オーラルセッション
- 第2日 6月23日（木） 9:40～10:00 C会場（411，412）
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2C-O1-0940 PDF
SIMSを用いた局所高精度マグネシウム同位体比分析法の開発と地球外物質への応用
Magnesium has three naturally occurring stable isotopes, which allow us to investigate mass-dependent and mass-independent isotope fractionation induced by the thermal processes occurred in the Solar protoplanetary disk. Here we developed high precision Mg isotope analysis by Secondary Ion Mass Spectrometry (SIMS) and applied it for cometary olivine particles that have been recovered from comet 81P/Wild 2 by NASA Stardust mission, in order to understand the origin and evolution of solid materials in the outer Solar System.
The magnitude of instrumental mass fractionation (IMF) are a complex function of olivine Fo content between 60 and 100. We also found the similar complex relationship between the Mg+/Si+ relative sensitivities and olivine Fo contents. On the basis of these observations, we propose IMF correction procedures for SIMS Mg isotope analyses of olivine using the combination of the Mg+/Si+ relative sensitivities and Fo contents of olivine.
One of the five cometary olivine particles we analyzed shows negative Mg isotope fractionation relative to the chondritic Mg isotopic composition, suggesting that the olivine particle formed by condensation from the hot solar nebula. This olivine particle might have formed probably near the proto-Sun, and then was transported to Kuiper belt, where comet 81P/Wild 2 likely accreted.