基盤セッション
- 第1日 5月15日（月） 10:36～10:54 B会場（会議室1202）
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1B-O-1036 PDF
SIMSを用いた高精度アルミニウム-マグネシウム同位体分析法の改良と隕石中コンドルールへの応用
Secondary Ion Mass spectrometry (SIMS) is a powerful tool for revealing the timescale of geological and cosmochemical events recorded in small (~µm to tens of µm) solids. In the earliest stage of our Solar System evolution, the presence of short-lived radionuclides such as Aluminum-26 (26Al), which decays to 26Mg with a half-life of 0.7 million years (Ma), has been inferred from SIMS analyses of the Solar System oldest solids (Ca-Al-rich inclusions: CAIs). Here we improved the precision and accuracy of SIMS Al-Mg analysis for plagioclase (Na, Ca)(Si, Al)4O8 and Al-rich glass, in order to better understand the formation timescale of asteroidal seeds, called chondrules. To improve the precision and accuracy of SIMS Al-Mg analyses, we developed analytical methods using the multi-collector SIMS CAMECA IMS 1280 equipped with the radio-frequency plasma ion source at the University of Wisconsin-Madison. The uncertainties (2σ) on the determined chondrule formation ages are typically ±0.1–0.2 Ma, which are ~2–3 times better than those in previous studies. Based on the newly determined high-precision chondrule formation ages, we will discuss the timescale of chondrule formation and the implications for the evolution of the Solar protoplanetary disk.