Presenter: Masaki OGAWA
Abstract:
We developed a two-dimensional numerical model of magmatism in the convecting wet mantle to understand the history of Martian magmatism and its influence on the surface environment. The mantle is internally heated by incompatible heat-producing elements (HPEs). Magmatism occurs as a permeable flow of basaltic magma generated by decompression melting through the mantle. The mantle is initially hot and wet. The high initial temperature causes an extensive magmatism that is invigorated by a positive feedback that operates between magmatism and mantle convection. This vigorous magmatism efficiently extracts heat and water from the mantle, and also induces a compositionally stratified structure with the deep mantle occupied by compositionally dense basaltic materials that are enriched in HPEs and still retain some water. Because of the cooling and stratification of the mantle, magmatism becomes quiescent for the next several hundred million years. Then plume magmatism begins, as HPEs raise the temperature in the deep mantle. This plume magmatism further extracts HPEs and water from the deep mantle to let the plume magmatism itself decline with time. The early quiescent period suggests that the surface of Mars was arid after the initial extensive magmatism that formed the crust, until plume magmatism begins.