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在阿佐尔群岛,有循环的古老海洋地幔石化层的证据
Bruce F Schaefer1, Simon Turner, Ian Parkinson
1Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.
Nature
|November 26, 2002
概括
来自阿佐尔群岛玄武岩的同位素数据揭示了耗尽的哈兹堡地幔来源,这表明古老的海洋石化层的深层地幔回收. 这一发现限制了地幔对流模型和羽毛异性.
科学领域:
- 地质化学 地质化学
- 同位素地球化学 同位素地球化学
- 地幔石器学地幔石器学
背景情况:
- 地幔对流和羽毛动力学影响着玄武岩的组成.
- 玄武岩化学的空间变化可能反映了地幔异质性.
- 海洋岛基岩 (OIBs) 和中海基岩 (MORBs) 呈现出明显的组成差异.
研究的目的:
- 使用同位素数据调查地幔羽毛异质的起源.
- 限制阿佐尔斯半岛地幔羽毛的组成和起源.
- 探索地幔对流动和地球深层过程的影响.
主要方法:
- 在阿佐尔群岛的岩中分析 (Os) 同位素比例 (187Os/188Os).
- 将Os同位素数据与已知的OIB和MORB组成进行比较.
- 耗 (Re-dep) 模型年龄计算.
主要成果:
- 阿佐尔斯岛的岩在假定的羽毛中表现出对称的同位素组成模式.
- 许多中央岩岩显示的187Os/188Os比率低于典型的OIB,其中一些延伸到亚粒体值.
- 低的187Os/188Os比率表明它来自一个枯竭的哈兹堡地幔源.
- 重深模型的年龄达到25亿年 (Gyr).
结论:
- 奥斯同位素的特征不太可能起源于伊比利亚次大陆的岩层地幔.
- 数据表明,阿佐尔群岛羽毛的签名来自深层地幔.
- 这些发现支持了阿古时代海洋地幔石化层的分层和回收.
- 提供了深层地幔沉积和石质层储存的证据.
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