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Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: Implications for extension-related origin and mantle source characteristics

Abstract : Collisional and post-collisional volcanic rocks in the Ulubey (Ordu) area at the western edge of the Eastern Pontide Tertiary Volcanic Province (EPTVP) in NE Turkey are divided into four suites; Middle Eocene (49.4- 44.6 Ma) aged Andesite-Trachyandesite (AT), Trachyandesite-Trachydacite-Rhyolite (TTR), Trachydacite- Dacite (TD) suites, and Middle Miocene (15.1 Ma) aged Trachybasalt (TB) suite. Local stratigraphy in the Ulubey area starts with shallow marine environment sediments of the Paleocene-Eocene time and then continues extensively with sub-aerial andesitic to rhyolitic and rare basaltic volcanism during the Eocene and Miocene time, respectively. Petrographically, the volcanic rocks are composed primarily of andesites/ trachyandesites, withminor trachydacites/rhyolites, basalts/trachybasalts and pyroclastics, and show porphyric, hyalo-microlitic porphyric and rarely glomeroporphyric, intersertal, intergranular, fluidal and sieve textures. The Ulubey (Ordu) volcanic rocks indicate magma evolution from tholeiitic-alkaline to calc-alkaline with medium-K contents. Primitive mantle normalized trace element and chondrite normalized rare earth element (REE) patterns show that the volcanic rocks have moderate light rare earth element (LREE)/heavy rare earth element (HREE) ratios relative to E-TypeMORB and depletion in Nb, Ta and Ti. High Th/Yb ratios indicate parental magma(s) derived from an enriched source formed bymixing of slab and asthenospheric melts previouslymodified by fluids and sediments froma subduction zone. All of the volcanic rocks share similar incompatible element ratios (e.g., La/Sm, Zr/Nb, La/Nb) and chondrite-normalized REE patterns, indicating that the basic to acidic rocks originated from the same source. The volcanic rocks were produced by the slab dehydration-induced melting of an existing metasomatized mantle source, and the fluids from the slab dehydration introduced significant large ion lithophile element (LILE) and LREE to the source,masking its inherent HFSE-enriched characteristics. The initial 87Sr/86Sr (0.7044-0.7050) and åNd (.0.3 to+3.4) ratios of the volcanics suggest that they originated from an enriched lithosphericmantle source with low Sm/Nd ratios. Integration of the geochemical, petrological and isotopical with regional and local geological data suggest that the Tertiary volcanic rocks from the Ulubey (Ordu) area were derived from an enriched mantle, which had been previously metasomatized by fluids derived from subducted slab during the Eocene toMiocene in a collisional and post-collisional extension-related geodynamic setting following Late Mesozoic continental collision between the Eurasian plate and the Tauride-Anatolide platform.
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https://hal-insu.archives-ouvertes.fr/insu-00665728
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Submitted on : Thursday, February 2, 2012 - 3:44:38 PM
Last modification on : Friday, April 5, 2019 - 8:22:41 PM

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Irfan Temizel, Mehmet Arslan, Gilles Ruffet, Jean-Jacques Peucat. Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: Implications for extension-related origin and mantle source characteristics. Lithos, Elsevier, 2012, 128-131, pp.126-147. ⟨10.1016/j.lithos.2011.10.006⟩. ⟨insu-00665728⟩

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