Petrological and geochemical characteristics of cenozoic high-K calc-alkaline volcanism in Konya, central Anatolia, Turkey

Late Miocene to Pliocene volcanic rocks outcrop west, northwest and southwest of the Konya area in Central Anatolia, Turkey. Volcanic products are lava domes, nuee ardentes and ignimbrite deposits, predominantly andesitic to dasitic in composition, together with rare basalt, basaltic andesite, basaltic trachyandesite and trachyandesite (50.35-69.39% SiO2). The serie exhibits high-K calc-alkaline affinities. Fractional crystallization of pyroxene, plagioclase and Fe-Ti oxides is the main process in the magmatic evolution of Konya volcanic rocks. Volcanic units exhibit typical high-K calc-alkaline character. Their geochemical characteristics (e.g., enrichments in Ln elements such as K, Rb, Ba, Sr, depletion in HFSE such as Ti, Nb, and high Ba/Nb and Low Nb/Y ratios) sire consistent with those of active continental margin regions. High Sr-87/Sr-86 (0.704841-0.707340) and low Nd-143/Nd-144 (0.512390-0.512618) ratios suggest crustal involvement in their petrogenesis. Correlations between Sr-86/Sr-87 isotope with Rb, Rb/Mb, Rb/Ba, and Rb/Sr also emphasize the effect of crustal contamination on the andesitic and dacitic magmas. As a consequence, Konya volcanic rocks are products of assimilation and fractional crystallization (AFC) processes of a magma which seems to be linked to the subduction of the African plate underneath the Anatolian plate during Miocene. (C) 1998 Elsevier Science B.V. All rights reserved.