侵襲的なマグマティズムによって制御された初期の地球上の大陸の地殻形成
A B Rozel1, G J Golabek2, C Jain1
1Institute of Geophysics, ETH Zurich, 8092 Zurich, Switzerland.
Nature
|May 9, 2017
まとめ
初期の地球
科学分野:
- 地理科学
- 惑星科学
- 初期の地球力学
背景:
- プレートテクトニクスの前の初期の地球の地動力学的な体制は議論されている.
- 古代のマントルの気温とマグマティズムは今日より高かった.
- 熱管構造 (火山学が支配する) と プルトニクスの柔らかい蓋 (侵入性マグマティズムが支配する) の2つのモデルが存在する.
研究 の 目的:
- 原始的なトナリート・トンドヘミット・グラノディオライト (TTG) の大陸地殻の形成を調査する.
- 熱管とプルトニクスの構造を 検証する
- 観測されたTTGの組成を最もよく説明する初期の地球地力学的体制を決定する.
主な方法:
- グローバル熱化学コンベクションの自己一貫した数値モデルを使用した.
- モデルにマグマを組み込みました
- 噴火効率に関する体系的なパラメータ研究を行いました.
主要な成果:
- 熱管構造モデルは冷たい地殻の地熱を生み出し,地球のような原始の大陸地殻を生成しなかった.
- プルトニクスの柔らかい蓋のモデルは,地殻のより熱い地熱を生み出し,観測されたTTG岩の割合を成功裏に再現した.
- プルトニックのスプッシー・デックモデルでは,低圧,中圧,高圧TTGのフィールドデータと一致する噴火効率が40%以下であった.
結論:
- 侵襲的なマグマティズムによって特徴づけられる プルトニックの柔らかい蓋の構造は,熱管構造よりも初期の地球の地殻形成のより妥当なモデルである.
- この発見は,プレート構造の出現以前には,地球全体でプルトニクスの柔らかい蓋の体制の下で活動していたことを示唆している.
- この研究は,原始的なTTGの地殻の発生を説明するために,プルトニックの柔らかい蓋のモデルに強力な数値的な支持を提供します.
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