The Mt. Erciyes stratovolcano was built up in an intraplate tectonic environment as a consequence of Eurasian and Afro-Arabian continental collision. However, the volcanic products generally exhibit a calc-alkaline character; minor amounts of tholeiitic basalts are also present. Tholeiitic basalts show high Fe2O3, Mgo, CaO, low K2O, and depleted Ba, Nb, and especially Rb (2.3-5.97 ppm) contents, low Sr-87/Sr-86(0.703344-0.703964), and high Nd-143/Nd-144 (0.512920-0.512780) isotopic ratios. These compositional features show that they were derived from a depleted asthenospheric mantle source, possibly a MORB-like source component. In contrast, calc-alkaline basaltic rocks exhibit relatively high large-ion-lithophile and high-field-strength elements, high Sr-81/Sr-86 (0.704591-0.70507) and low Nd-143/Nd-114 (0.51272-0.512394) isotopic ratios.