Diversity of nucleosynthetic Sr anomaly in fine-grained inclusions from Allende meteorite

Abstract

Calcium and Aluminum rich Inclusion (CAI) from carbonaceous chondrites is the oldest substance that condensed from a gaseous reservoir in the early solar system. The nucleosynthetic isotope anomalies for heavy elements found in CAIs reflect isotopic heterogeneity in the early solar system. Unlike the igneous CAIs (coarse-grained, e.g. Type Bs), the fine-grained CAIs (FG) are considered to have escaped remelting and homogenization by shock heating. As such, FG is expected to preserve primitive isotope features in the solar system. In this study, we measured elemental compositions and Sr isotope ratios in FGs from the Allende meteorite. A variety of Sr isotope anomalies and elemental compositions were found in FGs, which is consistent with previous studies. We consider that the observed elemental and isotopic variabilities in FGs are not due to parent body processes including aqueous alteration. Rather, the variations would be intrinsic properties of FGs, reflecting the diversity in physical and chemical conditions under which they were formed.