Experimental Study on the Phase Relations in the System Fe-Ni-O-S Up to 15 Gpa

  1. Murli H. Manghnani and
  2. Yasuhiko Syono
  1. S. Urakawa1,
  2. M. Kato1 and
  3. M. Kumazawa2

Published Online: 21 MAR 2013

DOI: 10.1029/GM039p0095

High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto

High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto

How to Cite

Urakawa, S., Kato, M. and Kumazawa, M. (1987) Experimental Study on the Phase Relations in the System Fe-Ni-O-S Up to 15 Gpa, in High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto (eds M. H. Manghnani and Y. Syono), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM039p0095

Author Information

  1. 1

    Department of Earth Sciences, Nagoya University, Chikusa-Ku, Nagoya 464, Japan

  2. 2

    Department of Geophysics, University of Tokyo, Bunkyo-Ku, Tokyo 113, Japan

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1987

ISBN Information

Print ISBN: 9780875900667

Online ISBN: 9781118664124

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Keywords:

  • Mineralogy and Crystal Chemistry;
  • Phase transformations;
  • High Pressure-High Temperature Research

Summary

The effects of nickel, oxygen, and sulfur alloying on the melting relations of iron have been experimentally investigated up to a pressure of 15 GPa to provide information on problems involved in investigation of the earth's core. The Fe-rich portion of the system Fe-Ni-O-S is a eutectic system with a wide region of liquid immiscibility which is reduced with increasing pressure and which disappears above 20–25 GPa. The oxygen solubility in the eutectic liquid increases with pressure, from 1 atomic percent at 6 GPa to about 2–3 atomic percent at 15 GPa. The sulfur content is about 34 atomic percent at 6 GPa and decreases with pressure. The change of the eutectic composition is related to reduction of liquid immiscibility. The eutectic temperature in the system Fe-Ni-O-S is about 825°C at 6 GPa and increases with a small pressure gradient of 6 K/GPa.

A sufficient amount of oxygen, sulfur, and other light elements (such as carbon and hydrogen) are available in the primordial earth, and the melting temperature of the actual core-forming material is less than 800°C. The oxygen and sulfur bearing metallic liquid can easily penetrate the polycrystalline texture of silicates by chemical corrosion because of the low interfacial energy. Separation of the core material should have started in the accretionally growing earth. Thus core formation is considered to be a process of chemical equilibration between the mantle material and the molten iron alloy that is travelling down to the core.