Discovery of Miocene adakitic dacite from the Eastern Pontides Belt (NE Turkey) and a revised geodynamic model for the late Cenozoic evolution of the Eastern Mediterranean region

Yener Eyuboglu, M. Santosh, Keewook Yi, Osman Bektaş, Sanghoon Kwon

Research output: Contribution to journalArticle

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Abstract

The Cenozoic magmatic record within the ca. 500km long eastern Pontides orogen, located within the Alpine metallogenic belt, is critical to evaluate the tectonic history and geodynamic evolution of the eastern Mediterranean region. In this paper we report for the first time late Miocene adakitic rocks from the southeastern part of the eastern Pontides belt and present results from geochemical and Sr-Nd isotopic studies as well as zircon U-Pb geochronology. The Tavdagi dacite that we investigate in this study is exposed as round or ellipsoidal shaped bodies, sills, and dikes in the southeastern part of the belt. Zircons in the dacite show euhedral crystal morphology with oscillatory zoning and high Th/U values (up to 1.69) typical of magmatic origin. Zircon LA-ICPMS analysis yielded a weighted mean 206Pb/ 238U age of 7.86±0.15Ma. SHRIMP analyses of zircons with typical magmatic zoning from another sample yielded a weighted mean 206Pb/ 238U age of 8.79±0.19Ma. Both ages are identical and constrain the timing of dacitic magmatism as late Miocene. The Miocene Tavdagi dacite shows adakitic affinity with high SiO 2 (68.95-71.41wt.%), Al 2O 3 (14.88-16.02wt.%), Na 2O (3.27-4.12wt.%), Sr (331.4-462.1ppm), Sr/Y (85-103.7), La N/Yb N (34.3-50.9) and low Y (3.2-5ppm) values. Their initial 143Nd/ 144Nd (0.512723-0.512736) and 87Sr/ 86Sr (0.70484-0.70494) ratios are, respectively, lower and higher than those of normal oceanic crust. The geological, geochemical and isotopic data suggest that the adakitic magmatism was generated by partial melting of the mafic lower crust in the southeastern part of the eastern Pontide belt during the late Miocene. Based on the results presented in this study and a synthesis of the geological and tectonic information on the region, we propose that the entire northern edge of the eastern Pontides-Lesser Caucasus-Elbruz magmatic arc was an active continental margin during the Cenozoic. We identify a migration of the Cenozoic magmatism towards north over time resulting from the roll-back of the southward subducted Tethys oceanic lithosphere. Slab break-off during Pliocene is proposed to have triggered asthenospheric upwelling and partial melting of the subduction-modified mantle wedge which generated the alkaline magmatic rocks exposed in the northern part of the magmatic arc.

Original languageEnglish
Pages (from-to)218-232
Number of pages15
JournalLithos
Volume146-147
DOIs
Publication statusPublished - 2012 Aug 1

Fingerprint

Geodynamics
dacite
geodynamics
zircon
Miocene
magmatism
Zoning
Tectonics
zoning
partial melting
Melting
Rocks
Geochronology
tectonics
Levees
oceanic lithosphere
Tethys
sill
geochronology
rock

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

Cite this

@article{cbea4b2187b44b1d9a8da10c3b9fc41a,
title = "Discovery of Miocene adakitic dacite from the Eastern Pontides Belt (NE Turkey) and a revised geodynamic model for the late Cenozoic evolution of the Eastern Mediterranean region",
abstract = "The Cenozoic magmatic record within the ca. 500km long eastern Pontides orogen, located within the Alpine metallogenic belt, is critical to evaluate the tectonic history and geodynamic evolution of the eastern Mediterranean region. In this paper we report for the first time late Miocene adakitic rocks from the southeastern part of the eastern Pontides belt and present results from geochemical and Sr-Nd isotopic studies as well as zircon U-Pb geochronology. The Tavdagi dacite that we investigate in this study is exposed as round or ellipsoidal shaped bodies, sills, and dikes in the southeastern part of the belt. Zircons in the dacite show euhedral crystal morphology with oscillatory zoning and high Th/U values (up to 1.69) typical of magmatic origin. Zircon LA-ICPMS analysis yielded a weighted mean 206Pb/ 238U age of 7.86±0.15Ma. SHRIMP analyses of zircons with typical magmatic zoning from another sample yielded a weighted mean 206Pb/ 238U age of 8.79±0.19Ma. Both ages are identical and constrain the timing of dacitic magmatism as late Miocene. The Miocene Tavdagi dacite shows adakitic affinity with high SiO 2 (68.95-71.41wt.{\%}), Al 2O 3 (14.88-16.02wt.{\%}), Na 2O (3.27-4.12wt.{\%}), Sr (331.4-462.1ppm), Sr/Y (85-103.7), La N/Yb N (34.3-50.9) and low Y (3.2-5ppm) values. Their initial 143Nd/ 144Nd (0.512723-0.512736) and 87Sr/ 86Sr (0.70484-0.70494) ratios are, respectively, lower and higher than those of normal oceanic crust. The geological, geochemical and isotopic data suggest that the adakitic magmatism was generated by partial melting of the mafic lower crust in the southeastern part of the eastern Pontide belt during the late Miocene. Based on the results presented in this study and a synthesis of the geological and tectonic information on the region, we propose that the entire northern edge of the eastern Pontides-Lesser Caucasus-Elbruz magmatic arc was an active continental margin during the Cenozoic. We identify a migration of the Cenozoic magmatism towards north over time resulting from the roll-back of the southward subducted Tethys oceanic lithosphere. Slab break-off during Pliocene is proposed to have triggered asthenospheric upwelling and partial melting of the subduction-modified mantle wedge which generated the alkaline magmatic rocks exposed in the northern part of the magmatic arc.",
author = "Yener Eyuboglu and M. Santosh and Keewook Yi and Osman Bektaş and Sanghoon Kwon",
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Discovery of Miocene adakitic dacite from the Eastern Pontides Belt (NE Turkey) and a revised geodynamic model for the late Cenozoic evolution of the Eastern Mediterranean region. / Eyuboglu, Yener; Santosh, M.; Yi, Keewook; Bektaş, Osman; Kwon, Sanghoon.

