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Keiko Sato, Hidenori Kumagai, Takeshi Hanyu, Hajimu Tamura
Pages
201-
Published: 2019
Released on J-STAGE: November 20, 2019
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For radiometric dating by K-Ar and/or Ar-Ar method, we frequently use inter-laboratory standards to calibrate the age, radiogenic 40Ar and potassium contents, and eventually to reduce their systematic error. We practically analyze unknown samples with such age standards at K-Ar/ Ar-Ar dating and/or noble gas analysis to evaluate any inter laboratory offset. Under recent hard-to-access circumstances for Neogene standards, an aphyric andesite was prepared as a new dating standard for inter-laboratory calibration. It showed well agreement of ages by multiple dating analysis within analytical uncertainties.
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Kenta Ueki, Nozomu Takeuchi, Tsuyoshi Iizuka, Sanshiro Enomoto
Pages
202-
Published: 2019
Released on J-STAGE: November 20, 2019
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Keita Itano, Tomoaki Morishita, Akihiro Tamura, Ikuya Nishio, Juan Mig ...
Pages
203-
Published: 2019
Released on J-STAGE: November 20, 2019
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Yuki Matsukida, Tsuyoshi IIzuka, Takayuki Ushikubo, Kenji Shimizu, Nob ...
Pages
204-
Published: 2019
Released on J-STAGE: November 20, 2019
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Chikara Shito, Hiroyuki Kagi, Asami Sano―Furukawa, Sho Kakizawa, Kazuk ...
Pages
205-
Published: 2019
Released on J-STAGE: November 20, 2019
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Sho Kakizawa, Inoue Toru, Abe Ryotaro, Kuroda Minami, Sakamoto Naoya, ...
Pages
206-
Published: 2019
Released on J-STAGE: November 20, 2019
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Ko Fukuyama, Hiroyuki Kagi, Toru Inoue, Sho Kakizawa, Toru Shinmei, Sh ...
Pages
207-
Published: 2019
Released on J-STAGE: November 20, 2019
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Kenji Kawai, Anselme Borgeaud, Yuki Suzuki
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208-
Published: 2019
Released on J-STAGE: November 20, 2019
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Takeshi Hanyu, Jun―Ichi Kimura, Chang Qing, Morihisa Hamada, Kenji Shi ...
Pages
209-
Published: 2019
Released on J-STAGE: November 20, 2019
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Hiroyuki Kagi, Ayaka Saito, Kazuki Komatsu, Shiho Marugata, Jun Kawano
Pages
210-
Published: 2019
Released on J-STAGE: November 20, 2019
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Sung Hi Choi
Pages
211-
Published: 2019
Released on J-STAGE: November 20, 2019
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Late Cenozoic intraplate basaltic rocks in northeastern China have been interpreted as being derived from a mantle source composed of DMM (depleted MORB mantle) and EM1 (enriched mantle type 1) components. To constrain the origin of the enriched mantle component, we have now determined the geochemical compositions (including Sr, Nd, Pb, Hf, and Mg isotopes) of basaltic rocks from the active Mt. Baekdu volcano on the border of China and North Korea. Also obtained are major and trace element concentrations of olivine-hosted rehomogenized melt inclusions in the basalts. The samples show light rare earth element (LREE)-enriched patterns with (La/Yb)N ratios of 3.2–20.0. However, most of the samples have positive Eu and negative Ce anomalies. On a primitive-mantle-normalized trace element distribution diagram, they show typical oceanic island basalt (OIB)-like large-ion lithophile element (LILE) enrichments without significant Nb or Ta depletions. However, compared with OIB, they show enrichments in Ba, Rb, K, Pb, Sr, and P. In addition, the CaO and P2O5 contents of the melt inclusions are positively correlated, indicating the presence of tuite and K-hollandite in the source. The Nb/U ratios of the basalts are generally within the range of OIB, but the Ce/Pb ratios are lower than those of OIB. The Mt. Baekdu basalts do not show meaningful correlations between SiO2 (wt%) and Sr–Nd–Hf isotopic compositions, suggesting a