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Séminaire "Insight into the volatile content of Mars from the zinc isotopic composition of SNC meteorites" par Marine Paquet (post doc IPGP)

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Jeudi 09 Juin 2022, 13:00 - 14:00
par Stéphanie BEAUNAY

 

Abstract : Barring a sample return mission to Mars, martian meteorites are the sole tangible records of its crust. These samples provide insights into the composition of Mars, as well as the processes that led to its accretion and differentiation. Relative to CI-chondrites or the Sun, terrestrial planets are depleted in moderately volatile elements (MVE) (e.g., Palme and Jones, 2003). Recent work showed that martian meteorites have systematically heavier K isotopic compositions than the Bulk Silicate Earth (BSE), suggesting a greater volatile depletion and stronger K isotope fractionation relative to their potential precursor materials (Tian et al., 2021). However, this interpretation is in contrast with the abundances of other volatile elements, such as Zn or Rb that are present in greater abundances in the martian mantle than in the BSE (Khan et al., 2022). Zinc, like K, is a moderately volatile, lithophile element, whose isotope composition provides independent constraints on volatile delivery and loss during planetary accretion. Previous Zn isotopic data for martian meteorites range from δ66Zn = +0.13 to +0.35‰ (Paniello et al., 2012), values that are not resolvable from that of the BSE (δ66Zn = 0.16 ±0.06‰, Sossi et al., 2018) within error. To better evaluate the Zn isotopic composition of Mars, we present new high precision Zn isotope data for ten martian meteorites, spanning the major petrologic types. Combined with previous measurements, this new dataset permits a precise assessment of the martian mantle Zn isotope composition, representative of the Bulk Silicate Mars (BSM), and to test if the model proposed for volatile depletion based on K isotopes (Tian et al., 2021) holds for Zn. 

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