著者

秋澤 紀克 小澤 一仁 芳川 雅子

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.127, no.5, pp.269-291, 2021-05-15 (Released:2021-09-29)

参考文献数

77

被引用文献数

1

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地球表面に露出しているかんらん岩は,過去においてマントルに存在していた物質であり,マントル物質の化石である.かんらん岩が経験した圧力-温度-変形史(P-T-d-t経路)を復元することができれば,どのようにマントルが地球内部で運動し,それに伴いどのように温度変化と変形が進行したのかを明らかにすることができる.そのP-T-d-t経路を,かんらん岩の地表への上昇による“化石化”の時点から連続的かつできるだけ過去に遡ることができれば,長期間にわたるマントルダイナミクスの理解を深めることができる.日高変成帯南部に位置する幌満かんらん岩体では,かんらん岩に記録された過去のP-T-d-t経路を詳細に読み解く研究が盛んに行われてきた.本稿では,幌満かんらん岩体のP-T-d-t経路の研究に焦点をあてレビューを行い,定置に至るまでの最終上昇時からできるだけ過去に遡って幌満かんらん岩体が辿った運動・熱・変形史を整理・概観し,新たな提案をする.

著者

城戸 太朗 秋澤 紀克 鈴木 庸平

雑誌

一般社団法人日本鉱物科学会2023年年会・総会

巻号頁・発行日

2023-08-10

著者

秋澤 紀克

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.52, no.1, pp.230204, 2023 (Released:2023-06-17)

参考文献数

84

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The life cycle of the oceanic lithosphere commences in the spreading axis and ends in the subduction zone. To trace the cooling and evolutional history of the Earth, the change in thermochemical state during the life cycle of present‒day oceanic lithosphere is desired to be elucidated. In terms of the material science, spatial limitation of human‒accessible Earth interior is a bottleneck in reconstructing the thermochemical state of the oceanic lithosphere. Yet, by combining active sampling methods using ocean research vessels (ocean drilling, ocean bottom dredging, submersible survey, etc.) and passive sampling methods using Earth’s deep materials exposed to the surface owing to tectonic forces and volcanoes, we can collect samples that cover a considerable dimension. Here, I present efforts toward the elucidation of the thermochemical state of the oceanic lithosphere during its life cycle from the spreading axis to the subduction zone. The Oman ophiolite is presented as an analogue of oceanic lithosphere formed in the vicinity of a fast‒spreading axis, whereas the peridotite xenoliths from Tahiti Island are treated as an analogue of thermochemically disturbed oceanic lithosphere by a mantle plume, and those from petit‒spots are considered as an analogue less affected by thermochemical disturbance considering the lack of mantle plume beneath the petit‒spots. A heterogeneous thermal state corresponding to the segment structure is inferred in the fast‒spreading axis. The thermochemical state of the aging oceanic lithosphere is modified by mantle plume and petit‒spot magmatism, but pristine state can be reconstructed by using suitable peridotite xenoliths whose heating‒cooling and melting history is well characterized. The peridotite xenoliths from the petit‒spots can enhance a step toward reconstructing the thermochemical state of the deep oceanic lithosphere because deep‒rooted garnet‒stable peridotite xenoliths can be found.

著者

秋澤 紀克

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.56, no.4, pp.52-63, 2022-12-25 (Released:2022-12-25)

参考文献数

85

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The oceanic crust is in contact with sea water, and thus water is likely to penetrate downward into the solid earth. Meanwhile, the oceanic crust is a place where water is partitioned from the magma. Water that is incorporated into the oceanic crust as hydrous minerals is mainly 1. water in differentiated magma, 2. water released from subducted oceanic plate and supplied to magma via wedge mantle in the back-arc spreading system, and 3. sea water causing hydrothermal circulation. Here, I give an overview of behavior of the water partitioned from the magma into the lower oceanic crust, which is of particular difficulty to access, and the actual state of water is difficult to grasp. In addition, I present the deep-rooted hydrothermal circulation reaching to the lower oceanic crust.

著者

三國 和音 平野 直人 秋澤 紀克 町田 嗣樹

雑誌

日本地質学会第129年学術大会

巻号頁・発行日

2022-08-08