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arXiv · 2101.10073

Origin of isolated olivine grains in carbonaceous chondrites

Emmanuel Jacquet·Maxime Piralla·Pauline Kersaho·Yves Marrocchi
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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), 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 $\Delta^{17}O < -4\permil$ 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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Emmanuel Jacquet, Maxime Piralla, Pauline Kersaho, Yves Marrocchi. 2021-01-25. Origin of isolated olivine grains in carbonaceous chondrites. https://doi.org/10.1111/maps.13583

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