A partially equilibrated initial mantle and core indicated by stress-induced percolative core formation through a bridgmanite matrix.

Abstract

The Earth's core formation mechanism determines the siderophile and light elements abundance in the Earth's mantle and core. Previous studies suggest that the sink of massive liquid metal through a solid silicate mantle resulted in an unequilibrated core and the lower mantle. Here, we show that percolation can be an effective core formation mechanism in a convective mantle and modify the compositions of the lower mantle and the core through partial equilibration between them. This grain-scale metal flow has a high velocity to meet the time constraint of core formation. The Earth's core could have been enriched with light elements, and the abundance of the moderately siderophile elements in the mantle could have been elevated to the current value during this process. The trapped core-forming melt in the mantle during the stress-induced percolation can also explain the highly siderophile element abundance in the Earth's mantle.