日本地球惑星科学連合2018年大会

講演情報

[JJ] Eveningポスター発表

セッション記号 S (固体地球科学) » S-MP 岩石学・鉱物学

[S-MP38] 鉱物の物理化学

2018年5月24日(木) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:大藤 弘明(愛媛大学地球深部ダイナミクス研究センター)、鎌田 誠司(東北大学学際科学フロンティア研究所)

[SMP38-P01] Single crystal X-ray structure study of δ-phase AlOOH-FeOOH-MgSiO2(OH)2

*石井 貴之1大平 格2川添 貴章1,4Tiziana Boffa Ballaran1鈴木 昭夫2大谷 栄治3,2 (1.バイロイト大学バイエルン地球科学研究所、2.東北大学、3.V.S. Sobolev Institute of Geology and Mineralogy、4.広島大学)

キーワード:水、単結晶X線回折、含水鉱物、マルチアンビル高圧発生装置、高圧合成、マントル

δ-AlOOH is an important hydrous phase for understanding the Earth’s deep water cycle, which is stable in hydrous pyrolite, hydrous basalt and hydrous sediment component of slabs subducted into the mantle transition zone and lower mantle. This phase forms a solid solution with ε-FeOOH and MgSiO2(OH)2 (Phase H). Therefore, the physical and chemical properties of δ-phase AlOOH-FeOOH-MgSiO2(OH)2 solid solution are of fundamental importance to understanding the water cycle in the deep mantle. In this study, we conducted structure analyses of δ-phase AlOOH-FeOOH-MgSiO2(OH)2 solid solution by single crystal X-ray diffraction. Single crystals of pure δ-AlOOH and δ-(Al,Fe)OOH and δ-(Al,Fe,Mg,Si)OOH with Fe, Mg and Si components up to about 10 mol% were synthesized at 21 GPa and 1480 K for 4 h using a Kawai-type multi-anvil apparatus. Single crystal structure analyses of synthetic crystals were conducted by the SHELXL-97 program. The compositions for crystal structure refinements were fixed using compositional data determined with an electron microprobe operating in wavelength-dispersive mode, in which all Fe were calculated as ferric iron. Reliability factors for each crystal were converged within 6% after the anisotropic displacement factors were refined, which indicate refined structures are reasonable. Space group of δ-AlOOH (P21nm) is not changed by substitution of Al to only Fe, whereas is changed to Pnnm by addition of MgSiO2(OH)2 component. This symmetry change by MgSiO2(OH)2 components may be one of the reasons why δ-AlOOH can accommodate a large amount of MgSiO2(OH)2 component (23-44 mol%) in the deep lower mantle.