The petrography and geochemistry of the Tepekent (Konya) area volcanic rocks

In this study, Miocene aged dasitic, rhyolitic and basaltic roks and their pyroclastics cropping out in the Tepekent region in northwest of Konya were examined in terms of mineralogical, petrographic, geochemical and petrological, and studies were carried out to reveal the relationship between the geology of the region and magmatism. Miocene aged rocks in Tepekent region have basaltic trachy-andesite dasite and rhyolite composition according to TAS diagram. Basaltic trachy-andesites are named as shoshonite according to their Na2O-K2O content. In field observations, enclaves varying from mm to dm were observed in dasitic rocks and these enclaves fall into the trachy-basalt area in the TAS diagram. Basaltic trachy-andesites show holocrystalline porphyritic texture and contain olivine and clinopyroxene as mafic minerals, locally zeolitized and olivines iddingsified. Dacites contain volcanic glass, they show hypocrystalline porphyritic texture and contain amphibole, biotite, quartz, Fe-Ti oxide. The enclaves in dacitic rocks contain amphibole, the main mafic mineral, they have textural features such as quenched amphibole, blade-like biotite and sieve-textured plagioclase found in magma-mixed enclaves. Rhyolites have more volcanic glass content than dacites and show hypohyaline texture. Rhyolites contain quartz, sanidine, biotite, plagioclase and Fe-Ti oxides. In the Primitive mantle normalized trace element diagram of the investigated rocks, enrichment is observed in elements with large ion radius (LILE: K, Rb, Sr, Ba and Th), while depletion was observed in elements with high field energy (HFSE: Zr, Nb, Ta, Ti, Y). The chondrite normalized rare earth element distributions (La/Lu)N vary between 14-15. While spoon pattern indicating amphibole fractionation is observed in this diagram, this pattern is not observed in rhyolites and negative Eu anomaly indicating plagioclase fractionation and negative Ba anomaly indicating sanidine fractionation are observed. According to all geochemical results, it is thought that the rocks are the products of high K content bimodal volcanism after the subduction bearing collision and are derived from the enriched lithospheric mantle.