Two‐stage spin transition of iron in FeAl‐bearing phase D at lower mantle. Issue 9 (17th September 2016)

• Record Type: Journal Article
• Authors: Wu, Xiang; Wu, Ye; Lin, Jung‐Fu; Liu, Jin; Mao, Zhu; Guo, Xinzhuan; Yoshino, Takashi; McCammon, Catherine; Prakapenka, Vitali B.; Xiao, Yuming
• Is Part Of: Journal of geophysical research. Volume 121:Issue 9(2016:Sep.)
• Page Start: 6411
• Page End: 6420
• Publication Date: 2016-09-17
• Subjects: phase D -- spin transition of iron -- lower mantle; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2016JB013209
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: 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 Fe 2+ at 37–41 GPa and for Fe 3+ 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. Key Points: FeAl‐bearing phase D undergoes a two‐stage spin transition of iron at high pressure The spin transitions are associated with an increase in density and a decrease in bulk modulus and bulk sound velocity The dense low‐spin FeAl‐bearing phase D can contribute to observed seismic anisotropies and heterogeneities in the middle‐lower mantle