在里昂热点源中通过异常的Nd/Nd比率保存的酸盐差异化
Bradley J Peters1, Richard W Carlson1, James M D Day2
1Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington DC 20015, USA.
Nature
|March 2, 2018
概括
在里昂尼奥岛的玄武岩中发现了超过43.9亿年历史的古老地球领域. 这些火山岩显示出早期差异化和混合的同位素证据,
科学领域:
- 地质化学
- 同位素地质学
- 星球科学
背景情况:
- 活跃的火山热点进入了地球的深层区域,
- 同位素揭示了地球在最初的5000万年中的早期差异化.
- 新同位素很难用于追踪早期的地球组成事件.
研究的目的:
- 在里昂尼岛岩石中研究新同位素组成 (Nd/Nd144).
- 为了确定这些岩石是否跟踪了地球前5亿年的组成事件.
- 了解地球内部古老异质的形成和保存.
主要方法:
- 在里昂尼岛岩石中分析142Nd/144Nd比率.
- 同位素比的142和144的相关性分析 (3和4).
主要成果:
- 里昂尼奥岛的岩石呈现142Nd/144Nd比率,比现代的上层地幔域高或低.
- 142和144的比率与3和4的比率相关,这表明在早期的酸盐分化过程中 (可能早在43.9亿年前) 有平行行为.
- 观察到的142Nd/144Nd比率表明,至少有一次哈迪时代的融化事件 (4.56至40亿年前) 的融化和残留物混合在一起.
结论:
- 雷昂尼火山的岩石来自一个古老的原始源头,
- 这些同位素标志表明,高效的哈迪时代后混合几乎消除了异常的早期Nd标志.
- 这些发现提供了关于地球深处古老异质的形成和保存的见解.
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