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Updated: Jun 24, 2026

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Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level
Published on: June 6, 2018
226Ra-230Thの系統学から,島弧の溶融の源から表面への超高速移動
S Turner1, P Evans, C Hawkesworth
1Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK. simon.turner@bristol.ac.uk
まとめ
アイランド・アーク・ラバは,他の火山岩よりも高いラジウム-226の過剰を示しており,これはプレート流体の潜水によって導入されたことを示している. この急速な輸送は,マントルの溶融分離とチャネル形成が急速に起こることを示唆しています.
科学分野:
- 地質化学 地質化学
- イソトープ地球化学 イソトープ地球化学
- マントル・ペトロロジー マントル・ペトロロジー
背景:
- アイランド・アーク・ラバは,高濃度のラジウム-226 (226Ra) を含む独特の地化学的特徴を示しています.
- これらの過剰は,海中ベースタルト (MORB) や海洋島ベースタルト (OIB) に見られるものよりも著しく高い.
研究 の 目的:
- 島岩のラジウム-226過剰の起源を調査する.
- サブドクションゾーンにおける溶融輸送とマントルの過程の時間スケールを制限するために.
主な方法:
- 原始的および微分された島弧の溶岩におけるラジウム-226とトリウム-230の比率の分析.
- 226Ra/230Th比の主要元素および微量元素の組成 (例えば,Ba/Th) との相関.
主要な成果:
- アイランド・アーク・ラバは,MORBとOIBを上回る226Raを大幅に上回っている.
- 初期226Ra/230Th比が最も高いのは,最も原始的な溶岩で観察され,高いBa/Th比と相関しています.
- ラジウム-226の過剰は,マグマの分化が増加するにつれて減少する.
結論:
- 潜水したプレート液体は,マントルの溶融柱の底部にある226Ra濃縮の発生源である可能性が高い.
- 226Ra信号の保存は,表面への急速な輸送 (数百年) を意味します.
- 平均的な融解速度は,年間約1000メートルに制限されており,迅速なマントルの融解分離とチャネル形成を示している.
関連する概念動画
Radioactivity and Nuclear Equations
Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for hydrogen, neutrons. The number of protons in the nucleus is called the atomic number (Z) of the element, and the sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are isotopes of the same element.
A nuclide of an element has a specific number of protons and...
A nuclide of an element has a specific number of protons and...
Types of Radioactivity
The most common types of radioactivity are α decay, β decay, γ decay, neutron emission, and electron capture.
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
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...
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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 Fission
Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger binding energies per nucleon—that is, mass numbers and binding energies per nucleon that are closer to the “peak” of the binding energy graph near 56. Sometimes neutrons are also produced. This decomposition of a large nucleus into smaller pieces is called fission. The breaking is rather random with the formation of a large number of different...
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...

