Nucleosynthetic titanium isotope anomalies in fine-grained CAIs from Allende meteorite

Abstract

Calcium-Aluminum-rich inclusions (CAIs), condensed from nebular gas in the earliest solar system, are the oldest materials in the solar system. Nucleosynthetic isotope anomalies for heavy elements observed in CAIs are important information for elucidating the isotopic heterogeneity and the influx, transport, and mixing of materials in the protoplanetary disk. It has recently been found that the degree of Ti isotope anomalies in coarse-grained CAIs that have experienced remelting were different from those in fine-grained CAIs that have not melted. In this study, we measured the Ti isotope ratios of ten fine-grained CAIs extracted from Allende meteorite. The obtained Ti isotope ratios were consistent with the values of previous studies. On the other hand, when compared to our previously measured Sr isotopic composition of the Ti isotope values of each fine-grained CAI, there was no clear correlation between the Ti and Sr isotopic compositions. This observation implies that the carriers of Ti isotope anomalies were different from those of Sr isotope anomalies in fine-grained CAIs, suggesting that the fine-grained CAIs randomly acquired isotopically anomalous carriers of each element that were heterogeneously distributed in the nebular gas.