Percolation of Core Melts at Lower Mantle Conditions

Abstract

Experiments at high pressure and temperature to determine the dihedral angle of core melts in lower mantle phases yielded a value of ∼71° for perovskite-dominated matrices. This angle, although greater than the 60° required for completely efficient percolation, is considerably less than the angles observed in mineral matrices at upper mantle pressure-temperature conditions in experiments. In other words, molten iron alloy can flow much more easily in lower mantle mineralogies than in upper mantle mineralogies. Accordingly, although segregation of core material by melt percolation is probably not feasible in the upper mantle, core formation by percolation may be possible in the lower mantle.