New host for carbon in the deep Earth

作者: E. Boulard , A. Gloter , A. Corgne , D. Antonangeli , A.-L. Auzende

DOI: 10.1073/PNAS.1016934108

关键词: Mantle (geology)Core–mantle boundaryCarbon cyclePlanetGeologyVolcanismPhase diagramMagnetiteSubductionMineralogy

摘要: The global geochemical carbon cycle involves exchanges between the Earth's interior and surface. Carbon is recycled into mantle via subduction mainly as carbonates released to atmosphere volcanism mostly CO2. stability of versus decarbonation melting therefore great interest for understanding cycle. For all these reasons, thermodynamic properties phase diagrams minerals are needed up core boundary conditions. However, nature C-bearing at conditions remains unclear. Here we show existence a new Mg-Fe carbon-bearing compound depths greater than 1,800 km. Its structure, based on three-membered rings corner-sharing ðCO4Þ4− tetrahedra, in close agreement with predictions by first principles quantum calculations [Oganov AR, et al. (2008) Novel high-pressure structures MgCO3, CaCO3 CO2 their role lower mantle. Earth Planet Sci Lett 273:38-47]. This polymorph concentrates large amount FeðIIIÞ result intracrystalline reaction FeðIIÞ ðCO3Þ2− groups schematically written 4FeO þ → 2Fe2O3 C. results an assemblage phase, magnetite nanodiamonds.

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