The Spatial Origin of Chondrules in Individual Chondrites: Constraints from Modeling Chondrule Mixing

Abstract

Abstract Chondrules are a major component of chondritic meteorites and potentially populated the entire protoplanetary disk before planet formation. Chondrules provide insights into the physical and chemical evolution of the protoplanetary disk. An important constraint for the protoplanetary disk is whether chondrules in individual chondrite groups formed in spatially separate reservoirs and were then transported and mixed throughout the disk, finally accreting in chondrites, or did chondrules in individual chondrite groups form and then accrete in the same reservoir and locality, without large-scale transport and mixing involved. Both scenarios have been proposed. Here we use bulk chondrule compositional data from the recently published ChondriteDB database in combination with a mixing model we developed to test whether the compositional distributions of chondrule populations in individual chondrites (1) are the result of mixing chondrules from multiple parental reservoirs or (2) originated from single parental reservoirs. We thereby provide a fundamental framework that each mixing model needs to obey. Although one mixing model is principally possible, this particular model is unlikely, and it therefore appears more reasonable that chondrules in individual chondrites originated from single, although different, parental reservoirs. Significant disk-wide transport or mixing of chondrules seems unlikely, while chondrule-forming models that produce chondrules from single reservoirs seem more likely. Anomalous minor element and nucleosynthetic isotope chondrule compositions are possibly best explained by admixing tiny nuggets such as refractory or presolar grains with distinct elemental or isotopic compositions into chondrules.