MESUT AYGÜL, GÜLTEKİN TOPUZ, ARAL I. OKAY, MUHARREM SATIR, HANS-PETER MEYER

The Kemer Metamorphic Complex (NW Turkey): A Subducted Continental Margin of the Sakarya Zone

High-pressure and ultrahigh-pressure metamorphic rocks crop out widely in the northern Aegean. In many instances their ages and tectonic setting are poorly constrained. Here we report newly discovered high-pressure rocks of continental crustal origin and of Late Cretaceous age southwest of the Marmara Sea. They occur at the contact between the Rhodope-Strandja Zone in the north and the Sakarya Zone in the south. The Kemer Metamorphic Complex is composed mainly of mica schist, calcschist and marble with minor metabasite and serpentinite. The mica schists contain garnet, phengite (3.30-3.44 c.p.f.u), (±) paragonite, albite, epidote, calcite, chlorite and titanite. The high-pressure metamorphic origin of the mica schists is shown by the high silica contents of the white micas and by glaucophane inclusions in garnet. In the metabasites the mineral assemblage is garnet, barroisite, epidote, albite, titanite, quartz, phengite and chlorite; no evidence is left for the former presence of high-pressure minerals. Metamorphic conditions are constrained by mineral equilibria: a 560-640°C temperature at a minimum pressure of 10 kbar. The metamorphism is dated at 64-84 Ma by the Rb-Sr phengite-whole rock method. The Kemer Metamorphic Complex is in tectonic contact with an accretionary ophiolitic mélange consisting of limestone, basalt, serpentinite, greywacke, radiolarian chert and metabasite. Some of the metabasites in the mélange contain Na-amphibole and lawsonite, indicating a subduction origin. The ages of the limestone blocks in the mélange range from Late Triassic to Late Cretaceous and that of the radiolarite blocks from Middle Jurassic to Early Cretaceous, indicating an oceanic domain dating back to Late Triassic at least. The Kemer Metamorphic Complex and the Çetmi Mélange are intruded by a granodiorite of Early Eocene (52 Ma) age and are unconformably covered by a Late Eocene volcano-sedimentary succession. The lithology of the Kemer Metamorphic Complex resembles a continental margin rather than an oceanic accretionary complex. This and the presence of a Late Cretaceous magmatic arc in the north (Sredna-Gora-Pontide) suggest that the Kemer metamorphic rocks were initially deposited on the northern passive margin of the Sakarya Zone, which was subducted under the Rhodope-Strandja continental domain.

Anahtar Kelimeler:

Kemer Metamorphic Complex, ophiolitic mélange, HP/LT metamorphism, Sakarya Zone, continental margin

The Kemer Metamorphic Complex (NW Turkey): A Subducted Continental Margin of the Sakarya Zone

Keywords:

Kemer Metamorphic Complex, ophiolitic mélange, HP/LT metamorphism, Sakarya Zone, continental margin,

