Hidden Oceans? Unraveling the Structure of Hydrous Defects in the Earth’s Deep Interior
| Autor: | Jürgen Senker, Daniel J. Frost, Helen Grüninger, Dominik Greim, Tiziana Boffa-Ballaran, Katherine Armstrong |
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| Rok vydání: | 2017 |
| Předmět: |
Range (particle radiation)
Chemistry Spinel Mineralogy Charge (physics) General Chemistry Nuclear magnetic resonance spectroscopy engineering.material 010402 general chemistry 010502 geochemistry & geophysics 01 natural sciences Biochemistry Catalysis 0104 chemical sciences Ringwoodite Colloid and Surface Chemistry Chemical physics engineering Density functional theory Earth (classical element) 0105 earth and related environmental sciences |
| Zdroj: | Journal of the American Chemical Society. 139:10499-10505 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/jacs.7b05432 |
| Popis: | High-pressure silicates making up the main proportion of the earth’s interior can incorporate a significant amount of water in the form of OH defects. Generally, they are charge balanced by removing low-valent cations such as Mg2+. By combining high-resolution multidimensional single- and double-quantum 1H solid-state NMR spectroscopy with density functional theory calculations, we show that, for ringwoodite (γ-Mg2SiO4), additionally, Si4+ vacancies are formed, even at a water content as low as 0.1 wt %. They are charge balanced by either four protons or one Mg2+ and two protons. Surprisingly, also a significant proportion of coupled Mg and Si vacancies are present. Furthermore, all defect types feature a pronounced orientational disorder of the OH groups, which results in a significant range of OH···O bond distributions. As such, we are able to present unique insight into the defect chemistry of ringwoodite’s spinel structure, which not only accounts for a potentially large fraction of the earth’s entire... |
| Databáze: | OpenAIRE |
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