Evidence for Fe-Si-O liquid immiscibility at deep Earth pressures

Sarah M. Arveson, Jie Deng, Bijaya B. Karki, Kanani K.M. Lee

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Seismic observations suggest that the uppermost region of Earth's liquid outer core is buoyant, with slower velocities than the bulk outer core. One possible mechanism for the formation of a stably stratified layer is immiscibility in molten iron alloy systems, which has yet to be demonstrated at core pressures. We find immiscibility between liquid Fe-Si and Fe-Si-O persisting to at least 140 GPa through a combination of laser-heated diamond-anvil cell experiments and first-principles molecular dynamics simulations. High-pressure immiscibility in the Fe-Si-O system may explain a stratified layer atop the outer core, complicate differentiation and evolution of the deep Earth, and affect the structure and intensity of Earth's magnetic field. Our results support silicon and oxygen as coexisting light elements in the core and suggest that SiO2 does not crystallize out of molten Fe-Si-O at the core-mantle boundary.

Original languageEnglish (US)
Pages (from-to)10238-10243
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume116
Issue number21
DOIs
StatePublished - 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • alloys
  • core composition
  • high pressure
  • melting

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