with that of the not only the sequential evidence (Þengün et al, North Anatolian fault zone 1990) but also the paleontological (Alkaya, 1990). OUTLINE OF THE GEOLOGIC EVOLUTION OF THE ANATOLIAN SEGMENT OF 3- The sequential and paleontologic evidence TETHYS/NEOTETHYS (Akdeniz, 1985; Erdoðan. 1990) shows that the Bursa- Ýzmir segment of the Ýzmir-Ankara zone 1- Initiation of the formation of the Tethys at (Brinkmann, 1972) is intra-Gondwanian. the end of Precambrian. ANATOLIAN SUTURE BELTS 25

2- Initiation of rifting in the Anatolian segment ACKNOWLEDGEMENTS of northern Gondwana and onset of northward Tethyan subduction in Early Triassic. The author is indebted to Mr. M. A. Çaðlayan and Dr. E. Yazgan for discussion on various 3- Obduction of marginal ophiolites onto the issues. We are thankful to M. Atilla Çaðlayan, Mustafa Sevin and halil Keskin who corrected Pontian active margin as the consequence of the and rewieved the article after the author's death, dextral rotation of Western Pontides during consistent with his last will from them, before he Lower and Middle Triassic. died.

4- Recess of the subduction zone and initia- The manuscript received on May 29, 2006 tion of the Pontian arc in Early Upper Triassic. REFERENCES 5- Detachment of the Anatolian microconti- nent from Africa in Upper Triassic-Liassic. Adamia, S. A., Lordkipanidze, M. B. and Zakariadze, G. S., 1977, Evolution of an active continental 6- Northward drift of the Anatolian microconti- margin as exemplified by the Alpine history of the Caucasus. Tectonophysics, 40: 183-189. nent during Jurassic and Cretaceous.

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MTA Dergisi, 133, 31-40, 2006

PRELIMINARY APPROACH TO GENESIS OF BERYL GROUP MINERALS IN KAYMAZ, NW SÝVRÝHÝSAR, ESKÝÞEHÝR

Hülya ERKOYUN*, Rifat BOZKURT* and Selahattin KADÝR*

ABSTRACT.- Kaymaz (Sivrihisar) is located at 80 km east of the Eskiþehir. The study area consists of metamor- phites, ophiolites, phonolites and pegmatites. Beryl crystals are detected in the sediments which cut the meta- morphic units. Optical microscopic determinations show that beryl crystals have 35 µm diameter, green and pale greenish blue colours, hexagonal features, basal cleavages, no = 1.584 and ne = 1.584 refractive indexes, uni- axial (-) and euhedral hexagonal prismatic characters which was supported by scanning images (SEM). Be con- tent of phonolites between 9-31 ppm, of pegmatites between 4-17 ppm and of metamorphic units as 1 ppm were determined. Elements associated with beryllium in phonolites with F (260-440 ppm), Ba (1088-3106 ppm), La (300 ppm), Y (16-19 ppm) content, pegmatite with F (300 ppm), W (10 ppm), Sn (5 ppm) contents and presence of beryl crystals in the sediments cutting the metamorphic units which have tectonic relation with phonolite and pegmatite, seem to imply that formation of the beryl minerals have close releationship with these units.

Key words: Beryl, phonolite, pegmatite, metamorphite, Sivrihisar

INTRODUCTION MATERIAL AND METHOD

The study area, situated in 80 km east of 29 clastic and 29 rock samples were collect- Eskiþehir province, northwest of Sivrihisar, is ed along creek valleys cutting metamorphics, shown on the 1/25.000 scaled Eskiþehir Ý-26 c4 ophiolites and pegmatites, complying with the map sheet (Figure 1). principles of geochemical prospecting. Transpa- rent and opaque minerals collected from clastic Regional geology was explored by Romieux samples by using stereomicroscope are classi- (1942), Weingart (1954), Kulaksýz (1981), and fied as groups based on their color and crystal Gözler et al. (1996). However, there is not any forms. Of transparent minerals, colored minerals known study related with mineralogy, geochem- considered to be beryl were separated, and istry and origin of emerald and accociated miner- refractive indexes of these minerals were deter- als originated from Sivrihisar locality famous for mined under polarized light with using 0.002 mm gemstones market and recorded at historical spaced immersion oils, and their optical proper- times. ties were also determined. In addition, these If world beryllium occurrences are taken into beryl crystals were analyzed by electron micro- considerations in general, they seem to form scope (SEM) (Zeiss Supra 50 VP). Rock sam- mostly in schists, nepheline syenites, phonolites ples were petrographically analyzed and their and pegmatites within ophiolite belts. Based on mineral constituents and textures were deter- these informations and carrying the whole mined. Trace element analyses of 12 samples parameters, Sivrihisar region seems to be a suit- were performed for the presence of beryl to be able locality to be considered carefully for this determined with ICP-AES method at ACME lab- research. oratory (Canada).

* Eskiþehir Osmangazi Üniversitesi, Jeoloji Mühendisliði Bölümü, Meþelik, 26480, Eskiþehir E-Mail: [email protected]; [email protected]; [email protected] 32 Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

posits in the study area are Quaternary alluviums N (Figure 3 ).

Emerald and aquamarine were detected by optical analyses on creek sands collected from the valley of Karakýz Creek cutting metamorphics to research beryl mineralization. Phonolites were selected as second area within the ophiolites. Pegmatitic vein within granodiorite is considered as third area.

