| Project/Area Number |
11640487
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
地球化学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
NAGAO Keisuke University of Tokyo, Graduate School of Science, Professor, 大学院・理学系研究科, 教授 (40131619)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Yayoi University of Tokyo, Earthquake Research Institute, Research Assistant, 地震研究所, 助手 (90282730)
NAKAMURA Tomoki Kyushu University, Faculty of Science, Associate Professor, 大学院・理学研究院, 助教授 (20260721)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1999: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | noble gas isotopes / meteorites / Allende carbonaceous chondrite / secondary neutron / halogen / neutron capture / laser microprobe analysis / CAI / 希ガス / 隕石中のハロゲン元素 / レーザープローブ / コンドルール |
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| Research Abstract |
We have observed very high concentrations of Cl, Br and I in Yamato-74191 and in CAIs of Allende(CV3) chondrite. Because halogens are generally thought to have behaved as volatile elements when solid condensates were produced in solar nebula, mechanism to produce the observed high concentrations of halogens in CAIs is difficult to understand. This is due to a lack of knowledge about the cosmochemical behavior of halogens. Laser microprobe noble gas analysis was applied to Allende meteorite traversing the CAI and matrix with a space resolution of about 150μm. The high concentrations of ^<129>Xe show good correlation with the chlorine concentrations determined with EPMA analysis. ^<80>Kr/^<84>Kr and ^<128>Xe/^<132>Xe ratios are also high in the measured portions with high ^<129>Xe/^<132>Xe ratios. The ^<80>Kr and ^<128>Xe can be produced by neutron capture on ^<79>Br and ^<127>I, respectively, in space.
The present results show that halogens have penetrated into the CAIs from outside through the disordered boundary of CAI, when aqueous alteration produced sodalite inside the CAIs. Since we could not find halogen-derived noble gases in surrounding matrix materials, the halogen-rich materials in CAIs must have been produced in the solar nebular, and not in parent body after embedded in matrices. The high concentrations of ^<129>Xe in sodalite-rich materials indicate that the aqueous alteration must occur at the very early stage of solar system when abundant ^<129>I was still alive.
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