Japan Geoscience Union Meeting 2019

Presentation information

[E] Poster

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG51] Role of volatiles on Earth and planetary dynamics

Thu. May 30, 2019 10:45 AM - 12:15 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Takayuki Ishii(Bavarian Research Institute, University of Bayreuth), Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University), Michihiko Nakamura(Division of Earth and Planetary Materials Science, Department of Earth Science, Graduate School of Science, Tohoku University), Bjorn Mysen(Geophysical Laboratory, Carnegie Inst. Washington)

[SCG51-P06] Discovery of two hexagonal phases in (Fe,Al)OOH under the P-T conditions of the deep lower mantle

*Lu Liu1,2, Li Zhang1, Hongsheng Yuan1 (1.Center for High Pressure Science and Technology Advanced Research, 2.University of Science and Technology of China)

Keywords:High temperature and high pressure experiment, hydrous phase, diamond anvil cell

Deep water can cause a series of complex seismological phenomena by changing the density and thermal stability of lower mantle components. δ-H solid solution phase (AlOOH-MgSiO2(OH)) is stable at lower mantle conditions1,because the crystallographic frameworks of the phase H is similar to that of the δ-AlOOH phase, with very strong hydrogen bonds2,3. δ-AlOOH and ε-FeOOH can also form solid solution4 (δ-ε solution). It is reasonable to infer that δ-ε solid solution may have similar thermal stability as that of H-δ solution, considering their similar crystal structure5. In our experiments, we synthesized the δ-ε solution at 79GPa and 1600K in a laser-heated diamond anvil cell. As the temperature increases to 2100k, the orthorhombic δ-ε solution transformed into a hexagonal-structured phase. By combining powder X-ray diffraction techniques with multigrain indexation6, we determined its hexagonal lattice with a=b=10.019Å and c=2.614Å. At 79GPa and 2400K, the hexagonal phase transforms into another hexagonal phase, with the lattice parameters of a=b=2.733Å and c=9.343Å. The discovery of these two new phases may provide new insights into the deep-water storage.

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2.Ohtani, E., Amaike, Y., Kamada, S., Sakamaki, T. and Hirao, N. Stability of hydrous phase H MgSiO4H2 under lower mantle conditions. Geophys. Res. Lett. 41, -8287 (2014).
3.Nishi M,Kuwayama Y,Tsuchiya J,et al.The pyrite-type high-pressure form of FeOOH[J]. Nature,2017,54(7662):205-208.
4.T Kawazoe,I Ohira,T Ishii et al. Single crystal synthesis of δ-(Al,Fe)OOH American Mineralogist. Volume 102, pages 1953–1956, (2017)
5.Gleason A E,Quiroga C E,Suzuki A,et al.Symmetrization driven spin transition in ε-FeOOH at high pressure[J]. Earth and Planetary Science Letters, 2013, 379: 49-55.
6.Zhang L,Yuan H,Meng Y,et al.Discovery of a hexagonal ultradense hydrous phase in (Fe, Al) OOH[J]. Proceedings of the National Academy of Sciences,2018,115(12):2908-2911.