| Project/Area Number |
02640622
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
鉱物学(含岩石・鉱床学)
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| Research Institution | University of Tokyo |
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Principal Investigator |
TOMEOKA Kazushige Univ. Tokyo, Fac. Sci., Res. Assoc., 理学部, 助手 (00201658)
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1991: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1990: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Meteorite / Carbonaceous chondrite / Solar nebula / Plantesimal / Chondrule / Shock metamorphism / Electron microscopy / Aqueous alteration / 惑星間塵 / 太陽星雲 / コンドライト / サ-ペンティン / 水質変成 |
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| Research Abstract |
1. We have studied three new CI carbonaceous chondrites(Yamato82162, Yamato-86720, Belgica-7904)from Antarctica by using electron microscopes. Our study reveals that they have many mineralogical features different from non-Antarctic CI chondrites. Two of them are mineralogically more similar to CM chondrites. All of the three chondrites apparently have undergone thermal metamorphism at temperatures 500-600'C Such significant thermal effects have not been known from other CI and CM chiondrites. These results indicate that the new CI chondrites have experienced considerably different formation histories from those for ordinary CI and CM chondrites, and suggest that there was an event in which some CI and CM parent bodies have been heated to significantly high temperatures.
2. We have found fracture-filling veins of phyllosilicates in one of the new CI chondrites(Y82162). The finding provides new evidence that the phyllosilicates in CI chondrites were formed by the activity of aqueous solutions on the meteorite parent body, and that phyllosilicate formation overlapped the period of impact brecciation.
3. CV type chondrites have been generally considered to have not been affected by aqueous alteration after accretion. However, we have found considerable amounts of phyllosilicates in the Mokoia CV chondrite. Evidence was found that the phyllosilicates in Mokoia were formed by aqueous alteration of olivine and pyroxene. The mechanism to form saponite from olivine is not found from terrestrial. analogues and suggests that the alteration occurred by reaction with the solar nebula in an oxidizing condition.
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