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An I-Xe Constraint on the Age of the CB Chondrites, and a Reevaluation of the Closure Age of Shallowater Enstatite

Research output: Contribution to journalJournal article

Published

  • Jamie Gilmour
  • Sarah Crowther
  • Alli Busfield
  • Greg Holland
  • James Whitby
Journal publication date04/2009
JournalMeteoritics and Planetary Science
Journal number4
Volume44
Number of pages7
Pages573-579
Original languageEnglish

Abstract

The iodine-xenon system has been analyzed in samples of 7 chondrules from the CB chondrites Gujba and Hammadah al Hamra (HaH) 237. One sample from Gujba defined a high temperature iodine-xenon isochron corresponding to closure 1.87 ± 0.4 Ma before closure of Shallowater enstatite. Motivated by this result, we employ outlier rejection to re-evaluate the Shallowater age, leading to a modified value of 4562.3 ± 0.4 Ma (1s̀). In this process, the datum obtained by combining our I-Xe age for Gujba with the literature Pb-Pb age is rejected as an outlier, indicating that in this sample the I-Xe system closed earlier than the accepted Pb-Pb age of chondrules from CB chondrites. The need for a formation environment distinct from that of chondrules from other meteorites is thus reduced.