Timing and Origin of the Angrite Parent Body Inferred from Cr Isotopes

Type Article
Date 2019-05
Language English
Author(s) Zhu Ke1, Moynier Frederic1, 2, Wielandt Daniel3, 4, Larsen Kirsten K.3, 4, Barrat Jean-Alix5, 6, Bizzarro MartinORCID3, 4
Affiliation(s) 1 : Univ Paris, CNRS, Inst Phys Globe Paris, 1 Rue Jussieu, F-75005 Paris, France.
2 : Inst Univ France, 103 Blvd St Michel, F-75005 Paris, France.
3 : Univ Copenhagen, Ctr Star & Planet Format, Oster Voldgade 5-7, DK-1350 Copenhagen, Denmark.
4 : Univ Copenhagen, Nat Hist Museum Denmark, Oster Voldgade 5-7, DK-1350 Copenhagen, Denmark.
5 : Univ Bretagne Occidentale, UMR CNRS 6538, Lab Geosci Ocean, Pl Nicolas Copernic, F-29280 Plouzane, France.
6 : Inst Univ Europeen Mer, Pl Nicolas Copernic, F-29280 Plouzane, France.
Source Astrophysical Journal Letters (2041-8205) (Iop Publishing Ltd), 2019-05 , Vol. 877 , N. 1 , P. L13 (8p.)
DOI 10.3847/2041-8213/ab2044
WOS© Times Cited 37
Keyword(s) astrochemistry, meteorites, meteors, meteoroids, nuclear reactions, nucleosynthesis, abundances

Angrite meteorites are some of the oldest materials in the solar system. They provide important information on the earliest evolution of the solar system and accretion timescales of protoplanets. Here, we show that the Cr-54/Cr-52 ratio is homogeneously distributed among angrite meteorites within 13 parts per million, indicating that precursor materials must have experienced a global-scale melting such as a magma ocean. The Cr-53/Cr-52 and Mn/Cr ratios are correlated, which is evidence for an initial Mn-53/Mn-55 ratio of (3.16 +/- 0.11) x 10(-6). When anchored to the U-corrected Pb-Pb age for the D'Orbigny angrite, this initial 53Mn/55Mn corresponds to an absolute age of 4563.2 +/- 0.3 Ma, i.e., 4.1 +/- 0.3 Ma after Ca-Al-rich inclusion-formation. This age is distinct from that of the volatile depletion events dated by the Sr-87/Sr-86 initial ratio and therefore must correspond to the age of crystallization of the magma ocean and crust formation of the angrite parent body (APB), which can also constrain a slightly bigger size of APB than that of Vesta. Furthermore, this age is similar to those obtained from internal isochrons of the oldest volcanic angrites that cooled rapidly at the surface of the parent body (with ages of 4564 similar to 4563 Ma), while older than those obtained from plutonic angrites (4561 similar to 4556 Ma) that cooled down slowly, located deeper within the parent body. This implies that cooling of the APB took at least similar to 8 Myr after its differentiation.

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