22-EPN3-064: Investigating Oxygen Isotopes within Ca-Al-rich inclusions (CAIs) and Compound-Chondrule-CAI (CCCAIs) Populations within CM chondrites
Visit by Pierre-Etienne Martin and Luke Daly of the University of Glasgow (UK) to TA2.9 Ion Probe Facility (IPF), CRPG (France)
Dates of visit: 24-28 April 2023
Report Summary: Compound-chondrule-Calcium-Aluminium-rich Inclusions (CCCAIs) are rare occurrences within carbonaceous chondrites. They have been reported sporadically within most major groups (CO, CV, and CH) and only described four times within CM (Mighei-like) carbonaceous chondrites of various degrees of aqueous alteration, such as Aguas Zarcas (CM2; Martin & Lee, 2021) and Paris (CM2.7; Rubin, 2015). These objects have been described as CAIs enclosing chondrules or as chondrules enclosing CAIs. The existence of CCCAIs suggests that chondrules and CAIs interacted within high particle density environments in the protoplanetary disk prior to their incorporation into their mutual parent bodies.
In this study, we investigated two such objects within the Aguas Zarcas meteorite using oxygen isotope
analysis in order to characterize the CAI and chondrule components of the CCCAIs in comparison with CAIs and chondrules within the rest of the two Aguas Zarcas samples. Results show that the CAI and chondrule components of CCCAIs originate from the same O isotope reservoirs as their regular counterparts, suggesting that no isotopic exchange occurred between the two types of components, and that the components originate from the same O isotope reservoirs as the CAIs and chondrules of the meteorite breccia. An exception is the ‘Cicero’s’ chondrule part, which has a very primitive O isotope composition similar Amoeboid Olivine Aggregate (AOA). Due to the very primitive O isotope composition of AOAs, their formation is thought to have occurred in a near-solar environment. Further evidence is needed, but the existence of these objects can better our understanding of the evolution of the protoplanetary disk and provide a new way to study the chondrule forming environment(s).
