Open-system behavior during chondrule formation

The question of whether chondrules behaved as open systems during formation is crucial to our understanding of both chondrule and chondrite formation. The very large range of chondrule types is best summarized by the compositional classification scheme, wherein the primitive chondrule groups (i.e., those not produced by metamorphic processes) are A1, A2, A5, and B1. In the Semarkona (LL3.0) chondrite, 10.5%, 25.0%, 5.0%, and 56.9% (by number) of the chondrules are groups A1, A2, A5, and B1, respectively. We argue that groups A1 and A2 were produced by reduction and evaporation during chondrule formation of material originally resembling group B1 chondrules.