Geology of the quaternary volcanic centres of the east Anatolia

Following the collision along the Bitlis-Zagros suture, a north-south conve rgence between the Arabian Platform and Laurasia has continued uninterrupte d until the present. As a result, the continental crust has been shortened, thickened and consequently elevated to form the Turkish-Iranian high plate au. On the high plateau volcanic activity began during the Neogene, intensi fied during the late Miocene-Pliocene and continued until historical times. Large volcanic centres have been developed during the Quaternary which for m significant peaks above the Turkish-Iranian high plateau. Among the Quate rnary volcanoes, the major volcanic centres are Ararat, Tendurek, Suphan an d Nemrut. Ararat (Agri Dagi) is the largest volcanic center and is a compou nd stratovolcano, consisting of Greater Ararat and lesser Ararat. The forme r represents the highest elevation of Anatolia reaching over 5000 m in heig ht. Tendurek is a double-peaked shield volcano, which produced a voluminous amount of basalt lava as extensive pahoehoe, and aa flows. It has an ill-d efined semi-caldera. Suphan is an isolated stratovolcano, capped by silicic dome. It represents the second highest topographic elevation in Anatolia, with a height of over 4000 m. A cluster of subsidiary cones and small domes surrounds the volcano. Nemrut is the largest member of a group of volcanoe s, which trend north-south. It it; a stratovolcano, having a well-defined c ollapse caldera and a caldera lake. Various volcanic ejecta have been extru ded from these volcanic centres over the last 1 to 2 million years. The Qua ternary volcanic centres, although temporally and spatially closely associa ted, display a wide range of lavas from basalt to rhyolite. The volcanoes h ave diverse compositional trends; Ararat is distinctly subalkaline, Suphan is mildly subalkaline, Nemrut is mildly alkaline and Tendurek is strongly a lkaline. The major and trace element compositions together with the isotope ratios indicate that their magmas were generated. from a heterogeneous man tle source. Each of the volcanic centres has undergone a partly different m agmatic evolution. (C) 1998 Elsevier Science B.V. All rights reserved.