Effects of mantle heat source distribution on supercontinent stability

A two-dimensional Cartesian geometry numerical model is used to study the influence of internal heating on the ability of mantle convection to rift and disperse an assembled supercontinent. Our wide aspect ratio models incorporate migrating plate boundaries and finite thickness rigid mobile oceanic and continental plates (similar to 12,000 km across). We examine models characterized by both whole mantle and upper mantle convection parameters. Specifying different degrees of internal heating in the mantle, we compare the patterns of convection that develop below stationary continental plates that form as a result of the aggregation of smaller mobile continents. Following continental collisions, we find that a reorganization of mantle flow may result in the development of deviatoric Stresses at the base of the continental lithosphere, which are capable of initiating continental breakup. Our results suggest that continental basal stresses are largely controlled by the wavelength of the subcontinental convection pattern and that the inclusion of internal heating in the mantle generally increases this wavelength. For models with 80% internal heating (in which active upwellings are intrinsically absent), basal stresses arise primarily from subduction at the continental margins and result in a geologically reasonable duration for our model supercontinent assemblages (similar to 200 Myr). For models with 40% or less internal heating, continental breakup is controlled by mantle upwellings and our supercontinents remain intact much longer (similar to 600-700 Myr).