Sound velocities of hydrous ringwoodite to 16 GPa and 673 K

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• 作者：Zhu Mao^a ; ; Jung-Fu Lin^a ; Steven D. Jacobsen^b ; Thomas S. Duffy^c ; Yun-Yuan Chang^b ; Joseph R. Smyth^d ; Daniel J. Frost^e ; Erik H. Hauri^f ; Vitali B. Prakapenka^g
• 关键词：hydrous ringwoodite ; single-crystal elasticity ; high pressure&ndash ; temperature ; Brillouin scattering
• 刊名：Earth and Planetary Science Letters
• 出版年：2012
• 期刊代码：18_0012821x
• 类别：ph
• 出版时间：15 May, 2012
• 卷：331-332
• 期：Complete
• 页码：112-119
• 文件大小：1162 K

摘要

To understand the effect of hydration on the sound velocities of major mantle minerals and to constrain the mantle's H₂O budget, we have measured the single-crystal elastic moduli of hydrous ringwoodite, (Mg_1.633Fe^2 +_0.231Fe^3 +_0.026)Si_1.00H_0.179O₄ with 1.1 wt.%H₂O 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.%H₂O 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 螖T = 100 K leads to a 1.3-2.4%reduction in the elastic moduli (C₁₁, C₁₂, and C₁₄). Comparing our results with seismic observations, we have evaluated the potential H₂O 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 ~ 0.1 wt.%H₂O.