Quantification of water in hydrous ringwoodite
Journal Article
·
· Frontiers in Earth Science
- Univ. of Nevada, Las Vegas, NV (United States); Carnegie Institution of Washington
- Northwestern Univ., Evanston, IL (United States)
- Univ. de Bundeswehr Munchen, Neubiberg (Germany)
- Carnegie Inst. of Washington, Washington, D.C. (United States)
- Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum (GFZ), Potsdam (Germany)
- Univ. of Colorado, Boulder, CO (United States)
Here, ringwoodite, γ-(Mg,Fe)2SiO4, in the lower 150 km of Earth’s mantle transition zone (410-660 km depth) can incorporate up to 1.5-2 wt% H2O as hydroxyl defects. We present a mineral-specific IR calibration for the absolute water content in hydrous ringwoodite by combining results from Raman spectroscopy, secondary ion mass spectrometery (SIMS) and proton-proton (pp)-scattering on a suite of synthetic Mg- and Fe-bearing hydrous ringwoodites. H2O concentrations in the crystals studied here range from 0.46 to 1.7 wt% H2O (absolute methods), with the maximum H2O in the same sample giving 2.5 wt% by SIMS calibration. Anchoring our spectroscopic results to absolute H-atom concentrations from pp-scattering measurements, we report frequency-dependent integrated IR-absorption coefficients for water in ringwoodite ranging from 78180 to 158880 L mol-1cm-2, depending upon frequency of the OH absorption. We further report a linear wavenumber IR calibration for H2O quantification in hydrous ringwoodite across the Mg2SiO4-Fe2SiO4 solid solution, which will lead to more accurate estimations of the water content in both laboratory-grown and naturally occurring ringwoodites. Re-evaluation of the IR spectrum for a natural hydrous ringwoodite inclusion in diamond from the study of the crystal contains 1.43 ± 0.27 wt% H2O, thus confirming near-maximum amounts of H2O for this sample from the transition zone.
- Research Organization:
- Carnegie Inst. of Washington, Washington, DC (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- NA0002006
- OSTI ID:
- 1335510
- Journal Information:
- Frontiers in Earth Science, Journal Name: Frontiers in Earth Science Vol. 2; ISSN 2296-6463
- Publisher:
- Frontiers Research FoundationCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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