Some features of the structure of the mantle of the East Mediterranean and their geodynamic interpretation
© O.B. Gintov, T.A. Tsvetkova, I.V. Bugaenko, A.V. Murovskaya, 2016
We consider specific velocity anomalies and the corresponding mantle structures of the East Mediterranean-Black Sea-Caspian region.
The anomalies are located on latitudinal and longitudinal seismic tomography sections obtained by constructing 3D P-velocity model of Eurasia
applying the Taylor approximation method. The depth of the study is of 50-2900 km. The accuracy of determination of the velocity Vð is about ± 0,015 km/s.
Velocity sections are shown in residual
values Vð. Physical and
mineralogical mantle model of Pushcharovsky was used for the cross sections specification.
Key words: seismic tomography, high-velocity section, plume, slab, down-welling, mantle, P-waves, micro-plates, subduction.
In the 25-30°E cross sections between latitudes of the 34-48°N high-velocity slabs sinking from the northern edge of the African plate
and the southern parts of the East-European plate towards each other are seen. Slabs are connected at a depth of about 600 km in the upper
mantle transition zone in the area of 42-43°N. Below the slabs junction high-velocity mantle zone thickens and extends to a depth of 1000-1200 km that
occurs as a result of slabs relatively high-velocity material accumulation. From this area down-welling begins which can be traced on latitude
sections of 35-45°N as an almost continuous inclined layer of ~ 1100 km width and ~ 1900 km length. Down-welling submerges from a depth
of 450-550 km at Moesian and Aegean micro-plates area to a depth of 1600-1900 km beneath the East Black Sea, Anatolian micro-plates and
the northern part of the Arabian plate. The mechanism of the inclined layer formation is discussed with the involvement of global seismic
tomography data, and the numerical simulation performed by L.I. Lobkovsky.
In the 42-44°N and 34-36°E sections we trace column type vertical structure, which crosses almost the entire mantle at depths of 50-100 to > 2500 km.
In the middle of the column on its axis there is a relatively high-velocity anomaly, which reduces in size and values downward. The shape and
structure of the mantle column resembles a "tornado". We consider two possible alternative mechanisms of its formation: a) steep subduction of
the West Black Sea micro plate beneath the Central Black Sea Ridge, "wedging" of the mantle and the extension stresses occurrence in
border zone I and middle mantle; b) rising of the plume from zone D'', formation of extension area in middle and upper mantle, lithosphere
pulling inward and the subduction zone formation.