重元素安定同位体の高精度分析による原始太陽系星雲の物質不均質分布の解明

2013 Fiscal Year Annual Research Report

• Project/Area Number: 23340171
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: 横山 哲也 東京工業大学, 理工学研究科, 准教授 (00467028)
• Co-Investigator(Kenkyū-buntansha): 平田 岳史 京都大学, 理学(系)研究科(研究院), 教授 (10251612) ; 中本 泰史 東京工業大学, 理工学研究科, 准教授 (60261757)
• Project Period (FY): 2011-04-01 – 2014-03-31
• Keywords: 高精度同位体分析 / 原始太陽系星雲 / 隕石 / 安定同位体 / TIMS

Research Abstract

これまでに開発された技術を用いて、隕石の全岩および構成要素（酸リーチング液など）の超高精度重元素安定同位体測定を行った。太陽系における重元素同位体異常について、我々のグループで測定した元素（Sr・Nd・Te・Mo・Os）に加え、これまで報告された隕石の同位体異常データをコンパイルすることにより、同位体異常が生じるメカニズムについて考察を行った。まず、各元素は①隕石全岩および隕石構成要素ともに同位体異常を持つ（Sr・Mo・Ru・Crなど）、②隕石全岩に同位体異常はなく、隕石構成要素に同位体異常を持つ（Os・Hfなど）、および③隕石全岩および構成要素ともに同位体異常を持たない（Teなど）という3つのグループに大別されることが明らかとなった。それぞれのグループは元素の揮発性と強い相関があり、②は50%凝縮温度が1600K以上の難揮発性元素、③は50%凝縮温度が1300K以下のやや揮発性元素、①はその中間の凝縮温度を持つ。従って、隕石母天体スケールの同位体異常を引き起こすのは50%凝縮温度が1300-1600K程度の元素に限られることが分かった。このことは初期太陽系に存在したダストの温度安定性と各元素の揮発性により同位体異常が引き起こされたことを意味しており、これまで考えられてきた超新星粒子のインプットやダストのサイズによる分別よりも、太陽系の温度構造とその進化が同位体異常の原因に強く寄与していることを示唆する。
理論面では原始惑星系円盤中のダストの移動を調べるためのコード開発を行ってきたが、新たに円盤の温度構造や、ダストの化学種と温度安定性に関する情報を付加する必要があることが分かった。これは本研究の期間を超えて取り組むべき新たな課題であり、今後の太陽系研究における重要な転換点となる可能性がある。