PETROGRAPHIC STUDIES

Figure 1- Location map. a- Rock Petrography

Petrographic studies present that metamor- GEOLOGICAL SETTING phics seem to include garnet-glaucophane schist, epidote-chlorite schist, garnet-lawsonite- The study area consists of metamorphics, glaucophane schist, epidotite, chlorite-lawsonite Karabayýr Metaophiolites, Karakaya Granodio- schist and marbles, Karabayýr Metaophiolites rite, Höyüklü formation and Sarýkaya formation contain diabase, serpentinite, ophicalcite and (Kulaksýz 1981). Metamorphics of Upper Creta- phonolites, and Karakaya Granodiorite seems to ceous aged units forming the basement in the bear a pegmatitic vein as well. study area include an intercalation of meta- quartzite, metapelite, marble, calcschist, metab- In thin sections of lepidoporphyroblastic-tex- asite, serpentine schist and metacalcirudite tured garnet glaucophane schist traces of chlori- (Okay, 1984; Figure 2). Tectonically overlying tization are present on the edges of subhedral Karabayýr Metaophiolites contain of metagabbro, garnets with varying sizes between 0.25 and metahornblendite, metapyroxenite, metaharzbur- 0.75 mm (Plate I - Figure 1). Prismatic glauco- gite, metaserpentine and metaperidotites. There phane crystals with varying sizes between 0.125 are also phonolite domes intruding serpentinite mm and 0.5 mm have significant strong pleo- along the crack formed by a fault line which have chroism. With using immersion oils, refractory effects up to penetrating depths. K-Ar age of index of glaucophane is determined as phonolites is given as Middle Miocene (Özgenç, nx= 1.642, ny = 1.656 ve nz = 1.657 and it implies 1982). Karakaya Granodiorite of Upper Creta- crossite of glaucophane series. As well as garnet ceous intruding ophiolites as a pluton bears a and glaucophane, there are muscovite, epidote, pegmatitic vein with quartz, feldspar, tourmaline chlorite and quartz. and pyrite. Höyüklü Formation of Miocene is composed of volcanogenic sandstone, grey- In lepidoblastic - textured epidote - chlorite wacke, tuff, agglomerate and lava flows. Over- schist, there are epidote as elongate crystals in lying all these units, Sarýkaya Formation of Plio- the direction of b axis, clinozoisites with bluish cene begins with volcanic tuff and conglomerate interference colors, and chlorite with no aligned at the bottom and lasts with lacustrine limestone, groups of crystals. sandstone, claystone and marl units. This forma- tion overlays locally metaophiolites with angular In nematoporphyroblastic-textured garnet- unconformity (Kulaksýz, 1977). The youngest de- lawsonite-glaucophane schist, glaucophane min- BERYL GROUP MINERALS OF SÝVRÝHÝSAR REGION 33

50 52 54 56 58 60 62 86 x x Tha x x x x x x Tha x x x pzks x x N Halilbaðý x x Taþkesti H. Küçükhöyüklü H. H-1 *H3 H-2 Kocadevebaðýrtan H. H-11 H-13 H-15 x H-28 H-16 x H-4 Kocasivri T. H-19 x pzggl x * pzggl H-17 x x H-10 H-5 Deðirmen H. x 84 Karaburun sivri H. H-8 H-6 x H-18 Yalýncak H. * H-12x H-7 x H14 x xx H-9 *x H-20 Tsk

Karakiz deresi x x Tsk Kavakçalý H. Okçu x x x pzgm pzks Kocaçal H. Çamlýk H. Tsk

Kötüpinar Deresi x p 82 x p x p x p

pzgs Qal Tsk pzggl Ahmetçal H. pzggl Karaburhan

80 Tskr Akçal H. pzks pzgs Azizin T.

pzgs pzgm

78 Karacaören x p x Hisar H. x p x p x x p p x p x p x p p x p pzgm x p x p x p

76 Pasaçal H. pzgm H-24 H-26 H-21 Kg H-22 H-25 H-27 Büyük Dere + ++ + + + + H-29 74 Tsk pzgm

Sand 2 km Metamorphic Pegmatite Karakaya Pzggl Metamorphics + +++ Tsk Clay Glauoophanecohict Kg Granodiorite Granodiorite Sarýkaya Sample location Marl Formation Metaserp. Thruct Pzgm Marble Pzks Tskr Laouctrine Ist. Moacohict Peritotite Volcanic tüff Höyüklü Fault Metaquaezite Phonolite Tha Pzgs Karabayýr Greywaeke Formation Calocohict Agglomerate Qal Alluvium x Metaophiolites X Diabasc X X X p x p x p x Pyrosenite

Figure 2- Geological map of the study area (modified from Kulaksýz, 1981). erals have sizes between 0.2 and 0.3 mm. Law- In nematoblastic-textured chlorite lawsonite sonite minerals varying sizes between 0.08 and schist, foliated crystals of chlorites surround law- 0.22 mm are short prismatic crystals. There are sonite and epidote minerals in bunches. Law- inclusions in garnet minerals. Epidote minerals sonite minerals are short prismatic crystals and are between 0.2 and 0.65 mm, in size. show parallel extinction. Epidote minerals are 0.13 mm in size and augite minerals are between In nematoblastic-textured epidotite, euhedral 0.15 and 0.3 mm in size (Plate I - Figure 3). albit crystals are found together with epidotes. The size of the calcite mineral inclusions seem In marble sample enclosed in metamorphics, to be between 0.15 and 0.3 mm. Ýn size (Plate I - there are very few quartz, sericite, plagioclase Figure 2). and orthoclase besides calcite. Twin glidings and 34 Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

Figure 3- Generalized vertical section of the study area (modified from Kulaksýz, 1981; Okay, 1984) bendings on these twin lamellas are observed in chrysotiles. In the porphyritic-textured phonolite calcite crystals. They show symmetrical extinc- sample (H18), there are euhedral phenocrysts of tions according to the traces of cleavages. sanidine varying between 0.2 and 0.7 mm size, Quartz minerals are of anhedral rounded grains hornblende with 0.015 mm. size and leucite min- and sericite minerals are flakelike assemblages. erals. Its groundmass consists of volcanic glass Few plagioclase and orthoclases of Carlsbad and rock fragments (Plate I - Figure 4). Phonolite twinning are observed. sample numbered H28 showing typically trachyt- ic texture contains nepheline and apatite mine- Ophitic-textured diabase dyke within Kara- rals (Plate I - Figure 5). Sieve-textured ophical- bayýr metaophiolites contain of oligoclase, diop- cite include twin lamellar calcite, fibrous chry- site, actinolite and zeolite minerals. Diopsites sotile and subparallel aligned antigorite crystals. performing uralitization were converted to partial or completely acicular actinolites. Zeolite miner- Pegmatite sample enclosed in Karakaya gra- al, defined as natrolite, are found as acicular- nodiorite consists of orthoclase, biotite and fibrous aggregates. In serpentinite, there are an- quartz minerals. Some of orthoclase minerals tigorite bearing olivine remnants, and fibrous show Carlsbad twinnings, some have a combina- BERYL GROUP MINERALS OF SÝVRÝHÝSAR REGION 35

