Solid Solution and Compression Behavior of Hydroxides in the Lower Mantle. Issue 10 (24th October 2019)

• Record Type: Journal Article
• Authors: Nishi, M.; Tsuchiya, J.; Kuwayama, Y.; Arimoto, T.; Tange, Y.; Higo, Y.; Hatakeyama, T.; Irifune, T.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 10(2019)
• Page Start: 10231
• Page End: 10239
• Publication Date: 2019-10-24
• Subjects: hydrous mineral -- high pressure -- multianvil press -- solid solution; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2019JB018146
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: The high‐pressure solid solution and compression behavior of hydroxides in the ternary MgSiO4 H2 ‐AlOOH‐FeOOH system were studied at pressures of 16–60 GPa and temperatures of 300–1513 K. We applied in situ X‐ray measurements in conjunction with a multianvil apparatus using sintered diamond anvils to achieve homogeneous temperature distributions within large sample volumes. Our results show that CaCl2 ‐type hydroxides form solid solutions over a wide composition range. We also observed the volume reductions in the solid solutions accompanied by a spin transition of iron at ~50 GPa, and the wide compositional ranges are maintained through this process. Consequently, water may be transported into the deep lower mantle by the hydrous CaCl2 ‐type solid solution with changing its composition depending on the chemical and thermal environments. Plain Language Summary: A significant amount of water has been transported into the Earth's interior via subduction of hydrous phases in cold plates since plate tectonics started to operate billions of years ago. Recent theoretical and experimental studies revealed that hydrous phases with compositions of MgSiO4 H2, AlOOH, and FeOOH are stable at the high pressures occurring in the lower mantle, suggesting that a certain amount of water may be delivered to the core‐mantle boundary (~2, 900‐km depth). However, hydroxides in multicomponent systems relevant to the actual mantle and subducting slabs are not well studied. Here we compressed multicomponent hydroxides in the ternary MgSiO4 H2 ‐AlOOH‐FeOOH system using multianvil technology and found that hydroxide subducted into the lower mantle can retain Earth's major elements, such as Mg, Si, Al, Fe, and O. Key Points: The solid solution and compression behavior of hydroxides were studied by in situ X‐ray measurements and a multianvil press CaCl2 ‐type hydroxides form solid solutions over a wide composition range in the MgSiO4 H2 ‐AlOOH‐FeOOH system The volume of CaCl2 ‐type hydroxides decreases due to a spin transition of iron at ~50 GPa