ストロンチウム・ルビジウム 鉄隕石の年代
まとめ
ウェークルーステーションの隕石のシリケートノードルのルビジアム-ストロンチウム年代測定は,47億年前の年齢を明らかにします. これは,他の鉄隕石の年代推定と対照的に,急速な太陽系形成期を支えている.
科学分野:
- 地質化学 地質化学
- 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
背景:
- 隕石内のシリケート結節は,初期の太陽系プロセスについての洞察を提供します.
- ルビジアム・ストロンチウム (Rb-Sr) の同位体体系は,惑星物質の年代測定に極めて重要です.
研究 の 目的:
- ウィークルーステーションの隕石から採取したシリケートノードルに含まれるルビジアムとストロンチウムの同位体組成と濃度を測定する.
- 隕石の年齢を確定し,太陽系微分化のタイミングを推測する.
主な方法:
- ルビジアムとストロンチウム濃度の同位体分析.
- Sr(87):Sr(86) とRb/Srの比率を用いたストロンチウム進化図の構築.
- イソクロン年代測定法を使用して隕石の年齢を計算する.
主要な成果:
- ストロンチウムの同位体比 (Sr(87):Sr(86) は0.729から0.768の範囲で,アコンドライトと比較して濃度が高いことが示された.
- データポイントはアイソクロンを形成し,最初のSr(87):Sr(86) の比率は0.6960.702.6でした.
- 推定年齢は47億年,これは地球と隕石の形成年代と一致する.
結論:
- ウィークルー・ステーションの隕石は,約47億年前に形成されました.
- この時代は,太陽系の主要な化学的,物理的差異の急速で狭い間隔を支えている.
- 他の鉄隕石からのAr{40) -K{40) 年代との不一致は,多様な同位体調査の必要性を強調しています.
さらに関連する動画
09:45Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria
Published on: July 24, 2016
09:41Isolation of Quartz Grains for Optically Stimulated Luminescence (OSL) Dating of Quaternary Sediments for Paleoenvironmental Research
Published on: August 2, 2021
関連する概念動画
Radioactive Decay and Radiometric Dating
Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
Nuclear Transmutation
Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed protons being...
Nuclear Stability
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together in the...
To hold positively charged protons together in the...
Microbes and Other Elemental Cycles
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...
Atomic Mass
Atoms — and the protons, neutrons, and electrons that compose them — are extremely small. For example, a carbon atom weighs less than 2 × 10−23 g. When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the atomic mass unit (amu). The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are...
Conditions on Early Earth
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
