カリフォルニアの急激な後期白期の地殻形成のためのラマーク・グラノディオライトからの証拠
Science (New York, N.Y.)
|December 18, 1992
まとめ
ストロンチウムとネオジミウムの同位体は,シエラネバダのバトロリスのラマークの侵入的なスイートを明らかにし,豊かなマントルの源泉から発生した. この発見は,米国における白期のマグマチズム中に,重要な若年地殻の追加を示唆しています.
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.
- ペトロロジー・ペトロロジーとは
背景:
- シエラネバダのバトロリフは北米のコルディレラの主要な構成要素です.
- その石油生成を理解することは,地殻の成長プロセスを解読する鍵です.
- ラマークの侵入スイートは,バトロリフ内の重要なマグマイベントを表しています.
研究 の 目的:
- ラマークの侵入的なスイートの起源と進化を調査するために.
- シエラネバダバソリスの形成におけるマントル源の役割を評価する.
- 米国西部の地殻の成長率の推定を精査する.
主な方法:
- ストロンチウムとネオジミウムの同位体の分析. ギャブロイク岩と花岩の岩石.
- ラマークの侵入スイートの地化学的特徴.
- 既知のマントルと地殻の貯蔵庫との同位体データの比較.
主要な成果:
- 同位体データ (ストロンチウムとネオジミウム) は,ラマークスイートの組成スペクトル全体で最小の変動を示しています.
- ガブロの侵入は同一の同位体シグネチャを生成し,マントルの豊かな源から派生したものである.
- この発見は,この地域の地殻の成長に関する以前の仮定に異議を唱えている.
結論:
- ラマークの侵入性スイートは,マントルの濃縮された源から形成された可能性があり,局所的なマントルの関与を示しています.
- この関与は,米国における地殻の成長率の見積もりを見直す必要がある.
- シエラネバダのバトロリスの一部は,白亜紀中に形成された主に若年層の地殻を表している可能性があります.
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