Phase Relations of CO2 in the Earth's Mantle Using Single-Crystal X-ray Diffraction
Abstract
Several high-pressure polymorphs have been suggested for carbon dioxide over the past decade. The immense diversity of CO2 in chemical bonding and intermolecular interactions has been explored at the Earth's mantle pressure and temperature conditions, mainly through the combination of theoretical calculation with powder X-ray diffraction and/or optical spectroscopy experiments. The case of the CO2-V phase (β-cristobalite-type structure, I-42d), which forms at ~45 GPa and ~1400 K, is particularly interesting since it consists of three-dimensional frameworks of carbon tetrahedrally coordinated to oxygen. Other CO4-based structures have been reported recently for carbonate minerals at pressures and temperatures exceeding ~75 GPa and 2000 K, respectively, that invite analogies to metasilicates and have great implications on the Earth's deep carbon cycle. However, the great majority of the above phases belong to new structure types and thus, their structure characterization has been rather controversial in the literature so far. Single-crystal X-ray diffraction has traditionally allowed us to obtain explicit solutions of complex structures. The method is becoming more and more appealing in the high-pressure research community nowadays as one of the most advanced techniques that can provide in situ characterization of the chemical compositions of novel and metastable compounds at extreme conditions. Here, we present our work on the phase relations of CO2, as well as, its chemical reactions and phase stability in the presence of major mantle mineral components. Our results highlight the merits of the single-crystal X-ray diffraction technique in laser-heated diamond anvils cells at high-pressure dedicated beamlines, such as the 13-IDD (GSECARS, APS, USA).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMMR23D0140C
- Keywords:
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- 3919 Equations of state;
- MINERAL PHYSICS;
- 3924 High-pressure behavior;
- MINERAL PHYSICS;
- 3939 Physical thermodynamics;
- MINERAL PHYSICS;
- 3994 Instruments and techniques;
- MINERAL PHYSICS