Department of Earth and Planetary Sciences, Faculty of Science, Kyusyu University/Institute for Study of the Earth's Interior, Okayama University/Institute for Study of the Earth's Interior, Okayama University
抄録(英)
Yamato-74063 : The correlation in a three-isotope plot of Ne indicates Ne-A as the trapped component and a cosmogenic ^<22>Ne/^<21>Ne ratio as high as 1.31±0.10. Considerable amounts of trapped gases are present in both metal and silicate separates. Trapped ^<36>Ar/^<132>Xe is different for metal and silicate, 72 and 17,respectively. The isotopic compositions of Kr and Xe are homogeneous and identical within errors for almost all temperature fractions of both separates. This observation includes even ^<129>Xe/^<132>Xe. It is likely that the gases were acquired from a single gas-reservoir after most of radioactive ^<129>I had decayed to ^<129>Xe. There is a correlation between ^<36>Ar/^<132>Xe and ^<84>Kr/^<132>Xe for Y-74063,other unique meteorites and planetary Q-gas. The origin of trapped gas with low Ar/Xe is discussed. On laser ablation, most mineral grains released large amounts of trapped gases, suggesting that the trapped gases are not contained in specific carrier phases but in many major minerals. Y-74357 : The meteorite contains very little trapped gases. The cosmogenic ^<22>Ne/^<21>Ne ratio of 1.076 indicates that the stone was irradiated at an intermediate depth of a meteoroid. However, cosmogenic ^3He/^<21>Ne and ^<38>Ar/^<21>Ne are significantly lower than the ratios of production rates calculated for chondritic target chemistry, indicating that the stone is enriched in Mg and depleted in Ca. Correction for target chemistry (Mg) gives a tentative cosmic-ray exposure age of 10.1Ma.
雑誌書誌ID
AA10784627
雑誌名
Proceedings of the NIPR Symposium on Antarctic Meteorites
Noble gases in the unique meteorites Yamato-74063 and -74357
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KJ00000036411
(1.07MB)
概要
