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523 results on '"Kimura, Jun-Ichi"'

105. Roll-Back, Extension and Mantle Upwelling Triggered Eocene Potassic Magmatism in NW Iran

Author

Shafaii Moghadam, Hadi, primary, Griffin, William L, additional, Kirchenbaur, Maria, additional, Garbe-Schönberg, Dieter, additional, Zakie Khedr, Mohamed, additional, Kimura, Jun-Ichi, additional, Stern, Robert J, additional, Ghorbani, Ghasem, additional, Murphy, Rosanna, additional, O’Reilly, Suzanne Y, additional, Arai, Shoji, additional, and Maghdour-Mashhour, Reza, additional

Published
2018
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107. The tremendous potential of deep-sea mud as a source of rare-earth elements

Author

Takaya, Yutaro, primary, Yasukawa, Kazutaka, additional, Kawasaki, Takehiro, additional, Fujinaga, Koichiro, additional, Ohta, Junichiro, additional, Usui, Yoichi, additional, Nakamura, Kentaro, additional, Kimura, Jun-Ichi, additional, Chang, Qing, additional, Hamada, Morihisa, additional, Dodbiba, Gjergj, additional, Nozaki, Tatsuo, additional, Iijima, Koichi, additional, Morisawa, Tomohiro, additional, Kuwahara, Takuma, additional, Ishida, Yasuyuki, additional, Ichimura, Takao, additional, Kitazume, Masaki, additional, Fujita, Toyohisa, additional, and Kato, Yasuhiro, additional

Published
2018
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110. U-Pb dating of calcite using LA-ICP-MS: Instrumental setup for non-matrix-matched age dating and determination of analytical areas using elemental imaging

Author

Yokoyama, Tatsunori, primary, Kimura, Jun-ichi, additional, Mitsuguchi, Takehiro, additional, Danhara, Toru, additional, Hirata, Takafumi, additional, Sakata, Shuhei, additional, Iwano, Hideki, additional, Maruyama, Seiji, additional, Chang, Qing, additional, Miyazaki, Takashi, additional, Murakami, Hiroaki, additional, and Saito-Kokubu, Yoko, additional

Published
2018
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114. Paleoceanographic conditions on the São Paulo Ridge, SW Atlantic Ocean, for the past 30 million years inferred from Os and Pb isotopes of a hydrogenous ferromanganese crust

Author

Goto, Kosuke T., primary, Nozaki, Tatsuo, additional, Toyofuku, Takashi, additional, Augustin, Adolpho H., additional, Shimoda, Gen, additional, Chang, Qing, additional, Kimura, Jun–Ichi, additional, Kameo, Koji, additional, Kitazato, Hiroshi, additional, and Suzuki, Katsuhiko, additional

Published
2017
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115. Missing western half of the Pacific Plate: Geochemical nature of the Izanagi-Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles

Author

Miyazaki, Takashi, Kimura, Jun-Ichi, Senda, Ryoko, Vaglarov, Bogdan S., Chang, Qing, Takahashi, Toshiro, Hirahara, Yuka, Hauff, Folkmar, Hayasaka, Yasutaka, Sano, Sakae, Shimoda, Gen, Ishizuka, Osamu, Kawabata, Hiroshi, Hirano, Naoto, Machida, Shiki, Ishii, Teruaki, Tani, Kenichiro, and Yoshida, Takeyoshi

Abstract

The source mantle of the basaltic ocean crust on the western half of the Pacific Plate was examined using Pb–Nd–Hf isotopes. The results showed that the subducted Izanagi–Pacific Ridge (IPR) formed from both Pacific (180–∼80 Ma) and Indian (∼80–70 Ma) mantles. The western Pacific Plate becomes younger westward and is thought to have formed from the IPR. The ridge was subducted along the Kurile–Japan–Nankai–Ryukyu (KJNR) Trench at 60–55 Ma and leading edge of the Pacific Plate is currently stagnated in the mantle transition zone. Conversely, the entire eastern half of the Pacific Plate, formed from isotopically distinct Pacific mantle along the East Pacific Rise and the Juan de Fuca Ridge, largely remains on the seafloor. The subducted IPR is inaccessible; therefore, questions regarding which mantle might be responsible for the formation of the western half of the Pacific Plate remain controversial. Knowing the source of the IPR basalts provides insight into the Indian–Pacific mantle boundary before the Cenozoic. Isotopic compositions of the basalts from borehole cores (165–130 Ma) in the western Pacific show that the surface oceanic crust is of Pacific mantle origin. However, the accreted ocean floor basalts (∼80–70 Ma) in the accretionary prism along the KJNR Trench have Indian mantle signatures. This indicates the younger western Pacific Plate of IPR origin formed partly from Indian mantle and that the Indian–Pacific mantle boundary has been stationary in the western Pacific at least since the Cretaceous.

