日本地球惑星科学連合2018年大会

講演情報

[EE] ポスター発表

セッション記号 S (固体地球科学) » S-IT 地球内部科学・地球惑星テクトニクス

[S-IT22] 核-マントルの相互作用と共進化

2018年5月22日(火) 10:45 〜 12:15 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:飯塚 毅(東京大学)、渋谷 秀敏(熊本大学大学院先端科学研究部基礎科学部門地球環境科学分野)、土屋 卓久(愛媛大学地球深部ダイナミクス研究センター、共同)、太田 健二(東京工業大学大学院理工学研究科地球惑星科学専攻)

[SIT22-P09] Stability of hydrous aluminosilicates at the transition zone and the lower mantle

阿部 涼太1柴崎 裕樹2小澤 信1大平 格1戸邉 宙1、*鈴木 昭夫1 (1.東北大学大学院理学研究科地学専攻、2.東北大学学際科学フロンティア研究所)

キーワード:含水アルミノケイ酸塩、phase Egg、放射光X線回折、下部マントル、沈み込むスラブ

Water is transported into the deep Earth’s interior by hydrous minerals in the descending slabs. Previous studies showed that hydrous aluminosilicates would be stable in the sedimentary layer of subducting slab. Discovery of phase Egg in the diamond inclusion also supports that hydrous aluminosilicate could exist in the earth’s deep interior. Topaz-OH II was synthesized by Kanzaki (2010 Am. Mineral.) at the pressure of 14 GPa and the temperature of 1400 °C. In the high pressure and high temperature experiment using starting materials of Al2SiO4(OH)2 composition have reported stable regions only at 26 GPa (Pamato et al., 2014 Nature Geoschi.). The phase relation of Al2SiO4(OH)2 aluminosilicates between 14 and 26 GPa is important for the discussion of water transport from the mantle transition layer to the shallow part of the lower mantle. In this study, quench experiments and in situ X-ray diffraction studies on the phase relation of Al2SiO4(OH)2 were conducted in the pressure range of 12.0–32.2 GPa and in the temperature range of 800–1600 °C. We observed the coexistence of delta-AlOOH and stishovite at 31.0 GPa and 1500 °C and the formation of phase Egg together with corundum at 30.6 GPa and 1600 °C. These results indicate that phase Egg is stable at least up to 30.6 GPa and 1600 °C, which is higher pressure and temperature condition than that reported previously. Phase Egg should be the important water carrier after the avalanche of the stagnant slab up to the depth of approximately 900 km in the lower mantle.