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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
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An effect of variations in relative sensitivity factors on Al-Mg systematics of Ca-Al-rich inclusions in meteorites with secondary ion mass spectrometry

Noriyuki Kawasaki, Changkun Park, Shigeyuki Wakaki, Hwayoung Kim, Sunyoung Park, Toshihiro Yoshimura, Kazuya Nagaishi, Hyun Na Kim, Naoya Sakamoto, Hisayoshi Yurimoto
Geochemical Journal, Vol. 55, No. , P. 283-287, 2021

ABSTRACT

Instrumental mass fractionation of Mg-isotopes and the relative sensitivity factor (RSF) for 27Al/24Mg ratios for in situ analysis by secondary ion mass spectrometry were investigated for minerals in Ca-Al-rich inclusions (CAIs) of meteorites, to verify systematic errors in Al-Mg chronological systematics of CAIs. We synthesized seventeen glasses with different chemical compositions that imitate those for CAI minerals and measured their Al-Mg isotopic compositions. In particular, the variation range of RSFs for six melilite glasses almost covering chemical compositions of CAI melilite is 2.0 ± 0.3%, indicating that systematic error for 27Al/24Mg for melilite is less than 2.0 ± 0.3% and likely corresponds to that of an 26Al-26Mg relative age of ∼0.01 Myr for melilite-rich CAIs. Our data strongly support the robustness of variations in initial 26Al/27Al ratios among CAIs, corresponding to a formation age spread of ∼0.4 Myr at the very beginning of the Solar System formation.

KEYWORDS

Ca-Al-rich inclusions, Al-Mg systematics, secondary ion mass spectrometry, instrumental mass fractionation, relative sensitivity factor

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