Published
2015

116. Preferential oxidation of carbon monoxide catalyzed by platinum nanoparticles in mesoporous silica

Author

Fukuoka, Atsushi, Oshio, Tadashi, Sakamoto, Yuzuru, Ichikawa, Masaru, and Kimura, Jun-ichi

Subjects
Silica -- Spectra, Infrared spectroscopy -- Usage, Platinum compounds -- Spectra, Chemistry
Abstract

The promotional effect of mesoporous silica in the Pt-catalyzed PROX reaction by infrared spectroscopy is studied. The findings reveal that CO oxidation is promoted by the attack of the surface OH groups to CO on Pt without forming water.

Published
2007

117. Genesis of ultra-high-Ni olivine in high-Mg andesite lava triggered by seamount subduction

Author

Nishizawa, Tatsuji, primary, Nakamura, Hitomi, additional, Churikova, Tatiana, additional, Gordeychik, Boris, additional, Ishizuka, Osamu, additional, Haraguchi, Satoru, additional, Miyazaki, Takashi, additional, Vaglarov, Bogdan Stefanov, additional, Chang, Qing, additional, Hamada, Morihisa, additional, Kimura, Jun-Ichi, additional, Ueki, Kenta, additional, Toyama, Chiaki, additional, Nakao, Atsushi, additional, and Iwamori, Hikaru, additional

Published
2017
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118. Depositional Age of a Fossil Whale Bone from São Paulo Ridge, South Atlantic Ocean, Based on Os Isotope Stratigraphy of a Ferromanganese Crust

Author

Nozaki, Tatsuo, primary, Takaya, Yutaro, additional, Toyofuku, Takashi, additional, Tokumaru, Ayaka, additional, Goto, Kosuke T., additional, Chang, Qing, additional, Kimura, Jun-ichi, additional, Kato, Yasuhiro, additional, Suzuki, Katsuhiko, additional, Augustin, Adolpho Herbert, additional, and Kitazato, Hiroshi, additional

Published
2017
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133. Recycled ancient ghost carbonate in the Pitcairn mantle plume.

Author

Xiao-Jun Wang, Li-Hui Chen, Hofmann, Albrecht W., Takeshi Hanyuc, Hiroshi Kawabata, Yuan Zhong, Lie-Wen Xie, Jin-Hua Shi, Takashi Miyazaki, Yuka Hirahara, Toshiro Takahashi, Ryoko Senda, Qing Chang, Vaglarov, Bogdan S., and Kimura, Jun-Ichi

Subjects
CARBONATES, CARBONIC acid, BASALT, MAFIC rocks, GEOCHEMISTRY
Abstract

The extreme Sr, Nd, Hf, and Pb isotopic compositions found in Pitcairn Island basalts have been labeled enriched mantle 1 (EM1), characterizing them as one of the isotopic mantle end members. The EM1 origin has been vigorously debated for over 25 years, with interpretations ranging from delaminated subcontinental lithosphere, to recycled lower continental crust, to recycled oceanic crust carrying ancient pelagic sediments, all of which may potentially generate the requisite radiogenic isotopic composition. Here we find that δ26Mg ratios in Pitcairn EM1 basalts are significantly lower than in normal mantle and are the lowest values so far recorded in oceanic basalts. A global survey of Mg isotopic compositions of potentially recycled components shows that marine carbonates constitute the most common and typical reservoir invariably characterized by extremely low δ26Mg values. We therefore infer that the subnormal δ26Mg of the Pitcairn EM1 component originates from subducted marine carbonates. This, combined with previously published evidence showing exceptionally unradiogenic Pb as well as sulfur isotopes affected by mass-independent fractionation, suggests that the Pitcairn EM1 component is most likely derived from late Archean subducted carbonatebearing sediments. However, the low Ca/Al ratios of Pitcairn lavas are inconsistent with experimental evidence showing high Ca/Al ratios in melts derived from carbonate-bearing mantle sources. We suggest that carbonate-silicate reactions in the late Archean subducted sediments exhausted the carbonates, but the isotopically light magnesium of the carbonate was incorporated in the silicates, which then entered the lower mantle and ultimately became the Pitcairn plume source. [ABSTRACT FROM AUTHOR]

Published
2018
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134. Roll-Back, Extension and Mantle Upwelling Triggered Eocene Potassic Magmatism in NW Iran.

