Elasticity of single‐crystal superhydrous phase B at simultaneous high pressure‐temperature conditions

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• 作者：Xinyang Li ; Zhu Mao ; Ningyu Sun ; Yifan Liao ; Shuangmeng Zhai ; Yi Wang ; Huaiwei Ni ; Jingyun Wang ; Sergey N. Tkachev ; Jung‐Fu Lin
• 刊名：Geophysical Research Letters
• 出版年：2016
• 出版时间：28 August 2016
• 年：2016
• 卷：43
• 期：16
• 页码：8458-8465
• 全文大小：670.3KB
• ISSN：1944-8007

文摘

We investigated the combined effect of pressure and temperature on the elasticity of single-crystal superhydrous phase B (Shy-B) using Brillouin scattering and X-ray diffraction up to 12 GPa and 700 K. Using the obtained elasticity, we modeled the anisotropy of Shy-B along slab geotherms, showing that Shy-B has a low anisotropy and cannot be the major cause of the observed anisotropy in the region. Modeled velocities of Shy-B show that Shy-B will be shown as positive velocity anomalies at the bottom transition zone. Once Shy-B is transported to the topmost lower mantle, it will exhibit a seismic signature of lower velocities than topmost lower mantle. We speculate that an accumulation of hydrous phases, such as Shy-B, at the topmost lower mantle with a weight percentage of ~17–26% in the peridotite layer as subduction progresses could help explain the observed 2–3% low shear velocity anomalies in the region.