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| Titel |
New U-Pb and Rb-Sr ages from northwest Turkey; Early Cretaceous continental collision in the western Pontides |
| VerfasserIn |
K. Akbayram, A. Okay, M. Satir, G. Topuz |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025590
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| Zusammenfassung |
| Keywords: Intra-Pontide suture, Ä°stanbul Zone, Sakarya Zone, U-Pb zircon ages, Rb-Sr mica
ages
We provide new isotopic data from the Intra-Pontide Suture Zone, which indicate
Early Cretaceous collision between the Sakarya and Ä°stanbul terranes following the
consumption of the Intra-Pontide Ocean. The study area is located south of Sapanca
Lake between the Ä°stanbul and Sakarya terranes in northwest Turkey. These two
terranes show different geological histories, as reflected in their stratigraphic record,
and are juxtaposed along the Intra-Pontide suture. The new U/Pb zircon and Rb/Sr
mica ages come from south of the Sapanca Lake, south of the North Anatolian
Fault in northwest Turkey. The Ä°stanbul terrane has a late Proterozoic basement
(Chen et al., 2002; 570 Ma) overlain by a sedimentary sequence of Ordovician to
Carboniferous age. The Sakarya terrane is characterized by Carboniferous (330-310 Ma)
high temperature metamorphism (Okay et al., 2006), Paleozoic granitic plutonism
(Topuz et al., 2007) and by the presence of Palaeo-Tethyan subduction-accretion
units.
South of the Sapanca Lake, three main tectonostratigraphic units have been differentiated
forming a northeastward dipping thrust stack. At the top of the thrust stack is an
amphibolite-facies metamorphic unit consisting of an intercalation of amphibolite,
metaperidotite, metapyroxenite and gneiss representing a Proterozoic metaophiolite in the
basement of the Istanbul Zone. This old metaophiolite is underlain by a Cretaceous
accretionary complex of metabasite, metachert, slate and serpentinite. The lowermost tectonic
unit in the thrust stack is a metasandstone, slate, phyllite and marble unit metamorphosed in
greenschist facies.
Our U/Pb geochronological data comes from the basement gneisses and the
metasedimentary unit. The age of deposition and metamorphism of this metasedimentary unit
were not constrained. The U/Pb ages of the clastic zircons from metasandstones are
between 500-317 Ma. These new clastic zircon ages from the metasedimentary unit
show that deposition of the sandstones must be later than Carboniferous (316±2,4
Ma).
The Rb-Sr muscovite and biotite ages from metasedimentary unit and the basement
gneisses give Early Cretaceous (138-111 Ma) ages. The muscovite ages of metasandstones
are 138±1,5 Ma represents the metamorphic age of metasedimentary unit and the biotite
Cretaceous cooling age of 111,3±1,1 Ma from the reheating of the Proterozoic
basement.
The new Rb/Sr ages indicate that the collision between the Istanbul and Sakarya terranes
occurred during the Early Cretaceous.
REFERENCES
Chen, F., Siebel, W., Sati r, M., TerzioÄlu, N., Saka, K., 2002. Geochronology of the
Karadere basement (NW Turkey) and implications for the geological evolution of the
Ä°stanbul Zone. Int. J. Earth Sci., 91, 469-481.
Okay, A.I., Sati r, M. & Siebel, W., 2006, Pre-Alpide orogenic events in the
Eastern
Mediterranean region. In: European Lithosphere Dynamics (eds. Gee, D. G.,
and
Stephenson, R. A.), Geological Society, London, Memoirs 32, 389-405.
Topuz, G., Altherr, R., Schwartz,W.H., Dokuz, A.,Meyer, H.-P., 2007. Variscan
amphibolites-facies rocks from the KurtoÄlu metamorphic complex
(Gümüşhane area, Eastern Pontides, Turkey). Int. J. Earth Sci. 96, 861–873.
Please fill in your abstract text. |
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