Implications for the Melting Phase Relations in the MgO-FeO System at Core-Mantle Boundary Conditions

Jie Deng, Yoshinori Miyazaki, Kanani K.M. Lee

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

At nearly 2,900-km depth, the core-mantle boundary (CMB) represents the largest density increase within the Earth going from a rocky mantle into an iron-alloy core. This compositional change sets up steep temperature gradients, which in turn influences mantle flow, structure, and seismic velocities. Here we resolve the thermodynamic parameters of (Mg,Fe)O and compute the melting phase relations of the MgO-FeO binary system at CMB conditions. Based on this phase diagram, we revisit iron infiltration into solid ferropericlase along the CMB by morphological instability and find that the length scale of infiltration is comparable with the high electrical conductivity layer inferred from core nutations. We also compute the (Mg,Fe)O-SiO 2 pseudo-binary system and find that the solidus melting temperatures near the CMB decrease with FeO and SiO 2 content, becoming potentially important for ultralow velocity zones. Therefore, an ultralow velocity zone composed of solid-state bridgmanite and ferropericlase may be relatively enriched in MgO and depleted in SiO 2 and FeO along a hot CMB.

Original languageEnglish (US)
Pages (from-to)1294-1304
Number of pages11
JournalJournal of Geophysical Research: Solid Earth
Volume124
Issue number2
DOIs
StatePublished - Feb 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Keywords

  • core-mantle boundary
  • ferropericlase
  • iron infiltration
  • melting
  • ultralow velocity zones

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