Eastern Anatolia: A Hot Spot in a Collision Zone Without a Mantle Plume (Kenyonte talk)


KESKİN M.

American Geophysical Union (AGU) Chapman Conference, The Great Plume Debate: The Origin and Impact of LIPs and Hot Spots, Fort William, Scotland, U.K, United Kingdom, 1 - 04 August 2005, pp.73

  • Publication Type: Conference Paper / Summary Text
  • Country: United Kingdom
  • Page Numbers: pp.73

Abstract

 

The Eastern Anatolian region is considered to be one of the best examples of a continental collision zone in the world. It contains one of the highest plateaus of the Alpine-Himalayan mountain belt with an average elevation of 2 km above sea level. Geological records indicate that the region was beneath sea level until Serravalian (~13 Ma), and then experienced an abrupt block uplift, consequently being elevated above sea level. This was followed by a widespread subaerial volcanism in Eastern Anatolia and the surrounding regions (e.g. Georgia, Armenia, Azerbaijan and Iran). Volcanic activity produced a wide range of volcanic products (i.e. lavas and pyroclastic units), spanning the whole compositional range from basalts to rhyolites. Great volumes of volcanic material reaching over 1 km in thickness in places erupted onto the surface, covering almost two-thirds of the region. The region gradually gained a regional domal shape comparable to that of the Ethiopian High Plateau, although the Anatolian dome has a north-south shortened asymmetrical shape possibly due to collision (Sengor et al., 2003).

The existence of a regional dome structure and widespread magmatism are both regarded as evidence for the existence of a mantle plume and these do indeed exist in Eastern Anatolia. By these properties, the Eastern Anatolia region can be regarded as the site of a "melting anomaly" or "hotspot" resembling closely the setting proposed for mantle plumes. However, geologic and geochemical data provide evidence against a plume origin. The results of the Eastern Turkey Seismic Experiment Project (Sandvol et al., 2003), coupled with geological and geochemical findings, support the view that both domal uplift and extensive magma generation can be linked to the mechanical removal of a portion or the whole thickness of the mantle lithosphere, accompanied by passive upwelling of normal-temperature asthenospheric mantle to a depth as shallow as 38 to 50 km. This process might have taken place either by delamination (Pearce et al., 1990; Keskin et al., 1998), slab-steepening & breakoff (Keskin, 2003), or a combination of both. The Eastern Anatolian example is important in showing that not only plumes but also shallow plate tectonic processes have the potential to generate regional domal structures in the Earth's lithosphere as well as large volumes of magma.