マグマ海洋からの溶融分離によって生成されたハデアンマントルの微量元素分化
Guillaume Caro1, Bernard Bourdon, Bernard J Wood
1Laboratoire de Géochimie et Cosmochimie IPGP-CNRS, 4 Place Jussieu, 75252 Paris cedex 05, France. caro@ipgp.jussieu.fr
Nature
|July 15, 2005
まとめ
初期の地球 初期の地球
科学分野:
- 地質化学 地質化学
- 惑星科学は惑星科学である.
- 初期の地球の歴史 初期の地球の歴史
背景:
- 初期の地球は,蓄積過程による大量溶融でした.
- マントルの分化は,地球の増殖期 (4,46 ± 0.11 Gyr前) の終わり近くに発生した.
- この分化により,マントルが枯渇し,Sm/Nd比が上昇した.
研究 の 目的:
- 初期の地球の地化学的シグネチャーの背後にあるプロセスを調査するために.
- 初期アーカイアン時代の岩石から得られた矛盾するNdとHfの同位体データを調和させるため.
- 初期の地上の原地殻の形成を理解するために.
主な方法:
- 西グリーンランドの3.6~3.8ギアルの古い岩の分析.
- サマリウム・ネオジミウム (Sm-Nd) とルテチウム・ハフニウム (Lu-Hf) のクロノメトリーの適用.
- 高圧マントルの鉱物の鉱物分断データを使用した.
主要な成果:
- 観測されたNd同位体シグネチャはマントルの枯渇を示唆しているが,Hfシグネチャはコンドリート源を示唆している.
- これは,Sm-NdとLu-Hfが共変的に分割する典型的な地殻形成プロセスと対照的です.
- 高圧鉱物溶融の分断データは,観測されたNdとHfシグネチャーを説明します.
結論:
- 観測された地化学的シグネチャは,結晶化したマグマ海洋からの溶融分離と一致しています.
- このプロセスは,地球の歴史の初期に,上層マントルの圧力で起こった.
- 残った溶融は,おそらく最も初期の地上の原地殻を形成した.
関連する概念動画
Classifying Matter by Composition
78.6K
Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories — pure substances and mixtures.
A pure substance is a form of matter that has a constant composition throughout with uniform properties. For example, any sample of sucrose has the same composition and same physical properties, such as melting point, color, and sweetness, regardless of the source from which it is isolated.
A mixture is composed of two or...
According to its composition, the matter can be classified into two broad categories — pure substances and mixtures.
A pure substance is a form of matter that has a constant composition throughout with uniform properties. For example, any sample of sucrose has the same composition and same physical properties, such as melting point, color, and sweetness, regardless of the source from which it is isolated.
A mixture is composed of two or...
78.6K
Phase Transitions: Melting and Freezing
11.7K
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
11.7K
Qualitative Analysis
21.9K
For solutions containing mixtures of different cations, the identity of each cation can be determined by qualitative analysis. This technique involves a series of selective precipitations with different chemical reagents, each reaction producing a characteristic precipitate for a specific group of cations. Metal ions within a group are further separated by varying the pH, heating the mixture to redissolve a precipitate, or adding other reagents to form complex ions.
For instance, group IV...
For instance, group IV...
21.9K
Subcellular Fractionation
7.2K
The homogenate obtained after cell lysis contains various membrane-bound organelles that can be further separated into pure fractions by subcellular fractionation. These isolates are used to study specific cellular components, analyze localized protein activity, and are even employed in diagnostics. Fractionation is typically achieved using centrifugation methods, the most common being density-gradient and differential centrifugation.
Differential Centrifugation
Differential centrifugation is...
Differential Centrifugation
Differential centrifugation is...
7.2K
Segregation in Fresh Concrete
1.3K
Segregation in fresh concrete is a phenomenon where the components of the concrete mix separate, leading to uneven distribution and compromised structural integrity. This separation typically occurs when concrete is subjected to excessive horizontal movement within forms, or when it is dropped from considerable heights or forced through narrow, winding paths. As a result, heavier coarse aggregate particles settle at the bottom, while lighter, finer materials such as cement and water rise to the...
1.3K
Microbes and Other Elemental Cycles
89
Microbial activity plays a pivotal role in the biogeochemical cycling of iron and manganese, especially at the redox gradients characteristic of stratified aquatic environments. These cycles are driven by microbial transformations between oxidized and reduced forms of the metals, allowing organisms to exploit them for metabolic energy and structural purposes.Iron Cycling Across Redox GradientsIn neutral, oxygen-rich surface waters, iron is predominantly found in its oxidized, insoluble ferric...
89


