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Oxygen isotopic variations in a type A Ca–Al‐rich inclusion revealed by high‐precision secondary ion mass spectrometry analysis with micrometer resolution
Author(s) -
Park C.,
Wakaki S.,
Yurimoto H.
Publication year - 2012
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.3871
Subject(s) - melilite , isotopes of oxygen , analytical chemistry (journal) , chondrite , mass spectrometry , chemistry , oxygen , secondary ion mass spectrometry , allende meteorite , pyroxene , mantle (geology) , meteorite , mineralogy , geology , astrobiology , olivine , geochemistry , spinel , environmental chemistry , nuclear chemistry , paleontology , physics , organic chemistry , chromatography
Ca–Al‐rich inclusions (CAIs) are thought to be the oldest rocks in the solar system. CAIs have oxygen isotope heterogeneities on inter‐mineral and intra‐mineral scales that provide information about environments of the early solar system. We studied a type A CAI from the Allende meteorite, showing a core–mantle structure. Reversely zoned melilite found in the mantle was identified by a combination of energy dispersive X‐ray spectrometer and electron back‐scattered diffraction techniques. For investigation of oxygen isotopic variations of reversely zoned melilite, we developed a high‐precision secondary ion mass spectrometry method that achieves to ~1‰ (1 σ ) under the spatial resolution of ~3 µm in diameter. Oxygen isotopic composition of core melilite is uniformly 16 O‐poor (δ 17, 18 O ≈ −5 to 0‰), whereas mantle melilite varies widely from 16 O‐poor (δ 17, 18 O ≈ −5‰) to rich (δ 17, 18 O ≈ −45‰) at the micrometer scale. The variation possibly suggests that the oxygen isotopic composition of solar nebular gas was changed from 16 O‐poor to 16 O‐rich at the last stage of the CAI formation. Copyright © 2011 John Wiley & Sons, Ltd.