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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS013 Oral Presentation 2225
European mantle lithosphere as a mosaic of plates with their own preassembly
anisotropy signature
Dr. Vladislav Babuska
Seismology Geophysical Institute, Czech Acad. Sci. IASPEI
Jaroslava Plomerova
The concept of mobile terranes, or micro-continents, is considered as one of the most important
additions to plate tectonics. However, we have only vague ideas about a role of large volumes of the
mantle lithosphere in the formation of paleo-continents, in their brake-up and in later assemblage of
their pieces into a new continent. Knowledge of seismic anisotropy is key to our understanding of
tectonic fabrics in the deep lithosphere and sublithospheric mantle. To study building elements of the
European continent, we have modelled three-dimensional seismic anisotropy of the mantle lithosphere
from anisotropic parameters of teleseismic body waves. We invert and interpret jointly shear-wave
splitting parameters and P residual spheres based on data from dense networks of temporary and
permanent stations in several European regions. Changes in orientation of the large-scale anisotropy,
caused by systematic preferred orientation of olivine, identify boundaries of domains of mantle
lithosphere. Individual domains are characterized by a consistent large-scale orientation of anisotropy
approximated by hexagonal or orthorhombic symmetry with generally inclined symmetry axes. The
domains are separated by mapped tectonic boundaries (sutures), which cut the entire lithosphere. Such
boundaries play important role in the lithosphere architecture and its dynamics, e.g. in the location of
intraplate earthquakes and volcanic fields. Besides the change of anisotropy orientation at domain
boundaries, we often observe a change of the lithosphere and/or crust thicknesses. We do not detect
any fabric of the mantle lithosphere, which could have been produced by a collision of microcontinents
in a volume detectable by large-scale seismic anisotropy. The observations of consistent anisotropy
within individual blocks of the mantle lithosphere reflect frozen-in olivine preferred orientation, most
probably formed prior to the assembly of microcontinents that created the modern European landmass.
Therefore, our findings support a plate-tectonic view of the continental lithosphere as a mosaic of rigid
blocks of the mantle lithosphere with complicated but relatively sharp contact zones. These contacts are
blurred by the easily deformed overlying crust terranes.
Keywords: european mantle lithosphere, fossil seismic anisotropy, mosaic of microplates