在夏威夷玄武岩的源头中,有Hf同位素证据显示有海底沉积物
Blichert-Toft1, Frey, Albarede
1Ecole Normale Superieure de Lyon, 69364 Lyon Cedex 7, France. Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science (New York, N.Y.)
|August 7, 1999
概括
对夏威夷基岩石的同位素分析显示,在地幔源中存在再生的古代海洋地和沉积物. 这表明热点火山活动主要涉及沉积物质,不包括上层地幔的贡献.
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
- 石化学 石化学是一门学科.
背景情况:
- 海洋岛基岩 (OIBs) 提供了对地幔组成和过程的洞察力.
- OIB地幔源的起源,特别是回收地的作用,是地幔地化学中的一个关键辩论.
- 夏威夷的火山是OIB的经典例子,这使得它们对于理解地幔演变至关重要.
研究的目的:
- 研究夏威夷玄武岩的同位素组成,以确定它们的地幔来源的性质.
- 测试回收海洋地和沉积物对海洋岛屿玄武岩的来源有所贡献的假设.
- 为了限制上层地幔物质参与夏威夷热点玄武岩的产生.
主要方法:
- 在夏威夷玄武岩样本中测量 (Pb),氧 (O) 和 (Os) 的同位素比率.
- 高精度的哈夫 (Hf) 同位素分析来自多个夏威夷火山的岩.
- 测量的同位素比率与回收海洋地和海底沉积物的推断比率的比较.
- 分析-哈夫 (Pb-Hf) 的同位素关系.
主要成果:
- 夏威夷玄武岩中的,氧和同位素比例与回收的古代海洋地预期的比例非常接近.
- 哈夫同位素数据表明,夏威夷岩的地幔来源中存在古老的海底沉积物.
- 过度波动的Pb-Hf同位素趋势表明,上层地幔成分并不是夏威夷热点玄武岩的重要贡献者.
结论:
- 这些发现强烈支持回收假设,证实夏威夷玄武岩的地幔来源包含古老的海底地和沉积物.
- 同位素数据表明,夏威夷的热点火山活动主要由回收的岩层物质提供燃料,而不是原始的上层地幔.
- 这项研究强调了潜水过程在塑造地球地幔长期化学演变中的重要性.
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