2021/12/22 更新

写真a

オオタ ツトム
太田 努
OTA Tsutomu
所属
惑星物質研究所 主任スーパーテクニシャン
職名
主任スーパーテクニシャン
外部リンク

学位

  • 博士(理学) ( 新潟大学 )

研究キーワード

  • geochemistry

  • Petrology

  • 地球化学

  • 岩石学

研究分野

  • 自然科学一般 / 固体地球科学

学歴

  • 新潟大学    

    - 1997年

      詳細を見る

    国名: 日本国

    researchmap

  • 新潟大学   Graduate School, Division of Science and Technology  

    - 1997年

      詳細を見る

  • 愛媛大学   理学部   地球科学科

    - 1991年

      詳細を見る

    国名: 日本国

    researchmap

  • 愛媛大学   Faculty of Science  

    - 1991年

      詳細を見る

 

MISC

  • Supervolcano eruptions driven by melt buoyancy in large silicic magma chambers

    Wim J. Malfait, Rita Seifert, Sylvain Petitgirard, Jean-Philippe Perrillat, Mohamed Mezouar, Tsutomu Ota, Eizo Nakamura, Philippe Lerch, Carmen Sanchez-Valle

    NATURE GEOSCIENCE   7 ( 2 )   122 - 125   2014年2月

     詳細を見る

    記述言語:英語   出版者・発行元:NATURE PUBLISHING GROUP  

    Super-eruptions that dwarf all historical volcanic episodes in erupted volume(1) and environmental impact(2) are abundant in the geological record. Such eruptions of silica-rich magmas form large calderas. The mechanisms that trigger these super-eruptions are elusive because the processes occurring in conventional volcanic systems cannot simply be scaled up to the much larger magma chambers beneath supervolcanoes. Over-pressurization of the magma reservoir, caused by magma recharge, is a common trigger for smaller eruptions(3), but is insufficient to generate eruptions from large supervolcano magma chambers(4). Magma buoyancy can potentially create sufficient overpressure(4), but the efficiency of this trigger mechanism has not been tested. Here we use synchrotron measurements of X-ray absorption(5) to determine the density of silica-rich magmas at pressures and temperatures of up to 3.6 GPa and 1,950 K, respectively. We combine our results with existing measurements of silica-rich magma density at ambient pressures(6,7) to show that magma buoyancy can generate an overpressure on the roof of a large supervolcano magma chamber that exceeds the critical overpressure of 10-40 MPa required to induce dyke propagation(4), even when the magma is undersaturated in volatiles. We conclude that magma buoyancy alone is a viable mechanism to trigger a super-eruption, although magma recharge and mush rejuvenation(8), volatile saturation(9) or tectonic stress(10) may have been important during specific eruptions.

    DOI: 10.1038/NGEO2042

    Web of Science

    researchmap

  • Supervolcano eruptions driven by melt buoyancy in large silicic magma chambers

    Wim J. Malfait, Rita Seifert, Sylvain Petitgirard, Jean-Philippe Perrillat, Mohamed Mezouar, Tsutomu Ota, Eizo Nakamura, Philippe Lerch, Carmen Sanchez-Valle

    NATURE GEOSCIENCE   7 ( 2 )   122 - 125   2014年2月

     詳細を見る

    記述言語:英語   出版者・発行元:NATURE PUBLISHING GROUP  

    Super-eruptions that dwarf all historical volcanic episodes in erupted volume(1) and environmental impact(2) are abundant in the geological record. Such eruptions of silica-rich magmas form large calderas. The mechanisms that trigger these super-eruptions are elusive because the processes occurring in conventional volcanic systems cannot simply be scaled up to the much larger magma chambers beneath supervolcanoes. Over-pressurization of the magma reservoir, caused by magma recharge, is a common trigger for smaller eruptions(3), but is insufficient to generate eruptions from large supervolcano magma chambers(4). Magma buoyancy can potentially create sufficient overpressure(4), but the efficiency of this trigger mechanism has not been tested. Here we use synchrotron measurements of X-ray absorption(5) to determine the density of silica-rich magmas at pressures and temperatures of up to 3.6 GPa and 1,950 K, respectively. We combine our results with existing measurements of silica-rich magma density at ambient pressures(6,7) to show that magma buoyancy can generate an overpressure on the roof of a large supervolcano magma chamber that exceeds the critical overpressure of 10-40 MPa required to induce dyke propagation(4), even when the magma is undersaturated in volatiles. We conclude that magma buoyancy alone is a viable mechanism to trigger a super-eruption, although magma recharge and mush rejuvenation(8), volatile saturation(9) or tectonic stress(10) may have been important during specific eruptions.

