Abstract DGP2026-119

During the early evolution of rocky planets, partial melting in the upper mantle leads to the redistribution of water from the mantle to the crust. Buoyant melt enriched in volatiles and trace elements rises toward the surface, where it contributes to the formation of enriched crust. This redistribution, together with following outgassing, progressively reduces the mantle water budget over geological timescales.

With the help of mineral/melt partition coefficients we can quantify the amount of the redistributed trace elements and volatiles like H2O. Partition coefficients depend heavily on pressure, temperature, and composition. However, due to the lack of high-pressure constraints, partition coefficients are commonly treated as constant in planetary interior evolution models.

In this study, we apply the pressure, temperature, and composition dependent partition coefficient model of Schmidt and Noack (2021) to both a 1D thermo-chemical evolution model and a 2D mantle evolution model for rocky planets. We investigate the resulting effects on volatile redistribution and outgassing as a function of planetary mass. Our results show that H2O partition coefficients rise with planet mass, which reduces the redistribution and limits the potential outgassing into the atmosphere of super-Earths.

Schmidt, J.M. and Noack, L. (2021): Clinopyroxene/Melt Partitioning: Models for Higher Upper Mantle Pressures Applied to Sodium and Potassium, SysMea, 13(3&4), 125-136.