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| Titel |
The Amphiolite Layers In The Cumulate Gabbros, (Northern-Turkey) |
| VerfasserIn |
Mutlu Özkan, Ömer Faruk Çelik, İsmail Emir Altıntaş, Sarah Sherlock, Cyril Chelle-Michou, Andrea Marzoli, Alexey Ulianov, Rahmi Melih Çörtük, Gültekin Topuz |
| 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 |
250132004
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| Publikation (Nr.) |
 EGU/EGU2016-12466.pdf |
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| Zusammenfassung |
| The Early-Middle Jurassic SSZ type dismembered ophiolite sequence, which is remnants
of the Tethyan oceanic lithosphere, crop out in the accretionary complex around
Tokat-Çamlıbel region (Northern Turkey). The main lithology of the ophiolite sequence are
cumulate gabbros, isotropic gabbros and basalts. The amphibolite layers, which their
thickness are up to 2 m, are observed in the cumulate gabbros. In this study, we
aim to discuss a possible formation mechanism of the amphibolitic rocks in the
cumulate gabbros, based on the field, mineralogical, geochemical and geochronological
data.
The cumulate gabbros (olivine-gabbro, gabbro-norite and gabbro) have generally well
developed magmatic layers and they show cumulate texture. They are cross cut by
pegmatite gabbros, dolerites and plagiogranite dikes. In terms of the mechanism
of formation, the amphibolite layers in the cumulate gabbros are different from
dolerite, pegmatite gabbro and plagiogranite dikes crosscutting the cumulate gabbros.
Although the cumulate gabbros, the mafic and felsic dikes have not undergone any
metamorphism (except the hydrothermal metamorphism), the amphibolite layers show
well developed foliation and banded structure. Moreover, field and petrographic
observations showed that the amphibolitic rocks were highly subjected to shearing. The
amphibolitic rocks are mainly composed of magnesio-hornblende + plagioclase
(andesine), ± biotite and opaque minerals and they exhibit nematoblastic texture. The
amphibolite layers in the cumulate gabbros are crosscut by the plagiogranite dikes. The
plagiogranites consist mainly of quartz, plagioclase, biotite and opaque minerals and
they show granular texture. Undulose extinction and sub-grain formation in quartz
minerals indicate to the presence of deformation phase affecting the plagiogranite
dikes.
LA-ICP-MS dating on zircon from plagiogranite dikes which is cross-cutting of the
amphibolite layers, yielded Middle Jurassic ages. 40Ar/39Ar dating of amphiboles from
the amphibolite yielded a cooling age of 166.5 ± 7.4 Ma (2σ) (Middle Jurassic).
Metamorphic temperature of the amphibolites was calculated as 688 ± 12 ˚ C for about 0.2
Gpa.
Transform faults boundaries and the other fractures in the oceanic crust can be
appropriate places for the dikes injection and circulation of hydrothermal fluids. Accordingly
the amphibolite layers in the cumulate gabbros were probably occurred by the activity of
these faults.
This study was funded by TUBITAK (project no: 112Y123). |
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