tion of Carlsbad and Baveno twinnings (Plate I - GEOCHEMICAL ANALYSES Figure 6). Chloritization of biotites ranging sizes from 1 to 4.75 mm are seen from the edges. 12 samples were taken so as to determine if Quartz grains are between 0.25 and 0.5 mm in beryl is existed by performing chemical analyses, size. in the probable emerald promising areas. Of these samples, 6 samples were taken from Ka- b- Beryl Mineralogy rakýz Creek cutting metamorphics (H1-H6), one sample was taken from Kötüpýnar Creek cutting Beryl, with displaying dark green color is phonolites (H18) and one sample was taken from defined as emerald, and displaying bluish green Büyük Creek clastics cutting pegmatites (H29). to blue coloration, called as aquamarine, and is Rock samples were analyzed as metamorphics beryllium aluminosilicate in reality, carrying a for- (H1), phonolites (H18 and H28), and pegmatites mula as Be3Al2Si6O18 . (H29). To compare sediments and rock samples and if there is possibility of any rock types to bear 25 green and light-green colored beryl grains beryllium mineralizations, both rock and sedi- owning the largest size as 35 µm, numbered as ment samples were analyzed. H1 from Karakýz Creek cutting metamorphics, were defined as emerald and aquamarine based Samples taken from Karakýz creek (H1- H6) on the analyses (Plate II - Figure 1). bear 1 ppm Be, creek sands taken from Büyük Creek (H21) cutting pegmatites contain 4 ppm Views of green crystals (grains) on a stere- Be (Chart 1). The highest Be value were deter- omicroscope imply that they are crystallized in mined as 9 ppm on creek sands taken from hexagonal systems (Plate I - Figure 2). Kötüpýnar Creek (H18) cutting phonolites. With using immersion oils having 0.002 dif- Related with these sediments, Be content of ferent values, refractory indexes of the grains Karaburunsivri phonolite sample (H18) is 31 ppm, of Kocasivri phonolite (H28) is 19 ppm, of were found as no=1.568, ne=1.584 using (Plate II Figure 3). pegmatitic rock (H29) is 17 ppm and metamor- phics (H1) bear less than 1 ppm Be. These data Beryl minerals, in optical studies, determined show us beryl has probably been derived and as uniaxial (-) and existed as hexagonal prismat- enriched from alkaline phonolitic and pegmatitic ic euhedral crystals were defined as emerald rocks. when green, and as aquamarine when light bluish green varieties at polarized light in immer- Useful indicators to determine presence of sion oils. (Plate II - Figure 4). Basal cleavage beryl are F, Li, Rb, Cs, Sn, W, and accociated (0001) is significant (Plate II - Figure 5). elements are Ba, Sr, B, Sc, Y, and other rare earth elements are U, Th, Nb, Ta, P, Ti, Mo and Beryl crystals determined on stereomicro- Mn (Boyle, 1974). Because of Be and Li, Rb, Cs, scope were analyzed by SEM (Plate III - Figs 1 Sr, Ba, B, Sc, Y, Ti, Th, P, V, Nb, Ta, Cr, W, U, Mn and 2) as well. Beryl crystals are euhedral and F are lithophile elements, they are interrela- hezagonal prismatic in general. 0001 planar sec- ted (Akyol et al., 1985). Of accompanying ele- tions of these crystals are six cornered and local- ments with beryllium, various cations of small ly circular. Prismatic beryl crystals showing circu- radius and often greater valence (U 10-22, Th 4- lar and elipsoidal 0001 planar sections were 142, Mo 2-14, W 4-17, Nb 3-182, Sn 2-5 ppm) probably derived from partial abrasion of hexag- are called as incompatible elements. Owing to onal prismatic crystals resulting from probable ionic radius and valences, the element Exchange transportation within detrital sediments. with major ions in silicate minerals seem to be 36 Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

Table 1- Results of geochemical analyses of the samples taken from the study area BERYL GROUP MINERALS OF SÝVRÝHÝSAR REGION 37

difficult (Krauskopf, 1979). On phonolite samples llium containing samples bear alkaline elements (H18,H28) values of U as 15-22, of Th as 5-142, of considerably enriched values (0.04 - 5.86 %) of Nb as 9-182, of Mn as 1033-1474, of Sr as like Na and K. In fact, Kocasivri and Karabu- 467-976, of La as 21- 64, of Ba as 1088-3106, of runsivri phonolitic rock samples enriched in Na, Al as 8.26-10.4, of Y as 16-19, and of F, a signi- K and Al, and depleted in Ca and Mg show that ficant indicator for determining beryl, as 440-260 these rocks carry alkaline character. ppm were determined. On pegmatitic rock sam- ple (H29) higher values of W as 10, of Sn as 5, It is indicated that there is a slight positive cor- of F as 300 ppm than other rock samples support relation between beryllium and Nb, Mo, Sn, F, that beryllium occurrences on the veins and Ba, Sr, U, Th and La elements; a negative corre- pyrometasomatic beds own a geochemical affi- lation between beryllium and Sc, P, Ti, Mn, Cr nity between beryllium and W, Sn and F in parti- and V, and no correlation between W and Y cular. (Warner et al., 1959). (Figure 4).

On clastics from Karakýz Creek cutting meta- Results of chemical analyses show that a morphics, the values of Cu, Ni, Co, Mn, Ca, Cr, positive correlation between Be and Al may exist Mg, Sc, V, and Fe; on a garnet-glaucophane rock except for H1 sample, and Be element enters the sample taken from the surroundings of same lattice structure of Al-bearing minerals (sanidine, creek values of Ni and Cr associated with mafic leucite, nepheline, hornblende, biotite, ortho- volcanic and ultramafic rocks; on garnet, glauco- clase). Because ionic radii and ionic valences of phane, epidote and chlorite minerals values of Be and Al are similar, these elements are isomor- Co, Fe, Ca, and Mg are high. It is noteworthy that phic. the rock sample bear less Cu, Mn, Sc and V than clastic sample does. DISCUSSION

