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タイトル: Asthenospheric injection and back-arc opening: Isotopic evidence from Northeast Japan
著者: Nohda, Susumu
Tatsumi, Yoshiyuki
Otofuji, Yo-ichiro
Matsuda, Takaaki
Ishizaka, Kyoichi
キーワード: Asthenospheric injection
Back-arc opening
Isotopic composition
Northeast Japan
雑誌名: Report of the Institute of the Kuroshio Sphere, Kochi University. Special series = くろしお. 特別号 : 高知大学黒潮圏研究所所報
発行日: 20-Dec-1989
出版者: The Institute of The Kuroshio Sphere, Kochi University
抄録: Nd and Sr isotopic compositions were determined for the Tertiary volcanics from the back-arc side of the NE Japan arc. Sr isotopes show a linear trend through time from an enriched signature (^<87>Sr/ ^<86>Sr = 0.705437) to a depleted signature (^<87>Sr/ ^<86>Sr = 0.70270). In a complementary fashion, Nd isotopes start at low value ( ∈_<Nd> = -0.80)and show a gradual increase ( ∈_<Nd> = 8.3) with decreasing age. Isotopic change of Nd and Sr from the enriched signature to the depleted one is synchronous with the opening of the Japan sea at ~15 Ma. This synchronism indicates that the opening of the Japan Sea was initiated by the injection of the asthenosphere. During the pre-opening stage, the mantle wedge was composed of a two-layered structure: the sub-continental lithosphere and the underlying asthenosphere. The volcanics of this stage characterized by an enriched isotopic signature were derived from a source with a higher proportion of sub-continental lithosphere. The sub-continintal lithosphere of the back-arc side was thinned by the injection of the depleted asthenosphere, which accelerated the growth of the MORB source within the mantle wedge of the back-arc side and resulted in magma generation with the depleted isotopic signature of Nd and Sr at the post-opening stage.
注記: Japanese WESTPAC Symposium. June 6-7, 1989. Ocean Research Institute, University of Tokyo. 西太平洋におけるマイクロプレートテクトニクスと古環境地図に関する研究会. 1989年6月6日-7日. 東京大学海洋研究所.
URI: http://hdl.handle.net/10126/4519
出現コレクション:02 くろしお:高知大学黒潮圏研究所 所報  1(1986)-11(2001)

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