2025-10-10 東京科学大学
図1. 本研究でわかったオントンジャワ海台のプレートの模式図 ©せき・らんうん
図2.オントンジャワ海台の位置
＜関連情報＞
- https://www.isct.ac.jp/ja/news/7jvkodojuplz
- https://www.isct.ac.jp/plugins/cms/component_download_file.php?type=2&pageId=&contentsId=1&contentsDataId=2456&prevId=&key=9db936a9d4fee4e18a2a70e1ecf7c6c3.pdf
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL115219
オントンジャワ海台下の海洋リソスフェアにおける岩脈群 Dike Swarms in the Oceanic Lithosphere Beneath the Ontong Java Plateau
Azusa Shito, Daisuke Suetsugu, Akira Ishikawa, Masako Yoshikawa, Takehi Isse, Hajime Shiobara, Hiroko Sugioka, Aki Ito, Yasushi Ishihara …
Geophysical Research Letters Published: 30 September 2025
DOI:https://doi.org/10.1029/2025GL115219
Abstract
The Ontong Java Plateau (OJP) is believed to have formed through large-scale Cretaceous volcanism, but the impact of the massive volcanism on the lithosphere remains largely unknown. In this study, the ascent process of the thermochemical plume and its impact on the physicochemical properties of the pre-existing lithosphere were explored. High-frequency seismic wave analysis revealed that the internal structure of the lithosphere beneath the OJP is a hybrid structure comprising dike swarms that are superimposed on the laminar structure. Moreover, the lithosphere exhibits lower seismic wave velocities than normal oceanic lithosphere, suggesting that the lithospheric mantle was physicochemically altered by the intrusion of dike swarms filled with magma from a large-scale thermochemical plume. Our results advance the current understanding of the alterations in the lithosphere caused by a thermochemical plume.
Plain Language Summary
This study investigates the impact of a rising thermochemical plume on the lithospheric mantle beneath the Ontong Java Plateau (OJP), the largest oceanic plateau on Earth. We used high-frequency seismic wave analysis and numerical modeling of seismic-wave propagation to reveal the internal structure of the lithosphere of the OJP. The study revealed that the lithosphere of OJP is characterized by a hybrid structure comprising dike swarms that are superimposed on the laminar structure. Additionally, we observed that the lithosphere beneath the OJP exhibited lower velocities than the normal oceanic lithosphere. These results suggest that the lithosphere undergone significant physicochemical alterations due to the intrusion of magma from a thermochemical plume. Our study provides a more comprehensive understanding of the lithospheric processes.
Key Points
- High-frequency seismic wave analysis reveals the internal structure of the lithosphere beneath the Ontong Java Plateau (OJP)
- The lithosphere beneath the OJP is a hybrid structure comprising dike swarms superimposed on the laminar structure
- The lithosphere beneath the OJP is suggested to have been altered physicochemically by the intrusion of dike swarms filled with magma