    DOI: 10.1038/NGEO2042

    Web of Science

    researchmap

  • Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft

    Eizo Nakamura, Akio Makishima, Takuya Moriguti, Katsura Kobayashi, Ryoji Tanaka, Tak Kunihiro, Tatsuki Tsujimori, Chie Sakaguchi, Hiroshi Kitagawa, Tsutomu Ota, Yusuke Yachi, Toru Yada, Masanao Abe, Akio Fujimura, Munetaka Ueno, Toshifumi Mukai, Makoto Yoshikawa, Jun'ichiro Kawaguchi

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA   109 ( 11 )   E624 - E629   2012年3月

     詳細を見る

    記述言語:英語   出版者・発行元:NATL ACAD SCIENCES  

    Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 mu m, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-mu m-sized craters but also a large number of sub-mu m-to several-mu m-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-mu m-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10(-9) to 10(4) meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.

    DOI: 10.1073/pnas.1116236109

    Web of Science

    researchmap

  • Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft

    Eizo Nakamura, Akio Makishima, Takuya Moriguti, Katsura Kobayashi, Ryoji Tanaka, Tak Kunihiro, Tatsuki Tsujimori, Chie Sakaguchi, Hiroshi Kitagawa, Tsutomu Ota, Yusuke Yachi, Toru Yada, Masanao Abe, Akio Fujimura, Munetaka Ueno, Toshifumi Mukai, Makoto Yoshikawa, Jun'ichiro Kawaguchi

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA   109 ( 11 )   E624 - E629   2012年3月

     詳細を見る

    記述言語:英語   出版者・発行元:NATL ACAD SCIENCES  

    Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 mu m, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-mu m-sized craters but also a large number of sub-mu m-to several-mu m-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-mu m-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10(-9) to 10(4) meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.

    DOI: 10.1073/pnas.1116236109

    Web of Science

    researchmap

  • In situ ion-microprobe determination of trace element partition coefficients for hornblende, plagioclase, orthopyroxene, and apatite in equilibrium with natural rhyolitic glass, Little Glass Mountain Rhyofite, California

    James G. Brophy, Tsutomu Ota, Tak Kunihro, Tatsuki Tsujimori, Eizo Nakamura

    AMERICAN MINERALOGIST   96 ( 11-12 )   1838 - 1850   2011年11月

     詳細を見る

    記述言語:英語   出版者・発行元:MINERALOGICAL SOC AMER  

    Partially crystalline hornblende gabbro inclusions from the Little Glass Mountain Rhyolite contain euhedral plagioclase, orthopyroxene, hornblende, and apatite crystals in contact with interstitial rhyolitic (71-76% SiO(2)) glass. Textural and mineral compositional data indicate that the gabbros crystallized sufficiently slowly that surface equilibrium was closely approached at the interface between crystals and the liquid. This rare occurrence represents a natural dynamic crystallization experiment with a "run time" that is not realistically achievable in the laboratory. SIMS analysis of mineral rim-glass pairs have permitted the determination of high-quality, equilibrium trace-element partition coefficients for all four minerals. These data augment the limited partition coefficient database for minerals in high-SiO(2) rhyolitic systems. For all minerals, the D values are consistent with those anticipated from crystal-chemical considerations. These data further support a liquid SiO(2) control on the REEs (and presumably other elements) partitioning wherein D values systematically increase with increasing liquid SiO(2) content.

