最近の落下例を含む隕石における宇宙線生成放射性核種 –コンドライトの宇宙線照射履歴への制約–  [in Japanese] Cosmogenic radionuclides in meteorites including recently fallen ones –Constraints on the exposure history of chondrites–  [in Japanese]

Access this Article

Search this Article

Author(s)

    • 井上 睦夫 INOUE Mutsuo
    • 金沢大学・理学部附属低レベル放射能実験施設 Low Level Radioactivity Laboratory (LLRL), Faculty of Science, Kanazawa University
    • 小村 和久 KOMURA Kazuhisa
    • 金沢大学・理学部附属低レベル放射能実験施設 Low Level Radioactivity Laboratory (LLRL), Faculty of Science, Kanazawa University

Abstract

Activities of cosmogenic nuclides have been numerously reported for extraterrestrial material, meteorites (especially chondrites). In addition to noble gases, cosmogenic radionuclides (e.g., <sup>22</sup>Na, <sup>26</sup>Al, <sup>46</sup>Sc, <sup>53</sup>Mn, <sup>54</sup>Mn and <sup>60</sup>Co) have also kept important records of their history during last ten million years. For example, low <sup>60</sup>Co activity observed in most chondrites (<30 dpm/kg) suggests that their preatmospheric radii are less than 〜30 cm, and activities of <sup>22</sup>Na and <sup>26</sup>Al reflect various irradiation conditions by cosmic-ray such as shielding effect, exposure age and cosmic-ray flux with time and space. Terrestrial age (Antarctic meteorites; H group, <0.4×10<sup>6</sup>y; L, LL,<10<sup>6</sup>y estimated from <sup>26</sup>Al, <sup>36</sup>Cl and <sup>14</sup>C activities) as well as exposure age (H, 3 -40×10<sup>6</sup>y; L, LL, 3 -50×10<sup>6</sup>y) shows different distributions between H- and L-, LL-group chondrites, which have possibly preserved the information about breakage of parent body and so on. The combined data of exposure age and activities of cosmogenic nuclides also give constraints on the complex history of chondrites (e.g., multi-stage irradiation as a result of fragmentation) until the collision with the Earth. Recently, with the progress of nondestructive γ-ray techniques, activities of relatively short-lived nuclides such as <sup>46</sup>Sc, <sup>22</sup>Na implied the irradiation conditions just before fall to the Earth. In this paper, "the evolution history of chondrites after separation from the parent body" is represented from activities of cosmogenic radionuclides in meteorites including recently fallen ones.

Journal

  • Chikyukagaku

    Chikyukagaku 35(1), 13-25, 2001

    The Geochemical Society of Japan

References:  65

Codes

  • NII Article ID (NAID)
    110008680014
  • NII NACSIS-CAT ID (NCID)
    AN00141280
  • Text Lang
    JPN
  • Article Type
    REV
  • ISSN
    0386-4073
  • NDL Article ID
    5711946
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-645
  • Data Source
    CJP  NDL  NII-ELS  IR  J-STAGE 
Page Top