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

Two- and three-dimensional spherical convection models are presented which investigate the convection structure beneath a crust inhomogeneously enrich ed in radioactive elements. The resulting convection patterns show a focusi ng of upwellings under the enriched part of the crust and downwellings unde r the not enriched part that maintain large-scale horizontal motion from th e warmer to the cooler region beneath the lithosphere and vice versa above the core-mantle boundary. This flow pattern is observed in all examined mod els 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 insignifican t for the surface heat flux distribution, which is dominated by crustal hea t generation. Implications of the results for Mars are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.