結合された186Osと187Osは,コアとマントルの相互作用の証拠です
1A. D. Brandon, R. J. Walker, J. W. Morgan, Isotope Geochemistry Laboratory, Department of Geology, University of Maryland, College Park, MD 20742, USA. J. W. Morgan, Department of Earth Resources, Colorado State University, Fort Collins, CO 80.
まとめ
オスミウムイソトープの分析により,ハワイのピクリティック・ラバには,外側のコア材料が含まれていることが明らかになった. これは,いくつかのマントルの羽根がコアマントルの境界で発生し,同位素のサインによって区別できると示唆しています.
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.
- 惑星科学は惑星科学である.
背景:
- マントルの羽根は,地球マントルから上昇する熱い岩の管道です.
- マントルの羽根の起源と構成は,地球の深い過程の洞察を提供します.
- オスミウムイソトープ (186Os/188Osと187Os/188Os) は,マントル源の敏感なトレーサーである.
研究 の 目的:
- オスミウム同位体地化学を用いてハワイのピクリティック・ラバの起源を調査する.
- マントルの羽根が地球の核からの物質を組み込むことができるかどうかを判断するために.
- オスミウムイソトープを深層マントル源と浅層マントル源を区別するためのツールとして確立する.
主な方法:
- オスミウム-186/オスミウム-188 (186Os/188Os) とオスミウム-187/オスミウム-188 (187Os/188Os) の比率をハワイのピクリティック・ラバサンプルで正確に測定した.
- 同位体データをコンドリート上層マントルと潜在的コア材料の組成と比較.
- マントルとコア材料の混合シナリオのモデリング.
主要な成果:
- ハワイのピクリト岩は,コンドリト上層マントルに比べて186Os/188Os (0.0080.018%) と187Os/188Os (5.49.0%) の濃度が著しく濃縮されている.
- これらのカップリングされた同位体濃縮は,D"層の一部に0.51重量%の外部コア金属の添加によって最もよく説明されます.
- この混合物は,観測されたピクリティック・ラバを形成するために上流した.
結論:
- ハワイの下にあるようなマントルの羽根は,コアとマントルの境界で発生する可能性がある.
- 外部コアの材料をマントルに組み込むことは,実行可能なプロセスです.
- オスミウムイソトープは,コア-マントルの境界を含む,浅い対深いマントルの領域からのマントルの羽根を区別するための強力なツールとして機能します.
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