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 converg ence since this period, the Anatolian block is displaced towards the W est along the North and East Anatolian strike-slip faults. Kinematic r econstructions show that the East Anatolian Fault is both sinistral an d 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 d omes as well as two strato-volcanoes, Hasan Dag and Erciyes Dag. The m onogenetic volcanism is bimodal (basalts and rhyolites), whereas the s tratovolcanoes exhibit a complete calc-alkaline suite, from basalts to rhyolites. Most of the igneous products are calc-alkaline. Basalts er upted mainly from the monogenetic cones, lava flows, and maars. Andesi tes are encountered in the strato-volcanoes as lava flows, domes, and nuees ardentes deposits. Dacites and rhyolites occur as ignimbrites an d dispersed maars and domes. Volcanic events were recorded up to histo rical times. Some basalts from monogenetic edifices, contemporaneous w ith the calc-alkaline suite, exhibit mineralogical and geochemical fea tures that are typical of intraplate alkaline suites, such as normativ e nepheline, alkali feldspars, and Ti and Cr-rich Cpx. Euhedral microl ites 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.