Heterogeneity of Mg Isotopes and Variable ^(26)Al/^(27)Al Ratio in FUN CAIs

Abstract

CAIs with fractionation and unidentified nuclear effects (FUN CAIs) are characterized by low initial ^(26)Al/^(27)Al ratios, large mass-dependent fractionation in Mg (F_(Mg)), Si, and O isotopes, and nucleosynthetic anomalies in several elements (e.g., Ca, Ti). Most Mg-isotope studies of FUN CAIs were performed more than 30 years ago with TIMS. Here we report high-precision Mg-isotope data of individual minerals from the Axtell 2271, BG82DH8, EK1-4-1, C1, TE, and CG14 FUN CAIs measured with the UH Cameca ims-1280. We followed the procedure described in [2]. Measured Mg-isotope data were correct-ed for fractionation using terrestrial standards assuming that their isotopic compositions are the same as values of [3], and an exponential law with a coefficient β = 0.514. The overall conclusions of this study do not change with the choice of β.

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