Thermophysical properties and phase diagrams in the system MgO–SiO 2 –FeO at upper mantle and transition zone conditions derived from a multiple-Einstein method

Michael H.G. Jacobs*, Rainer Schmid-Fetzer, Arie P. van den Berg

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

We applied a lattice vibrational technique, based on representing the vibrational density of states with multiple-Einstein frequencies, to determine consistency of data on thermophysical properties and phase diagrams in the system MgO–FeO–SiO 2 . We present analyses of these data in the temperature range between 0 and 2000 K and pressure range between 0 and 20 GPa. The result is a database containing phases relevant to the Earth upper mantle and transition zone. We show that consistency of different datasets associated with the dissociation of the ringwoodite form of Fe 2 SiO 4 depends on the crucible material that has been used to perform partitioning experiments between ringwoodite and ferropericlase, and that this results in different phase diagrams for FeSiO 3 and the post-spinel part of Mg 2 SiO 4 –Fe 2 SiO 4 . We show that the existence of a phase field coesite + ringwoodite in the phase diagram of FeSiO 3 is possible and that it might be used to fine-tune pressure scales. We demonstrate that the phase boundary between coesite and quartz is very sensitive to the low-temperature heat capacity of coesite and that heat capacity data of β-quartz are too large to be reconciled with the phase boundary between β-quartz and coesite. We compare our results with seismic data associated with the 410 km seismic discontinuity.

Original languageEnglish
Pages (from-to)513-534
Number of pages22
JournalPhysics and Chemistry of Minerals
Volume46
Issue number5
DOIs
Publication statusPublished - 1 May 2019

Keywords

  • Anharmonicity
  • Elasticity
  • Equation of state
  • Pressure scale
  • Vibrational density of states

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