Sound velocities of hydrous ringwoodite to 16 GPa and 673 K

Journal Article · Thu May 10 04:00:00 EDT 2012 · Earth Planet. Sci. Lett.

DOI:https://doi.org/10.1016/j.epsl.2012.03.001· OSTI ID:1038281

Mao, Zhu; Lin, Jung-Fu; Jacobsen, Steven D; Duffy, Thomas S; Chang, Yun-Yuan; Smyth, Joseph R; Frost, Daniel J; Hauri, Erik H; Prakapenka, Vitali B ^[1]

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1. Texas

To understand the effect of hydration on the sound velocities of major mantle minerals and to constrain the mantle's H{sub 2}O budget, we have measured the single-crystal elastic moduli of hydrous ringwoodite, (Mg{sub 1.633}Fe{sub 0.231}{sup 2+}Fe{sub 0.026}{sup 3+})Si{sub 1.00}H{sub 0.179}O{sub 4} with 1.1 wt.% H{sub 2}O using Brillouin scattering combined with X-ray diffraction in an externally-heated diamond anvil cell up to 16 GPa and 673 K. Up to 12 GPa at 300 K, the presence of 1.1 wt.% H{sub 2}O lowers the elastic moduli of ringwoodite by 5-9%, but does not affect the pressure derivatives of the elastic moduli compared to anhydrous ringwoodite. The reduction caused by hydration is significantly enhanced when temperatures are elevated at high pressures. At 12 GPa, increasing temperature by {Delta}T = 100 K leads to a 1.3-2.4% reduction in the elastic moduli (C{sub 11}, C{sub 12}, and C{sub 14}). Comparing our results with seismic observations, we have evaluated the potential H{sub 2}O content in the lower part of the transition zone. Our results indicate that the observed seismic velocity anomalies and related depth depression of the 660-km discontinuity could be attributed to thermal variations together with the presence of {approx} 0.1 wt.% H{sub 2}O.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSFOTHERDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1038281
• Journal Information: Earth Planet. Sci. Lett., Journal Name: Earth Planet. Sci. Lett. Journal Issue: 05, 2012 Vol. 331-332; ISSN 0012-821X; ISSN EPSLA2
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

58 GEOSCIENCES
BRILLOUIN EFFECT
ELASTICITY
HYDRATION
VELOCITY
X-RAY DIFFRACTION