Petrogenesis and geodynamics of plagiogranites from Central Turkey (Ekecikdag/Aksaray): new geochemical and isotopic data for generation in an arc basin system within the northern branch of Neotethys

Date

2017-06-01

Author

Köksal, Serhat
Toksoy Köksal, Fatma
Göncüoğlu, Mehmet Cemal

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In the Late Cretaceous, throughout the closure of the Neotethys Ocean, ophiolitic rocks from the A degrees zmir-Ankara-Erzincan ocean branch were overthrusted the northern margin of the Tauride-Anatolide Platform. The ophiolitic rocks in the Ekecikdag (Aksaray/Central Turkey) region typify the oceanic crust of the A degrees zmir-Ankara-Erzincan branch of Neotethys. The gabbros in the area are cut by copious plagiogranite dykes, and both rock units are intruded by mafic dykes. The plagiogranites are leucocratic, fine- to medium-grained calc-alkaline rocks characterized mainly by plagioclase and quartz, with minor amounts of biotite, hornblende and clinopyroxene, and accessory phases of zircon, titanite, apatite and opaque minerals. They are tonalite and trondhjemite in composition with high SiO2 (69.9-75.9 wt%) and exceptionally low K2O (< 0.5 wt%) contents. The plagiogranites in common with gabbros and mafic dykes show high large-ion lithophile elements/high-field strength element ratios with depletion in Nb, Ti and light rare-earth elements with respect to N-MORB. The plagiogranites together with gabbros and mafic dykes show low initial Sr-87/Sr-86 ratios (0.70419-0.70647), high AENd((T)) (6.0-7.5) values with Pb-206/Pb-204 (18.199-18.581), Pb-207/Pb-204 (15.571-15.639) and Pb-208/Pb-204 (38.292-38.605) ratios indicating a depleted mantle source modified with a subduction component. They show similar isotopic characteristics to the other supra-subduction zone (SSZ) ophiolites in the Eastern Mediterranean to East Anatolian-Lesser Caucasus and Iran regions. It is suggested that the Ekecikdag plagiogranite was generated in a short time interval from a depleted mantle source in a SSZ/fore-arc basin setting, and its nature was further modified by a subduction component during intra-oceanic subduction.

Subject Keywords

Plagiogranite, Ophiolite, Isotope, Turkey, Late Cretaceous

URI

https://hdl.handle.net/11511/31321

Journal

INTERNATIONAL JOURNAL OF EARTH SCIENCES

DOI

https://doi.org/10.1007/s00531-016-1401-5

Collections

Graduate School of Natural and Applied Sciences, Article

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Citation Formats

S. Köksal, F. Toksoy Köksal, and M. C. Göncüoğlu, “Petrogenesis and geodynamics of plagiogranites from Central Turkey (Ekecikdag/Aksaray): new geochemical and isotopic data for generation in an arc basin system within the northern branch of Neotethys,” INTERNATIONAL JOURNAL OF EARTH SCIENCES, pp. 1181–1203, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/31321.