Petrographic constraints on the diversity of chondrule reservoirs in the protoplanetary disk

– Chondrules from different chondrite groups show characteristic properties, including abundances of different chondrule textural types, chondrule sizes, oxygen isotope compositions, chondrule bulk compositions, and petrographic properties of type I and type II chondrules, including abundances of relict grains. Overall, it can be argued that each chondrite group sampled a unique chondrule reservoir, and that chondrite groups may represent fractions of larger reservoirs that are represented by chondrite classes. These observations provide constraints for models of the early solar system, in which it is necessary to establish multiple separate chondrule reservoirs and maintain them over extended time periods. Models for accretion of chondrite parent bodies must be able to account for localized accretion of chondrules that were formed in spatially or temporally separated reservoirs.