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40Ar/39Ar geochronology, geochemistry and petrology of volcanic rocks from the Simav Graben, western Turkey

40Ar/39Ar geochronology, geochemistry and petrology of volcanic rocks from the Simav Graben, western Turkey
40Ar/39Ar geochronology, geochemistry and petrology of volcanic rocks from the Simav Graben, western Turkey
Major and trace element compositions with Sr–Nd isotopic ratios, as well as Ar–Ar radiometric ages of the Miocene volcanic rocks from the Neogene units around Simav region (western Anatolia), are used to discuss the genetic relationship between (1) high-voluminous Lower–Middle Miocene high-potassic, calc-alkaline (HKCA) and (2) Middle Miocene small-voluminous high-MgO shoshonitic–ultrapotassic (SHO–UK) magmatic units in the region. All the HKCA rocks, including basaltic to rhyolitic (and granitic) samples, share similar trace element characteristics (enrichments of LILE and LREE and depletions in HFSE as a common feature of orogenic magmatic rocks), with subtle differences in their 87Sr/86Sr(i) ratios (basalts and rhyolites ~0.708, dacites ~0.710). Most of the samples of the high-MgO SHO–UK group are classified as shoshonite and latite, with some lamproites, sharing similar geochemical features with the other ultrapotassic rocks of the Mediterranean. All the rock groups have similar and high abundances of incompatible trace elements, and radiogenic Sr. Geochemical modeling of the trace element and isotopic ratios of the samples reveals that both the SHO–UK and HKCA groups were derived from a common mantle source which had been highly metasomatized and enriched by continental materials during partial subduction of the crustal metamorphic slices in a continental collision setting. The geochemical variations of these rocks were mainly controlled by source characteristics (such as heterogeneity) and variable degrees of partial melting and subsequent effects of fractional crystallization, with low degrees of crustal contamination. The HKCA series were derived by higher degrees of partial melting of the lithospheric mantle source than the SHO–UK rocks. The HKCA rocks then underwent two-stage fractional crystallization (clinopyroxene-dominated followed by feldspar-dominated fractionating mineral assemblages) to form the high-K calc-alkaline basalt to rhyolite series, whereas the SHO–UK rocks experienced comparatively little fractional crystallization. A tectonic scenario involving the rapidly extending and thinning of orogenic crust is compatible with the time-dependent compositional variation of the magmatic rocks.
Geochemistry, Geochronology, Calc-alkaline, Lamproite, Ultrapotassic, Western Anatolia
0010-7999
Article 24
Semiz, Barış
a4ee5871-b732-43b4-9a87-da7bfeec626d
Ersoy, E. Yalçın
2c4e6074-ea3b-4404-9faa-5e53611bff06
Özpınar, Yahya
510a8f31-5c00-40e6-896f-dfcd2cbdd864
Helvacı, Cahit
1bf18566-d59b-45fc-ba93-c81b2203e9d5
Palmer, Martin R.
d2e60e81-5d6e-4ddb-a243-602537286080
Billor, Mehmet Z.
eeba78e9-c4fd-4ca9-b769-d1e3752ed2ba
Semiz, Barış
a4ee5871-b732-43b4-9a87-da7bfeec626d
Ersoy, E. Yalçın
2c4e6074-ea3b-4404-9faa-5e53611bff06
Özpınar, Yahya
510a8f31-5c00-40e6-896f-dfcd2cbdd864
Helvacı, Cahit
1bf18566-d59b-45fc-ba93-c81b2203e9d5
Palmer, Martin R.
d2e60e81-5d6e-4ddb-a243-602537286080
Billor, Mehmet Z.
eeba78e9-c4fd-4ca9-b769-d1e3752ed2ba

Semiz, Barış, Ersoy, E. Yalçın, Özpınar, Yahya, Helvacı, Cahit, Palmer, Martin R. and Billor, Mehmet Z. (2015) 40Ar/39Ar geochronology, geochemistry and petrology of volcanic rocks from the Simav Graben, western Turkey. Contributions to Mineralogy and Petrology, 170 (2), Article 24. (doi:10.1007/s00410-015-1178-8).

Record type: Article

Abstract

Major and trace element compositions with Sr–Nd isotopic ratios, as well as Ar–Ar radiometric ages of the Miocene volcanic rocks from the Neogene units around Simav region (western Anatolia), are used to discuss the genetic relationship between (1) high-voluminous Lower–Middle Miocene high-potassic, calc-alkaline (HKCA) and (2) Middle Miocene small-voluminous high-MgO shoshonitic–ultrapotassic (SHO–UK) magmatic units in the region. All the HKCA rocks, including basaltic to rhyolitic (and granitic) samples, share similar trace element characteristics (enrichments of LILE and LREE and depletions in HFSE as a common feature of orogenic magmatic rocks), with subtle differences in their 87Sr/86Sr(i) ratios (basalts and rhyolites ~0.708, dacites ~0.710). Most of the samples of the high-MgO SHO–UK group are classified as shoshonite and latite, with some lamproites, sharing similar geochemical features with the other ultrapotassic rocks of the Mediterranean. All the rock groups have similar and high abundances of incompatible trace elements, and radiogenic Sr. Geochemical modeling of the trace element and isotopic ratios of the samples reveals that both the SHO–UK and HKCA groups were derived from a common mantle source which had been highly metasomatized and enriched by continental materials during partial subduction of the crustal metamorphic slices in a continental collision setting. The geochemical variations of these rocks were mainly controlled by source characteristics (such as heterogeneity) and variable degrees of partial melting and subsequent effects of fractional crystallization, with low degrees of crustal contamination. The HKCA series were derived by higher degrees of partial melting of the lithospheric mantle source than the SHO–UK rocks. The HKCA rocks then underwent two-stage fractional crystallization (clinopyroxene-dominated followed by feldspar-dominated fractionating mineral assemblages) to form the high-K calc-alkaline basalt to rhyolite series, whereas the SHO–UK rocks experienced comparatively little fractional crystallization. A tectonic scenario involving the rapidly extending and thinning of orogenic crust is compatible with the time-dependent compositional variation of the magmatic rocks.

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e-pub ahead of print date: 2015
Published date: August 2015
Keywords: Geochemistry, Geochronology, Calc-alkaline, Lamproite, Ultrapotassic, Western Anatolia
Organisations: Geochemistry

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Local EPrints ID: 383917
URI: http://eprints.soton.ac.uk/id/eprint/383917
ISSN: 0010-7999
PURE UUID: a935d6ae-4130-4413-af47-a1a38edeadef

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Date deposited: 11 Nov 2015 16:59
Last modified: 01 Mar 2019 17:31

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Author: Barış Semiz
Author: E. Yalçın Ersoy
Author: Yahya Özpınar
Author: Cahit Helvacı
Author: Mehmet Z. Billor

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