Current Status of Research Progress

Reason

25年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

25年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] Precise tellurium isotope analysis by negative thermal ionization mass spectrometry (N-TIMS) (2014)
  • Author(s): Fukami, Y. and Yokoyama, T
  • Journal Title: J. Anal. St. Spectrom Volume: 29 Pages: 520-528
  • DOI: 10.1039/c3ja50317h
  • Peer Reviewed
• [Journal Article] Chemical separation of Mo and W from Terrestrial and Extraterrestrial samples via Anion Exchange Chromatography (2014)
  • Author(s): Nagai, Y., Yokoyama, T.
  • Journal Title: Analytical Chemistry Volume: in press Pages: in press
  • DOI: 10.1021/ac404223t
  • Peer Reviewed
• [Journal Article] A comparative review of petrogenetic processes beneath the Cameroon Volcanic Line: Geochemical constraints (2014)
  • Author(s): Asaah, A.N.E, Yokoyama, T., Aka, F.T., Usui, T., Wirmvem, M.J., Tchambe, C.B., Ohba, T., Tanyileke, G., Hell, J.V.
  • Journal Title: Geoscience Frontiers Volume: in press Pages: in press
  • DOI: in press
  • Peer Reviewed
• [Journal Article] Elemental transport upon hydration of basic schists during regional metamorphism: Geochemical evidence from the Sanbagawa metamorphic belt, Japan (2014)
  • Author(s): Uno, M., Iwamori, H., Nakamura, H., Yokoyama, T., Ishikawa, T., Tanimizu, M.
  • Journal Title: Geochemical Journal Volume: 48 Pages: 29-49
  • DOI: 10.2343/geochemj.2.0283
  • Peer Reviewed
• [Journal Article] Sediment-enriched adakitic magmas from the Daisen volcanic field, Southwest Japan. (2013)
  • Author(s): Feineman, M., Moriguti, T., Yokoyama, T., Terui, S., Nakamura, E.
  • Journal Title: Geochem. Geophys. Geosystem. Volume: 14 Pages: 3009-3031
  • DOI: 10.1002/Ggge.20176
  • Peer Reviewed
• [Presentation] 142Nd isotope anomaly in chondrite revisited (2014)
  • Author(s): Yokoyama, T., Takahashi, H., Yamazaki, H.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Florence, Italy
  • Year and Date: 20140825-30
• [Presentation] Volatility control of isotope heterogeneity in the early solar system (2014)
  • Author(s): Yokoyama, T., Fukami., Y., Nagai, Y., Nakamoto, T
  • Organizer: Lunar and Planetary Science Conference
  • Place of Presentation: The Woodlands, TX, USA
  • Year and Date: 20140317-21
• [Presentation] Strontium isotope heterogeneity within single CAI from Allende (2014)
  • Author(s): Myojo, K., Yokoyama, T., Sano, Y., Takahata, N., Sugiura, N., Wakaki, S
  • Organizer: Lunar and Planetary Science Conference
  • Place of Presentation: The Woodlands, TX, USA
  • Year and Date: 20140317-21
• [Presentation] Strontium stable isotope anomalies in Allende chondrules (2014)
  • Author(s): Okui, W., Yokoyama, T., Usui, T., Iwamori, H., Uno, M
  • Organizer: Lunar and Planetary Science Conference
  • Place of Presentation: The Woodlands, TX, USA
  • Year and Date: 20140317-21
• [Presentation] Tellurium isotope anomaly in acid resistant fraction of Allende meteorite (2014)
  • Author(s): Fukami, Y., Yokoyama, T., Okui, W. okoyama, T., Usui, T., Iwamori, H., Uno, M
  • Organizer: Lunar and Planetary Science Conference
  • Place of Presentation: The Woodlands, TX, USA
  • Year and Date: 20140317-21
• [Presentation] Preliminary report on U-Th-Pb isotope systematics of olivine-phyric Shergottite Tissint (2014)
  • Author(s): Moriwaki, R., Usui, T., Yokoyama, T., Simon, J.I., Jones, J.H.
  • Organizer: Lunar and Planetary Science Conference
  • Place of Presentation: The Woodlands, TX, USA
  • Year and Date: 20140317-20140321
• [Presentation] Origin of U-Th Disequilibrium in Subduction Zone Volcanic Rocks (2014)
  • Author(s): Yokoyama, T., Ikemoto, A., Iwamori, H. and Ueki, K.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
  • Invited
• [Presentation] Chemical Separation of Mo and W from Extraterrestrial Samples by Anion Exchange Chromatography (2014)
  • Author(s): Nagai, Y., Yokoyama, T.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
• [Presentation] Os isotope anomalies in early acid leachates from chondrites (2014)
  • Author(s): Fukai, R., Yokoyama, T.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
