Origin of isolated olivine grains in carbonaceous chondrites

1Emmanuel Jacquet,2Maxime Piralla,2Pauline Kersaho,2Yves Marrocchi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13583]
1Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS, CP52 57 rue Cuvier, 75005 Paris, France
2Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, UMR 7358,, 54501 Vandœuvre‐lès‐Nancy, France
Published by arrangement with John Wiley & Sons

We report microscopic, cathodoluminescence, chemical, and O isotopic measurements of FeO‐poor isolated olivine grains (IOG) in the carbonaceous chondrites Allende (CV3), Northwest Africa 5958 (C2‐ung), Northwest Africa 11086 (CM2‐an), and Allan Hills 77307 (CO3.0). The general petrographic, chemical, and isotopic similarity with bona fide type I chondrules confirms that the IOG derived from them. The concentric CL zoning, reflecting a decrease in refractory elements toward the margins, and frequent rimming by enstatite are taken as evidence of interaction of the IOG with the gas as stand‐alone objects. This indicates that they were splashed out of chondrules when these were still partially molten. CaO‐rich refractory forsterites, which are restricted to ∆17O <−4‰ likely escaped equilibration at lower temperatures because of their large size and possibly quicker quenching. The IOG thus bear witness to frequent collisions in the chondrule‐forming regions.

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