Convection underneath a crust inhomogeneously enriched in heat sources: application to martian mantle dynamics

Abstract

Two- and three-dimensional spherical convection models are presented which investigate the convection structure beneath a crust inhomogeneously enriched in radioactive elements. The resulting convection patterns show a focusing of upwellings under the enriched part of the crust and downwellings under the not enriched part that maintain large-scale horizontal motion from the warmer to the cooler region beneath the lithosphere and vice versa above the core–mantle boundary. This flow pattern is observed in all examined models independent of the mantle heating mode. It is, however, more pronounced for models with a considerable amount of internal heating than for models with almost total bottom heating. Thermal blanketing of the mantle beneath the enriched part of the crust plays only a minor role in the lateral heat flux distribution within the lithospheric mantle and is almost insignificant for the surface heat flux distribution, which is dominated by crustal heat generation. Implications of the results for Mars are discussed.