Author

Moghadam, Hadi Shafaii, Griffin, William L, Kirchenbaur, Maria, Garbe-Schönberg, Dieter, Khedr, Mohamed Zakie, Kimura, Jun-Ichi, Stern, Robert J, Ghorbani, Ghasem, Murphy, Rosanna, and O'Reilly, Suzanne Y

Subjects
EOCENE paleobotany, MAGMATISM, INTERMEDIATES (Chemistry), ITERATIVE methods (Mathematics)
Abstract

Igneous activity in the rear-arc of the Paleogene Urumieh–Dokhtar Magmatic Belt of Iran has to date been poorly studied. An example of such activity, Late Eocene potassic mafic to intermediate magmatic rocks in the Lahrud area of NW Iran, is the focus of this work. These lavas include olivine-bearing clinopyroxene-phyric basalts, analcime-bearing leucite–clinopyroxene-phyric basalts, andesites, and trachytes, and Paleocene–Early Eocene pyroclastic rocks. Monzo-syenite plugs (dated here at ∼37 Ma), clinopyroxene-phyric basaltic dikes, and leucite-bearing clinopyroxene-phyric basaltic dikes intrude older lavas and pyroclastic rocks. Olivine-bearing clinopyroxene-phyric basalts and analcime-bearing leucite–clinopyroxene-phyric basalts are characterized by large phenocrysts of olivine, clinopyroxene, leucite, and analcime. Clinopyroxene-rich enclaves and partially resorbed mantle xenoliths also occur. Olivine phenocrysts are zoned from high-Mg# cores (Mg# = 90) to Fe-rich rims (Mg# = 66). Clinopyroxene phenocrysts from the olivine-bearing clinopyroxene-phyric basalts, analcime-bearing leucite–clinopyroxene-phyric basalts and clinopyroxene crystals in the enclaves show complex oscillatory zoning, sieve textures, and resorption textures, but with systematic core–rim compositional trends. Their 87Sr/86Sr isotopic compositions measured in situ range from 0·7037 to 0·7068 (mean = 0·7052 ± 0·0004), suggesting negligible crustal assimilation during fractional crystallization. The Lahrud lavas are potassic and are enriched in light rare earth elements and large ion lithophile elements such as Th, Rb, K and U. High field strength elements (HFSE), such as Nb, are depleted in the olivine-bearing clinopyroxene-phyric basalts and analcime-bearing leucite–clinopyroxene-phyric basalts, but enriched in the trachytes and trachytic ignimbrites. The isotopic compositions vary: 87Sr/86Srt from 0·7045 to 0·7052, εNd(t) from +2·8 to +3·3, and εHf(t) from +7·2 to +7·7. The rocks have radiogenic lead 206Pb/204Pb from 18·66 to 18·76, 207Pb/204Pb from 15·58 to 15·62, and 208Pb/204Pb from 38·73 to 38·81. Modeling of major and trace elements using the MELTS algorithm indicates that the geochemical variations in the basaltic to andesitic rocks are reasonably explained by shallow fractional crystallization with some complications owing to source heterogeneity, crustal assimilation, and magma mixing. The isotopic data imply that partial melting of old sub-continental lithospheric mantle was not responsible for the Lahrud potassic magmas; Hf isotopes and Zr/Nb ratios suggest derivation from an enriched mantle wedge, whereas ratios of incompatible trace elements (e.g. La/Yb, Ba/La, Ce/Pb, Th/Yb) and high 87Sr/86Sr suggest mantle metasomatized by slab-derived fluids or melts dominated by a sediment component. Geochemical modeling using the Arc Basalt Simulator version 5 reveals that the HFSE-depleted, olivine-bearing, clinopyroxene-phyric basalts originated from a high-temperature mantle wedge (2·2 GPa, 1310°C) fluxed intensively (5%) by melts from a deep hot slab (6 GPa, 1000°C). The moderately HFSE-depleted, olivine-bearing, clinopyroxene-phyric basalts reflect melting of a lower-temperature mantle wedge (2·2 GPa, 1300°C) with a lesser amount of slab melt flux (4%) from a lower temperature and shallower slab (3 GPa, 866°C). In contrast, the leucite–clinopyroxene-phyric basalts and andesites are from a similar source to the moderately HFSE-depleted, olivine-bearing, clinopyroxene-phyric basalts (3 GPa, 866°C) but with a contribution from a lower temperature mantle wedge (2·2 GPa, 1270°C). During Late Eocene times, slab retreat and upper-plate extension occurred in the rear-arc region of the Urumieh–Dokhtar Magmatic Belt. The Lahrud potassic magmas were generated from a high-temperature mantle wedge, which resulted in melting of the slab; this slab melt flux further promoted melting of the mantle wedge. [ABSTRACT FROM AUTHOR]

Published
2018
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135. マダガスカル東部地域における太古代クラトンの再変動

