オスミウム187/オスミウム186は,マンガンの結節と白期と三次期の境界にある
まとめ
惑星系におけるオスミウム187/オスミウム186の比率は,レニウム187の腐敗により,時間とともに進化する. 地球 地球 地球 地球 地球 地球
科学分野:
- 地質化学 地質化学
- 宇宙化学 (コスモケミストリー)
- 同位体地質学とは,同位体地質学である.
背景:
- レーニウム-187 (4.6 x 10^10年) からオスミウム-187への放射性崩壊は,惑星系におけるオスミウム-187/オスミウム-186の比率に影響を与える.
- この比率は時間の関数であり,初期レニウム187/オスミウム186の比率は,マントルや地殻などの異なる惑星の貯水池によって異なります.
研究 の 目的:
- 様々な地球と海洋のサンプルにおけるオスミウム187/オスミウム186の比率を調査する.
- 地質学的形成におけるオスミウムの起源を評価し,特に白亜紀と地質学界の境界で.
主な方法:
- オスミウム187/オスミウム186の比率を隕石,地球のマントル,大陸の地殻,海洋のマンガネスノードル,白期と三次期の境界層で分析した.
- オスミウムの起源と進化を追跡するために,同位体シグネチャーを利用する.
主要な成果:
- 典型的な隕石と地球のマントルのレニウム187/オスミウム186の比率は約3.2で,現在のオスミウム187/オスミウム186の比率は約1.6です.
- 地球の大陸地殻 (レニウム187/オスミウム186比率~400,年齢2×10^9年) は,オスミウム187/オスミウム186比率が~10.0と予想されている.
- 海洋マンガンのノードルには,大陸の入力とマントルのオスミウムと一致する比率 (6-8.4) が示されています.
- クレータ紀と三次紀の境界層にはオスミウム187/オスミウム186の比率が低い (1.65海洋,1.29大陸).
結論:
- クレタチウム-三次元の境界層で観測されたオスミウム187/オスミウム186の比率は,オスミウムの主に隕石の起源を示唆しています.
- 同位体分析は,惑星の進化における物質の源泉と混合を理解するための強力なツールです.
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