初期の地球の水星のような成分は,コアと高層マントル (142) NdNdでウランを生成します
Anke Wohlers1, Bernard J Wood1
1Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.
Nature
|April 17, 2015
まとめ
地球の核は,その異常な元素の組成の鍵を握っているかもしれない. 核の形成は,マントルの高サマリウム対ネオジミウム比 (Sm/Nd) を説明し,地質天候に欠けている熱源を提供する可能性がある.
科学分野:
- 地質化学 地質化学
- 惑星科学は惑星科学である.
- イソトープ地球化学 イソトープ地球化学
背景:
- 最近の (142) Nd同位体データは,地球のシリケート部分における超コンドリートサマリウム対ネオジミウム元素比 (Sm/Nd) を明らかにしています.
- この異常は,隠された貯蔵庫か,衝突による断層による早期の地殻喪失に起因する.
- 地殻の損失は,熱を生成する要素の除去により,地上の熱生産バランスに挑戦します.
研究 の 目的:
- 核形成がサマリウム (Sm) からネオジミウム (Nd) を分化できるかどうかを調査する.
- コアが熱生成要素のシンクとして機能するかどうかを判断する.
- 観測されたSm/Nd比と地球の熱予算を調和させるため.
主な方法:
- 原子核形成が元素分化に及ぼす影響をモデル化する.
- リトフィール元素 (U,Thなど) の核への分割を評価する.
- (142) Nd/(144) Nd.の同位体シグネチャーを分析する.
主要な成果:
- 初期の地球に硫黄に富んだ還元体 (水銀のようなもの,エンスタチット・コンドライトのようなもの) を加えると,マントルに超コンドライトのSm/Ndが生成されます.
- このプロセスは,コンドライトと比較して約14ppmの陽性 (142) Nd / (144) Nd異常を生成します.
- 硫黄が豊富な核は,ウランを効果的に分割し,少量ではトリウムを分割し,ジオダイナモの熱源に寄与します.
結論:
- 核の形成は,シリケート地球における観測された超コンドリートSm/Nd比の実行可能なメカニズムを提供します.
- 核は,ウランやソリウムなどの熱生成元素のための重要なシンクとして機能することができます.
- このモデルは,同位体異常と地球の内部熱予算を調和させ,惑星の進化における核形成の重要な役割を示唆しています.
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