日本地球惑星科学連合2018年大会

講演情報

[EE] 口頭発表

セッション記号 S (固体地球科学) » S-GC 固体地球化学

[S-GC45] Volatile Cycles in the Deep Earth - from Subduction Zone to Hot Spot

2018年5月21日(月) 13:45 〜 15:15 A05 (東京ベイ幕張ホール)

コンビーナ:佐野 有司(東京大学大気海洋研究所海洋地球システム研究系)、羽生 毅(海洋研究開発機構 地球内部物質循環研究分野)、角野 浩史(東京大学大学院総合文化研究科広域科学専攻相関基礎科学系)、座長:佐野 有司角野 浩史

15:00 〜 15:15

[SGC45-05] The search for water in the mantle transition zone

*Christine Houser1 (1.Earth-Life Science Institute, Tokyo Institute of Technology)

キーワード:mantle transition zone, water in the mantle, mantle seismology

Combining global maps of 410 and 660 km discontinuity topography and transition zone thickness with shear and compressional velocity variations is a powerful tool for constraining mantle transition zone chemistry, dynamics and mineralogy. Numerous seismic and mineral physics studies suggest that the 410 km discontinuity results from the phase change of olivine to wadsleyite and the 660 km discontinuity results from the phase change of ringwoodite to perovskite and magnesiowustite. We use underside reflections off the 410 and 660 km discontinuities, or SS precursors, to globally map discontinuity depth variations. We can then compare the observed discontinuity depth to global shear velocity models. Mineral physics studies have shown that water should decrease shear velocity, elevate the 410 km discontinuity, and depress the 660 km discontinuity. Combining the seismic data with results from mineral physics studies, there are few regions in the mantle transition zone that are compatible with measurable water content. Thus, the current seismic data do not find many oceans of water stored in the mantle transition zone.