PerspectiveGeochemistry

Deep Mantle Properties

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Science  08 Jan 2010:
Vol. 327, Issue 5962, pp. 151-152
DOI: 10.1126/science.1184786

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Summary

The lower mantle extends from 660 to 2890 km below the surface of the Earth. The rocks and minerals of the deep mantle are not accessible in nature, except those occurring infrequently as inclusions in diamond. However, they can be synthesized and examined at the relevant high pressure and temperature conditions in the laboratory. Recent such experimental investigations, as well as theoretical calculations, have suggested that the properties of lower-mantle minerals vary with increasing depth much more than was previously thought. On page 193 of this issue, Irifune et al. (1) report that iron (Fe) partitioning between the two main lower-mantle constituents, iron–magnesium silicate perovskite (Pv) and iron–magnesium oxide (ferropericlase, Fp), indeed changes in a natural mantle composition for conditions corresponding to depths below 1100 km. The results have profound implications for predicting the properties and dynamics of the deep mantle.