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Helium solubility in olivine and implications for high ~3He/~4He in ocean island basalts

机译:氦在橄榄石中的溶解度及其对大洋玄武岩中〜3He /〜4He的影响

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摘要

High ~3He/~4He ratios found in ocean island basalts are the main evidence for the existence of an undegassed mantle reservoir. However, models of helium isotope evolution depend critically on the chemical behaviour of helium during mantle melting. It is generally assumed that helium is strongly enriched in mantle melts relative to uranium and thorium, yet estimates of helium partitioning in mantle minerals have produced conflicting results. Here we present experimental measurements of helium solubility in olivine at atmospheric pressure. Natural and synthetic olivines were equilibrated with a 50% helium atmosphere and analysed by crushing in vacuo followed by melting, and yield a minimum olivine-melt partition coefficient of 0.0025 ± 0.0005 (s.d.) and a maximum of 0.0060 ± 0.0007 (s.d.). The results indicate that helium might be more compatible than uranium and thorium during mantle melting and that high ~3He/~4He ratios can be preserved in depleted residues of melting. A depleted source for high ~3He/~4He ocean island basalts would resolve the apparent discrepancy in the relative helium concentrations of ocean island and mid-ocean-ridge basalts.
机译:在大洋洲玄武岩中发现的〜3He /〜4He高比率是存在不脱气地幔储层的主要证据。但是,氦同位素演化的模型主要取决于地幔融化过程中氦的化学行为。一般认为,相对于铀和th,氦在地幔熔体中含量很高,但是对地幔矿物中氦分配的估计却产生了矛盾的结果。在这里,我们介绍大气压下氦在橄榄石中的溶解度的实验测量。天然和合成橄榄石在50%的氦气气氛中平衡,然后真空破碎然后熔融进行分析,得出最小的橄榄石-熔体分配系数为0.0025±0.0005(s.d。)和最大为0.0060±0.0007(s.d。)。结果表明,在地幔融化过程中氦可能比铀和th更具相容性,并且在贫化的熔融残余物中可以保留较高的〜3He /〜4He比。耗尽〜3He /〜4He大洋玄武岩的来源将解决海洋岛和中海脊玄武岩相对氦气浓度的明显差异。

著录项

  • 来源
    《Nature》 |2005年第7062期|p.1140-1143|共4页
  • 作者单位

    Department of Earth Sciences, University of Durham, Science Labs, Durham DH1 3LE, UK;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自然科学总论;
  • 关键词

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