Rethinking spreading model of the northwestern West Philippine Basin (WPB): 39Ar/40Ar dating and geochemical constraints

Ryuichi SHINJO; Osamu ISHIZUKA

Presentation information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT07] New constraints on the tectonic evolution of Northeast Asia

Mon. May 25, 2015 9:00 AM - 10:45 AM A03 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Jonny Wu(Department of Geosciences, National Taiwan University), Kyoko Okino(Ocean Research Institute, University of Tokyo), Cedric Legendre(Institute of Earth Sciences, Academia Sinica, Taiwan), Gaku Kimura(Department of Earth and Planetary Science of the Graduate School of Science, The University of Tokyo), Chair:Jonny Wu(Department of Geosciences, National Taiwan University), Kyoko Okino(Ocean Research Institute, University of Tokyo)

9:15 AM - 9:30 AM

[SIT07-02] Rethinking spreading model of the northwestern West Philippine Basin (WPB): 39Ar/40Ar dating and geochemical constraints

*Ryuichi SHINJO¹, Osamu ISHIZUKA² (1.Univ. Ryukyus, 2.Geological Survey of Japan, AIST)

We report 40Ar/39Ar dating results of basalts from the northwestern West Philippine Basin (around the Urdaneta Plateau area), with petrological/geochemical characteristics. Our samples are mostly from ROV KAIKO dives conducted in 2003.

Our dating results range from ~40 to ~32 Ma. These ages are younger than previously estimated seafloor ages based on studies for topography and magnetic anomaly lineations. In addition, geographical distribution of obtained ages appears to be incompatible with previous models. Therefore, if our dating results are correct, it requests rethinking about the spreading history of northwestern part of WPB.

Geochemical data revealed that basalts around the Urdaneta Plateau have OIB-like characteristics (as also reported in Ishizuka et al., 2013, Geology), confirming that plume activity involved in the spreading process of this part of basin.