Formation and upwelling of mantle diapirs through the cratonic lithosphere: Numerical thermomechanical modeling

This paper reports the results of the numerical modeling of gravitationally instable processes in the lithospheric mantle of ancient cratons. The gravitational instability is considered as a result of melting at the lithosphere base owing to its local heating by anomalous mantle. Modeling was based on a finite element method in 2D formulation and took into account the geological structure and thermomechanical parameters of the lithosphere of the Siberian platform. Numerical results revealed the main tendencies in the mantle diapirisim of the mafic and ultramafic magma ascending through the “cold” high-viscosity lithosphere. It was shown that the shape of diapiric magmatic bodies is controlled by realistic visco-elastic-plastic rheology of lithosphere. The ascent of diapir in lithosphere was modeled for diverse regimes differing in duration, temperature field, and upwelling depth. It was concluded that the ascent of melt through lithosphere to the crust-mantle boundary is mainly controlled by rheology, and conditions of oscillatory diapirism with recurrent magma replenishments were modeled. Modeling results may shed light on some features related to the trap magmatism of the Siberian igneous province. The duration and rate of magma upwelling as well as the parameters of periodical magma upwelling were estimated and attempt was made to explain the high-velocity seismic anomalies that were recorded in the subcrustal regions of the Siberian platform.