On clastics from the creek cutting pegmatite It can be referred that beryl minerals were Pb and K got concentrated, and pegmatite sam- formed due to phonolites and pegmatites in the ple (H29) enriched in W, Sn and F, and depleted northwest of Kaymaz (Sivrihisar). Beryllium ele- in Sr and Ba. This explains that pegmatite veins ment's indicating an anomaly on phonolitic and bear wolfram, tin and fluorine beds. On sediment pegmatitic units, and the determination of beryl sample taken from Kötüpýnar Creek cutting crystals in sediments cutting metamorphic rocks Karaburunsivri phonolite, the values of Al, Na, related with these units seem to exhibit signifi- Mo, Zn, As, Th, Sr, La, Ba, K, W, Zr, Y, and Nb cant geochemical relationship between Be and seem to be considerably high. On phonolite sam- the rocks. According to Marshall et al. (2003), ples (H18, H28), LFSE elements (Pb, Mn, Na, emerald occurrences are closely related with Cr Th, Sr, Ba, U, K), HFSE (Y, Nb, Zn, Ti, Zr), LREE ( +/- V) and Be-bearing solutions in general. The (La), transition elements (V, Sc ), lithophile ele- authors state that Cr and V could be derived from ments (W, F) and other elements (As, Cu, Fe, Al) local mafic and ultramafic rocks during hydro- got enriched. thermal alteration. At the sample of Kocasivri phonolite (H28), having a high value of V and a Beryl may include alkaline ions like Na and K, negative association, and a higher value of Cr in and its total alkaline content may rise up to 5-7 metamorphic rocks than that of other rocks indi- %. Beryllium replaces Na, on the contrary, does- cate that chromium transportation is probably n't replace K. Alkaline elements remain within resulted from thrusting. Optically determined hexagonal channels in the lattice structure of a beryl minerals might have been formed due to an beryl (Çelik ve Karakaya, 1998), so high-bery- association with schist minerals following the 38 Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

Figure 4- Correlation charts of elements associated with Be. metamorphism of original rock during a hydro- amounts of beryllium element, beryl minerals can thermal process. Depending with upthrust, alka- not be observed in thin sections of phonolite and line magma derived solutions were filled the fis- pegmatite rocks and are mostly determined by sures and joints of the metamorphic rocks, as chemical analysis methods. result, beryl got deposited as trace amounts. Beryllium containing solutions are products of A positive correlation between Be and Na, alkaline volcanism together with F in phonolites. and also K in phonolitic and pegmatitic rocks Be composing between 9 and 31 ppm, and F shows that beryllium could be present in a crys- between 260 and 440 ppm, and also Be between tal lattice structure of some Na and K-bearing 4 and 17 ppm, and F as 300 ppm in pegmatites minerals like in sanidine, nepheline, hornblende, show the presence of a positive correlation orthoclase and apatites. Because of trace between Be and F, and a probable relation as in BERYL GROUP MINERALS OF SÝVRÝHÝSAR REGION 39

origin, between them. Where beryllium's having axial (-). On the other hand, beryl crystals on hihger values, F gets high values, fluorine play a SEM are identified as euhedral hexagonal pris- reactive role separating F from a solution phase, matic forms. and beryllium was facilitated to get separate in pneumatolytic and hydrotermal solutions. Be- 3- For the identification and origin of be- bearing minerals form due to conditional chan- ryllium, Beryllium shows positive correlations ges of the solutions like pH, pressure and tem- with F, Ba, Sr, U, Th, La, Nb, Sn and, W ele- perature or due to decaying of complexes like ments, seem to be considerably important data. 2- - - [BeF4] , [BeF2] , [BeF2]°, [Be(CO3)F] ve 2- [Be(CO3)2] when they interact with surrounding 4- Beryl minerals associated with beryllium in rocks (Gökçe, 2000). Either beryllium enters a geochemistry as volcanogenic hydrothermal lattice structure of silicate minerals or enriches in products related to phonolites and pegmatites. residual solutions during magma crystallization. Which of these happened is dependent upon the ACKNOWLEDGMENTS fluorine content of magma, hydrostatic pressure, alkalinity of surrounding rocks and other factors. This paper is revealed from M. Sc. Thesis Therefore, Be either is deposited in granitic peg- study of the first author conducted by the super- matites or is carried with fluorine and formed in vising the second and third authors. The author hydrothermal occurrences and in greisens. thanks to Prof. Dr. Taner Ünlü (AÜ), Associate Higher F value on Kýzýlcaören fluoride barite ore Prof. Dr. Sönmez Sayýlý (AÜ), Dr. Neþat Konak formed at the contact of phonolites in the study and Dr. Eþref Atabey (MTA) with valuable critics area shows that they are derived from the same in revision of this paper. volcanism. Hence, beryl occurrences are associ- ated with phonolites and pegmatites in origin. It is The manuscript received February 10, 2006 also reported by Preinfalk and Morteani (2002) that similar occurrences derived from anatectic REFERENCES pegmatites in Belmont and Capoeriana (Minas Gerais, Brazil) reacted with Cr-rich ultrabasic Akçay, M. 2002. Jeokimya temel kavramlar ve rocks in metasomatism, Beryl occurrences in the uygulamaya aktarýmlarý. KTÜ yayýnlarý, study area might have been formed as a result of genel yayýn no: 204, Fakülte Yayýn No. 60, metasomatic reaction between pegmatites and 506s. Cr-rich ophiolitic rocks Akyol, A., Ýnan, K. and Suner, F. 1985. Jeokimyaya CONCLUSIONS giriþ. ÝTÜ Kütüphanesi Sayý 1308, 666s.

1- The presence of beryl as emerald is firstly Boyle, R.W. 1974. Elemental association in mineral identified in sediments of Kaymaz locality (NW of deposits and indicator elements of interest in Sivrihisar- Eskiþehir) in Turkey by mineralogical geochemical prospecting. Ener-gy, Mines and and geochemical studies. Resources Canada, Geological Survey Paper 74-45, 40s. 2- Optical properties of beryl minerals are hexagonal prismatic euhedral crystals, green- Çelik, M. and Karakaya, N. 1998. Sistematik mineralo- colored varieties called emerald, bluish green ji. Selçuk Üniversitesi, 434s. varieties called aquamarine, basal cleavage, determined light refractory indexes no= 1.568, Gökçe, A. 2000. Maden yataklarý. Cumhuriyet Üniver- ne= 1.584, 1st row interference colors and uni- sitesi Yayýnlarý no: 85, 335s. 40 Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

