マントルの希ガス同位体から探る地球集積・脱ガス過程・初期のマントル炭素量  [in Japanese] The Earth's accretion degassing processes, and mantle carbon abundance estimated from noble gas isotopic data of mantle  [in Japanese]

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Author(s)

    • 佐々木 晶 SASAKI Sho
    • 東京大学大学院理学系研究科地質学専攻 Geological Institute, School of Science, The University of Tokyo

Abstract

Noble gas data of mantle samples have distinct two end members: PLUME-type representing the lower mantle and MORB-type representing the upper mantle. The estimated high <sup>3</sup>He and <sup>22</sup>Ne abundance of the PLUME source should be remnant of the dissolved solar-type atmosphere into the magma ocean. Calculations of noble gas dissolution into the magma ocean of the accreting planet suggest that the estimated <sup>3</sup>He and <sup>22</sup>Ne abundance can be explained if the primary atmosphere existed until <i>M</i>〜0.4-0.5<i>M<sub>E</sub></i>. This means that the early accretion of the Earth should have proceeded in the presence of the protoplanetary gas disk. The lower <sup>4</sup>He/<sup>3</sup>He and <sup>21</sup>Ne/<sup>22</sup>Ne of the PLUME data than MORB data can be explained if the lower mantle was less degassed during magma ocean cooling. The upper limit of the initial carbon abundance in mantle can be also estimated using C/<sup>3</sup>He data. The upper mantle should contain 3.8×10<sup>21</sup> mole which is lower than the present crustal amount, whereas the lower mantle would contain 70 times as much carbon as the upper mantle.

Journal

  • Chikyukagaku

    Chikyukagaku 33(4), 265-274, 1999

    The Geochemical Society of Japan

References:  38

Codes

  • NII Article ID (NAID)
    110008679990
  • NII NACSIS-CAT ID (NCID)
    AN00141280
  • Text Lang
    JPN
  • Article Type
    REV
  • ISSN
    0386-4073
  • NDL Article ID
    4917773
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-645
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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