The quaternary Erciyes stratovolcano and its associated monogenetic cones exhibit tholeiitic, alkaline, and calc-alkaline suites, with the calc-alkaline series dominating. Calc-alkaline products are andesitic, dacitic, and rhyodacitic, showing moderate to low MgO and high K2O, plus LIL and HFS element contents. The andesites display trace-element patterns similar to those of the Central Mexican Volcanic belt, the Colville igneous complex (northeastern Washington, USA) and the Taos Plateau volcanic field (in north-central New Mexico, associated with northern Rio Grande Rift). Dacites from Erciyes also resemble these igneous complexes and give patterns similar to those of the upper crust. Furthermore, the high Ba/Nb ratio (> 28) is typical of arc volcanism (Fitton et al., 1988) ranging from 27 to 47 for andesites, and 27 to 50 for dacites at Erciyes. Calc-alkaline suites also show high Rb/Nb ratios (4-7.5). Moreover, Sr-87/Sr-86 and Nd-143/Nd-144 ratios range from 0.703434 to 0.705143, and 0.51294 to 0.5126 for andesites and dacites, respectively. These incompatible element and isotopic ratios suggest two possible mechanisms for the genesis of calc-alkaline suites: subduction enrichment or crustal involvement.