Numerical models of Martian mantle evolution induced by magmatism and solid-state convection beneath stagnant lithosphere

Numerical models of magmatism in a convecting mantle are presented to understand Martian mantle evolution. The viscosity is strongly temperature dependent, and the lithosphere is stagnant. Magmatism is modeled as a permeable flow of basaltic magma generated by decompression melting. When the initial mantle temperature is sufficiently high, a magma ocean develops to generate a thick basaltic crust and create a compositionally layered mantle. The upper layer of the mantle consists of compositionally buoyant residue of the basaltic crust, while the lower layer consists of compositionally denser materials that are not as depleted in the basaltic component. Hot plumes grow from the lower layer making it thinner with time by erosion. The hot plumes also induce magmatism, which extracts heat-producing elements (HPEs) from the mantle. The HPE extraction regulates plume magmatism activity and controls the duration of plume magmatism. Plume magmatism also keeps the mantle temperature below the solidus by efficiently extracting heat as soon as the mantle temperature exceeds the solidus. The Martian mantle is likely to have evolved as a relaxation from a compositionally layered state formed by the magma ocean, and plume magmatism has probably played a crucial role in the relaxation process.