lack of crustal contamination, and this means, therefore, that the low Ce/Pb ratios could be a characteristic of the mantle source. They have elevated Gd/Yb ratios within the range of melts from garnet peridotite. Olivine phenocrysts are characterized by low Ca and high Ni contents when compared with olivines from peridotite-derived melts for a given Fo value. The radiogenic isotopic characteristics (87Sr/86Sr = 0.70449 to 0.70554; εNd = –2.0 to +1.8; εHf = –1.7 to +6.1; 206Pb/204Pb = 17.26 to 18.12) suggest derivation from an EM1-like source together with an Indian MORB-like depleted mantle. The Mg isotopic compositions (δ26Mg = –0.39 ± 0.17‰) are generally lower than the average upper mantle (δ26Mg = –0.25 ± 0.04‰), indicating carbonates in the source. The 87Sr/86Sr ratios decrease with decreasing δ26Mg values whereas the 143Nd/144Nd and (Nb/La)N ratios increase. These observations suggest the mantle source of the Mt. Baekdu basalts contained at least two components that resided possibly in the mantle transition zone (MTZ): (1) recycled subducted ancient (~2.2 to 1.6 Ga) terrigenous silicate sediments, possessing EM1-like Sr–Nd–Pb–Hf isotopic signatures and relatively high values of δ26Mg; and (2) carbonated tuite-bearing eclogites with relatively MORB-like radiogenic isotopic compositions and low values of δ26Mg. These components might have acted as metasomatizing agents in refertilizing the asthenosphere, eventually influencing the composition of the MTZ-derived plume that produced the Mt. Baekdu volcanism.
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Hiroshi Sato, Shiki Machida, Ryoko Senda, Taichi Sato, Yoshifumi Nogi, ...
Pages
212-
Published: 2019
Released on J-STAGE: November 20, 2019
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Conrad Rise is one of the plateaux in the Indian Ocean. We recovered igneous rocks: massive lava, porous lava, and volcanic breccia. They are mostly alkali rocks, and lesser amounts of sub-alkali rock were recovered. They have similar trace element compositions to igneous rocks from seamounts and plateaux in the Indian Ocean, while trace element and isotopic ratios are different from Marion, Crozet, and Kerguelen volcanic rocks. Instead, they have similar trace element and isotopic ratios to Madagascar and Afanasy-Nikitin rocks. Tectonic reconstruction reveals that Conrad Rise, Del Cano Rise, and Madagascar Plateau had formed one massive edifice. Therefore, Conrad Rise, Del Cano Rise, Madagascar Plateau, and Afanasy-Nikitin Rise have a common origin, because Afanasy-Nikitin Rise was located near the edifices at that time.
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Chihiro Ohshima, Norikatsu Akizawa, Akira Ishikawa, Teruaki Ishii, Tet ...
Pages
213-
Published: 2019
Released on J-STAGE: November 20, 2019
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Katsuhiko Suzuki, Asako Takamasa, Yusuke Fukami, Tsuyoshi Iizuka, Yuji ...
Pages
214-
Published: 2019
Released on J-STAGE: November 20, 2019
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Hideharu Kuwahara, Shoichi Itoh, Ryoichi Nakada, Tetsuo Irifune
Pages
215-
Published: 2019
Released on J-STAGE: November 20, 2019
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Liquid metal-silicate partitioning of carbon under carbon-unsaturated conditions was investigated using multi-anvil high pressure apparatus. Carbon in quenched metallic and silicate phases was analyzed by electron probe micro-analyzer and secondary ion mass spectroscopy. Our results show that metal-silicate partition coefficient of carbon may be lower than previously thought and silicate melt may be saturated with carbon even at low-carbon concentration (i.e., 0.5 wt%). We also found that carbon solubility in peridotitic silicate melt under reducing conditions is consistent with carbon abundance in the Earth's mantle within errors. Previous studies have suggested that the accretion of carbon-rich body after core formation is necessary to explain carbon abundance in the Earth's mantle. However, if terrestrial magma ocean was saturated with carbon, the late accretion of carbon-rich body is not necessary to explain carbon abundance in the Earth's mantle.
