Calcium-aluminum-rich inclusions (CAIs) have radiometric age dates of 4.673 Ga and are believed to be among the first-formed solids in the solar system. Some of the refractory materials that they contain match those predicted by equilibrium thermodynamic calculations and so CAIs are also believed to have directly condensed from the solar nebula, the cloud of dust and gas that gave rise to our Sun and planetary system. The microstructure of CAIs can therefore provide a unique window into the chemistry of the early solar system. A special feature of many CAIs are multi-layered mineral rim sequences that surround them, called Wark-Lovering rims (WLRs). The origins of these WLRs have been ascribed to several processes including condensation, metasomatic exchange, and flash heating but are still under debate.<br/>Electron- and ion-beam analysis has been used extensively to study the two-dimensional composition and microstructure of WLRs. However, focused-ion-beam (FIB) tomography can provide 3D chemical and microstructural information on CAIs and WLRs if coupled with energy dispersive X-ray spectroscopy (EDS) and electron back-scattered diffraction (EBSD). The development of such techniques is critical for the analysis of samples to be returned by the JAXA Hayabusa-2 and NASA OSIRIS-REx missions but also for understanding the origins of planetary materials more broadly. Such materials include grains of stardust preserved inside of primitive meteorites and provide insight into the origins of ancient stars and the chemical evolution of the Galaxy.<br/>Here we present results of a FIB-tomography analysis of a WLR around a CAI that occurs within a petrographic thin section of the Allende CV3 chondrite. (University of Arizona collection 28-4). Backscattered electron imaging and compositional maps were obtained using the Cameca SX-100 microprobe at the Kuiper Materials Imaging and Characterization Facility (KMICF). Regions of interest were selected for FIB tomography, including secondary imaging and EDS analyses. Furthermore, grain size orientation will be analyzed using EBSD. Our results indicate a complex, very fine-grained microstructure of the sample, which makes the analyses via tomography especially challenging. Based on our results, we will discuss the formation mechanism of the Wark-Lovering rims in the Allende CV3 meteorite.

High resolution chemical and structural investigation of the formation conditions of Wark-Lovering rims in the Allende meteorite

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.