QUATERNARY VOLCANISM OF CENTRAL ANATOLIA (TURKEY) - ASSOCIATION OF CALC-ALKALINE AND ALKALINE MAGMATISMS IN A ZONE OF CONVERGENCE

Collision volcanism in Central Anatolia (Cappadocia) began at least in the late Miocene. Because of the North-South Arabian-Eurasian convergence since this period, the Anatolian block is displaced towards the West along the North and East Anatolian strike-slip faults. Kinematic reconstructions show that the East Anatolian Fault is both sinistral and convergent. As a consequence, the Anatolian block is currently being deformed. Quaternary volcanism in Central Anatolia is represented by several hundreds of monogenetic scoria cones, lava flows, maars, and domes as well as two strato-volcanoes, Hasan Dag and Erciyes Dag. The monogenetic volcanism is bimodal (basalts and rhyolites), whereas the stratovolcanoes exhibit a complete calc-alkaline suite, from basalts to rhyolites. Most of the igneous products are calc-alkaline. Basalts erupted mainly from the monogenetic cones, lava flows, and maars. Andesites are encountered in the strato-volcanoes as lava flows, domes, and nuees ardentes deposits. Dacites and rhyolites occur as ignimbrites and dispersed maars and domes. Volcanic events were recorded up to historical times. Some basalts from monogenetic edifices, contemporaneous with the calc-alkaline suite, exhibit mineralogical and geochemical features that are typical of intraplate alkaline suites, such as normative nepheline, alkali feldspars, and Ti and Cr-rich Cpx. Euhedral microlites of aluminous garnet, although rare, have been observed in basalts, rhyodacites, and rhyolites. This association of contemporaneous calc-alkaline and alkaline suites may be related to collision tectonics.