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Beccaletto, L. & Jenny, C. 2004. Geology and correlation of the Ezine Zone: a Rhodope fragment in NW Turkey? Turkish Journal of Earth Sciences 13, 145–176.
Beccaletto, L., Bartolini, A.C., Martini, R., Hochuli, P.A. & Kozur, H. 2005. Biostratigraphic data from Çetmi Melange, northwest Turkey: palaeogeographic and tectonic implications. Palaeogeography, Palaeoclimatology, Palaeoecology 221, 215– 244.
Beccaletto, L., Bonev, N., Bosch, D. & Bruguier, O. 2007. Record of a Palaegene syn-collisional extension in the north Aegean region: evidence from the Kemer micaschists (NW Turkey). Geological Magazine 144, 393–400.
Bonev, N. & Stampfli, G. 2008. Petrology, geochemistry and geodynamic implications of Jurassic island arc magmatism as revealed by mafi c volcanic rocks in the Mesozoic low-grade sequence, eastern Rhodope, Bulgaria. Lithos 100, 210–233.
Brinkmann, R., Gümüş, H., Plumhoff, F. & Salah, A.A. 1977. Höhere Oberfreide in nordwest Anatolien und Th rakien. Neues Jahrbuch für Geologie und Paleontologie Abhandlungen 154, 1–20.
Burg, J.P., Ricou, L.E., Ivanov, Z., Godfriaux, I., Dimov, D. & Klain, L. 1996. Syn-metamorphic nappe complex in the Rhodope Massif: structure and kinematics. Terra Nova 8, 6–15.
Cliff, R.A. 1985. Isotopic dating in metamorphic belts. Journal of the Geological Society, London 142, 97 –110.
Green, T.H. & Hellman, P.L. 1982. Fe-Mg partitioning between coexisting garnet and phengite at high pressure, and comments on a garnet-phengite geothermometer. Lithos 15, 253–266.
Holland, T. & Powell, R. 1998. An internally consistent thermodynamic data set for phases of petrological interest. Journal of Metamorphic Geology 16, 309–343.
Konak, N. 2002. Geological Map of Turkey. İzmir Sheet, Scale 1:500.000. Publication of the General Directorate of the Mineral Research and Exploration (MTA), Ankara.
Magganas, C.A. 2002. Constraints on the petrogenesis of Evros ophiolite extrusives, NE Greece. Lithos 65, 165–182.
Massonne, H.J. & Schreyer, W. 1987. Phengite geobarometry based on the limiting assemblage with K-feldspar, phlogopite and quartz. Contribution to Mineralogy and Petrology 96, 212– 224.
Mposkos, E. & Kostopoulos, D. 2001. Diamond, former coesite and supersilicic garnet in metasedimentary rocks from the Greek Rhodope: a new ultrahigh-pressure metamorphic province established. Earth and Planetary Science Letters 192, 497–506.
Okay, A.I. 1989. Tectonic units and sutures in the Pontides, Northern Turkey. In: Şengör, A.M.C. (ed), Tectonic Evolution of the Tethyan Region. Kluwer Academic Publishers, 109–116.
Okay, A.I. & Göncüoğlu, M.C. 2004. Karakaya Complex: a review of data and concepts. Turkish Journal of Earth Sciences 13, 77–95.
Okay, A.I. & Monie, P. 1997. Early Mesozoic subduction in the Eastern Mediterranean: evidence from Triassic eclogite in northwest Turkey. Geology 25, 595–598.
Okay, A.I., Monod, O. & Monie, P. 2002. Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction. Lithos 64, 155–178.
Okay, A.I. & Satir, M. 2000a. Upper Cretaceous eclogite-facies metamorphic rocks from the Biga Peninsula, Northwest Turkey. Turkish Journal of Earth Sciences 9, 47–56.
Okay, A.I. & Satir, M. 2000b. Coeval plutonism and metamorphism in a latest Oligocene metamorphic core complex in northwest Turkey. Geological Magazine 137, 495–516.
Okay, A.I., Sİyako, M. & Bürkan, K.A. 1991. Geology and tectonic evolution of the Biga Peninsula, northwest Turkey. Bulletin of the İstanbul Technical University 44, 191–256.
Okay, A.I., Satir, M., Maluski, H., Sİyako, M., Monie, P., Metzger, R. & Akyüz, S. 1996. Palaeo- and Neo-Tethyan events in northwest Turkey. In: Yin, E. & Harrison, M. (eds), Tectonics of Asia. Cambridge University Press, 420–441.
Okay, A.I., Satir, M. & Siebel, W. 2006. Pre-Alpide Palaeozoic and Mesozoic orogenic events in the Eastern Mediterranean region. In: Gee, D.G. & Stephenson, R.A. (eds), European Lithosphere Dynamics. Geological Society, London, Memoirs 32, 389–405.
Okay, A.I., Satir, M., Tüysüz, O., Akyüz, S. & Chen, F. 2001. Th e tectonics of the Strandja Massif: late-Variscan and mid- Mesozoic deformation and metamorphism in the northern Aegean. International Journal of Earth Sciences 90, 217–233.
Okay, A.I. & Tansel, İ. 1994. New data on the upper age of the Intra-Pontide ocean from north of Sarköy (Th race). Bulletin of Mineral Research and Exploration 114, 23–26.