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Riko Iizuka―Oku, Hirotada Gotou, Akio Suzuki, Hiroyuki Kagi
Pages
216-
Published: 2019
Released on J-STAGE: November 20, 2019
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Hirotaro Sagi, Tetsu Kogiso
Pages
217-
Published: 2019
Released on J-STAGE: November 20, 2019
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Akira Yamaguchi, Naoki Shirai, Jean―Alix Barrat
Pages
218-
Published: 2019
Released on J-STAGE: November 20, 2019
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Yoshitaka Homma, Tsuyoshi Iizuka, Akira Ishikawa
Pages
219-
Published: 2019
Released on J-STAGE: November 20, 2019
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Yasuhiro Oba, Yoshinori Takano, Hiroshi Naraoka, Naoki Watanabe, Akira ...
Pages
220-
Published: 2019
Released on J-STAGE: November 20, 2019
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Masahiro Yoda, Yasuhito Sekine, Keisuke Fukushi, Yoshio Takahashi, Tak ...
Pages
221-
Published: 2019
Released on J-STAGE: November 20, 2019
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Shinya Asano, Isao Yoda, Yasuji Muramatsu, Yoko Kebukawa, Kensei Kobay ...
Pages
222-
Published: 2019
Released on J-STAGE: November 20, 2019
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Hiroki Mawatari, Junko Isa, Hiroshi Naraoka
Pages
223-
Published: 2019
Released on J-STAGE: November 20, 2019
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Mizuho Koike, Ryoichi Nakada, Iori Kajitani, Tomohiro Usui, Yusuke Tam ...
Pages
224-
Published: 2019
Released on J-STAGE: November 20, 2019
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Tomoya Ishida, Hiroshi Naraoka
Pages
225-
Published: 2019
Released on J-STAGE: November 20, 2019
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Shigekazu Yoneda, Akira Yamaguchi, Tomoko Ojima, Makoto Kimura, Ryuji ...
Pages
226-
Published: 2019
Released on J-STAGE: November 20, 2019
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Motoo Ito, Hiroki Suga, Yu Kodama, Takuji Ohigashi, Roichi Nakada, Hir ...
Pages
227-
Published: 2019
Released on J-STAGE: November 20, 2019
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Sota Numaho, Takazo Shibuya, Hisahiro Ueda, Takuya Saito, Sakiko Kikuc ...
Pages
228-
Published: 2019
Released on J-STAGE: November 20, 2019
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Hisahiro Ueda, Yusuke Sawaki, Yuta Takei, Tuyoshi Ohno, Takazo Shibuya
Pages
229-
Published: 2019
Released on J-STAGE: November 20, 2019
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Ogawa Ryuzo, Ohno Takeshi, Fukami Yusuke, Suzuki Katuhiko
Pages
230-
Published: 2019
Released on J-STAGE: November 20, 2019
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Sato Shoich, Ayaka Masegi, Takeshi Ohno, Yusuke Fukami
Pages
231-
Published: 2019
Released on J-STAGE: November 20, 2019
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Yuta Takei, Yusuke Sawaki, Hisahiro Ueda, Takeshi Ohno
Pages
232-
Published: 2019
Released on J-STAGE: November 20, 2019
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Akane Ito, Akaya Murofushi, Tsubasa Otake, Kenzo Sanematsu, Tsutomu Sa ...
Pages
233-
Published: 2019
Released on J-STAGE: November 20, 2019
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Akihiro Okuyama, Keisuke Fukushi
Pages
234-
Published: 2019
Released on J-STAGE: November 20, 2019
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Kosuke Inoue, Keisuke Fukushi, Koki Morida, Hiroki Suga, Yoshio Takaha ...
Pages
235-
Published: 2019
Released on J-STAGE: November 20, 2019
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Kensuke Unami, Keisuke Fukushi, Yoshio Takahashi, Tetsumaru Itaya, Mas ...
Pages
236-
Published: 2019
Released on J-STAGE: November 20, 2019
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