No interconnection of ferro‐periclase in post‐spinel phase inferred from conductivity measurement

Abstract

Electrical conductivities of post‐spinel, which are thought to be a dominant assembly in the lower mantle, were investigated at the conditions of the uppermost lower mantle (25 GPa and temperatures ranging from 300 to 2000K) in a Kawai‐type multi‐anvil apparatus. Post‐spinel phases with a bulk composition of ((Mg,Fe)2SiO4: XFe = 0.09) were measured to constrain the bulk conductivity of the lower mantle. To investigate interconnectivity of ferro‐periclase in silicate perovskite matrix, a single phase composed of magnesium silicate perovskite ((Mg,Fe)SiO3: XFe = 0.1) and ferro‐periclase ((Mg,Fe)O: XFe = 0.13) were also measured. The conductivity values of the silicate perovskite are distinctly lower than those for the coexisting ferro‐pericalse. Both absolute values and change in activation enthalpy for the conductivity of the post‐spinel phases are similar to those for the silicate perovskite. These observations suggest that ferro‐periclase in post‐spinel are isolated in silicate perovskite matrix.