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DOI

10.19111/bulletinofmre.693353

Abstract

Volcanism that has been active since the early Miocene along a N-S trending line from Eskişehir to Isparta displays calc-alkaline and alkaline character and is closely associated with slab tearing processes. However, the geodynamic setting of these volcanic units between Afyon and Emirdağ is still poorly known. In this study, petrological characteristics of the Emirdağ and İscehisar volcanic units have been investigated using petrography, whole-rock geochemistry and Sr-Nd isotopes. The Emirdağ and İscehisar volcanic units overlap the SeydileIgnimbrites. The Emirdağ volcanic unit is trachyandesite and the İscehisar volcanic unit is trachyte, basaltic trachyandesite and trachydacite in composition. The Emirdağ volcanic unit displays calc-alkaline character, while the İscehisar volcanic unit is alkaline but the rocks from both the units have shoshonite character defined by their high K2O contents. The Emirdağ volcanic unit has 87Sr/86Sr ratios of 0.706790-0.706284 and 143Nd/144Nd ratios of 0.512472-0.512463, while these ratios in the İscehisar volcanic unit are of 0.707650-0.706527 and 0.512464-0.512424, respectively. Data revealed by this study indicate that these volcanic units were affected by crustal contamination, fractional crystallization and magma mixing. Rising of asthenosphere in the region due to the extensional regime in the Early Miocene appears to have caused formation of volcanism that pass from calc-alkaline to alkaline in character. The Emirdağ and İscehisar volcanic units are the products of the volcanism that developed in the late stages of southward slab roll-back and in the extensional regime prior to the slab tearing event.

https://doi.org/10.19111/bulletinofmre.693353

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