同位素证据表明,地幔偶尔融化和地生长
1Department of Earth Sciences, University of Durham, South Road, Durham DH1 3LE, UK. stephen.parman@durham.ac.uk
Nature
|April 20, 2007
概括
海洋岛屿玄武岩中的同位素揭示了地球大陆地的形成发生在偶尔的爆发中. 这一发现为地幔枯竭提供了比以前研究的同位素更清晰的记录.
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
- 行星科学 行星科学
背景情况:
- 地球大陆地形成的时间受到争议,模型表明早期形成,脉冲增长或稳定增长.
- 大陆地主要是由地幔的部分融化形成的,这一过程预计会留下同位素特征.
- 大多数地幔同位素系统 (例如,Sr,Nd,Pb) 都被海洋地沉降和地混合所掩盖,阻碍了地形成历史的重建.
研究的目的:
- 调查同位素是否可以提供更清晰的地幔枯竭和大陆地形成历史记录.
- 为了将海洋岛屿玄武岩中的同位素比例与拟议的大陆生长脉冲相关联.
- 测试一个新的地幔枯竭和地生长模型.
主要方法:
- 在海洋岛屿玄武岩中分析4He/3He比率的光谱.
- 同位素数据与大陆生长脉冲的拟议年龄的相关性.
- 利用同位素作为地幔枯竭的标志物,因为它的非回收性质.
主要成果:
- 海洋岛屿玄武岩中4He/3He比率的光谱与拟议的大陆生长脉冲的时间密切相关.
- 这种相关性成功地预测了中海基岩中占主导地位的4He/3He峰值.
- 该模型还提供了地球最初4He/3He比率的估计.
结论:
- 大陆地的形成是偶发的,标志着重要的,可能是全球性的融化事件.
- 同位素作为地幔枯竭历史的可靠追踪器,比其他同位素系统保持更清晰的记录.
- 拟议的同位素进化模型支持整个地幔对流,不需要原始的,无气的地幔储库.
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