Tectonic setting leading to subduction initiation of Izu-Bonin-Mariana Arc; new implications from the Philippine Sea basins

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Author(s): Ishizuka, Osamu; Tani, Kenichiro; Harigane, Yumiko; Shimoda, Gen; Sato, Taichi; Umino, Susumu; Sakamoto, Izumi; Ohara, Yasuhiko; Yokoyama, Yuka; Perez, Americus de Cahvez; Conway, Chris; Sekimoto, Shun
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
Geological Survey of Japan, Japan
National Museum of Nature and Science, Japan
Sangyo Gijutsu Sogo Ken, Japan
National Institute of Advanced Industrial Science and Technology, Japan
Kanazawa University, Japan
Tokai University, Japan
Kyoto University, Japan
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The origin and characteristics of juxtaposing plates is critical for understanding the tectonic setting and requirements leading to subduction initiation. In case of Izu-Bonin-Mariana (IBM) arc in the Western Pacific, arc basement could be preserved in rear arc area of its ancient rear arc (i.e., Kyushu-Palau Ridge). International Ocean Discovery Program Expedition 351 recovered basement of the IBM arc in its rear arc area (Amami Sankaku Basin), and revealed that ocean crust of this basin was generated by seafloor spreading at the time of subduction initiation (Arculus et al., 2015: Ishizuka et al., 2018). However, origin and formation age of the rest of the Philippine Sea basins in the ancient rear arc is still unknown, and this hampers the understanding of the tectonic setting leading to the subduction initiation along the IBM arc. Recent cruises in the Philippine Sea basins recovered basalts from ocean crust along the major tectonic lines such as the Oki-Daito Escarpment and Mindanao Fracture Zone. The data are still preliminary, but some fresh basalt samples returned well-defined 40Ar/39Ar ages older than the age of onset of subduction along the IBM arc at c. 52 Ma. This strongly implies that some part of the Philippine Sea basins such as the West Philippine Basin existed prior to the IBM arc, and these basins could be a part of overriding plate at subduction initiation. Temporal variation of geochemical characteristics of basalts in the Philippine Sea basins appears to indicate that major compositional variation occurred in sub-Philippine Sea mantle subsequent to subduction initiation. This might imply that sinking of large volume of Pacific Plate along the entire IBM arc margin triggered counterflow of asthenospheric mantle and reorganization of sub-Philippine Sea mantle.
Year of Publication: 2018
Research Program: IODP2 International Ocean Discovery Program
Key Words: 18 Geophysics, Solid-Earth; Crust; Expedition 351; International Ocean Discovery Program; Izu-Bonin-Mariana Arc; Lithosphere; North Pacific; Northwest Pacific; Oceanic crust; Oceanic lithosphere; Pacific Ocean; Philippine Sea; Plate tectonics; Subduction; Subduction zones; Tectonics; West Pacific
Coordinates: N272300 N272301 E1341907 E1341905
Record ID: 2019061742
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