コンドライトバリウム,ネオジミウム,サマリウムイソトープの異質性と初期の地球分化
Richard W Carlson1, Maud Boyet, Mary Horan
1Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015, USA. carlson@dtm.ciw.edu
まとめ
隕石内のバリウム,ネオジミウム,サマリウムの同位体変動は,初期の太陽系への多様な恒星の貢献を明らかにします. この研究は,初期の惑星の分化プロセスが隕石のネオジミウム-142 (142Nd) レベルに影響を与えたことを確認しています.
科学分野:
- 宇宙化学 (コスモケミストリー)
- イソトープ地球化学 イソトープ地球化学
- 惑星科学は惑星科学である.
背景:
- 炭酸性コンドライトは,初期の太陽系の同位体組成を保存しています.
- バリウム,ネオジム,サマリウムイソトープは,恒星の核合成と惑星の進化についての洞察を提供します.
- 以前の研究では,隕石の同位体異常が示されましたが,その起源についてはさらなる明確化が必要でした.
研究 の 目的:
- 炭酸性コンドリートにおけるバリウム,ネオジミウム,サマリウムの同位体の変動性を調査する.
- 初期の太陽系への恒星核合成の貢献を決定する.
- 同位体シグネチャーの形成における初期の惑星の微分化の役割を明らかにする.
主な方法:
- 148Nd/144Ndを使用し,sプロセスの欠陥を修正しました.
- コンドライトの 146Sm-142Nd イソクロンを作りました.
- 陸上の岩石サンプルとコンドライトの同位体比を比較した.
主要な成果:
- コンドライトの146Sm-142Nd同位子は,太陽系の初期146Smの量に関する以前の推定値と一致する.
- 陸上の岩石 (21 +/- 3 ppm) と比較して,より低い142Nd/144Nd比がコンドライトで測定されました.
- この同位体差は146Smの崩壊と初期の惑星の分化に起因する.
結論:
- Ba,Nd,Smの同位体変異は,新生太陽系への明確な恒星核合成の投入を反映しています.
- 陸上の岩石と比較して,コンドライトにおける観測された142Nd欠乏は,146Smの腐敗の結果である.
- 初期の惑星の分化プロセスは,これらの同位体差異を確立する上で重要な役割を果たしました.
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