Linkage between the basement rocks of the SE Asia and the proto-Philippine Sea Plate: Reconsidering the intra-oceanic nature of the IBM Arc

2014 Fiscal Year Final Research Report

• Project/Area Number: 24684037
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Partial Multi-year Fund
• Research Field: Geology
• Research Institution: National Museum of Nature and Science, Tokyo (2014); Japan Agency for Marine-Earth Science and Technology (2012-2013)
• Principal Investigator: TANI Kenichiro 独立行政法人国立科学博物館, 地学研究部, 研究員 (70359206)
• Research Collaborator: ISHIZUKA Osamu 産業技術総合研究所, 地質調査総合センター, 主任研究員 (90356444) ; UEDA Hayato 新潟大学, 理学部, 准教授 (70374197) ; GABO Jillian A. S. 九州大学, 地球資源システム工学部門, 非常勤研究員 ; DIMALANTA Carla フィリピン大学ディリマン校, 地質科学研究所, 教授
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 東南アジア / フィリピン海プレート / ジルコン年代 / 花崗岩 / 変成岩 / テクトニクス

Outline of Final Research Achievements

The Izu-Bonin-Mariana (IBM) Arc has been regarded as a typical intra-oceanic arc. However, little is known about the crustal structure of proto-Philippine Sea Plate (PSP), which existed during the subduction initiation in the Eocene. Submersible observations and rock sampling in the Daito Ridges, located in the NW PSP, revealed that the parts of the proto-PSP consist of continental granitic and metamorphic rocks with Mesozoic zircon ages.
To understand the origin of Mesozoic proto-PSP, comprehensive geological survey of the Philippine basement rocks were conducted. As a result, geochemical characteristics and zircon ages obtained from igneous basement complexes exposed in the SE Philippines match well with those of the Mesozoic rocks obtained from the Daito Ridges. This suggests that subduction of the IBM Arc initiated on the preexisting Mesozoic arc crust, correlating to the current SE Philippines, and later acquired intra-oceanic-like setting through formation of the backarc basins.

Free Research Field

岩石学・年代学