東太平洋の下の融解運動の制約は,230Th-238Uの不均衡から上昇する
Haibo Zou1, Alan Zindler, Yaoling Niu
1Department of Earth and Space Sciences, University of California at Los Angeles, Los Angeles, CA 90095, USA. hzou@ess.ucla.edu
まとめ
中洋のの玄武岩は,東太平洋上昇から対称的に噴火し,大規模な地下溶融輸送を示唆しています. この研究は,山脊軸から離れたところで見つかった濃縮された玄武岩の起源についての洞察を提供します.
科学分野:
- 地質化学 地質化学
- ペトロロジー・ペトロロジーとは
- 海洋地質学 海洋地質学
背景:
- 中洋のの玄武岩 (MORBs) は,地球のマントルのプロセスに関する重要な情報を提供します.
- off-axis火山活動を理解することは,マグマの輸送と分化を解読する鍵です.
- これまでの研究は,主にオンアックスプロセスに焦点を当てていました.
研究 の 目的:
- イースト・パシフィック・ライズから遠ざかるバザルト溶融の起源と輸送を調査する.
- オフ・アックス・ベザルトにおける230Th-238U不均衡を分析する.
- 互換性のない元素を濃縮した中洋ベースタルト (EMORBs) の石化を抑制する.
主な方法:
- バサルトサンプルにおける230Th-238U不均衡の分析.
- 普通の中洋のベースタルト (NMORBs) とEMORBsの地化学的特徴.
- ゲオロジカルマッピングと山頂軸から異なる距離にある火山岩のサンプリング.
主要な成果:
- NMORBとEMORBのほぼ対称な噴火は,軸から20kmまで観測されました.
- NMORBの溶解の大規模な地下横向輸送の証拠は,年に19〜21cmの速度で溶解しています.
- off-axis EMORBsで特定された明確な地化学的シグネチャー.
結論:
- 地下溶融輸送は,軸外火山活動において重要な役割を果たしています.
- オフアックスで見つかったEMORBは,ユニークなペトロジェネティックの歴史を持っています.
- この発見は,海中のマグマチズムに関する伝統的なモデルに異議を唱えている.
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