日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

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

2019年5月30日(木) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:石井 貴之(バイロイト大学バイエルン地球科学研究所)、大谷 栄治(東北大学大学院理学研究科地学専攻)、中村 美千彦(東北大学大学院理学研究科地学専攻地球惑星物質科学講座)、Mysen Bjorn(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 Liu1,2Li Zhang1Hongsheng Yuan1 (1.Center for High Pressure Science and Technology Advanced Research、2.University of Science and Technology of China)

キーワード: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.

References
1.Ohira I, Ohtani E, Sakai T, et al. Stability of a hydrous δ-phase, AlOOH-MgSiO2(OH)2, and a mechanism for water transport into the base of lower mantle[J].Earth and Planetary Science Letters, 2014, 401: 12-17.
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.