最も古い地上のマントルの貯水池が生き残った証拠
Matthew G Jackson1, Richard W Carlson, Mark D Kurz
1Department of Earth Sciences, Boston University, 675 Commonwealth Avenue, Boston, Massachusetts 02215, USA. jacksonm@bu.edu
Nature
|August 13, 2010
まとめ
バフィン島と西グリーンランドの溶岩のヘリウム同位体によって追跡された原始的なマントルの材料は,古代のソース年齢を明らかにします. これらの溶岩は,45~445億年前に遡る,地球で最も古いアクセス可能なマントルの貯水池の証拠を提供します.
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.
- 地球科学 地球科学 地球科学
背景:
- ヘリウム同位体 (3He/4He) は,地球マントルの原始的な物質の主要なトレーサーである.
- 3He/4Heの比率が高い海洋島ベースルトは,ガスのないマントルの貯蔵庫を示唆しています.
- 以前の研究では,古代マントルの形成年齢を確認する原始的な鉛同位体組成物が欠けていた.
研究 の 目的:
- バフィン島と西グリーンランドのケノゾイク期の溶岩の同位体組成を調査する.
- これらの溶岩が,原始的な鉛同位体組成物を宿しているかどうかを判断する.
- これらの古代の溶岩のマントル源の形成年齢を確立するために.
主な方法:
- 溶岩におけるヘリウム (3He/4He),鉛同位素,ネオジミウム同位素 (143Nd/144Nd) の比率の分析.
- 初期の地球マントルの形成に関するモデルと同位体データの比較.
- 同位体シグネチャーのジオクロノロジカルな解釈.
主要な成果:
- バフィン島と西グリーンランドの溶岩は,地殻と地殻の3He/4He比率が最も高い.
- これらの溶岩は原始的な鉛同位体比を有しており,古代マントルの源泉の年齢が45億~45億年であることを示しています.
- また,溶岩は143Nd/144Ndの比率を示しており,これは約45億年前の地上のマントルの貯水池と一致しています.
結論:
- 結合された同位体データは,バフィン島と西グリーンランドのラバが,地球で最も古いアクセス可能なマントルの貯水池から発生することを示唆しています.
- この古代の貯水池は,現代のすべての火山マントルの貯水池の親かもしれない.
- この発見は,地球マントルの内部で早期に形成された物質が保存されているという強力な証拠を提供します.
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