Tectonic depressions on the East-European and Siberian platforms: numerical modeling of convection beneath the Eurasian continent

Abstract

In modern concepts, the upper mantle of the Earth is a highly viscous incompressible liquid, and its flow is described using the Navier – Stokes equations in the Oberbeck – Boussinesq and geodynamic approximations. Convective flows in the upper mantle play a decisive role in the kinematics of lithospheric plates and the geological history of continental regions. Mathematical modeling is a basic method for studying convective processes in the mantle. Our paper presents a numerical model of convection, which is based on the implicit artificial compressibility method. This model is tested in detail by comparing our calculation results with the results of a well-known international test. It is demonstrated that the Fedorenko grids sequence method is highly efficient and reduces the computing time almost by a factor of eight. The numerical model is generalized in order to state the problem in a spherical system of coordinates. It is used to analyse the distribution of convective flows in the upper mantle underneath the Eurasian continent. The analysis shows that the thickness and geometrical parameters of the lithospheric blocks are the factors of significant influence on the distribution of convective flows in the upper mantle. The resulting structure of convective flows is manifested in the surface topography of large platform areas wherein the lithosphere thickness is increased. Thus, the locations of extended downward convection flows under the East European and Siberian platforms are clearly comparable to syneclises observed in the study area.