2021年,アイスランドのファグラダルスフィヤル火災中の地殻の深層吸収
James M D Day1, Savannah Kelly2, Valentin R Troll3,4
1Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA. jmdday@ucsd.edu.
Nature
|July 31, 2024
まとめ
2021年のFagradalsfjall噴火の溶岩は,典型的な2022年の溶岩とは異なり,重要な地殻汚染を示しています. これは最初のマグマの停滞と同化を示し,その後の噴火では効率的なマグマ輸送が続く.
科学分野:
- 地化学
- 火山学
- 同位体地質学
背景:
- 活発なベースルト噴火は,地化学的および地物理的なデータのタイムシリーズ分析の機会を提供します.
- アイスランドのレイクヤネス半島で2021年以来のFagradalsfjallとSundhnúkurの火山活動は,ユニークなケーススタディを提供します.
- 以前の解釈では 初期の溶岩は 深いマントルの源流を反映していた
研究 の 目的:
- 2021年のFagradalsfjall噴火からの溶岩の地化学組成を調査する.
- 最古の噴火産物における小分結晶化と地殻汚染の役割を決定する.
- 噴火過程の変化を理解するために2021年と2022年の溶岩の地化学的サインを比較する.
主な方法:
- 火山の溶岩におけるオスミウム (Os) の同位体の分析
- プラチナ (Pt) とイリジウム (Ir) の濃度測定
- アイソトープと元素の比率をアイスランドと世界の玄武岩と比較する.
主要な成果:
- 2021年のFagradalsfjallの溶岩は,非常に異常なオスミウム同位体比とプラチナ/イリジウム比を示し,重要な地殻汚染を示しています.
- 汚染は,大洋の真ん中の山頂のガブロと古い玄武岩の同化によって引き起こされた.
- 2022年の溶岩はアイスランドに特有の塩基岩の組成を示し,地殻汚染の証拠はありません.
結論:
- 2021年のファグラダルフヤル噴火の開始には,噴火前のマグマの停滞,断片的な結晶化,地殻物質の同化が含まれていた.
- 2022年に確立されたマグマ導管システムは,重要な地殻吸収なしに効率的なマグマ上昇を促進しました.
- オスミウムイソトープは,活発な火山系における地殻汚染を特定するための強力なトレーサーである.
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