Author

ICHIKI, Takashi, ISHIKAWA, Masahiro, OSANAI, Yasuhito, NAKANO, Nobuhiko, ADACHI, Tatsuro, KIMURA, Jun-Ichi, and SENDA, Ryoko

Abstract

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月30日（金） 統計数理研究所 ３階セミナー室

Published
2012

137. Missing western half of the Pacific Plate: Geochemical nature of the Izanagi-Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles

Author

Miyazaki, Takashi, primary, Kimura, Jun-Ichi, additional, Senda, Ryoko, additional, Vaglarov, Bogdan S., additional, Chang, Qing, additional, Takahashi, Toshiro, additional, Hirahara, Yuka, additional, Hauff, Folkmar, additional, Hayasaka, Yasutaka, additional, Sano, Sakae, additional, Shimoda, Gen, additional, Ishizuka, Osamu, additional, Kawabata, Hiroshi, additional, Hirano, Naoto, additional, Machida, Shiki, additional, Ishii, Teruaki, additional, Tani, Kenichiro, additional, and Yoshida, Takeyoshi, additional

Published
2015
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142. Geochemical variations in Japan Sea back‐arc basin basalts formed by high‐temperature adiabatic melting of mantle metasomatized by sediment subduction components

Author

Hirahara, Yuka, primary, Kimura, Jun‐Ichi, additional, Senda, Ryoko, additional, Miyazaki, Takashi, additional, Kawabata, Hiroshi, additional, Takahashi, Toshiro, additional, Chang, Qing, additional, Vaglarov, Bogdan S., additional, Sato, Takeshi, additional, and Kodaira, Shuichi, additional

Published
2015
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144. Fore-arc basalts and subduction initiation in the Izu-Bonin-Mariana system

Author

Regan, Mark K., Ishizuka, Osamu, Stern, Robert J., Kelley, Katherine A., Ohara, Yasuhiko, Blichert-Toft, Janne, Bloomer, Sherman H., Cash, Jennifer, Fryer, Patricia, Hanan, Barry, Hickey-Vargas, Rosemary, Ishii, Teruaki, Kimura, Jun-Ichi, Peate, David W., Rowe, Michael C., Woods, Melinda, Department of Geoscience, University of Iowa [Iowa City], Institute of Geoscience and Geoinformation, Geological Survey of Japan, Geoscience Department, University of Texas at Dallas [Richardson] (UT Dallas), Graduate School of Oceanography [Narragansett], University of Rhode Island (URI), Hydrographic and Ocean Department of Japan, Japan Coast Guard Academy, Laboratoire de Sciences de la Terre (LST), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Oregon State University (OSU), Hawaii Institute of Geophysics and Planetology (HIGP), University of Hawai‘i [Mānoa] (UHM), Department of Geological Sciences [San Diego], San Diego State University (SDSU), Department of Earth Sciences [Miami], Florida International University [Miami] (FIU), Institute for Research on Earth Evolution [Yokosuka] (IFREE), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), NSF : 0827817, 0405651, OCE0001824, NSF MARGINS : OCE0001902, EAR0840862, French Institut National des Sciences de l'Univers : INSU, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Department of Geological Sciences [San Diego State Univ] (Geology SDSU)

Subjects
fore arc, ophiolite, basal t, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Mariana, geochemistry
Abstract

International audience; Recent diving with the JAMSTEC Shinkai 6500 manned submersible in the Mariana fore arc southeast of Guam has discovered that MORB-like tholeiitic basalts crop out over large areas. These ''fore-arc basalts'' (FAB) underlie boninites and overlie diabasic and gabbroic rocks. Potential origins include eruption at a spreading center before subduction began or eruption during near-trench spreading after subduction began. FAB trace element patterns are similar to those of MORB and most Izu-Bonin-Mariana (IBM) back-arc lavas. However, Ti/V and Yb/V ratios are lower in FAB reflecting a stronger prior depletion of their mantle source compared to the source of basalts from mid-ocean ridges and back-arc basins. Some FAB also have higher concentrations of fluid-soluble elements than do spreading center lavas. Thus, the most likely origin of FAB is that they were the first lavas to erupt when the Pacific Plate began sinking beneath the Philippine Plate at about 51 Ma. The magmas were generated by mantle decompression during near-trench spreading with little or no mass transfer from the subducting plate. Boninites were generated later when the residual, highly depleted mantle melted at shallow levels after fluxing by a water-rich fluid derived from the sinking Pacific Plate. This magmatic stratigraphy of FAB overlain by transitional lavas and boninites is similar to that found in many ophiolites, suggesting that ophiolitic assemblages might commonly originate from near-trench volcanism caused by subduction initiation. Indeed, the widely dispersed Jurassic and Cretaceous Tethyan ophiolites could represent two such significant subduction initiation events.

Published
2010

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