^1,2Johanna Marin-Carbonne,¹Kevin D. McKeegan,^3,4Andrew M. Davis,⁵Glenn J. MacPherson,⁵Ruslan A. Mendybaev,⁵Frank M. Richter
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13971]
¹Department of Earth, Planetary, and Space Sciences, University of California—Los Angeles, Los Angeles, California, USA
²Institut des Sciences de la Terre, Université de Lausanne, Lausanne, Switzerland
³Department of the Geophysical Sciences, University of Chicago, Illinois, USA
⁴Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
⁵Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
Published by arrangement with John Wiley & Sons

Oxygen, magnesium, and silicon isotopic abundances in Vigarano 1623-5 were studied using secondary ion mass spectrometry to investigate correlations between isotopic and petrologic properties of this unique forsterite-bearing FUN inclusion. Vigarano 1623-5 displays large, correlated mass-dependent fractionation effects, tightly linked to mineralogy within distinct petrologic units of the inclusion. The pyroxene-rich and melilite-rich interior parts of the inclusion display highly mass-fractionated isotopic compositions of oxygen, magnesium, and silicon, consistent with Rayleigh distillation during evaporation of a melt with initial oxygen composition close to a solar composition. However, the chemical composition, enriched in magnesium and silicon, suggests a precursor already fractionated by prior melt evaporation. A discontinuous igneous rim was produced by a flash-melting event followed by isotopic exchange in the rim melilite with planetary-like oxygen, mechanical fragmentation, and reassembly with an accretionary rim of heterogeneous materials. Al-rich minerals in 1623-5 show evidence for having crystallized with live 26Al but at less than the “canonical” level of most CV calcium-aluminum-rich inclusions. However, well-defined 26Al-26Mg isochrons are not found and temporal implications are ambiguous.