40Ar/39Ar and U-Pb geochronology of the Iran Tepe volcanic complex, Eastern Rhodopes

Pages: 
pp. 3-12
Geological Institute of the Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Geological Institute of the Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland
Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland
Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland
Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland
Abstract: 

The Iran Tepe volcanic complex occurs in the south-eastern part of the Eastern Rhodope massif. The rocks are represented by calc-alkaline and high-K calc-alkaline basaltic andesite to dacite epiclastics, lava flows and dikes, which are crosscut by andesitic and latitic dikes and rhyolitic dykes from the Planinets dyke swarm. Stratigraphic data and existing K/Ar ages suggest that the Iran Tepe volcanic complex is Upper Eocene (35-39 Ma), and is one of the oldest volcanic structures in the Eastern Rhodopes. However, new 40Ar/39Ar laser fusion and incremental step-heating experiments on biotites and isotope dilution – thermal ionization mass spectrometry (ID-TIMS) U-Pb age data on single zircons from the bottom and top lava flows and dykes more precisely constrain the ages and time span of volcanic activity, and show that the volcanism is younger. Volcanic activity started with calc-alkaline andesites and dacites at the beginning of the Oligocene (~33.9 Ma) and culminated with the intrusion of latitic dykes at ~33.0 Ma. Rhyolites from the Planinets dyke swarm yield a similar age (32.8 Ma), but their genetic relationship with the more mafic Iran Tepe lavas remains unclear.

Keywords: 

Eastern Rhodopes, Oligocene volcanism, 40Ar/39Ar and U-Pb ages

VOLUME 39 (3)/December 2010

Geological Institute of the Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Geological Institute of the Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland
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Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland
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Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland
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Section des Sciences de la Terre et de l’Environnement, Université de Genève, Rue de Maraîchers 13, 1205 Genève, Switzerland

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 24; Sofia 1113, Bulgaria

Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Block 107, Sofia 1113, Bulgaria; Institute for Energy, Joint Research Centre, European Commission, P.O. Box 2, NL-1755 ZG Petten, The Netherlands
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Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Block 107, Sofia 1113, Bulgaria
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Institute for Energy, Joint Research Centre, European Commission, P.O. Box 2, NL-1755 ZG Petten, The Netherlands
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Institute for Energy, Joint Research Centre, European Commission, P.O. Box 2, NL-1755 ZG Petten, The Netherlands

Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Block 107, Sofia 1113, Bulgaria;Institute for Energy, Joint Research Centre, European Commission, P.O. Box 2, NL-1755 ZG Petten, The Netherlands
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Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Block 107, Sofia 1113, Bulgaria
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Institute for Energy, Joint Research Centre, European Commission, P.O. Box 2, NL-1755 ZG Petten, The Netherlands
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Institute for Energy, Joint Research Centre, European Commission, P.O. Box 2, NL-1755 ZG Petten, The Netherlands

DIPSA , University of Firenze, Italy
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DISAT, University of L’Aquila, Italy

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 24, 1113 Sofia, Bulgaria