In: Lithos, Vol. 146-147, 01.08.2012, p. 218-232.

Research output: Contribution to journalArticle

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T1 - Discovery of Miocene adakitic dacite from the Eastern Pontides Belt (NE Turkey) and a revised geodynamic model for the late Cenozoic evolution of the Eastern Mediterranean region

AU - Eyuboglu, Yener

AU - Santosh, M.

AU - Yi, Keewook

AU - Bektaş, Osman

AU - Kwon, Sanghoon

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N2 - The Cenozoic magmatic record within the ca. 500km long eastern Pontides orogen, located within the Alpine metallogenic belt, is critical to evaluate the tectonic history and geodynamic evolution of the eastern Mediterranean region. In this paper we report for the first time late Miocene adakitic rocks from the southeastern part of the eastern Pontides belt and present results from geochemical and Sr-Nd isotopic studies as well as zircon U-Pb geochronology. The Tavdagi dacite that we investigate in this study is exposed as round or ellipsoidal shaped bodies, sills, and dikes in the southeastern part of the belt. Zircons in the dacite show euhedral crystal morphology with oscillatory zoning and high Th/U values (up to 1.69) typical of magmatic origin. Zircon LA-ICPMS analysis yielded a weighted mean 206Pb/ 238U age of 7.86±0.15Ma. SHRIMP analyses of zircons with typical magmatic zoning from another sample yielded a weighted mean 206Pb/ 238U age of 8.79±0.19Ma. Both ages are identical and constrain the timing of dacitic magmatism as late Miocene. The Miocene Tavdagi dacite shows adakitic affinity with high SiO 2 (68.95-71.41wt.%), Al 2O 3 (14.88-16.02wt.%), Na 2O (3.27-4.12wt.%), Sr (331.4-462.1ppm), Sr/Y (85-103.7), La N/Yb N (34.3-50.9) and low Y (3.2-5ppm) values. Their initial 143Nd/ 144Nd (0.512723-0.512736) and 87Sr/ 86Sr (0.70484-0.70494) ratios are, respectively, lower and higher than those of normal oceanic crust. The geological, geochemical and isotopic data suggest that the adakitic magmatism was generated by partial melting of the mafic lower crust in the southeastern part of the eastern Pontide belt during the late Miocene. Based on the results presented in this study and a synthesis of the geological and tectonic information on the region, we propose that the entire northern edge of the eastern Pontides-Lesser Caucasus-Elbruz magmatic arc was an active continental margin during the Cenozoic. We identify a migration of the Cenozoic magmatism towards north over time resulting from the roll-back of the southward subducted Tethys oceanic lithosphere. Slab break-off during Pliocene is proposed to have triggered asthenospheric upwelling and partial melting of the subduction-modified mantle wedge which generated the alkaline magmatic rocks exposed in the northern part of the magmatic arc.

AB - The Cenozoic magmatic record within the ca. 500km long eastern Pontides orogen, located within the Alpine metallogenic belt, is critical to evaluate the tectonic history and geodynamic evolution of the eastern Mediterranean region. In this paper we report for the first time late Miocene adakitic rocks from the southeastern part of the eastern Pontides belt and present results from geochemical and Sr-Nd isotopic studies as well as zircon U-Pb geochronology. The Tavdagi dacite that we investigate in this study is exposed as round or ellipsoidal shaped bodies, sills, and dikes in the southeastern part of the belt. Zircons in the dacite show euhedral crystal morphology with oscillatory zoning and high Th/U values (up to 1.69) typical of magmatic origin. Zircon LA-ICPMS analysis yielded a weighted mean 206Pb/ 238U age of 7.86±0.15Ma. SHRIMP analyses of zircons with typical magmatic zoning from another sample yielded a weighted mean 206Pb/ 238U age of 8.79±0.19Ma. Both ages are identical and constrain the timing of dacitic magmatism as late Miocene. The Miocene Tavdagi dacite shows adakitic affinity with high SiO 2 (68.95-71.41wt.%), Al 2O 3 (14.88-16.02wt.%), Na 2O (3.27-4.12wt.%), Sr (331.4-462.1ppm), Sr/Y (85-103.7), La N/Yb N (34.3-50.9) and low Y (3.2-5ppm) values. Their initial 143Nd/ 144Nd (0.512723-0.512736) and 87Sr/ 86Sr (0.70484-0.70494) ratios are, respectively, lower and higher than those of normal oceanic crust. The geological, geochemical and isotopic data suggest that the adakitic magmatism was generated by partial melting of the mafic lower crust in the southeastern part of the eastern Pontide belt during the late Miocene. Based on the results presented in this study and a synthesis of the geological and tectonic information on the region, we propose that the entire northern edge of the eastern Pontides-Lesser Caucasus-Elbruz magmatic arc was an active continental margin during the Cenozoic. We identify a migration of the Cenozoic magmatism towards north over time resulting from the roll-back of the southward subducted Tethys oceanic lithosphere. Slab break-off during Pliocene is proposed to have triggered asthenospheric upwelling and partial melting of the subduction-modified mantle wedge which generated the alkaline magmatic rocks exposed in the northern part of the magmatic arc.

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