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Origin of isolated olivine grains in carbonaceous chondrites

Jacquet, E. ; Piralla, M. ; Kersaho, P. ; Marrocchi, Y., MAPS

Origin of isolated olivine grains in carbonaceous chondrites

Jacquet, E. ; Piralla, M. ; Kersaho, P. ; Marrocchi, Y.,

Meteoritics & Planetary Science, 2021, 56, 1, 13-33

Abstract :

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 standalone objects. This indicates that they were splashed out of chondrules when these were still partially molten. CaO-rich refractory forsterites, which are restricted to Δ17O <-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.

Voir en ligne : https://doi.org/doi:10.1111/maps.13583




publié jeudi 4 mars 2021