The impact history and prolonged magmatism of the angrite parent body

B. G. Rider-Stokes*, Mahesh Anand, Lee Francis White, J. R. Darling, Romain Tartèse, M. J. Whitehouse, I. Franchi, R. C. Greenwood, G. Degli-Alessandrini

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

As some of the oldest differentiated materials in our solar system, angrite meteorites can provide unique insights into the earliest stages of planetary evolution. However, the timing of planetary mixing, as evidenced by oxygen isotope variations in the quenched angrites, and the extent of magmatism on the angrite parent body (APB) remain poorly understood. Here, we report on microstructurally guided in situ geochemical and Pb-Pb isotopic measurements on angrites aimed at better understanding of the timing and nature of magmatic processes, as well as impact events, on the APB. The quenched angrite Northwest Africa (NWA) 12320 yielded a Pb-Pb date of 4571.2 ± 9.4 Ma, which we interpret as corresponding to the timing of planetary mixing. The only known shocked quenched angrite, NWA 7203, also yielded an ancient Pb-Pb date of 4562.9 ± 9.3 Ma, which is identical to the Pb-Pb date of 4563.6 ± 7.9 Ma obtained for the texturally intermediate angrite NWA 10463. Pb-Pb analyses in phosphates in the dunitic angrite NWA 8535 yielded a much younger date of 4514 ± 30 Ma, representing the youngest Pb-Pb date ever recorded for an angrite. Based on the evidence from the lack of shock deformation, olivine major and trace element compositions, and no apparent contamination in the oxygen isotope composition of NWA 8535, our findings are consistent with prolonged magmatism on the APB. This finding is consistent with a large size for the APB.
Original languageEnglish
Number of pages17
JournalMeteoritics and Planetary Science
Early online date27 Nov 2023
DOIs
Publication statusEarly online - 27 Nov 2023

Keywords

  • planetary geology
  • planetary science
  • asteroids
  • geochronology
  • meteorite
  • meteorite impact
  • solar system
  • scanning electron microscopy (SEM)
  • laser ablation ICP-MS
  • SIMS
  • apatite
  • merrillite
  • UKRI
  • STFC
  • ST/T000228/1

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