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

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

doi:10.1016/j.gsf.2018.10.003

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

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Martirosyan, N.
0 Pre-GFZ, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Litasov, Konstantin D.
External Organizations;

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Lobanov, S. S.
3.6 Chemistry and Physics of Earth Materials, 3.0 Geochemistry, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Goncharov, Alexander F.
External Organizations;

Shatskiy, Anton
External Organizations;

Ohfuji, Hiroaki
External Organizations;

Prakapenka, Vitali
External Organizations;

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Citation

Martirosyan, N., Litasov, K. D., Lobanov, S. S., Goncharov, A. F., Shatskiy, A., Ohfuji, H., Prakapenka, V. (2019): The Mg-carbonate–Fe interaction: implication for the fate of subducted carbonates and formation of diamond in the lower mantle. - Geoscience Frontiers, 10, 4, 1449-1458.
https://doi.org/10.1016/j.gsf.2018.10.003

Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_3602895

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: 6MgCO3 + 19Fe = 8FeO +10(Mg0.6Fe0.4)O + Fe7C3 + 3C. 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.