CRUSTAL STRUCTURE IN EURASIA
We provide an extensive summary of the tectonic and geodynamic evolution of the region and discuss the origin of crustal heterogeneity and processes of crustal evolution in the Precambrian cratons of Europe and Siberia, and major Phanerozoic basins, orogens, and rift zones. We conclude that for all tectonic settings there are significant variations in depth to Moho and crustal structure, essentially controlled by the age of the last major tectono-thermal event. We demonstrate that generally-adopted global averages of crustal parameters are incorrect for any particular tectonic setting in Europe and in Siberia, and conclude that we cannot define a “typical cratonic” crust. We show that relative thickness of the upper-middle crystalline crust (Vp<6.8 km/s) and the lower (Vp>6.8 km/s) crust is indicative of the crustal origin, i.e. oceanic, transitional, platform, or extended crust. Continental rifting generally thins the upper-middle crust without changing the average Vp. Thinning of the lower crust during rifting is less significant and generally occurs without significant change in lower crustal average Vp, suggesting a complex interplay of magmatic underplating, gabbro-eclogite phase transition and delamination. The Barents Sea shelf differs from rifted continental crust in structure of the crystalline crust and average Vp velocities, indicating that processes other than rifting have also been involved in its evolution.