The effect of mantle convection modulated by mantle temperature heterogeneity on rifting propagation

The rifting, which is driven by extensional stress due to the relative motion of plates and mantle upwelling, is one of the most crucial processes in forming new oceanic plates and the subsequent material circulation of the earth. Previous studies based on analogue and numerical modeling have suggested that the mantle convection beneath the lithosphere affects the rifting propagation. The mantle rheology, depending on temperature structure, strongly controls the regime of mantle convection. In the present study, we built 3D rifting models using the ASPECT to analyze the effect of interaction between mantle temperature heterogeneity and lithospheric extension on the velocity of rifting propagation. We vary the magnitude of temperature heterogeneity and extension velocity for investigating the degree of coupling between the two factors. The extensional boundary conditions initiate the localized vigorous mantle convection adjacent to the temperature heterogeneity, which triggers a rifting propagation from warm to cold regions. We confirmed that the larger temperature heterogeneities, when the boundary condition is fixed, promote faster rifting nucleation and propagation. On the other hand, weak or no mantle convection appears without the boundary condition, leading to the static surface of the models. Thus, we argue that the stronger small-scale mantle convection driven by larger temperature heterogeneity enhances lithospheric extension and propagation under the far-field extensional tectonic stress.