Nitrogen isotopes in chondrules: signatures of precursors and formation processes

Nitrogen isotope abundance of 68 individual chondrules separated from six ordinary, two carbonaceous and two enstatite chondrites has been analysed. N composition of chondrules from ordinary and carbonaceous chondrites generally shows large variation and differs from that of their host. This large range of N composition suggests the presence of different N components in their precursors. Chondrules from the enstatite chondrites on the other hand show N isotopic composition similar to that of their host, suggesting precursors with similar N components for both chondrules and their host meteorites. Nitrogen isotopic systematics therefore distinguishes chondrules in enstatite chondrites from those in ordinary and carbonaceous chondrites. Chondrules in ordinary and carbonaceous chondrites require precursors that are different from those of their parent meteorites and formation in nebular environment, whereas chondrules in enstatite chondrites are formed from the same precursors as those of their host chondrites and presumably in the same region.