^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.

^1,2,3Ying-Kui Xu,^1,4Zhi Li,^1,2Shi-Jie Li,³Ze-Zhou Wang,^1,4De-Liang Wang,^1,5Yan Fan,^1,2Xiong-Yao Li,^1,2Jian-Zhong Liu,^6,2Dan Zhu
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.03.031]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
²CAS Center for Excellence in Comparative Planetology, Hefei, 230022, China
³Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
⁴University of Chinese Academy of Sciences, Beijing, 100049, China
⁵Department of Geology, Northwest University, Xi’an, 710069, China
⁶State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
Copyright Elsevier

To constrain how impacts influence the behavior of moderately volatile elements (MVEs), we report potassium (K) and zinc (Zn) contents and isotopic compositions of shock melt pockets (SMPs) and unmelted parts of three heavily shocked ordinary chondrites and bulk rocks of Chelyabinsk meteorite. All SMPs are enriched in K content and have lower isotopic values (δ41K = -1.99‰, -1.22‰ and -1.40‰) while the adjacent unmelted parts are enriched in heavy K isotopes (δ41K = -0.41‰, -0.01‰ and 0.04‰) compared to the bulk rocks of Chelyabinsk meteorite (δ41K = -0.77‰ and -0.73‰). By contrast, Zn is depleted in SMPs and the isotopic compositions are heavier (δ66Zn = -0.19‰, 2.42‰, 1.74‰) in SMPs than that in unmelted parts (δ66Zn = -0.65‰, 1.76‰, -0.97‰). Our results indicate a decoupling between the two MVEs that Zn is lost from shock melts while K is dramatically enriched in shock melts during impacts. The isotope fractionation of Zn is probably caused by evaporation of shock melts, while K isotope fractionation is most likely caused by solid-melt diffusion which is controlled by its incompatibility. The isotopic decoupling of K from Zn during major impacts further enhances our understanding of high temperature elemental and isotopic behavior of MVEs and may shed new light on the variously heterogeneous distribution of MVEs in solar system.