| Project/Area Number |
13440168
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | National Institute of Polar Research |
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Principal Investigator |
MISAWA Keiji National Institute of Polar Research, Antarctic Meteorite Research Center, Associate Professor, 南極隕石研究センター, 助教授 (70212230)
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| Co-Investigator(Kenkyū-buntansha) |
KAIDEN Hiroshi National Institute of Polar Research, Antarctic Meteorite Research Center, Research Associate, 南極隕石研究センター, 助手 (10302811)
YAMAGUCHI Akira National Institute of Polar Research, Antarctic Meteorite Research Center, Research Associate, 南極隕石研究センター, 助手 (70321560)
IMAE Naoya National Institute of Polar Research, Antarctic Meteorite Research Center, Research Associate, 南極隕石研究センター, 助手 (60271037)
小島 秀康 国立極地研究所, 南極隕石研究センター, 教授 (10113896)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2002: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2001: ¥4,500,000 (Direct Cost: ¥4,500,000)
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| Keywords | eucrite / secondary ion mass spectrometry / zircon / U-Pb age / thermal metamorphism / Mn-Cr age / shock metamorphism |
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| Research Abstract |
We have undertaken petrologic and U-Th-Pb isotopic studies on zircons from basaltic eucrites with different thermal and shock histories. Zircon occurs are associated with ilmenite in most cases. Eucritic zircon is in many cases subeuhedral shape composed of several domains in the cathodeluminessence images probably due to metamorphic effects after initial crystallization. Concentrations of uranium and thorium in zircons from unmetamorphosed eucrite are higher than those from metamorphosed eucrites, suggesting bulk unmetamorphosed eucrites may be enriched in incompatible elements representing more evolved material. The U-Pb ages of eucritic zircons are almost concordant. However, small zircon grains show reverse discordance, suggesting excess radiogenic lead components. The ^<207>Pb-^<206>Pb age of zircons from most eucrites analyzed in this study are 4551 ± 8 Ma (n = 24, error is 95% confidence limit), which strongly suggest early and short volcanic activities occurred on the eucrite parent body. The obtained zircon U-Pb ages are older than the U-Pb, Sm-Nd and Rb-Sr ages of silicates, suggesting the difference of closure temperatures of each isotopic systems or silicates are more susceptible shock metamorphism/terrestrial weathering.
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