THE IMPORTANCE OF THE HEATING MODE OF THE MANTLE IN SUPERCONTINENT INSULATION

Elevated temperatures resulting from an accumulation of heat below aggregated continents have been widely suggested as the source of energy responsible for the ultimate breakup of supercontinents. Modeling studies have shown that the aggregation of continents along a convergent plate boundary initially overlying a deeply extending mantle downwelling can initiate a reorganization of mantle convection planform, ultimately resulting in the formation of sub-continental upwellings. In addition, model supercontinents that inhibit heat loss from the underlying internally heated mantle are able to elevate mantle temperatures even in the absence of the appearance of mantle plumes.

However, the processes described require periods well in excess of a mantle transit time in order to replace regions initially characterized by downwelling mantle flow with buoyant upwellings.

The total time required for this transition is strongly dependent on the heating mode of the mantle and the presence of active upwellings. Here, we examine the role of the heating mode of the mantle in the elevation of sub-supercontinent temperatures and, following the formation of a supercontinent above an initially cool region associated with a convergent plate boundary, we evaluate the periods required for the subcontinental mantle to climb above sub-oceanic temperatures. Our 3D plane-layer geometry models feature both insulating continents and multiple oceanic plates. We find that low Rayleigh number mantle convection models amplify the effectiveness of continental insulation in elevating sub-continental temperatures when compared to models with higher convective vigor. Anomalously hot sub-continental mantle is not easily obtained with an Earth-like Rayleigh number and isothermal basal boundary conditions (simulating a well mixed core). In our most Earth-like models, sub-continental temperatures do not exceed sub-oceanic temperatures over timescales relevant to supercontinent aggregation.