Quantification of water in majoritic garnet

Journal Article · Fri May 01 00:00:00 EDT 2015 · American Mineralogist

DOI:https://doi.org/10.2138/am-2015-5136· OSTI ID:1335511

Thomas, Sylvia -Monique ^[1]; Wilson, Kathryn ^[1]; Koch-Muller, Monika ^[2]; Hauri, Erik H. ^[3]; McCammon, Catherine ^[4]; Jacobsen, Steven D. ^[5]; Lazarz, John ^[5]; Rhede, Dieter ^[2]; Ren, Minghua ^[1]; Blair, Neal ^[5]; Lenz, Stephan ^[2]

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1. Univ. of Nevada, Las Vegas, NV (United States)
2. Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum (GFZ), Potsdam (Germany)
3. Carnegie Institution of Washington, Washington, D.C. (United States)
4. Univ. Bayreuth, Bayreuth (Germany)
5. Dept. of Earth and Planetary Sciences, Evanston, IL (United States)

Majoritic garnet, characterized by an excess of silicon (>3 Si per formula unit), is considered one of the major phases of the Earth’s transition zone from 410-660 km depth. Quantifying the H₂O content of nominally anhydrous mantle minerals is necessary to evaluate their water storage capacity from experiments and modeling the Earth’s deep water cycle. We present mineral-specific infrared absorption coefficients for the purpose of quantifying the amount of water incorporated into majorite as hydroxyl point defects. A suite of majoritic garnet samples with varying proportions of Si, Fe, Al, Cr and H₂O was synthesized at conditions of 18-19 GPa and 1500-1800°C. Single-crystals were characterized using X-ray diffraction, electron microprobe analysis, secondary Ion Mass spectrometry (SIMS), IR, Raman and Mössbauer spectroscopy. We utilize SIMS and Raman spectroscopy in combination with IR spectroscopy to provide IR absorption coefficients for water in majoritic garnets with the general mineral formula (Mg,Fe)₃(Si,Mg,Fe,Al,Cr)₂[SiO4]₃. Furthermore, the IR absorption coefficient for majoritic garnet in the OH stretching region is frequency-dependent and ranges from 10 470 ± 3100 Lmol-1cm-2 to 23 400 ± 2300 Lmol^-1cm^-2.

• Research Organization: Carnegie Institution of Washington, Washington, D.C. (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0002006
• OSTI ID: 1335511
• Journal Information: American Mineralogist, Vol. 100, Issue 5-6; ISSN 0003-004X
• Publisher: Mineralogical Society of America
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
IR spectroscopy
water in nominally anhydrous minerals
transition zone
integral molar absorption coefficient
SIMS
high pressure
Raman spectroscopy