AI Article Synopsis
- Phase transitions in minerals like olivine affect how scientists interpret the Earth's deep structure and dynamics.
- A significant change in the iron-magnesium partition coefficient is noted at around 40 gigapascals due to a spin transition that occurs at lower pressures than expected.
- The findings support that pyrolite represents the upper to middle layers of the lower mantle, as the density profile aligns with seismological models, indicating minimal changes in mineral proportions or density.
Article 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.
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| http://dx.doi.org/10.1126/science.1181443 | DOI Listing |
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