    DOI: 10.2138/am.2011.3857

    Web of Science

    researchmap

  • In situ ion-microprobe determination of trace element partition coefficients for hornblende, plagioclase, orthopyroxene, and apatite in equilibrium with natural rhyolitic glass, Little Glass Mountain Rhyofite, California

    James G. Brophy, Tsutomu Ota, Tak Kunihro, Tatsuki Tsujimori, Eizo Nakamura

    AMERICAN MINERALOGIST   96 ( 11-12 )   1838 - 1850   2011年11月

     詳細を見る

    記述言語:英語   出版者・発行元:MINERALOGICAL SOC AMER  

    Partially crystalline hornblende gabbro inclusions from the Little Glass Mountain Rhyolite contain euhedral plagioclase, orthopyroxene, hornblende, and apatite crystals in contact with interstitial rhyolitic (71-76% SiO(2)) glass. Textural and mineral compositional data indicate that the gabbros crystallized sufficiently slowly that surface equilibrium was closely approached at the interface between crystals and the liquid. This rare occurrence represents a natural dynamic crystallization experiment with a "run time" that is not realistically achievable in the laboratory. SIMS analysis of mineral rim-glass pairs have permitted the determination of high-quality, equilibrium trace-element partition coefficients for all four minerals. These data augment the limited partition coefficient database for minerals in high-SiO(2) rhyolitic systems. For all minerals, the D values are consistent with those anticipated from crystal-chemical considerations. These data further support a liquid SiO(2) control on the REEs (and presumably other elements) partitioning wherein D values systematically increase with increasing liquid SiO(2) content.

    DOI: 10.2138/am.2011.3857

    Web of Science

    researchmap

  • Blueschists, eclogites, and subduction zone tectonics: Insights from a review of Late Miocene blueschists and eclogites, and related young high-pressure metamorphic rocks

    Tsutomu Ota, Yoshiyuki Kaneko

    GONDWANA RESEARCH   18 ( 1 )   167 - 188   2010年7月

     詳細を見る

    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    In this paper, Late Miocene blueschist and eclogite belts, including the world's youngest blueschist belt in Timor-Tanimbar Island chain, eastern Indonesia, and the world's youngest coesite-bearing eclogite, Papua New Guinea, together with selected Cenozoic high-pressure and ultrahigh-pressure metamorphic rocks are reviewed. From a synthesis of the geology, metamorphism and chronology of these rocks, the formation and exhumation process are evaluated and the significance on tectonics at convergent plate boundaries is discussed. (c) 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.gr.2010.02.013

    Web of Science

    researchmap

  • Blueschists, eclogites, and subduction zone tectonics: Insights from a review of Late Miocene blueschists and eclogites, and related young high-pressure metamorphic rocks

    Tsutomu Ota, Yoshiyuki Kaneko

    GONDWANA RESEARCH   18 ( 1 )   167 - 188   2010年7月

     詳細を見る

    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    In this paper, Late Miocene blueschist and eclogite belts, including the world's youngest blueschist belt in Timor-Tanimbar Island chain, eastern Indonesia, and the world's youngest coesite-bearing eclogite, Papua New Guinea, together with selected Cenozoic high-pressure and ultrahigh-pressure metamorphic rocks are reviewed. From a synthesis of the geology, metamorphism and chronology of these rocks, the formation and exhumation process are evaluated and the significance on tectonics at convergent plate boundaries is discussed. (c) 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.gr.2010.02.013

    Web of Science

    researchmap

  • Boron cycling by subducted lithosphere; insights from diamondiferous tourmaline from the Kokchetav ultrahigh-pressure metamorphic belt

