Two‐stage spin transition of iron in FeAl‐bearing phase D at lower mantle

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• 作者：Xiang Wu ; Ye Wu ; Jung‐Fu Lin ; Jin Liu ; Zhu Mao ; Xinzhuan Guo ; Takashi Yoshino ; Catherine McCammon ; Vitali B. Prakapenka ; Yuming Xiao
• 刊名：Journal of Geophysical Research: Solid Earth
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：121
• 期：9
• 页码：6411-6420
• 全文大小：994.9KB
• ISSN：2169-9356

文摘

Hydrous magnesium silicate phase D plays a key role in the transport of water from the upper to the lower mantle via subducted slabs. Here we report pressure dependence hyperfine and lattice parameters of FeAl-bearing phase D up to megabar pressures using synchrotron nuclear forward scattering and X-ray diffraction in a diamond anvil cell at room temperature. FeAl-bearing phase D undergoes a two-stage high-spin to low-spin transition of iron for Fe²⁺ at 37–41 GPa and for Fe³⁺ at 64–68 GPa. These transitions are accompanied by an increase in density and a significant softening in the bulk modulus and bulk velocity at their respective pressure range. The occurrence of the dense low-spin FeAl-bearing phase D with relatively high velocity anisotropies in deep-subducted slabs can potentially contribute to small-scale seismic heterogeneities in the middle-lower mantle beneath the circum-Pacific area.