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Abstract: High precision Mg isotope measurements have been performed to determine radiogenic 26Mg of CAI minerals by secondary ion mass spectrometry using Faraday cup multi-collection system. Terrestrial samples of spinel and augite, and synthetic glasses of melilite and fassaite, were prepared to correct instrumental mass fractionation. Reproducibility of Mg isotope measurements for each standard were limited to ∼0.4‰ (2σ). On the other hand, the standard errors for one spot are ∼0.05‰ (2σ). The poor reproducibility resulted from variations of instrumental mass fractionation among individual measurement spots. We propose novel calculation method of radiogenic 26Mg considering instrumental and natural mass fractionation for each mineral. The overall measurement error of radiogenic 26Mg of the minerals can be calculated less than 0.2‰ (2σ). This provides that the time resolution of early solar system chronometer was improved up to 100K year for ∼20μm scale objects formed in the early solar system. [Copyright &y& Elsevier]

Abstract: We report a discovery of a chemically and isotopically unique material distributed ubiquitously in fine-grained matrix of a primitive carbonaceous chondrite Acfer 094. The observations were made in situ using a novel high precision imaging technique adopted direct-imaging method. The material is extremely enriched in heavy oxygen isotopes of 17O and 18O of +18% relative to the Earth''s ocean while previously reported variation of oxygen isotopes is as large as a range from −8% to 0%. Based on the unique chemical composition of the material, the abundance of the material in the meteorite matrix is calculated to be 94±20ppm (σ) by volume using elemental mapping with a 7μm2 spatial resolution by FE-SEM-EDS on the meteorite thin section. The average size of identified materials is 5μm×5μm×5μm. Therefore, isotope imaging capability over 500μm×500μm area with micron resolution and an isotopic ratio precision of 1% is required to investigate about the presence of such material. [Copyright &y& Elsevier]