Fate of primordial noble gases during core-mantle differentiation from ab initio simulations

Early planetary accretion and giant impacts likely generated a global magma ocean on the proto-Earth, enabling extensive dissolution of primordial volatiles from the solar nebula into silicate melts. During subsequent core-mantle differentiation, the partitioning of noble gases between pyrolitic silicate melts and iron-sulfur (Fe-S) melts would have controlled their redistribution and long-term preservation in Earth’s deep interior. The contrasting noble gas signatures observed in mid-ocean ridge basalts and mantle plume sources, particularly in He/Ne ratios, motivated the existence of a deep primitive reservoir potentially linked to early core-mantle differentiation. Here, we use ab initio molecular dynamics simulations combined with thermodynamic integration to quantify the partition coefficients of He, Ne, Ar, Kr, and Xe between pyrolitic silicate melts and Fe-S melts. We further assess the effects of melt composition by comparing pyrolite with MgSiO₃ melts and Fe-S with metallic iron melts. Our results reveal systematic variations in noble gas partitioning with atomic size and melt chemistry. Based on these partitioning coefficients, we estimate the potential noble gas inventories preserved in the mantle and core. These results provide new quantitative constraints on the fate of primordial noble gases and the origin of deep-mantle volatile reservoirs.