The Mg-carbonate–Fe interaction: Implication for the fate of subducted carbonates and formation of diamond in the lower mantle

Naira S. Martirosyan, Konstantin D. Litasov, Sergey S. Lobanov, Alexander F. Goncharov, Anton Shatskiy, Hiroaki Ohfuji, Vitali Prakapenka

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The fate of subducted carbonates in the lower mantle and at the core-mantle boundary was modelled via experiments in the MgCO3-Fe0 system at 70–150 GPa and 800–2600 K in a laser-heated diamond anvil cell. Using in situ synchrotron X-ray diffraction and ex situ transmission electron microscopy we show that the reduction of Mg-carbonate can be exemplified by: 6 MgCO3 + 19 Fe = 8 FeO +10 (Mg0.6Fe0.4)O + Fe7C3 + 3 C. The presented results suggest that the interaction of carbonates with Fe0 or Fe0-bearing rocks can produce Fe-carbide and diamond, which can accumulate in the D’’ region, depending on its carbon to Fe ratio. Due to the sluggish kinetics of the transformation, diamond can remain metastable at the core-mantle boundary (CMB) unless it is in a direct contact with Fe-metal. In addition, it can be remobilized by redox melting accompanying the generation of mantle plumes.

Original languageEnglish
Pages (from-to)1449-1458
Number of pages10
JournalGeoscience Frontiers
Volume10
Issue number4
DOIs
Publication statusPublished - 1 Jul 2019

Keywords

  • Carbide
  • Carbonate
  • Deep carbon cycle
  • High pressure
  • Iron
  • Redox reaction
  • SYSTEM
  • HIGH-PRESSURE
  • DEEP LOWER MANTLE
  • EARTHS MANTLE
  • IRON-CARBIDE
  • STABILITY
  • DIFFRACTION DATA
  • EQUATION-OF-STATE
  • TRANSITION ZONE
  • PHASE-RELATIONS

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