Correlation of 26Al ages with bulk compositions of Type I chondrules in CO condrite

Abstract

We obtained ²⁶Al ages of Type I chondrules in a least equilibrated carbonaceous chondrite (CC) Y-81020 (CO3.0). Bulk chemical compositions of Type I chondrules in the MgO-(CaO+Al₂O₃)-SiO₂ ternary diagram vary from near CI compositions to relatively Ca-Al-Si-rich compositions toward Al-rich chondrules. The chondrules with near CI composition tend to be older (1-2Myr after CAIs) than more Ca-Al-Si-rich ones (2-3Myr after CAIs). Considering the texture and chemical zoning profiles of individual chondrules, Type I chondrules in CC initially had near solar compositions and added Ca-Al-rich component with time, and Si evaporated and recondensed during heating, which resulted in compositional zoning in individual chondrules.