A Reconstruction of Mantle Plume Evolution by Optimal Heat and Mass Transportation: Impact of Mantle Diffusion and Viscosity

The ascent and evolution of mantle plumes depend on the properties of the source region and the viscosity and thermal diffusivity of the ambient mantle. While mantle properties are relatively constant during a hundred Myr lifetime of most plumes, source region properties can vary substantially with time as the thermal boundary layer feeding the plumes is depleted of hot material. Complete local depletion of the boundary layer cuts the plumes off from their source. It is the subsequent evolution of the plumes and the reconstruction of this evolution that interests us here. We study effects of the heat diffusion on the evolution of mantle plumes at lower Rayleigh numbers (Ra). Numerical experiments show that a delay or interruption in plume heat and mass transfer results in the diffusive disappearance of plume tails first and plume heads later. This is the most likely explanation for the seismically detected mid-mantle plumes. We restore these diffused plumes to their prominent states in the past and analyze the restoration errors for various Ra. Also we study the effect of the lower viscosity of mantle plumes on their evolution and restoration.