¹Jillian Kirk, ¹Myriam Telus, ¹Pranvera Hyseni, ¹Fatima Jorge-Chavez, ²Vanessa Mendoza, ³Steven J. Desch, ⁴Dale Burns, ⁵Steven Simon
Icarus (in Press) Open Access Link to Article [DOI: 10.1016/j.icarus.2026.117263]
¹University of California Santa Cruz, Department of Earth and Planetary Sciences, 1156 High Street, Santa Cruz, 95064, CA, USA
²Western Washington University, Geology Department, 516 High St, Bellingham, 98225, WA, USA
³Arizona State University, School of Earth and Space Exploration, 781 Terrace Mall, Tempe, 85287, AZ, USA
⁴Stanford University, Department of Geological Sciences, 450 Jane Stanford Way, Stanford, 94305, CA, USA
⁵University of New Mexico, Institute of Meteoritics, 221 Yale Blvd NE MSC03 2050, Albuquerque, 87131, NM, USA
Copyright Elsevier

Chondrules are small igneous particles that formed in the protoplanetary disk and make up the bulk of chondrites. Chondrule rims offer insights into the composition of dust in the solar nebula and the conditions and heating mechanisms associated with chondrule formation. High-resolution elemental mapping of pristine CO3 chondrite thin sections revealed igneous chondrule rims enriched in manganese, a moderately volatile element (MVE), which is sensitive to thermal processing. These chondrule rims have not previously been characterized, in part due to their small thicknesses (
30
m). Characterization of Mn-rich rims in CO3 chondrites reveals that this enrichment exists in a variety of textures, some of which are associated with non-igneous fine-grained rims, while many clearly formed from a melt. Mn-rich pyroxenes in CO3 chondrule rims are also enriched in Na, K, and Cr, as compared to pyroxene in host chondrules (i.e., chondrules hosting the Mn-rich rims) and no-rim chondrules (chondrules without Mn-rich rims). These enrichments seem to be the result of nebular processing of chondrules as opposed to parent-body processing, as enrichments do not correlate with petrologic subtypes. Pyroxene with similar enrichments in these elements occur within igneous chondrule rims seen in CR chondrites, indicating that these rims may have formed across different locations and times in the nebula. Previous studies have suggested that MVE enrichment of chondrule rims occurred during interaction with MVE-enriched nebular gas. Our results could support an alternative scenario involving accretion of MVE-enriched dust onto solidified chondrules, which subsequently experienced varying degrees of thermal processing, possibly facilitated by a planetesimal or planetary embryo bow shock, resulting in MVE-enriched chondrule rims. Future work is needed to validate this idea. This study highlights the potential role of outgassing planetesimals and/or planetary embryos as a source of MVE-rich dust in the solar nebula.