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| Titel |
New U-Pb ages from dykes cross-cutting the Demirci metamorphics, NW Turkey:
Implications for multiple orogenic events |
| VerfasserIn |
Fatih Sen, Hayrettin Koral, Irena Peytcheva |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124152
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| Publikation (Nr.) |
 EGU/EGU2016-3532.pdf |
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| Zusammenfassung |
| A high-grade metamorphic sequence in the Sünnice Mountains, Bolu, NW Turkey, is
represented by migmatitic quartzo-feldspathic gneisses in amphibolite facies called the
Demirci metamorphics/paragneisses, and a sequence of low-grade meta-volcanics containing
meta-andesites with minor meta-rhyolites and meta-sedimentary rocks called the Yellice
meta-volcanics. They are intruded by the Dirgine granite with an age of Upper Ediacaran
(576-565 Ma) and are considered a part of the İstanbul-Zonguldak Tectonic Unit. The
Demirci paragneisses are also intruded by a number of dykes in various directions,
traditionally considered without radiometric dating to have been emplaced in a single
magmatic phase in the Eocene related to post-collision regime of the Anatolide-Tauride
platform.
Mafic-intermediate-felsic dykes cross-cutting the Demirci paragneisses have
been investigated in maps of 1/1000 scale, and their U-Pb zircon age, major-trace
element and kinematic data have been obtained. The mafics dykes cross-cutting the
Yellice meta-volcanics, equivalents of those in the Demirci paragneisses, occur in
N400-500E orientations and have calc-alkaline basalt compositions with a subduction
signature. The intermediate dykes occur in N650W, N800W orientations and have
calc-alkaline basaltic andesite to andesitic compositions with a subduction signature.
Some felsics occur in N150W and N800E orientations and have calc-alkaline dacitic
compositions with a collisional tectonic setting. Other calc-alkaline granitic dykes occur
in N750E orientation and calc-alkaline granitic compositions with a subduction
signature.
U–Pb LA-ICP-MS dating of zircons yield ages from 485.7±3.6 Ma (i.e.
Cambro-Ordovician) for N800E trending dacite dykes; 443.0±5.4 Ma (i.e. Ordovician-Silurian)
for N150W trending dacite dykes; 301.0±1.6 Ma (i.e. Upper Pennsylvanian-Carboniferous)
for N650W trending basaltic andesite dykes; 268.2±2.4 Ma (i.e. Guadalupian-Permian) for
N40-500E trending basalt dykes; 262.9±3.4 Ma (i.e. Guadalupian-Permian) for N750E
trending granitic dykes; and 261.4±1.7 Ma (i.e. Guadalupian-Permian) for N800W trending
andesite dykes.
New radiometric ages from the dykes cross-cutting the Demirci metamorphics-paragneisses
in the İstanbul-Zonguldak Tectonic Unit imply several consecutive orogenic phases. The
Cambro-Ordovician and Ordovician-Silurian ages are concordant with the Caledonian
Orogeny-first and second closure phase of the Tersseyre-Tornquist Sea, a branch of the
Iapetus; the Upper Carboniferous age with the Variscan Orogeny-late closure phase of the
Rheic Ocean, and Permian ages with the Hercynian Orogeny-initial closure phase of
Palaeo-Tethys Ocean. |
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