Immiscible two-liquid regions in the Fe-O-S system at high pressure: Implications for planetary cores

Kyusei Tsuno, Eiji Ohtani, Hidenori Terasaki

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)


We have determined phase relations in the Fe-O and Fe-O-S systems in the range of 15-21 GPa and 1825-2300 °C. Below the liquidus temperatures, solid FeO and metallic liquids are observed in both the Fe-O and the Fe-O-S systems. An immiscible two-liquid region exists in the Fe-O binary system in the pressure range investigated, and the immiscibility gap between Fe-rich metallic liquid and FeO-rich ionic liquid does not greatly change with either pressure or temperature. On the other hand, an immiscible two-liquid region in the Fe-O-S ternary system narrows significantly with increasing pressure at constant temperature and vice versa, and it almost disappears at 21 GPa, and 2300 °C. Immiscible two-liquid regions are thus not expected to exist in the Fe-O-S system in the Earth's core, suggesting that both oxygen and sulfur can be incorporated into the core. Our results are consistent with a geochemical model for the core containing 5.8 wt.% oxygen and 1.9 wt.% sulfur as proposed by McDonough and Sun [McDonough, W.F., Sun, S.-S., 1995. The composition of the Earth. Chem. Geol. 120, 223-253].

Original languageEnglish
Pages (from-to)75-85
Number of pages11
JournalPhysics of the Earth and Planetary Interiors
Issue number1
Publication statusPublished - Jan 16 2007
Externally publishedYes


  • Core
  • Fe-alloys
  • High pressure
  • Liquid immiscibility
  • Miscibility

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science


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