まとめ
ウランやソリウムのような放射性元素は,マグマの起源の時間スケールを明らかにします. その崩壊産物は,マントルの融解と地殻の分化プロセスを追跡し,火山岩の形成に関する洞察を提供している.
科学分野:
- 地質化学 地質化学
- 同位体地質学とは,同位体地質学である.
- 火山学 火山学とは
背景:
- ウランとトーリウムの短命放射性分解産物は,地質学的過程の敏感な指標である.
- ウラン-238,ソーリウム-230,ラジウム-226を含む放射性不均衡は,火山岩でよく見られる.
研究 の 目的:
- 火山岩の放射性不均衡とソリウムイソトープがマグマ発生の時間スケールを制限する方法を調査する.
- これらの同位体シグネチャーに対する融解の範囲,速度,蒸気の存在の影響を理解するために.
主な方法:
- 放射性不均衡の分析,特にウラン-238,ソーリウム-230,ラジウム-226の間の分析.
- 火山の標本におけるトリウムの同位体の組成を調べる.
主要な成果:
- 放射性不均衡は火山岩に広く存在し,マグマの発生過程を反映している.
- マントルの溶解の程度と速度は,蒸気条件とともに,観測された不均衡とトーリウム同位体に大きな影響を与える.
- マントルの融解は,数百ミレニアムにわたって起こり得るが,マグマの上昇と微分化は,より短い時間スケールで起こる.
結論:
- 短命なウラン・ソリウム分解産物は,マントルの融解と地殻の分化のタイミングに決定的な制約を与える.
- これらの元素の同位体分析は,マグマの形成と噴火の複雑な歴史を再構築するのに役立ちます.
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:
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...
Biological Effects of Radiation
All radioactive nuclides emit high-energy particles or electromagnetic waves. When this radiation encounters living cells, it can cause heating, break chemical bonds, or ionize molecules. The most serious biological damage results when these radioactive emissions fragment or ionize molecules. For example, α and β particles emitted from nuclear decay reactions possess much higher energies than ordinary chemical bond energies. When these particles strike and penetrate matter, they produce ions...
Isotopes and Radioisotopes
In the early 1900s, English chemist Frederick Soddy realized that an element could have atoms with different masses that were chemically indistinguishable. These different types are called isotopes — atoms of the same element that differ in mass. Isotopes differ in mass because they have different numbers of neutrons but are chemically identical because they have the same number of protons. Soddy was awarded the Nobel Prize in Chemistry in 1921 for this discovery.
An isotope containing more...
An isotope containing more...


