日本地球惑星科学連合2022年大会

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[E] 口頭発表

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-IT20] New perspectives on accretion and exhumation processes during oblique plate convergence

2022年5月23日(月) 09:00 〜 10:30 101 (幕張メッセ国際会議場)

コンビーナ:Byrne Timothy B(University of Connecticut)、コンビーナ:Lee Jian-Cheng(Academia Sinica)、山口 飛鳥(東京大学大気海洋研究所)、コンビーナ:纐纈 佑衣(名古屋大学大学院 環境学研究科)、座長:纐纈 佑衣(名古屋大学大学院 環境学研究科)、山口 飛鳥(東京大学大気海洋研究所)

09:00 〜 09:15

[SIT20-01] Cretaceous to Cenozoic NW Panthalassa plate-reconstruction and implications for the evolution of NE Asia convergence plate boundary

★Invited Papers

*Tsung-Jui Wu1Jonny Wu1 (1.Department of Earth and Atmospheric Sciences, University of Houston)

The Eurasian continental margin of NE Asia records abundant Mesozoic to present igneous activity and accretionary orogen in response to Pacific and Panthalassa (paleo-Pacific) subduction. Plate tectonics studies typically reconstruct long-lived plate convergence involving subduction of the Panthalassa/Pacific plates since 200 Ma. However, many first-order details of NW Panthalassa plate tectonic reconstructions remain controversial, including ridge-trench intersections and intra-oceanic arc accretions along Eurasia since the Early Cretaceous. Here we investigate the Mesozoic to Cenozoic magmatic and plate tectonic history of the 31-52 °N NE Asian continental active margin (Japan, Korea, NE China, and southern Russian Far East). We synthesized a regional magmatic database from published data (n>800) that is compared to published structural geology, stratigraphy, paleomagnetism, and an unpublished fully-kinematic ‘tomographic’ NE Asian-Pacific plate tectonic reconstruction.
We show the following plate tectonic stages along the NE Asian margin since the Cretaceous: (1) subduction of one or more marginal sea plates during the Early Cretaceous; (2) a ~130-100 Ma intra-oceanic arc(s) accretion event with adakitic magmatism from subducted-slab melting; (3) ~100-50 Ma Izanagi slab subduction with ultrafast convergence (12 to 24 cm/yr) and high-angle subduction (between 65°~89°) toward a general NE-SW plate boundary along NE Asia, corresponding to a high magmatic flux (~1000 km2 /Myr); (4) ~50 Ma Pacific-Izanagi spreading ridge subduction with a ~56-46 Ma arc magmatic hiatus; and (5) ~50-0 Ma slower (2 to 8 cm/yr) Pacific plate with more oblique convergence (generally between 33°~60°) toward the Eurasian continental margin, corresponding to a lower magmatic flux (~400 km2 /Myr). We discuss the setting of Japan since ~100 Ma within the East Asian plate system in terms of high-angle/oblique subduction periods. The convergence angle and velocity of subducting plate(s) prior to ~100 Ma remain unconstraint in this model and will be discussed with early Cretaceous NE Asia geology, including the Sambagawa belt.