爆破岩の希少ガス体系論:上層マントルの同位体および元素組成
1Universite Denis Diderot-Paris 7, Laboratoire de Geochimie et Cosmochimie, Institut de Physique du Globe de Paris, CNRS Unite de Recherche Associee Number 1758, 4 Place Jussieu, 75252 Paris Cedex 05, France.
Science (New York, N.Y.)
|March 4, 1998
まとめ
噴出岩の希少ガス同位体に関する新しい研究は,地球の上層マントルの低い40Ar/36Ar比 (<44,000) と129Xe/130Xe比 (<8.2) を示唆しています. これは,地球が,そのガス組成を変えた惑星性物質から形成されたことを示している.
科学分野:
- 地質化学 地質化学
- 同位体地質学とは,同位体地質学である.
- 惑星科学は惑星科学である.
背景:
- 地球の大気とマントルの構成の起源と進化を理解することは極めて重要です.
- 高貴なガス (ネオン,アルゴン,クセノン) は,惑星形成過程のユニークなトレーサーを提供します.
- 以前のモデルは,地球の原始大気の異なる同位体組成を示唆した.
研究 の 目的:
- 爆破岩の希少ガスのイソトープと元素の豊富なパターンを調査するために.
- 地球上の上層マントルの40Ar/36Ar比を制限するために.
- 地球の構成要素の性質とそのガス進化を推論する.
主な方法:
- ネオン,アルゴン,クセノンの同位体変化の分析.
- 希少ガスの元素の豊富さの測定. 希少ガスの元素の豊富さの測定. 希少ガスの元素の豊富さの測定.
- 惑星の蓄積モデルの文脈におけるデータの解釈.
主要な成果:
- 上層マントルの40Ar/36Ar比は44,000未満と推定されている.
- 129Xe/130Xe比は8.2.より小さいと判断される.
- 希少ガスの元素的多量パターンはコンドリート状で,太陽のパターンと大きく異なっています.
結論:
- 地球は,希少なガス予算の変容を経験したプラネティシマルから増加した可能性が高い.
- この変換により,ガスの組成は太陽のようなものからコンドリートのようなものに変化した.
- マントルの希少ガスの同位体組成は,この変容にもかかわらず,太陽のパターンから大きく変わっていない可能性があります.
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