Okay, A.I & Tüysüz, O. 1999. Tethyan sutures of northern Turkey. In: Durand, B., Jolivet, L., Horvath, F. & Seranne, M. (eds), Th e Mediterranean Basins: Tertiary Extension Within the Alpine Orogen. Geological Society, London, Special Publications 156, 475–515.
Okay, A.I., Özcan, E., Cavazza, W., Okay, N. & Less, G. 2010. Basement types, Lower Eocene series, Upper Eocene olistostromes and the initiation of the southern Th race Basin, NW Turkey. Turkish Journal of Earth Sciences 19, 1–25.
Özcan, E., Less, G., Okay, A.I., Báldi-Beke, M., Kollanyi, K. & Yılmaz, İ. Ö. 2010. Stratigraphy and larger foraminifera of the Eocene shallow-marine and olistostromal units of the southern part of the Th race Basin, NW Turkey. Turkish Journal of Earth Sciences 19, 27–77.
Pouchou, J.L. & Pıchoır, F. 1984. A new model for quantitative analyses. I. Application to the analysis of homogeneous samples. La Recherche Aerospatiale 3, 13–38.
Pouchou, J.L. & Pıchoır, F. 1985. ‘PAP’ (f-r-Z) correction procedure for improved quantitative microanalysis. In: Armstrong, J.T (ed), Microbeam Analysis. San Francisco Press, San Francisco, CA, 104–106.
Powell, R. & Holland, T. 1988. An internally consistent thermodynamic dataset with uncertainties and correlations: 3. Application methods, worked examples and a computer program. Journal of Metamorphic Geology 6, 173–204.
Ricou, L.E., Burg, J.P., Godfriaux, I. & Ivanov, Z. 1998. Rhodope and Vardar: the metamorphic and the olistostromic paired belts related to the Cretaceous subduction under Europe. Geodinamica Acta 11, 285–309.
Schıffman, P. & Day, H.W. 1999. Petrological methods for the study of very low-grade metabasites. In: Frey, M. & Robınson, D. (eds), Low-Grade Metamorphism. Blackwell Science Ltd., Oxford, London.
Şengör, A.M.C & Yilmaz, Y. 1981. Tethyan evolution of Turkey: a plate tectonic approach. Tectonophysics 75, 181 –241.
Sİrel, E. & Acar, Ş. 1982. Praebullalveolina, a new foraminifal genus from the Upper Eocene of the Afyon and Çanakkale region (west of Turkey). Eclogae Geologicae Helvetiae 75, 821–839.
Spaggiari, C.V., Gray, D.R. & Foster, D.A. 2002. Blueschist metamorphism during accretion in the Lachlan Orogen, south-eastern Australia. Journal of Metamorphic Geology 20, 711–726.
Sunal, G., Natal’in, B., Satir, M. & Toroman, E. 2006. Paleozoic magmatic events in the Strandja Massif, NW Turkey. Geodinamica Acta 19, 283–300.
Sunal, G., Satır, M., Natalin, B.A., Topuz, G. & Vonderschmidt, O. 2011. Metamorphism and diachronous cooling in a contractional orogen: the Strandja Massif, NW Turkey. Geological Magazine 148, 580–596.
Sunal, G., Satır, M., Natalin, B.A. & Toraman, E. 2008. Paleotectonic position of the Strandja Massif and surrounding continental blocks based on zircon Pb-Pb age studies. International Geology Review 60, 519–545.
Topuz, G., Altherr, R., Kalt, A., Satır, M., Werner, O. & Schwarz, W.H. 2004a. Aluminous granulites from the Pulur complex, NE Turkey: a case of partial melting, effi cient melt extraction and crystallisation. Lithos 72, 183–207.
Topuz, G., Altherr, R., Satir, M. & Schwartz, W.H. 2004b. Low-grade metamorphic rocks from the Pulur Complex, NE Turkey: implications for the pre-Liassic evolution of the Eastern Pontides. International Journal of Earth Sciences 93, 72–91.
Topuz, G., Altherr, R., Schwartz, W.H., Dokuz, A. & Meyer, H.P. 2007. Variscan amphibolites-facies rocks from the Kurtoğlu metamorphic complex (Gümüşhane area, Eastern Pontides, Turkey). International Journal of Earth Sciences 96, 861–873.
Topuz, G., Okay, A.I., Altherr, R., Satır, M. & Schwarz, W.H. 2008. Late Cretaceous blueschist facies metamorphism in southern Th race (Turkey) and its geodynamic implications. Journal of Metamorphic Geology 26, 895–913.
Topuz, G., Altherr, R., Sıebel, W., Schwarz, W.H., Zack, T., Hasözbek, A., Barth, M., Satır, M. & Şen, C. 2010. Carboniferous high-potassium I-type granitoid magmatism in the Eastern Pontides: the Gümüşhane pluton (NE Turkey). Lithos 116, 92–110.
Türkecan, A. & Yurtsever, A. 2002. Geological Map of Turkey. İstanbul Sheet, Scale 1:500.000. Publication of the General Directorate of the Mineral Research and Exploration (MTA), Ankara.
Villa, I.M. 1998. Isotopic closure. Terra Nova 10, 42–47.
Wu, C.M., Wang, X.S., Yang, C.H., Geng, Y.S., & Lıu, F.L. 2002. Empirical garnet-muscovite geothermometry in metapelites. Lithos 62, 1–13.