TERRAPUB Geochemical Journal

Geochemical Journal, Vol. 52, 2018

Beryllium-boron relative sensitivity factors for melilitic glasses measured with a NanoSIMS ion microprobe

Kohei FUKUDA1*, Wataru FUJIYA2, Hajime HIYAGON1, Yoshiki MAKINO4, Naoji SUGIURA1, Naoto TAKAHATA3, Takafumi HIRATA4, and Yuji SANO3

1Department of Earth and Planetary Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
2College of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan
3Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba 277-8564, Japan
4Geochemical Research Center, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

(Received June 25, 2017; Accepted November 26, 2017)

Abstract: The short-lived radionuclide 10Be (t1/2 = 1.4 Myr) present in the Early Solar System (ESS) provides important information about the astrophysical environment in which the solar system formed. However, the origin of 10Be in the ESS remains controversial. To reveal its origin, it is important to determine precise and accurate 10Be abundances in meteoritic components. The initial 10Be/9Be ratio can be estimated using ion microprobe analysis and a 10B/11B-9Be/11B correlation. The relative sensitivities for Be and B must be determined to obtain 9Be/11B ratios of unknowns. Here, we report Be/B relative sensitivities for synthetic melilitic glasses and silica-rich NIST SRM 610 glass measured with a NanoSIMS ion microprobe. The Be/B relative sensitivities for melilitic glasses are identical to that of the NIST 610 glass within uncertainties, which suggests that the matrix effects, at least between the NIST 610 glass and melilite, are not significant with respect to Be-B measurements. The present results confirm that the observed variations in the 10Be/9Be ratios for CV calcium-aluminum-rich inclusions (CAIs) are real and the origin of 10Be must be attributed to irradiation by the active early sun. It is also inferred that the 10Be/9Be ratios of fractionation and unidentified nuclear effect (FUN) CV CAIs are not significantly lower than those for normal (non-FUN) CV CAIs, suggesting similar formation conditions.
Key words: secondary ion mass spectrometry, Berrylium-10, relative sensitivity, melilite, early solar system

*Corresponding author E-mail: k.fukuda@eps.s.u-tokyo.ac.jp

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