High fluences of neutrons determined from Sm and Gd isotopic compositions in aubrites

Hiroshi Hidaka*, Mitsuru Ebihara, Shigekazu Yoneda

*この研究の対応する著者

研究成果: Article査読

40 被引用数 (Scopus)

抄録

Large isotopic deviations of 149Sm-150Sm and 157Gd-158Gd derived from neutron capture effects were observed in five enstatite achondrites (aubrites); Norton County, ALH78113, Cumberland Falls, Bishopville and Mayo Belwa. The isotopic variations of these aubrites (ε149Sm = -32 to -7, ε150Sm = +11 to +57, ε157Gd = -42 to -14 and ε158Gd = +9 to +26) correspond to irradiation with neutron fluence of (1.17 - 3.99) x 1016 n cm-2, which is within the range of estimated neutron fluence values of some lunar samples. These results indicate that aubrites may have been located near the surface of their parent body for several hundreds of Ma. Furthermore, the neutron energy spectrum obtained from the combination of Sm and Gd isotope systematics (ε(Sm)/ε(Gd)) suggests that the energy of thermalized neutrons in five aubrites was in the range of 200-400 K, and was lower than those in lunar samples A-12 and A-15. In addition, we analyzed one anomalous aubrite (Mt. Egerton), and two enstatite chondrites (Happy Canyon and Abee) to investigate the relationship of their origin with aubrites. However, these three meteorites showed no evidence for intensive neutron irradiation observed in the aubrites.

本文言語English
ページ(範囲)41-51
ページ数11
ジャーナルEarth and Planetary Science Letters
173
1-2
DOI
出版ステータスPublished - 1999 11月 15
外部発表はい

ASJC Scopus subject areas

  • 地球物理学
  • 地球化学および岩石学
  • 地球惑星科学(その他)
  • 宇宙惑星科学

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