title: Iron partitioning and density changes of pyrolite in Earth's lower mantle.
abstract: Phase transitions and the chemical composition of minerals in Earth's interior influence geophysical interpretations of its deep structure and dynamics. A pressure-induced spin transition in olivine has been suggested to influence iron partitioning and depletion, resulting in a distinct layered structure in Earth's lower mantle. For a more realistic mantle composition (pyrolite), we observed a considerable change in the iron-magnesium partition coefficient at about 40 gigapascals that is explained by a spin transition at much lower pressures. However, only a small depletion of iron is observed in the major high-pressure phase (magnesium silicate perovskite), which may be explained by preferential retention of the iron ion Fe3+. Changes in mineral proportions or density are not associated with the change in partition coefficient. The observed density profile agrees well with seismological models, which suggests that pyrolite is a good model composition for the upper to middle parts of the lower mantle.
authors: Geodynamics Research Center, Ehime University, Matsuyama 790-8577, Japan. irifune@dpc.ehime-u.ac.jp
authors: Tetsuo
authors: T
authors: Irifune
authors: Toru
authors: T
authors: Shinmei
authors: Catherine A
authors: CA
authors: McCammon
authors: Nobuyoshi
authors: N
authors: Miyajima
authors: David C
authors: DC
authors: Rubie
authors: Daniel J
authors: DJ
authors: Frost