コンドルルと耐火性インクルージョンの同時形成のためのMg同位体の証拠
Martin Bizzarro1, Joel A Baker, Henning Haack
1Danish Lithosphere Centre, Øster Voldgade 10, Denmark. mbi@dlc.ku.dk
Nature
|September 17, 2004
まとめ
原始的な隕石は,初期の太陽系形成を明らかにしています. カルシウムとアルミニウムに富んだインクルージョン (CAI) とコンドルールは同時に形成され,これらの古代の太陽系物質に対する以前の時間スケールに挑戦しました.
科学分野:
- 宇宙化学 (コスモケミストリー)
- 惑星科学は惑星科学である.
- 初期の太陽系進化について
背景:
- 原始的な隕石 (コンドライト) は,初期の太陽系の蓄積円盤の記録を保存しています.
- カルシウムとアルミニウムが豊富なインクルージョン (CAI) とコンドルールは,霧状固体の熱処理によって形成された最も古い材料の1つです.
- 既存のモデルは,コンドルールがCAIから数百万年後に形成されたことを示唆しており,これは粒子の動力学と矛盾する時間スケールである.
研究 の 目的:
- 同位体分析を用いてCAIとコンドルルの形成時間スケールを調査する.
- これらの原始的な太陽系天体の形成年代を動的制約と調和させるため.
主な方法:
- 短命アルミニウム26 (26Al) の腐敗から生じた過剰マグネシウム-26 (26Mg) の分析. アレンデ隕石からのCAIとコンドルル.
- 26Al-26Mgシステムを用いた放射線年代測定により,最初の26Al/27Al比率とモデル年齢を決定する.
主要な成果:
- 6つのCAIは,初期26Al/27Al比率 (5.25 ± 0.10) x 10−5を示したアイソクロンを得ており,モデルの年齢は±30,000年ほど正確です.
- これらのCAIは,およそ5万年の非常に短い期間で形成されたことを示唆しています.
- ホンドルルは,初期26Al/27Al比の範囲を (5.66 ± 0.80) x 10−5から (1.36 ± 0.52) x 10−5まで示し,CAIと同時期の形成を示し,少なくとも1400万年もの間続いた.
結論:
- アレンデのコンドルールの形成は,以前考えられていたように数百万年後にではなく,CAIの形成と同時に始まった.
- コンドルル形成の過程は,おそらく少なくとも1400万年,若い太陽系ではおそらく2~300万年続いた.
- これらの発見は,初期の太陽系の熱的および動的進化のモデルを改訂することを必要としています.
さらに関連する動画
11:50Metal-silicate Partitioning at High Pressure and Temperature: Experimental Methods and a Protocol to Suppress Highly Siderophile Element Inclusions
Published on: June 13, 2015
07:46Nanothermite with Meringue-like Morphology: From Loose Powder to Ultra-porous Objects
Published on: December 24, 2017
関連する概念動画
Molecules and Compounds
Atoms and Molecules
Experimental Determination of Chemical Formula
The elemental makeup of a compound defines its chemical identity, and chemical formulas are the most concise way of representing this elemental makeup. When a compound’s formula is unknown, measuring the mass of its constituent elements is often the first step in determining the formula experimentally.
Ionic Crystal Structures
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Metallic Solids
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
Qualitative Analysis
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...
Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
