Zinc isotopes in HEDs: clues to the formation of 4-Vesta, and the unique composition of Pecora Escarpment 82502

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Paniello, Randal, Moynier, Frédéric, Beck, Pierre, Barrat, Jean-Alix, J-A, Podosek, Frank, Pichat, Sylvain
• Other Authors: Department of Earth and Planetary Sciences St Louis, Washington University in Saint Louis (WUSTL), McDonnell Center for Space Sciences, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: DIOGENITE PARENT BODY; ASTEROID 4 VESTA; ANTARCTIC METEORITES; IRON-METEORITES; OXYGEN-ISOTOPE; TREND EUCRITES; TRACE-ELEMENTS; LUNAR-SAMPLES; GEOCHEMISTRY; IMPACT; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; Antarc*; Antarctic
• Online Access: https://insu.hal.science/insu-00670085; https://insu.hal.science/insu-00670085/document; https://insu.hal.science/insu-00670085/file/GCA-Barrat-2010.pdf; https://doi.org/10.1016/j.gca.2012.01.045

International audience The δ66Zn (permil deviation of the 66Zn/64Zn ratio from a terrestrial standard) values for a suite of 20 non-Antarctic HED (howardite - eucrite - diogenite) meteorites and one mesosiderite, and for 8 Antarctic eucrites and diogenites, were measured in order to determine the role of volatization in the formation of their presumed parent body, the asteroid 4-Vesta. The 20 non-Antarctic HEDs had δ66Zn values that ranged from -2.0 ‰ to +1.67 ‰, with a mean value of -0.01 ± 0.39 ‰ (2se); this range likely represents a small-scale heterogeneity due to brecciation induced by multiple impacts. The non-Antarctic eucrites (δ66Zn = +0.00 ± 0.58 ‰ (2se), n=12) were isotopically the same as the diogenites (δ66Zn = -0.31 ± 0.80 ‰ (2se), n=4), and the howardites (δ66Zn = +0.26 ± 0.37 ‰ (2se), n=4). On average, non-Antarctic eucrite falls were isotopically heavier (+0.50 ‰) than non-Antarctic finds (-1.00 ‰). The Antarctic finds studied were all unbrecciated samples, and they were significantly heavier than the non-Antarctic samples with a δ66Zn range of +1.63 to +6.22‰ for 4 eucrites (mean, +4.32‰) and +0.94 to +1.60‰ for 3 diogenites (mean +1.23‰), excluding one anomalous sample, while their Zn concentration is significantly lower than the brecciated samples. These data suggest that the unbrecciated eucrites probably represent the eucritic crust shortly after differentiation and cooling of the parent asteroid, at which time volatization of lighter zinc isotopes led to an isotopically heavy crust. Early impact events caused the ejection of these unbrecciated meteorites, which were subsequently spared from brecciation caused by multiple additional impacts on the much larger Vesta. The range of δ66Zn values and Zn concentration for the brecciated HEDs in this study supports a major contribution to the Vestan surface by chondritic impactors (-1.30 < δ66Zn < +0.76 ‰ for ordinary and carbonaceous chondrites). The anomalous eucrite PCA 82502 (δ66Zn= -7.75 ‰) is significantly isotopically lighter than ...