[S-CG59] 沈み込み帯へのインプット：海洋プレートの進化と不均質

[SCG59-10] 東北沖プチスポット掘削：IODP Expedition 502

★招待講演

*山口 飛鳥¹、北島 弘子²、奥津 なつみ³、Toczko Sean³ (1.東京大学大気海洋研究所、2.テキサスA&M大学、3.海洋研究開発機構)

キーワード：IODP3、プチスポット、日本海溝

International Ocean Drilling Programme (IODP³) Expedition 502 plans to explore the nature of the acoustic basement in the outer rise area of the NW Pacific subduction system, where layer-1 pelagic sediment of the subducting old (120–130 Ma) Pacific Plate is exceptionally thin. The hypothesis is that the acoustically thin sediment cover can be attributed to basalt sill intrusions or sheet lava extrusions in and on the pelagic sediment package by basalts fed by petit-spot magmatism. This hypothesis will be tested to see if petit-spot magmatism at the outer rise is more widely distributed than previously thought. The existence of widely-distributed petit-spots would strongly impact the subduction system, including rupture nucleation and slip propagation of plate boundary megathrust earthquakes, as well as effect changes to the geochemical cycle of arc magmatism and the global volatile cycle due to the differing materials associated with the subducted oceanic plate. In this presentation we will show the latest update of IODP³ Expedition 502.