    Tsutomu Ota, Katsura Kobayashi, Takuya Kunihiro, Eizo Nakamura

    GEOCHIMICA ET COSMOCHIMICA ACTA   72 ( 14 )   3531 - 3541   2008年7月

     詳細を見る

    記述言語:英語   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Subduction of lithosphere, involving surficial materials, into the deep mantle is fundamental to the chemical evolution of the Earth. However, the chemical evolution of the lithosphere during subduction to depth remains equivocal. In order to identify materials subjected to geological processes near the surface and at depths in subduction zones, we examined B and Li isotopes behavior in a unique diamondiferous, K-rich tourmaline (K-tourmaline) from the Kokchetav ultrahigh-pressure metamorphic belt. The K-tourmaline, which includes microdiamonds in its core, is enriched in B-11 relative to B-10 (delta B-11 = -1.2 to +7.7) and Li-7 relative to Li-6 (delta Li-7 = -1.1 to +3.1). It is suggested that the K-tourmaline crystallized at high-pressure in the diamond stability field from a silicate melt generated at high-pressure and temperature conditions of the Kokchetav peak metamorphism. The heavy isotope signature of this K-tourmaline differs from that of ordinary Na-tourmalines in crustal rocks, enriched in the light B isotope (delta B-11 = -16.6 to -2.3), which experienced isotope fractionation through metamorphic dehydration reactions. A possible source of the heavy B-isotope signature is serpentine in the subducted lithospheric mantle. Serpentinization of the lithospheric mantle, with enrichment of heavy B-isotope, can be produced by normal faulting at trench-outer rise or trench slope regions, followed by penetration of seawater into the lithospheric mantle. Serpentine breakdown in the lithospheric mantle subducted in subarc regions likely provided fluids with the heavy B-isotope signature, which was acquired during the serpentinization prior to subduction. The fluids could ascend and cause partial melting of the overlying crustal layer, and the resultant silicate melt could inherit the heavy B-isotope signature. The subducting lithospheric mantle is a key repository for modeling the flux of fluids and associated elements acquired at a near the surface into the deep mantle. (c) 2008 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.gca.2008.05.002

    Web of Science

    researchmap

  • Boron cycling by subducted lithosphere; insights from diamondiferous tourmaline from the Kokchetav ultrahigh-pressure metamorphic belt

    Tsutomu Ota, Katsura Kobayashi, Takuya Kunihiro, Eizo Nakamura

    GEOCHIMICA ET COSMOCHIMICA ACTA   72 ( 14 )   3531 - 3541   2008年7月

     詳細を見る

    記述言語:英語   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Subduction of lithosphere, involving surficial materials, into the deep mantle is fundamental to the chemical evolution of the Earth. However, the chemical evolution of the lithosphere during subduction to depth remains equivocal. In order to identify materials subjected to geological processes near the surface and at depths in subduction zones, we examined B and Li isotopes behavior in a unique diamondiferous, K-rich tourmaline (K-tourmaline) from the Kokchetav ultrahigh-pressure metamorphic belt. The K-tourmaline, which includes microdiamonds in its core, is enriched in B-11 relative to B-10 (delta B-11 = -1.2 to +7.7) and Li-7 relative to Li-6 (delta Li-7 = -1.1 to +3.1). It is suggested that the K-tourmaline crystallized at high-pressure in the diamond stability field from a silicate melt generated at high-pressure and temperature conditions of the Kokchetav peak metamorphism. The heavy isotope signature of this K-tourmaline differs from that of ordinary Na-tourmalines in crustal rocks, enriched in the light B isotope (delta B-11 = -16.6 to -2.3), which experienced isotope fractionation through metamorphic dehydration reactions. A possible source of the heavy B-isotope signature is serpentine in the subducted lithospheric mantle. Serpentinization of the lithospheric mantle, with enrichment of heavy B-isotope, can be produced by normal faulting at trench-outer rise or trench slope regions, followed by penetration of seawater into the lithospheric mantle. Serpentine breakdown in the lithospheric mantle subducted in subarc regions likely provided fluids with the heavy B-isotope signature, which was acquired during the serpentinization prior to subduction. The fluids could ascend and cause partial melting of the overlying crustal layer, and the resultant silicate melt could inherit the heavy B-isotope signature. The subducting lithospheric mantle is a key repository for modeling the flux of fluids and associated elements acquired at a near the surface into the deep mantle. (c) 2008 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.gca.2008.05.002

    Web of Science

    researchmap

  • Tourmaline breakdown in a pelitic system: implications for boron cycling through subduction zones

