Magnesite formation from MgO and CO₂ at the pressures and temperatures of Earth's mantle

Journal Article · Fri Aug 02 00:00:00 EDT 2013 · American Mineralogist

DOI:https://doi.org/10.2138/am.2013.4260· OSTI ID:1087737

Scott, Henry P.; Doczy, Vincent M.; Frank, Mark R.; Hasan, Maggie; Lin, Jung-Fu; Yang, Jing ^[1]

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1. NIU

Magnesite (MgCO₃) is an important phase for the carbon cycle in and out of the Earth’s mantle. Its comparably large P-T stability has been inferred for several years based on the absence of its decomposition in experiments. Here we report the first experimental evidence for synthesis of magnesite out of its oxide components (MgO and CO₂) at P-T conditions relevant to the Earth’s mantle. Magnesite formation was observed in situ using synchrotron X-ray diffraction, coupled with laser-heated diamond-anvil cells (DACs), at pressures and temperatures of Earth’s mantle. Despite the existence of multiple high-pressure CO₂ polymorphs, the magnesite-forming reaction was observed to proceed at pressures ranging from 5 to 40 GPa and temperatures between 1400 and 1800 K. No other pressure-quenchable materials were observed to form via the MgO + CO₂ = MgCO₃ reaction. This work further strengthens the notion that magnesite may indeed be the primary host phase for oxidized carbon in the deep Earth.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: NSFDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1087737
• Journal Information: American Mineralogist, Vol. 98, Issue (7) ; 07, 2013; ISSN 0003-004X
• Country of Publication: United States
• Language: ENGLISH