Geochemical and Pb–Sr–Nd isotopic composition of the ultrapotassic volcanic rocks from the extension-related Çamardı-Ulukışla basin, Niğde Province, Central Anatolia, Turkey

Abstract

Major, trace element and Sr–Nd–Pb isotope data are presented for the ultrapotassic lavas and dykes from the Late Cretaceous-Early Tertiary Ulukışla Basin in the Central Anatolia. All samples have geochemical characteristics belonging to Group III ultrapotassic rocks (Foley, S.F., Venturelli, G., Green, D.H., Toscani, L., 1987, The ultrapotassic rocks: characteristics, classification and constraints for petrogenetic models, Earth Science Reviews, 24, 81–134.). These rocks have unusually high contents of large-ion-lithophile elements (LILE) (e.g. Ba up to 5900 ppm, K 2O up to 8 wt% in lava and 10 wt% in dykes). Negative Nb and Ti anomalies and LREE enrichments relative to HREE on chondrite normalized trace and rare earth element patterns indicate that subduction related material is present in the mantle source region. Their high initial 87Sr/ 86Sr (0.70798–0.70917) and low 143Nd/ 144Nd (0,512109–0,512239) ratios suggest that they originated from an enriched lithospheric mantle source with low Sm/Nd ratios. The elevated 207Pb/ 206Pb (15.743–15.797), low 143Nd/ 144Nd ratios and geochemical features such as low Nb/La and elevated Ce/Sr ratios may reflect the involvement of sediments as a metasomatic agent for the source region. The steep trend on the 207Pb/ 204Pb vs 206Pb/ 204Pb diagram also imply that the metasomatic component represents recycled continent-derived material in the source region. Integration of the geochemistry with regional and local geological data suggest that the ultrapotassic volcanic rocks from the Çamardı-Ulukışla basin were derived from a lithospheric mantle material in a post-collisional extension-related geodynamic setting following Late Mesozoic continental collision between the Eurasian plate and Tauride-Anatolide platform, as a result of convergence between the Eurasian and Afro-Arabian plates.