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Letter. Forsterite, wadsleyite, and ringwoodite (Mg2SiO4): 29Si NMR constraints on structural disorder and effects of paramagnetic impurity ions
-
Jonathan F. Stebbins
,
Wendy R. Panero
Veröffentlicht/Copyright:
1. April 2015
Abstract
We present here high-resolution 29Si MAS NMR data for synthetic samples of forsterite (α-Mg2SiO4), wadsleyite (β), and ringwoodite (γ). Enrichment to >99% 29Si provides greatly enhanced signal-tonoise ratios and thus great sensitivity to small features in the spectra. At a detection limit of 0.1 to 0.5%, no six-coordinated Si (VISi) is observed in any of the polymorphs, although these results could be consistent with theoretical predications of 1 to 2% Mg-Si site disorder in ringwoodite if re-ordering occurs rapidly during cooling. Several small IVSi peaks in ringwoodite samples may be related to residual defects from this process. In forsterite and wadsleyite, several very small “extra” peaks are observed, many of which are at positions far outside the known range of chemical shifts for 29Si in silicates. These may be caused by “pseudo-contact” shifts from dipolar interactions with unpaired electron spins on trace impurities of paramagnetic transition metal cations.
Received: 2008-11-6
Accepted: 2008-12-5
Published Online: 2015-4-1
Published in Print: 2009-4-1
© 2015 by Walter de Gruyter Berlin/Boston
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Schlagwörter für diesen Artikel
NMR spectroscopy;
forsterite;
ringwoodite;
wadsleyite;
high-pressure studies
Artikel in diesem Heft
- Growth controls in colloform pyrite
- Parageneses and Th-U distributions among allanite, monazite, and xenotime in Barroviantype metapelites, Imjingang belt, central Korea
- Magmatic vs. hydrothermal origins for zircon associated with tantalum mineralization in the Tanco pegmatite, Manitoba, Canada
- Molecular conformation and anion configuration variations for As4S4 and As4Se4 in an anion-substituted solid solution
- Low-pressure clino- to high-pressure clinoenstatite phase transition: A phonon-related mechanism
- Coordination study of rare earth elements on Fe oxyhydroxide and Mn dioxides: Part I. Influence of a multi-electron excitation on EXAFS analyses of La, Pr, Nd, and Sm
- Coordination study of rare earth elements on Fe oxyhydroxide and Mn dioxides: Part II. Correspondence of structural change to irregular variations of partitioning coefficients and tetrad effect variations appearing in interatomic distances
- Aluminocerite-Ce: A new species from Baveno, Italy: Description and crystal-structure determination
- A thermodynamic model for the plagioclase-liquid hygrometer/thermometer
- Solid-state NMR and IR spectroscopic investigation of the role of structural water and F in carbonate-rich fluorapatite
- Chemical-structural modularity in the tetradymite group: A HRTEM study
- Stability of pargasite during ultrahigh-temperature metamorphism: A consequence of titanium and REE partitioning?
- Raman spectroscopic and microscopic criteria for the distinction of microdiamonds in ultrahigh-pressure metamorphic rocks from diamonds in sample preparation materials
- Lattice compression and structural behavior of NaVSi2O6 clinopyroxene to 11 GPa
- A predictive model for the enthalpies of hydration of zeolites
- Thermal decomposition of calcite: Mechanisms of formation and textural evolution of CaO nanocrystals
- Synchrotron Mössbauer spectroscopic study of ferropericlase at high pressures and temperatures
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