• [Presentation] Tellurium isotope anomaly in acid residue of Allende meteorite (2014)
  • Author(s): Fukami, Y., Yokoyama, T., Okui, W.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
• [Presentation] 147Sm-143Nd and 146Sm-142Nd chronology of a basaltic Eucrite, Juvinas (2014)
  • Author(s): Kagami, S., Yokoyama, T.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
• [Presentation] Preliminary report on U-Th-Pb isotope systematics of the olivine-phyric Shergottite Tissint (2014)
  • Author(s): Moriwaki, R., Usui, T., Yokoyama, T.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
• [Presentation] Strontium isotope anomalies in chondrules from carbonaceous chondrite (2014)
  • Author(s): Okui, W., Yokoyama, T., Usui, T., Iwamori, H., Uno, M.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
• [Presentation] Strontium Isotope Anomalies and 26Al-26Mg Chronology in CAIs from CV Chondrites (2014)
  • Author(s): Myojo, K., Yokoyama, T., Sano, Y., Takahata, N., Sugiura, N., Iwamori, H., Uno, M.
  • Organizer: Geofluid 3
  • Place of Presentation: Tokyo
  • Year and Date: 20140228-20140303
• [Presentation] コンドライト隕石の超高精度Sr同位体測定に向けた新しい試料分解法の開発 (2013)
  • Author(s): 横山哲也、山崎洋
  • Organizer: 地球化学会
  • Place of Presentation: つくば
  • Year and Date: 20130913-20130913
• [Presentation] 表面電離型質量分析計（TIMS）を用いた微小地球外試料の重元素精密同位体分析 (2013)
  • Author(s): 横山哲也
  • Organizer: 第61回質量分析学会討論会
  • Place of Presentation: つくば
  • Year and Date: 20130910-20130910
  • Invited
• [Presentation] Molybdenum Isotopic Compositions in Allende Chondrules (2013)
  • Author(s): Nagai, Y., Yokoyama, T., Okui, W.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Florence, Italy
  • Year and Date: 20130825-20130830
• [Presentation] Sr stable isotopic anomalies in primitive meteorites and chondrules (2013)
  • Author(s): Okui, W., Yokoyama, T., Uno, M., Iwamori, H., Takahashi, E., Sasaki, O., Nakamura, M., Okumura, S.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Florence, Italy
  • Year and Date: 20130825-20130830
• [Presentation] Strontium Isotope Anomalies and 26Al-26Mg Chronology in CAIs from CV Chondrites (2013)
  • Author(s): Myojo, K., Yokoyama, T., Sano, Y., Takahata, N., Sugiura, N., Iwamori, H., Uno, M.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Florence, Italy
  • Year and Date: 20130825-20130830
• [Presentation] U-series isotope disequilibrium in subduction zone volcanic rocks. (2013)
  • Author(s): Yokoyama, T.
  • Organizer: MNR 2013
  • Place of Presentation: Tokyo
  • Year and Date: 20130613-20130613
  • Invited
• [Presentation] 142Nd isotope anomalies in chondrites revisited (2013)
  • Author(s): Yokoyama, T., Takahashi, H., Yamazaki, H.
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 幕張メッセ
  • Year and Date: 20130519-20130524
• [Presentation] Determination of extremely small amount of U and Th by ID-TIMS for the study of U-Th cosmochronology (2013)
  • Author(s): Watanabe, T., Yokoyama, T.
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 幕張メッセ
  • Year and Date: 20130519-20130524
• [Presentation] Development of highly precise and accurate molybdenum isotope analysis using N-TIMS for the study of nucleosynthetic isotope anomalies in meteorites (2013)
  • Author(s): Nagai, Y., Yokoyama, T.
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 幕張メッセ
  • Year and Date: 20130519-20130524
• [Presentation] Determination of in-situ Os isotope compositions in metal phases from CB chondrites using a micro sampling technique (2013)
  • Author(s): Nakanishi, N., Yokoyama, T., Usui, T., Uno, M., Iwamori, H.
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 幕張メッセ
  • Year and Date: 20130519-20130524
• [Presentation] Geochemical characterization of lavas from the Oku Volcanic Group, Cameroon Volcanic line, West Africa (2013)
  • Author(s): Asaah, A.N.E, Yokoyama, T., Aka, F.T., Usui, T., Wirmvem, M.J., Tchambe, C.B., Ohba, T., Tanyileke, G., Hell, J.V.
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 幕張メッセ
  • Year and Date: 20130519-20130524
• [Remarks] 横山研究室
  • URL: http://www.geo.titech.ac.jp/lab/yokoyama/