まとめ
ルビジアム・ストロンチウム年代測定により,バーモント州のバーレ型花岩は少なくとも3億8千万年前のものであることが明らかになった. この発見は,アカディアのオーロゲニーが急速な出来事であり,おそらく大陸板の衝突によって引き起こされたことを示唆しています.
科学分野:
- 地質学 地質学 地質学
- ジオクロノロジー (Geochronology) について
- テクトニクス (地質学) とは
背景:
- アカディアのオロジェニー (Acadian orogeny) は,北アパラチア山脈における重要な地質学的出来事である.
- 以前のモデルでは,アカディアのオロゲニーが長期間続いたと示唆されていた.
- 岩質体の位置のタイミングは,オロゲニックプロセスを理解するために重要なデータを提供します.
研究 の 目的:
- ヴァーモント州東部のバーレ型花岩の正確な年齢を決定するために.
- アカディアのオロゲーニスのタイムラインを精錬するために.
- アカディアのオロゲニスを駆動する構造的メカニズムに関する仮説を検証する.
主な方法:
- ルビジアム・ストロンチウム (Rb-Sr) ジオクロノロジーは,花岩のサンプルの年代測定に用いられました.
- バール型花岩の特徴を特定するために,地化学分析が行われました.
- ヴァーモント州東部の地質学的な地図作成は,日付付きのサンプルに文脈を提供した.
主要な成果:
- ルビジアム・ストロンチウム年代測定により,バーレ型花岩の埋立年齢は少なくとも3億8千万年となった.
- データは,花岩の侵入の比較的短い時間枠を示しています.
- この発見は,アカディアの漸進的なオロゲーニスを提案するモデルと矛盾している.
結論:
- アカディアのオーロゲニーは,これまで考えられていたよりも急速に起こったのかもしれない.
- グラニット積層のタイミングは,2つのシアリックプレート間の大陸衝突のモデルをサポートしています.
- この研究は,アパラチア・テクトニック・モデルの重要な地質年代学的な制約を提供します.
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