Gözler, M.Z., Cevher, F., Ergül, E. and Asutay, H.J. incelemesi. Ege Üniversitesi Yerbilimleri Fakül- 1996. Orta Sakarya ve güneyinin jeolojisi. Ma- tesi, Doçentlik tezi. 83 s. den Tetkik Arama Genel Müdürlüðü Report No: 9973, 87s. Ankara (unpublished). Preinfalk, K.,Y. and Morteani, G. 2002. The pegmatites of the Nova Era-Itabira-Ferros pegmatite distict Krauskopf, K.B. 1979. Introduction to geochemistry. and the emerald mineralisation of Capoeriana McGraw Hill Book Company. 617 s. and Belmont (Minas Gerais, Brazil): geoche- mistry and Rb-Sr dating. Journal of South Ame- Kulaksýz, S. 1977. Sivrihisar kuzeybatý yöresinin jeolo- rican Earth Sciences, 14, 867-887. jisi. Hacettepe Üniversitesi, Doktora tezi. 200 s. Romieux, J. 1942. Sivrihisar, Paþa daðlarý ve Emir- ,1981. Sivrihisar kuzeybatý yöresinin jeolojisi. daðlarý bölgelerinin jeolojisi hakkýnda rapor. H.Ü. Yerbilimleri Dergisi, 8, 103-124. Maden Tetkik Arama Genel Müdürlüðü Report Marshall, D., Groat, L., Giuliani, G., Murphy, D., Mat- No:1431, Ankara (unpublished). tey, D., Ercit, TS., Wise, MA., Wengzynowski, W. and Eaton, WD. 2003. Pressure, tempera- Warner, L.A., Holser, W.T., Wilmorth, V.R. and Came- ture and fluid conditions during emerald preci- ron, E.N. 1959. Occurence of nonpegmatite pitation, southeastern Yukon, Canada: fluid inc- beryllium in the United States. U.S. Geol. lusion and isotope evidence. Chemical Geo- Survey Prof. Paper 318, 198s. logy, 194, (1-3), 187-199. Weingart, W. 1954. 56/2, 56/4 Sivrihisar ve 57/1, 57/3 Okay, A.I. 1984. Kuzeybatý Anadolu'da yer alan meta- Ankara paftalarýnýn jeoloji haritasý hakkýnda morfik kuþaklar. Ketin Sempozyumu, 83-92. rapor. Maden Tetkik Arama Genel Müdürlüðü Report No: 2248, Ankara (unpublished). Özgenç, Ý. 1982. Kýzýlcaören köyü (Beylikahýr- Eskiþe- hir) fluorit- barit- bastneazit yataðýnýn jenetik PLATES PLATE I

Figure 1- Garnet glaucophane schist (H1) Garnet (gr) indicating chloritization at its environs, and glaucophane (gl). Single nicole, Obx Ok= 5x10

Figure 2- Epidotite (H7) Epidote (ep) and calcite Double nicole, Obx Ok= 10x10

Figure 3- Chlorite lawsonite schist (H9) Chlorite (kl) with foliated crystals, and short prismatic crystals of lawsonite (lv), Double nicole, Obx Ok= 5x10

Figure 4- Karaburunsivri phonolite (H18) Hornblende (hnb), sanidine (sa) and leucite (lö) Double nicole, Obx Ok= 4x10

Figure 5- Kocasivri phonolite (H28) Hornblende (hnb) and sanidine (sa) minerals Single nicole, Obx Ok= 4x10

Figure 6- Pegmatite (H29) Baveno and Carsbad twins on orthoclase are seen. Double nicole, Obx Ok= 5x10 Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

PLATE - I

12

34

56 PLATE II

Figure 1- Stereomicroscobic view of the crystals of aquamarine (A) at the left, emerald (Z) at the right, enlargement = 35X

Figure 2- Emerald photo taken by stereomicroskobic view, enlargement = 35x

Figure 3- View of a beryl grain in a 1.60-immersion fluid

Figure 4- Emerald at single nicole, Obx Ok= 5x8

Figure 5- Basal cleavage (0001) on aquamarine is seen. Single nicole, Obx Ok= 5x8 Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

PLATE - II

12

34

5 PLATE III

Figure 1- General view of beryl crystals

Figure 2- Surficial view of a hexagonal prismatic beryl crystal (0001) Hülya ERKOYUN, Rifat BOZKURT and Selahattin KADÝR

PLATE - III

1

2 Mineral Res. Exp., Bull., 133, 41-49, 2006

THERMAL REACTION OF ANTIGORITE: A XRD, DTA-TG WORK

Gökçe GÜRTEKÝN* and Mustafa ALBAYRAK*

ABSTRACT.- It is very important to determine the stability limits of serpentine minerals for investigation of geo- logic processes taking place in the oceanic lithosphere which consists of serpentinized peridotites. As a result of temperature increase in the subducting oceanic lithosphere, thermal decomposition of serpentine minerals and new mineral formations have a great effect on geologic processes related to subducting plate. In this study, ser- pentine minerals (antigorite) collected from the Konya-Çayýrbaðý region were dehydrated under constant atmos- pheric pressure, then mineralogical changes were determined by using X-Ray diffraction and DTA-TG analyses and finally the stability limits of antigorite was determined. Dehydration reactions on antigorite started at approx- imately 100-150°C, dehydroxilation reactions started at approximately 550°C and beyond this temperature forsterite started to crystallize from antigorite+brucite. Association of antigorite+forsterite continued until 650°C at which enstatite started to be formed. During all the reactions, which were carried out at the atmospheric pressure, talc was not formed but some H2O and amorphous silica were released. Dehydroxilation reaction on antigorite occurred between 550°C and 690°C and antigorite was stable until 650°C-690°C.

