World Multidisciplinary Earth Sciences Symposium, Prag, Czech Republic, 5 - 09 September 2016, pp.12
Late Proterozoic -Early Palaeozoic rocks of the NW Anatolia-Turkey; a remnant of an active continental margin of the Pan-African oceanic realm
İsmail Onur Tunç*, Erdinç Yiğitbaş
Ardahan University, Faculty of Social Sciences and Humanities, Department of Geography,Ardahan, Turkey
Çanakkale Onsekiz Mart University, Department of Geological Engineering, Çanakkale, Turkey
ABSTRACT
In northwest Anatolia, three E–W-trending tectonic units can be distinguished; İstanbul Zone (IZ) in the north, Sakarya Zone (SZ) in the south, and the Armutlu-Ovacık Zone (AOZ) between them which is dominated by strike-slip systems and a tectonic mixture of the IZ and the SZ. The Biga Peninsula (NW Anatolia), which is located in the westernmost part of the SZ, was affected by late Mesozoic-early Tertiary strike-slip tectonics. Metamorphic assemblages crop out as two NE-SW trending belts in the Biga Peninsula, which were described and evaluated by different names, ages, geological and tectonic meanings. Previous studies suggest a suture zone between these two metamorphic belts, beneath a thick Tertiary-Quaternary volcanic and sedimentary cover. This suture was evaluated as Paleo-or Neo-Tethyan. Themetamorphic assemblages in the south of this suture were evaluated as the continuation of the SZ and the northern ones were assigned to the Rhodope and Serbo-Macedonian massifs.The northern metamorphic assemblages are represented by a calc-alkaline metavolcanic dominated sequence at the bottom and a metasedimentary sequence at the top, which are tectonically imbricated with metaophiolites and eclogitic rocks in various sizes from centimeters to meters. Geochoronological studies on the northern metamorphic massifs yielded the following data: maximum sedimentation ages of the protoliths of metasedimentary rocks in the range of 559 ±17 to 582 ± 30 Ma; crystallization age of the protolith of metavolcanic rock is of 577 ± 20 Ma, and crystallization age of the protolith of eclogitic rocks is of 565 ± 9Ma. On the other hand, a metamorphic unit called as Torasan formation, which crops out in the southern belt on the Kazdağ antiform, is cut by early Devonian metagranitoids and having 566 ± 7 Ma maximum sedimentation age according to U-Pd zircon dating. In addition to the similar U-Pb zircon ages and the patterns of the concordia diagrams of the northern and the southern belt metamorphic units, there is also a very strong correlation between these metamorphic units, in terms of their lithological, stratigraphical, structural and metamorphic features. When we consider this correlation and the data together, as a conclusion, the remnants of a late Ediacaran –early Paleozoic active continental margin juxtaposed to the Pan-African oceanic realm in the basement of northwestern Anatolia.
Key words:Late Proterozoic-Early Paleozoic;Pan-African;active continental margin;Northwest Anatolia;U-Pb zircon