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Reaction between liquid iron and (Mg,Fe)SiO3-perovskite and solubilities of Si and O in molten iron at 27 GPa

Abstract

The Earth’s core contains light elements and their identification is essential for our understanding of the thermal structure and convection in the core that drives the geodynamo and heat flow from the core to the mantle. Solubilities of Si and O in liquid iron coexisting with (Mg,Fe)SiO3-perovskite, a major constituent of the lower mantle, were investigated at temperatures between 2,320 and 3,040 K at 27 GPa. It was observed that Si dissolved in the liquid iron up to 1.70 wt% at 3,040 K and O dissolved in the liquid iron up to 7.5 wt% at 2,800 K. It was also clearly seen that liquid iron reacts with (Mg,Fe)SiO3-perovskite to form magnesiowüstite and it contains Si and O at 27 GPa and at 2,640 and 3,040 K. The amounts of Si and O in the liquid iron are 1.70 and 2.25 wt% at 3,040 K, respectively. The solubilities of Si and O in liquid iron coexisting with (Mg,Fe)SiO3-perovskite have strong positive temperature dependency. Hence, they can be plausible candidates for the light elements in the core.

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Acknowledgments

We thank Y. Ito and Y. Sato (nano-technical laboratory) for analyzing the run products with EPMA. We are grateful to two anonymous reviewers for helpful comments. This work was financially supported by the grant-in-aid of the Scientific Research (S) of the Ministry of Education, Culture, Science, Sport, and Technology of the Japanese Government (no. 14102009) to E.O., and conducted as a part of the twenty-first century center-of-excellence program of Tohoku University “Advanced Science and Technology Center for the Dynamic Earth”.

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Correspondence to T. Kawazoe.

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Kawazoe, T., Ohtani, E. Reaction between liquid iron and (Mg,Fe)SiO3-perovskite and solubilities of Si and O in molten iron at 27 GPa. Phys Chem Minerals 33, 227–234 (2006). https://doi.org/10.1007/s00269-006-0071-4

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Keywords:

  • (Mg,Fe)SiO3-perovskite
  • Liquid iron
  • Silicon
  • Oxygen
  • Earth’s core