Keywords: XRD, DTA-TG, Antigorite, Dehydration, Dehydroxilation

INTRODUCTION tekin, 2001). Hydrated oceanic crust material is composed of more than 90% of serpentine min- Although several types of serpentine minerals erals. During the subduction process, thermal are found in the nature, the most common ones reactions on serpentine minerals cause water are lizardite, chrysotile and antigorite. These release which can play an important role in sub- minerals have the general formula of duction-related volcanic processes. Completely Mg3Si2O5(OH)4 and are described as triocta- serpentinized peridotites contain significant hedric (1:1) layered silicates with MgO, SiO2 and amount of water (13%) which released as a H2O contents between 85-95%. result of subduction process this water can be transported to great depth which is represented Serpentine minerals are formed as a result of by high temperature-high pressure conditions at hydration of olivine, pyroxene and other Mg-rich which serpentine minerals can be stable and arc silicate minerals under suitable conditions, the magmatism starts. Therefore, thermal reactions process so called serpentinization. Lizardite and of serpentines and related mineralogical chan- chrysotile are formed at lower conditions of ges are very important for identification of some greenschist facies while antigorite mostly occurs geologic processes. at greenschist-amphibolite facies (Evans, 1977). The aim of this study is to describe serpentine In studies conducted on serpentine minerals, minerals on the basis of petrographic, X-ray and minerals are generally described by petrographi- DTA-TG methods, to investigate the mineralogi- cal methods and X-ray analyses and their for- cal changes occurring during the thermal reac- mation conditions are determined and thus the tions and to determine the stability of antigorite rock formation processes are investigated (Gür- under constant pressure. Samples used in the

* Maden Tektik ve Arama Genel Müdürlüðü, Maden Analizleri ve Teknolojisi Dairesi Baþkanlýðý, Ankara. E-mail: [email protected] 42 Gökçe GÜRTEKÝN and Mustafa ALBAYRAK

study were taken from the Çayýrbaðý ophiolite in as dehydration and loss of water in its crystal the Çayýrbaðý-Hatip region in Konya (Figure 1) structure is descbried as dehydroxilation. Pro- and serpantinites in the Hatip ophiolitic complex cess of thermal reactions in serpentine (dehydra- (Özcan et al., 1990). tion and dehydroxilation) and forming of olivine+ pyroxene+talc+chlorite, that minerals include a THERMAL REACTION OF SERPENTINE few or no water is described a deserpentinization MINERALS (O'Hanley, 1996). Because, lizardite is firstly formed from olivine during serpentinization, in Loosing of the absorbed water (H2O) related deserpentinization olivine mostly formed from to the increasing of heat in a mineral is described antigorite and lizardite in deserpentinization.

Figure 1- Geological and location maps of the study area (Revised fron Özcan et al., 1986) THERMAL REACTION OF ANTIGORITE 43

In general, thermal reactions in antigorite du- ray diffractometer at the MTA General Directora- ring recessing serpentinization are in the form of te. Samples were thermally treated at constant antigorite + brucite olivine + H2O orantigorite pressure at the laboratory and the resulting min- olivine ± talc + H2O and new minerals are for- eralogical changes were determined with the X- med at temperatures about 500-690°C (Evans, ray analyses. Since the main peaks have very 1977). Considering the stability boundaries of close values, secondary peaks are very impor- serpentine minerals (Figure 2), lizardite and tant for evaluation of serpentine minerals and chrysotile are found at lower conditions of green- therefore, analyses were conducted at 2 =0-70º. schist facies while antigorite is stable over a wide Following the routine analyses performed at range from lower green-schist to amphibolite ambient conditions, powdered samples were first facies. mixed with pure water and taken into suspension then they were dried on glass lamellas. Before the X-ray analyses, dried samples were left in furnace for about one hour at temperatures of P (kbar) 200°C, 400°C, 500°C, 550°C, 600°C, 650°C, Greenschist Amphibolite 260 350 450 550 670 700°C, 800°C, 900°C, 1000°C and 1100°C. In 15 order to prevent melting of glass lamellas, porce- 13 Forsterite + Enstatite Forsterite Enstatite lain containers were used for heating processes 11 Antigorite Brucite Antigorite at 900°C, 1000°C and 1100°C. 9 Antigorite Forsterite

Talc 7 Antigorite Chrysotile 5 DTA-TG analyses, which give information on Lizardite Antophyllite 3 Talc phase transformations in parallel to temperature Talc 1 Forsterite Antophyllite increase and the amount of mass loss, were per- Forsterite T(C)O 100 200 300 400 500 600 700 800 formed with Rigaku Thermoflex TG 8110 brand device at the MTA General Directorate. During the analyses which were conducted at tempera- tures between 18.7°C and 1100°C, temperature increasement were selected as 20°C/minute and Figure 2- Stability limits of serpentine minerals (Buc- 100 mg sample was used for the analyses. ker and Frey, 1994) Petrography MATERIAL AND METHOD In petrographical studies, source rock of ser- This work was conducted as two stages: pentines was found as harzburgite. In complete- X-ray analyses and DTA-TG analyses. However, ly serpentinized rocks with pseudomorphic tex- prior to X-ray and DTA-TG analyses, petrograph- ture, serpentine±talc±magnetite mineral parage- ical studies were carried out to determine textur- nesis is observed but olivine (forsterite) and al characteristics, mineral paragenesis and sour- orthopyroxene (enstatite) minerals are absent ce rock types of serpentinites. In petrographical and serpentinized (bastitized) orthopyroxene re- studies, mineral paragenesis and textural proper- licts showing plastic deformation signs were also ties of rocks were described and classifications detected. According to classification of Wicks of Wicks and Whittaker (1977) which were later and Whittaker (1977) and O'Hanley (1991, 1996) developed by O'Hanley (1991, 1996) were used. on the basis of textural features under micro- scope, antigorite±lizardite and vein-type chryso- X-ray analyses of 5 samples from the study tile were found in samples of pseudomorphic tex- area were made with Rigaku Geigerflex brand X- ture. 44 Gökçe GÜRTEKÝN and Mustafa ALBAYRAK

X-Ray Analyses (XRD)

