二酸化炭素に富んだシリケートは,地球の上層マントルで溶けます
Rajdeep Dasgupta1, Ananya Mallik, Kyusei Tsuno
1Department of Earth Science, Rice University, Houston, Texas 77005, USA. Rajdeep.Dasgupta@rice.edu
Nature
|January 11, 2013
まとめ
実験によると,地球マントルの炭酸シリケートの融解は,これまで考えられていたより深いところから始まり,惑星の進化とマントルの性質に影響を及ぼしている. この深層の融解の発生は,海洋上のマントルの重要な地質学的観測を説明する.
科学分野:
- 地化学と地球物理学
- 惑星科学 惑星科学
- マントル・ペトロロジー マントル・ペトロロジー
背景:
- 地球上の上層マントルの融解は,惑星の熱的進化,揮発性輸送,マントルの特性にとって極めて重要です.
- シリケート溶解の始まりの正確な深さと条件は,特に炭酸ペリドチートでは,依然として不確実です.
- 地質学的データは,約200kmの深さで融解の存在を示唆しているが,大きな融解分子は通常,浅い地域と関連している.
研究 の 目的:
- 炭酸ペリドタイトにおけるシリケート溶解の発生の圧力-温度条件と深さを実験的に制限する.
- 二酸化炭素 (CO2) と水 (H2O) が,中海の山脊の下にあるマントル・ソリドゥス (mantle solidus) に及ぼす影響を調査する.
- 低速帯と電気伝導性を含む,海洋上層マントルの地質学的観測と実験的発見を相関させる.
主な方法:
- 炭酸ペリドート石のサンプルを2~5GPaの圧力で高圧・高温実験を行った.
- 炭酸シリケート溶融曲線の圧力-温度傾斜の分析.
- 微量のH2Oが固体と融解の生成深さに与える影響をモデル化.
主要な成果:
- 炭酸シリケート溶融の圧力-温度傾きは,揮発性のないペリドチートの固体よりも急です.
- 乾燥したペリドータイトの二酸化炭素によるシリケート溶解は,山脊の下では,およそ180kmの深さで開始されます.
- 50〜200ppmのH2Oを組み込むことは,固体を圧縮し,シリケート融解の始まりを 220〜300kmの深さまで延長し, ~100ppmのCO2を持つサブリッジマントルの場合は ~100kmの深さまで延長します.
結論:
- レドックスフロント (250~200km深さ) で炭酸シリケート溶融生成は,海洋の低速帯とマントルの電気伝導性を説明する.
- 深い上層マントルは,溶融特性や導電性データによって示されるように,おそらくCO2が豊富だがH2Oが乏しい.
- 炭酸シリケート溶融は,炭酸塩の安定性を制限し,炭素,H2O,および不適合な元素の流れを制御します.
関連する概念動画
The Carbon Cycle
Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among living organisms, and one in which carbon is cycled over long periods of time through fossilized organic remains, weathering of rocks, and volcanic activity. Human activities, including increased agricultural practices and the burning of fossil fuels, has greatly affected the balance of the natural carbon cycle.
Network Covalent Solids
Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
The Sulfur Cycle
Sulfur, an important element in the chemical makeup of proteins, is recycled through the atmosphere and aquatic and terrestrial environments. Found in the atmosphere as sulfur dioxide (SO2), sulfur is released by decaying organisms, weathered rocks, geothermal vents, volcanos, and burning fossil fuels. It is deposited into the ecosystem, cycled through the biotic community, and either released back into the atmosphere as gas or deposited in marine sediment for long-term storage and eventual...
Microbes and the Sulfur Cycle
Sulfur is a vital element in Earth's biogeochemical systems. It transitions through various inorganic states, including sulfate (SO₄²⁻), elemental sulfur (S⁰), and sulfide (S²⁻). Abiotic and biological mechanisms across oxic and anoxic environments intricately mediate these transformations. Sulfate, the most oxidized form of sulfur, is predominantly stored in rocks, marine sediments, and oceanic waters, acting as a long-term reservoir in the global sulfur cycle.In oxic environments,...
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.
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.


