open access

https://hdl.handle.net/2115/88186

A super-refractory inclusion containing nonstoichiometric spinel from the CO3.0 chondrite Yamato 81020

英語

2022-02

John Wiley & Sons

Meteoritics & Planetary Science

57(2)

472-483

We studied a unique super-refractory inclusion with a core-mantle structure from CO3.0 Yamato 81020 by secondary ion mass spectrometry, electron microprobe, and scanning electron microscope techniques. The core consists largely of hibonite and nonstoichiometric Al-rich spinel indicating formation as a liquid at an exceptionally high temperature (>1900 degrees C). The mantle consists almost entirely of melilite with gehlenitic compositions (ranging from angstrom k(2) to angstrom k(25)). The oxygen- and magnesium-isotopic compositions of the core and mantle are very different; typically, Delta O-17 (equivalent to delta O-17 - 0.52 delta O-18) similar to-26 parts per thousand and integral(Mg) (mass fractionation of Mg isotopes) similar to 10 parts per thousand/amu in the core and Delta O-17 similar to-7 parts per thousand and integral(Mg) similar to 1 parts per thousand/amu in most of the mantle. The chemical and O, Mg-isotopic data indicate that the core and mantle formed in separate events, and that the melilite now in the core was formed during the mantle-melting event, probably filling preexisting voids and surficial cavities. Analyses of core and mantle phases plot along a single Al-26-Mg-26 isochron with initial (Al-26/Al-27)(0) corresponding to 4.8 +/- 1.0 (+/- 2 sigma) x 10(-5), suggesting a similar formation age to normal CAIs in chondrites.

学術雑誌論文

Accepted Manuscript

This is the peer reviewed version of the following article: Yurimoto, H., Rubin, A.E., Itoh, S. and Wasson, J.T. (2022), A super-refractory inclusion containing nonstoichiometric spinel from the CO3.0 chondrite Yamato 81020. Meteorit Planet Sci, 57: 472-483., which has been published in final form at https://doi.org/10.1111/maps.13652. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

1086-9379