Thermal response of the mantle following the formation of a “super‐plate”

Abstract

[1] Evidence indicating that the mantle below Pangea was characterized by elevated temperatures supports the widely held view that a supercontinent insulates the underlying mantle. Implementing a 3D model of mantle convection featuring distinct oceanic and continental plates, we explore different effects of supercontinent formation on mantle evolution. We find that a halt in subduction along the margins of the site of the continental collision is sufficient to enable the formation of mantle plumes below a composite "super-plate" and that the addition of continental properties that contribute to insulation have little effect on sub-continental temperature. Our findings show that the mean temperature below a supercontinent surpasses that below the oceanic plates when the former is a perfect insulator but that continental thermal insulation plays only a minor role in the growth of sub-supercontinent mantle plumes. We suggest that the growth of a super-oceanic plate can equally encourage the appearance of underlying upwellings. Citation: Heron, P. J., and J. P. Lowman (2010), Thermal response of the mantle following the formation of a "super-plate," Geophys.

The impact of Rayleigh number on assessing the significance of supercontinent insulation

“…Aside from the thermal blanket effect, isolation from subduction [ Lowman and Jarvis , ; Lowman and Gable , ], radiogenic heating at the core‒mantle boundary by chemically distinct oceanic slabs [ Maruyama et al , ; Senshu et al , ], and circumsupercontinent subduction [ Zhong et al , ; Trubitsyn et al , ; O'Neill et al , ; Zhang et al , ; Heron and Lowman , , ] have all been suggested to account for a sub‒supercontinent reversal in mantle flow. In a recent focus paper on the mechanics determining the formation and breakup of supercontinents, Murphy and Nance [] speculate that the reversal in continental plate motion (i.e., from continental accretion to continental dispersal) post supercontinent formation may be induced by a slab avalanche that triggers a rise of subcontinental superplumes from the core‒mantle boundary.…”

“…In a high‒Rayleigh number numerical simulation (where viscous oceanic plates are absent), Yoshida and Santosh [] show the buildup of heat from the thermal blanket effect generating a return flow upwelling sub‒supercontinent. However, recent numerical studies featuring thermally and mechanically distinct oceanic and continental plates fail to generate sub‒supercontinental temperatures much greater than suboceanic temperatures over timescales relevant to supercontinent episodes [ Heron and Lowman , , ; Yoshida , ].…”

“…In a series of models simulating supercontinent formation, the influence of continental insulation is seen to decrease as the vigor of convection is increased. Furthermore, in models approaching Earth‒like Rayleigh number, it is difficult to obtain subcontinental temperatures in excess of suboceanic temperatures on timescales relevant to supercontinent episodes [e.g., Heron and Lowman , , ; Yoshida , ], despite the thermal blanket effect and the formation of plumes beneath the continent. A recent study indicates that a reversal of mantle motion through the generation of plumes would be sufficient to disperse a supercontinent, despite suboceanic and subcontinental temperatures being comparable [ Yoshida , ].…”

“…In agreement with previous geodynamic modeling studies featuring insulating continents, we find that following supercontinent formation heat builds up under a stationary supercontinent. However, our study shows that when heat is trapped subcontinentally, it is not to an extent that would cause the subcontinental mantle to be substantially warmer than suboceanic mantle temperatures, in agreement with the findings of Heron and Lowman [, ] and Yoshida []. Moreover, the change in subcontinental temperature is strongly dependent on Rayleigh number.…”

The links between large igneous provinces, continental break-up and environmental change: evidence reviewed from Antarctica

“…Vaughan & Storey 2007). Various models exist for modification and evolution of upper mantle convection as a result of thermal insulation by thick continental lithosphere (Anderson 1982;Trubitsyn et al 2008;Heron & Lowman 2010), which can ultimately drive supercontinent fragmentation. However, recent modelling studies (Heron & Lowman 2011) indicate that supercontinent evolution is insufficient to change upper mantle temperatures on the timescale of supercontinent assembly, and that large subcontinental mantle plumes develop as a result of subduction patterns rather than thermal insulation by supercontinents.…”