Fall, classification, and exposure history of the Mifflin L5 chondrite

Noriko T. Kita, Kees C. Welten, John W. Valley, Michael J. Spicuzza, Daisuke Nakashima, Travis J. Tenner, Takayuki Ushikubo, Glenn J. MacPherson, Linda Welzenbach, Philipp R. Heck, Andrew M. Davis, Matthias M.M. Meier, Rainer Wieler, Marc W. Caffee, Matthias Laubenstein, Kunihiko Nishiizumi

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The Mifflin meteorite fell on the night of April 14, 2010, in southwestern Wisconsin. A bright fireball was observed throughout a wide area of the midwestern United States. The petrography, mineral compositions, and oxygen isotope ratios indicate that the meteorite is a L5 chondrite fragmental breccia with light/dark structure. The meteorite shows a low shock stage of S2, although some shock-melted veins are present. The U,Th-He age is 0.7 Ga, and the K-Ar age is 1.8 Ga, indicating that Mifflin might have been heated at the time of the 470 Ma L-chondrite parent body breakup and that U, Th-He, and K-Ar ages were partially reset. The cosmogenic radionuclide data indicate that Mifflin was exposed to cosmic rays while its radius was 30-65 cm. Assuming this exposure geometry, a cosmic-ray exposure age of 25 ± 3 Ma is calculated from cosmogenic noble gas concentrations. The low 22Ne/21Ne ratio may, however, indicate a two-stage exposure with a longer first-stage exposure at high shielding. Mifflin is unusual in having a low radiogenic gas content combined with a low shock stage and no evidence of late stage annealing; this inconsistency remains unexplained.

Original languageEnglish
Pages (from-to)641-655
Number of pages15
JournalMeteoritics and Planetary Science
Volume48
Issue number4
DOIs
Publication statusPublished - 2013 Apr
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

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