Effects of iron on the lattice thermal conductivity of Earth’s deep mantle and implications for mantle dynamics

Wen Pin Hsieh, Frédéric Deschamps, Takuo Okuchi, Jung Fu Lin

Research output: Contribution to journalArticle

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Abstract

Iron may critically influence the physical properties and thermochemical structures of Earth’s lower mantle. Its effects on thermal conductivity, with possible consequences on heat transfer and mantle dynamics, however, remain largely unknown. We measured the lattice thermal conductivity of lower-mantle ferropericlase to 120 GPa using the ultrafast optical pump-probe technique in a diamond anvil cell. The thermal conductivity of ferropericlase with 56% iron significantly drops by a factor of 1.8 across the spin transition around 53 GPa, while that with 8–10% iron increases monotonically with pressure, causing an enhanced iron substitution effect in the low-spin state. Combined with bridgmanite data, modeling of our results provides a self-consistent radial profile of lower-mantle thermal conductivity, which is dominated by pressure, temperature, and iron effects, and shows a twofold increase from top to bottom of the lower mantle. Such increase in thermal conductivity may delay the cooling of the core, while its decrease with iron content may enhance the dynamics of large low shear-wave velocity provinces. Our findings further show that, if hot and strongly enriched in iron, the seismic ultralow velocity zones have exceptionally low conductivity, thus delaying their cooling.

LanguageEnglish
Pages4099-4104
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number16
DOIs
StatePublished - Apr 17 2018

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thermal conductivity
mantle
iron
lower mantle
cooling
diamond anvil cell
seismic velocity
effect
heat transfer
wave velocity
S-wave
pump
substitution
conductivity
physical property
probe
modeling
temperature

Keywords

  • E
  • Ferropericlase
  • Geodynamics
  • Large low shear-wave
  • Thermal conductivity
  • Ultralow velocity zones
  • Velocity provinces

ASJC Scopus subject areas

  • General

Cite this

Effects of iron on the lattice thermal conductivity of Earth’s deep mantle and implications for mantle dynamics. / Hsieh, Wen Pin; Deschamps, Frédéric; Okuchi, Takuo; Lin, Jung Fu.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 115, No. 16, 17.04.2018, p. 4099-4104.

Research output: Contribution to journalArticle

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