In order to determine mineralogical changes as a result of thermal reactions, samples that were heated at certain temperature were subject- ed to X-ray analyses. For easily determination of mineralogical changes, block diagrams prepared using the Jade program that show the results of analyses at various temperatures were present- ed in figures 3, 4, 5, 6 and 7. Figure 3- XRD block diagram of sample 1. The num bers 1: Dried, 2:200°C, 3:400 °C, 4:500°C, Results of routine analyses are conformable 5:550°C, 6:600°C, 7:650°C, 8:700°C, with those of petrographic studies and antigorite 9:800°C, 10:900°C, 11:1000°C, 12:1100°C was the main mineral observed. However, due to show the XRD analyses at that temperatu- res. (atg: antigorite, fo: forsterite, ens:enstatite) its lower abundance (2-3%), chrysotile could not be detected in X-ray analyses. There was no mineralogical change in analyses of all samples conducted at 200°C, 400°C and 500°C while only a little decrease was observed in the antigorite abundance with temperature increase. It was observed that the antigorite abundance was con- tinued to decrease at 550°C and olivine (forsterite) started to crystallize. At 600°C, antig- orite abundance was significantly decreased and forsterite continued to crystallize and its abun- Figure 4- XRD block diagram of sample 6. The num- dance was increased. At 650°C, antigorite was bers 1: Dried, 2:200°C, 3:400 °C, 4:500°C, mostly disappeared and forsterite continued to 5:550°C, 6:600°C, 7:650°C, 8:700°C, crystallize and enstatite was started to appear. In 9:800°C, 10:900°C, 11:1000°C, 12:1100°C analyses performed at temperatures higher than show the XRD analyses at that temperatu- res. (atg: antigorite, fo: forsterite, ens:enstatite) 700°C, forsterite and enstatite continued to crys- tallize and their abundances were increased. Considering the analyses conducted at 550°C, 600°C and 650°C, a significant amorphousiza- tion was detected in samples 11S and 29A (Figure 8).

DTA-TG Analyses

According to results of DTA analyses, sam- ples 1 and 29A yielded endothermic and exother- mic peaks at 695°C and 810°C, respectively. Figure 5- XRD block diagram of sample 11B. The num- Samples 6, 11B and 11S also showed similar bers 1: Dried, 2:200°C, 3:400 °C, 4:500°C, features with three endothermic peaks at 210°C, 5:550°C, 6:600°C, 7:650°C, 8:700°C, 9:800°C, 10:900°C, 11:1000°C, 12:1100°C 380°C and 690°C and, one exothermic peak at show the XRD analyses at that temperatu- 810°C (Figures 9, 10, 11, 12 and 13). res. (atg: antigorite, fo: forsterite, ens:enstatite) THERMAL REACTION OF ANTIGORITE 45

while brucite gives only one endothermic peak at 356-455°C temperature range. Examination of DTA diagrams yields endothermic peaks of clay minerals at about 210°C and of brucite at 380°C. The endothermic peak expected for the clay min- erals at temperatures between 625°C and 750°C coincides with that of antigorite.

Antigorite peaks in all samples are observed as endothermic at 690°C and exothermic at Figure 6-XRD block diagram of sample 11S. The num- 810°C. As shown in DTA curves, dehydroxilation bers 1: Dried, 2:200°C, 3:400 °C, 4:500°C, was occurred at about 550°C to 690°C. As deter- 5:550°C, 6:600°C, 7:650°C, 8:700°C, 9:800°C, 10:900°C, 11:1000°C, 12:1100°C mined by the X-ray analyses, reactions associ- show the XRD analyses at that temperatu- ated with dehydroxilation resulted in formation of res. (atg: antigorite, fo: forsterite, ens:enstatite) forsterite from antigorite (Mg3Si2O5(OH)4) at tem- peratures above 550°C and enstatite (MgSiO3) at temperatures above 650°C. In XRD analyses, antigorite was lastly found at 650°C and consid- ering the results of both DTA and XRD analyses reveal that antigorite can be stable at tempera- tures mostly 650°C-690°C. At temperatures high- er than 690°C which defines the upper stability limit of antigorite, forsterite and enstatite contin- ued to crystallize and this new mineral formation was recorded on DTA diagrams as two exother- Figure 7-XRD block diagram of sample 29A. The num- mic peaks at around 810°C. As a result, all these bers 1: Dried, 2:200°C, 3:400 °C, 4:500°C, mineralogical changes determined with the XRD 5:550°C, 6:600°C, 7:650°C, 8:700°C, studies are found to be conformable with DTA 9:800°C, 10:900°C, 11:1000°C, 12:1100°C analyses. show the XRD analyses at that temperatu- res. (atg: antigorite, fo: forsterite, ens:enstatite) According to results of TG analyses, 11% mass decrease was found in all samples (Figu- Thermal reactions in antigorite are developed res 9, 10, 11, 12 and 13). in parallel to temperature increase and at a tem- perature of 100°C, free water in samples and ab- RESULTS AND DISCUSSION sorbed water on the surface are lost due to dehy- dration. Examination of DTA and TG curves re- Water plays an important role in formation of veals that there is such a change in all samples various geological processes. Serpentinized at 100°C. Endothermic peaks at 210°C and oceanic lithosphere is believed to be the source 380°C for samples 6, 11B and 11S are attributed of water that is effective in development of sub- to clay minerals and brucite within the serpentine duction-related calc-alkaline arc volcanism (Ul- minerals that could not be detected in X-ray mer and Trommsdorf, 1995). In this respect, sta- analyses due to their lower abundance. Accor- bilities of serpentine minerals are very important ding to McKenzie (1970), montmorillonite group for determination of mode of occurrence and clay minerals give two endothermic peaks at depth of these processes. Therefore, thermal 125-260°C and 625-750°C temperature range reactions of serpentine minerals and mineralogi- 46 Gökçe GÜRTEKÝN and Mustafa ALBAYRAK

Figure 8- The amorphousization at 600°C (Sample 29A, Atg: antigorite, Fo: Forsterite) cal changes occurring during these events are According to Ulmer and Trommsdorf (1995), primarily important. forsterite is formed by the reaction between an- tigorite and brucite (if available) at low tempera- A number of experimental works were con- tures (antigorite + brucite forsterite + H2O) ducted for determination of stabilities of serpen- and about 3.5% H2O is released. With further tine minerals (Wunder and Schreyer, 1997) (Fi- increase of pressure and temperature, brucite is gure 14). In this study, serpentine minerals were completely removed and as shown in reactions 4 and 5, different minerals are formed. Diagram subjected to thermal treatment to investigate the showing the stability limits of antigorite is shown upper stability limits of these minerals and result- in figure 15. ing new mineral paragenesis. In this study antig- orite was used which is more stable in compari- Antigorite forsterite + talc + H2O son to other serpentine minerals and, it was (low pressure) (4) determined that different mineral paragenesis were obtained under various pressure and tem- Antigorite forsterite + enstatite + H2O perature conditions. Wunder and Schreyer (high pressure) (5) (1997) compiled results of previous works (Figu- In this study, antigorite minerals were subject- re 14) and determined the stability limits of antig- ed to thermal treatment under constant pressure orite and following reactions were stated to be (laboratory conditions). Mineralogical changes taken place during dehydroxilation of antigorite: occurred during this process were determined with XRD and DTA-TG analyses and stability lim- Antigorite talc + forsterite + H2O its of antigorite were determined under constant (15 kbar, 640 °C) (1) atmosphere pressure.