    Tsutomu Ota, Katsura Kobayashi, Tomoo Katsura, Eizo Nakamura

    CONTRIBUTIONS TO MINERALOGY AND PETROLOGY   155 ( 1 )   19 - 32   2008年1月

     詳細を見る

    記述言語:英語   出版者・発行元:SPRINGER  

    Pressure-temperature conditions of tourmaline breakdown in a metapelite were determined by high-pressure experiments at 700-900 degrees C and 4-6 GPa. These experiments produced an eclogite-facies assemblage of garnet, clinopyroxene, phengite, coesite, kyanite and rare rutile. The modal proportions of tourmaline clearly decreased between 4.5 and 5 GPa at 700 degrees C, between 4 and 4.5 GPa at 800 degrees C, and between 800 and 850 degrees C at 4 GPa, with tourmaline that survived the higher temperature conditions appearing corroded and thus metastable. Decreases in the modal abundance of tourmaline are accompanied by decreasing modal abundance of coesite, and increasing that of clinopyroxene, garnet and kyanite; the boron content of phengite increases significantly. These changes suggest that, with increasing pressure and temperature, tourmaline reacts with coesite to produce clinopyroxene, garnet, kyanite, and boron-bearing phengite and fluid. Our results suggest that: (1) tourmaline breakdown occurs at lower pressures and temperatures in SiO(2)-saturated systems than in SiO(2)-undersaturated systems. (2) In even cold subduction zones, subducting sediments should release boron-rich fluids by tourmaline breakdown before reaching depths of 150 km, and (3) even after tourmaline breakdown, a significant amount of boron partitioned into phengite could be stored in deeply subducted sediments.

    DOI: 10.1007/s00410-007-0228-2

    Web of Science

    researchmap

  • Tourmaline breakdown in a pelitic system: implications for boron cycling through subduction zones

    Tsutomu Ota, Katsura Kobayashi, Tomoo Katsura, Eizo Nakamura

    CONTRIBUTIONS TO MINERALOGY AND PETROLOGY   155 ( 1 )   19 - 32   2008年1月

     詳細を見る

    記述言語:英語   出版者・発行元:SPRINGER  

    Pressure-temperature conditions of tourmaline breakdown in a metapelite were determined by high-pressure experiments at 700-900 degrees C and 4-6 GPa. These experiments produced an eclogite-facies assemblage of garnet, clinopyroxene, phengite, coesite, kyanite and rare rutile. The modal proportions of tourmaline clearly decreased between 4.5 and 5 GPa at 700 degrees C, between 4 and 4.5 GPa at 800 degrees C, and between 800 and 850 degrees C at 4 GPa, with tourmaline that survived the higher temperature conditions appearing corroded and thus metastable. Decreases in the modal abundance of tourmaline are accompanied by decreasing modal abundance of coesite, and increasing that of clinopyroxene, garnet and kyanite; the boron content of phengite increases significantly. These changes suggest that, with increasing pressure and temperature, tourmaline reacts with coesite to produce clinopyroxene, garnet, kyanite, and boron-bearing phengite and fluid. Our results suggest that: (1) tourmaline breakdown occurs at lower pressures and temperatures in SiO(2)-saturated systems than in SiO(2)-undersaturated systems. (2) In even cold subduction zones, subducting sediments should release boron-rich fluids by tourmaline breakdown before reaching depths of 150 km, and (3) even after tourmaline breakdown, a significant amount of boron partitioned into phengite could be stored in deeply subducted sediments.

    DOI: 10.1007/s00410-007-0228-2

    Web of Science

    researchmap

▼全件表示

共同研究・競争的資金等の研究

  • Chemical evolution of Earth through material differentiation at subduction zone

    2004年

    Cooperative Research 

      詳細を見る

    資金種別:競争的資金

    With approaches from experimental petrology and petrography on natural samples, we attempt to quantify a series of parameters on chemical interactions between fluid and crustal and mantle materials at depths of subduction zone, and to decode chemical evolution of Earth

    researchmap

  • 沈み込み帯における物質分化と地球の化学進化

    2004年

    共同研究 

      詳細を見る

    資金種別:競争的資金

    実験岩石学的手法,および天然試料の記載岩石学を通じて,プレート沈み込み帯深部で進行する流体ー岩石間の化学的相互作用を定量化し,地球の大部分を占めるマントルの化学進化過程を明らかにする.

    researchmap

  • 広域変成帯の形成・上昇と太平洋型造山運動

    1996年 - 2003年

    共同研究 

      詳細を見る

    資金種別:競争的資金

    researchmap

  • Regional metamorphism and Pacific-type orogeny

    1996年 - 2003年

    Cooperative Research 

      詳細を見る

    資金種別:競争的資金

    researchmap