| Autor: |
Kita,Noriko T., Togashi,Shigeko, Morishita,Yuichi, Terashima,Shigeru, Yurimoto,Hisayoshi |
| Přispěvatelé: |
Geological Survey of Japan/Geological Survey of Japan/Geological Survey of Japan/Geological Survey of Japan/Dept. Earth and Planetary Science, Faculty of Science, Tokyo Institute of Technology |
| Jazyk: |
angličtina |
| Rok vydání: |
1998 |
| Zdroj: |
Antarctic meteorite research. 11:103-121 |
| Popis: |
We have developed a technique for in-situ Ni isotopic analysis using the ion microprobe, in order to detect ^Ni excess from the decay of the short lived nuclide ^Fe (half life=1.5Ma) in ureilite samples. The silicate minerals from MET-78008 ureilite with an old U-Pb age of 4.563±0.006 Ga were analyzed. The ^Fe/^Ni ratios of olivine and orthopyroxene are between 2700 and 5400. In spite of the high Fe/Ni ratios, we could not observe any detectable ^Ni excess. From the mean value of olivine core data, we obtain an upper limit of the ^Fe/^Fe ratio at the time of ureilite formation of 1.8×10^. The time difference between CAI formation and ureilite formation was estimated to be more than 4 million years, which is consistent with the UPb data from the same meteorite. We concluded that the impact event for the disruption of the ureilite parent body happened more than 4 million years after CAI formation. However, a large uncertainty in the initial ^Fe/^Fe ratio is introduced by the possibility that the ^Ni excess observed in CAIs is of nucleosynthetic origin. Our conclusion may change if the initial ^Fe/^Fe ratio of the solar system using CAI data is too high. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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