摘要
We investigate the evolution of stress fields during the supercontinent cycle using the 2D Cartesian geometry model of thermochemical convection with the non-Newtonian rheology in the presence of floating deformable continents.In the course of the simulation,the supercontinent cycle is implemented several times.The number of continents considered in our model as a function of time oscillates around 3.The lifetime of a supercontinent depends on its dimension.Our results suggest that immediately before a supercontinent breakup,the over-lithostatic horizontal stresses in it(referring to the mean value by the computational area)are tensile and can reach-250 MPa.At the same time,a vast area beneath a supercontinent with an upward flow exhibits clearly the over-lithostatic compressive horizontal stresses of 50-100 МРа.The reason for the difference in stresses in the supercontinent and the underlying mantle is a sharp difference in their viscosity.In large parts of the mantle,the over-lithostatic horizontal stresses are in the range of±25 MPa,while the horizontal stresses along subduction zones and continental margins are significantly larger.During the process of continent-to-continent collisions,the compressive stresses can approximately reach 130 MPa,while within the subcontinental mantle,the tensile over-lithostatic stresses are about-50 MPa.The dynamic topography reflects the main features of the su-percontinent cycle and correlates with real ones.Before the breakup and immediately after the disin-tegration of the supercontinent,continents experience maximum uplift.During the supercontinent cycle,topographic heights of continents typically vary within the interval of about±1.5 km,relatively to a mean value.Topographic maxima of orogenic formations to about 2-4 km are detected along continent-to-continent collisions as well as when adjacent subduction zones interact with continental margins.
