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Ayaka Tokumaru

University of Tokyo

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oceans conference | 2011

Small-scale ROV mapping of the ferromanganese crusts over the seamounts in the NW pacific

Akira Usui; Mariko Tanaka; Blair Thornton; Ayaka Tokumaru; Tetsuro Urabe

We report the preliminary results of the two cruises of ROV (HyperDolphin 3K, operated by JAMSTEC) mapping of sea floor occurrence and in-situ sampling of hydrogenetic ferromanganese deposits. This is the first systematic joint scientific research on the crusts over the deep-sea floors, which unveiled the ubiquitous distribution of the crusts covering the rock substrates. The results of physical measurements of morphology and thickness of the crusts, geochemical characterization of very surface portions of intact samples, distribution patterns of occurrences and thickness. The successful operation and ongoing shorebased geochemical and geological analyses proved that the ROV is one of the best methos in careful mapping, sampling and in-situ observation of sea bottom.

Geochimica et Cosmochimica Acta | 2014

Uranium isotope systematics of ferromanganese crusts in the Pacific Ocean: Implications for the marine 238U/235U isotope system

Kosuke T. Goto; Ariel D. Anbar; Gwyneth W. Gordon; Stephen J. Romaniello; Gen Shimoda; Yutaro Takaya; Ayaka Tokumaru; Tatsuo Nozaki; Katsuhiko Suzuki; Shiki Machida; Takeshi Hanyu; Akira Usui

Geochemical Journal | 2015

Re–Os isotope geochemistry in the surface layers of ferromanganese crusts from the Takuyo Daigo Seamount, northwestern Pacific Ocean

Ayaka Tokumaru; Tatsuo Nozaki; Katsuhiko Suzuki; Kosuke T. Goto; Qing Chang; Jun-Ichi Kimura; Yutaro Takaya; Yasuhiro Kato; Akira Usui; Tetsuro Urabe

Ore Geology Reviews | 2017

Continuous growth of hydrogenetic ferromanganese crusts since 17 Myr ago on Takuyo-Daigo Seamount, NW Pacific, at water depths of 800–5500 m

Akira Usui; Keisuke Nishi; Hisaaki Sato; Yoshio Nakasato; Blair Thornton; Teruhiko Kashiwabara; Ayaka Tokumaru; A. Sakaguchi; Kyoko Yamaoka; Shingo Kato; Shota Nitahara; Katsuhiko Suzuki; Koichi Iijima; Tetsuro Urabe

Geochemical Journal | 2016

Major and trace element compositions and resource potential of ferromanganese crust at Takuyo Daigo Seamount, northwestern Pacific Ocean

Tatsuo Nozaki; Ayaka Tokumaru; Yutaro Takaya; Yasuhiro Kato; Katsuhiko Suzuki; Tetsuro Urabe

Resource Geology | 2017

Depositional Age of a Fossil Whale Bone from São Paulo Ridge, South Atlantic Ocean, Based on Os Isotope Stratigraphy of a Ferromanganese Crust

Tatsuo Nozaki; Yutaro Takaya; Takashi Toyofuku; Ayaka Tokumaru; Kosuke T. Goto; Qing Chang; Jun-Ichi Kimura; Yasuhiro Kato; Katsuhiko Suzuki; Adolpho Herbert Augustin; Hiroshi Kitazato

Japan Geoscience Union | 2014

Is the growth hiatus of ferromanganese crusts a local or global event

Tatsuo Nozaki; Kosuke T. Goto; Ayaka Tokumaru; Yutaro Takaya; Katsuhiko Suzuki; Qing Chang; Jun-Ichi Kimura; Yasuhiro Kato; Gen Shimoda; Takashi Toyofuku; Akira Usui; Tetsuro Urabe

Japan Geoscience Union | 2014

Uranium isotope composition in ferromanganese crusts: Implications for the paleoredox proxy

Kosuke T. Goto; Ariel D. Anbar; Gwyneth W. Gordon; Stephen J. Romaniello; Gen Shimoda; Yutaro Takaya; Ayaka Tokumaru; Tatsuo Nozaki; Katsuhiko Suzuki; Shiki Machida; Takeshi Hanyu; Akira Usui

Japan Geoscience Union | 2014

Comparing rare earth elements in the surface layers of ferromanganese crusts and ambient seawater from the Takuyo Daigo

Ayaka Tokumaru; Yanbei Zhu; Tatsuo Nozaki; Yutaro Takaya; Kosuke T. Goto; Katsuhiko Suzuki; Qing Chang; Jun-Ichi Kimura; Yasuhiro Kato; Akira Usui; Tetsuro Urabe; Yohey Suzuki

Japan Geoscience Union | 2014

Os isotope stratigraphy of a ferromanganese crust: Its principles and applications

Tatsuo Nozaki; Kosuke T. Goto; Ayaka Tokumaru; Yutaro Takaya; Katsuhiko Suzuki; Qing Chang; Jun-Ichi Kimura; Yasuhiro Kato; Gen Shimoda; Takashi Toyofuku; Akira Usui; Tetsuro Urabe

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Katsuhiko Suzuki

Japan Agency for Marine-Earth Science and Technology

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Tatsuo Nozaki

Japan Agency for Marine-Earth Science and Technology

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Tetsuro Urabe

University of Tokyo

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Yutaro Takaya

Japan Agency for Marine-Earth Science and Technology

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Kosuke T. Goto

National Institute of Advanced Industrial Science and Technology

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Jun-Ichi Kimura

Japan Agency for Marine-Earth Science and Technology

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Qing Chang

Japan Agency for Marine-Earth Science and Technology

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Yasuhiro Kato

University of Tokyo

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Gen Shimoda

National Institute of Advanced Industrial Science and Technology

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Takashi Toyofuku

Japan Agency for Marine-Earth Science and Technology

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