Antigorite forsterite + clinoenstatite + H2O All the samples are mostly composed of (77 kbar, 680 °C) (2) antigorite. However, on the basis of DTA analy- ses results, little amount of montmorillonite and Antigorite clinoenstatite + brucite + H20 brucite were also found in samples 6,11B and (>77 kbar, >680 °C) (3) 11S. THERMAL REACTION OF ANTIGORITE 47

Figure 9- DTA-TG curves of sample 1 Figure 12- DTA-TG curves of sample 11S

Figure 10- DTA-TG curves of sample 6 Figure 13- DTA-TG curves of sample 29A

Considering the results of XRD analyses, an- tigorite can be stable until a temperature range of 650°C-690°C but its abundance decreases depending on reactions associated with temper- ature increase. Increase in antigorite abundance was determined from peak intensities on XRD charts. In analyses at temperatures above 550°C, the amount of antigorite was further decreased and forsterite started to be formed. Antigorit+forsterite association at temperatures above 550°C was continued until 650-690°C and antigorite was removed at higher temperatures. Results of DTA analyses which were conforma- Figure 11- DTA-TG curves of sample 11B ble with X-ray determinations indicated that 48 Gökçe GÜRTEKÝN and Mustafa ALBAYRAK

Figure 15- Stability limit of antigorite (Ulmer ve Trommsdorf, 1995)

Figure 14- Previous experimental study of stability result of their reaction forsterite is formed and limit of serpentine minerals (Wunder ve some amount of water is released. In brucite-free Schreyer, 1997) samples (e.g., 1 and 29A), forsterite is formed from antigorite and similarly some amount of water is released. Examination of XRD analyses antigorite dehydroxilation reactions were started conducted at 550°C, 600°C and 650°C reveal the at 550°C and continued until 690°C. presence of amorphousization that is observed in all samples but particularly significant in samples X-ray analyses conducted at temperatures nos. 1 and 29A. The amorphousization is thought above 650°C reveal that in addition to forsterite, to be derived from silica that is released during enstatite also occurs and abundance of both the thermal reactions. Considering this, following minerals increases with temperature increase. reactions were first occurred during thermal reac- According to results of DTA analyses , endother- tion of antigorite: mic peak shown at 810°C following the dehyd- Antigorite + brucite forsterite + H2O + SiO2 roxilation at 690°C correspond to formation of (550°C-650°C) (6) forsterite and enstatite. However, XRD results imply that enstatite forms in a later stage than Antigorite forsterite + H2O + SiO2 forsterite (after 650°C). (550°C-650°C) (7)

In samples 6, 11B and 11S, antigorite is According to results of XRD analyses, during accompanied by little amount of brucite and, as a thermal reaction of antigorite enstatite is formed THERMAL REACTION OF ANTIGORITE 49

following the forsterite (650°C) and following Evans, B.W. 1977 Metamorphism of Alpine peri- reactions took place during the formation of dotites and serpentinites, Annual Review Earth enstatite: Planetary Science, 5, 397-448

Antigorite forsterite + enstatite + H2O Gürtekin, G. 2001 Mineralization stages of serpen- (650°C-690°C) (8) tinites in Çayýrbaðý (Konya) Ophiolites, Hacet- tepe University The Institute for Graduate Forsterite + SiO2 enstatite Studies in Science and Engineering, M.Sc. (>650°C) (9) Thesis, 93 page (unpublished)

As a result of dehydroxilation reactions occur- McKenzie, R. C. 1970 Differential Thermal Analysis, ring between 550-690°C it was found that first Volume 1, Fundamental Aspects, Academic forsterite forms antigorite. The amorphousization Press Inc. (London) LTD. 775 pp. that was determined by XRD analyses and observed in between dehydration and crystalliza- O'Hanley, D.S. 1991 Fault-Related phenomena asso- tion reactions may indicate that in addition to ciated with hydration and serpentine recrystal- water some amount of silica was also released lization during serpentinization, Canadian Mi- during these reactions. At temperature above neralogist, 29, 21-35 650°C forsterite is accompanied by enstatite. O'Hanley D. S. 1996 Serpentinites-Records of Tec- tonic and Petrological History, Oxford Mono- Considering all these data, antigorite was graphs on Geology and Geophysics No.34 found to be stable up to temperatures about 650 to 690°C. During dehydroxilation, antigorite- Özcan, A., Göncüoðlu, M. C., Turhan, N., Þentürk, K. forsterite association was observed at tempera- C. and Uysal, Þ. 1986 Geology map of the tures above 550°C and enstatite starts to crystal- Konya-Altýnekin-Kadýnhaný ve Ilgýn Regions, lize above 650°C. Forsterite+enstatite associa- MTA Map. tion is dominant by 690°C. Özcan, A., Göncüoðlu, M. C., Turhan, N., Þentürk, K. ACKNOWLEDGMENTS C. and Uysal, Þ. 1990 Geology of the Konya- Altýnekin-Kadýnhaný ve Ilgýn Regions, MTA Authors are grateful to the staff of Mineralogy- Report No: 9535 (unpublished). Petrography section of MAT Department of the MTA General Directorate for providing laboratory Ulmmer, P. and Trommsdorff, V. 1995 Serpentine sta- assistance. Appreciation is extended to Dr. bility to mantle depths and subduction-related Kývanç Zorlu (Mersin University, Geological magmatism, Science, 268, 858-861 Engineering Department) for his contributions. Wicks, F.J. and Whittaker, E.J.W. 1977 Serpentine Manuscript received on January 25, 2006 textures and serpentinization, Canadian Mine- ralogist, 15, 459-488 REFERENCES Wunder, B. and Schreyer, W. 1997 Antigorite: High- Bucher, K. and Frey, M. 1994, Petrogenesis of Me- pressure stability in the system MgO-SiO2-H2O tamorphic Rocks, sixth Edition, 318 pp. (MSH), Lithos, 41, 213-227