现代海洋岛基岩中的-182异质性
Andrea Mundl1, Mathieu Touboul2, Matthew G Jackson3
1Department of Geology, University of Maryland, College Park, MD 20742, USA. amundl@umd.edu.
概括
海洋岛基岩 (OIB) 的新研究揭示了含有金属和贵重气体的古老地球领域. 这些发现表明特定的深层地幔结构,超低速度区域,是独特的OIB同位素特征的来源.
科学领域:
- 地质化学
- 同位素地质学
- 星球科学
背景情况:
- 海洋岛基岩 (OIB) 提供了关于地球地幔组成和演变的见解.
- 之前的研究已经注意到OIB同位素组成的变化,暗示有异质地幔来源.
- 地球和太阳系的早期历史在某些地幔领域留下了独特的化学特征.
研究的目的:
- 调查来自夏威夷,萨摩亚和冰岛的OIB异常 (W) 同位素比例的来源.
- 将同位素数据与OIB中的同位素比率 (3He/4He) 相对应.
- 为了确定地球的深层结构负责托管古老的,化学上不同的地幔水库.
主要方法:
- 来自现代OIB样本的新同位素数据 (182W/184W) 的分析.
- 将W同位素数据与相同OIB样本的现有3He/4He数据进行比较.
- 地化学建模以推断潜在地幔源区域的特征.
主要成果:
- 来自夏威夷,萨摩亚和冰岛的OIB中的同位素比率显示出显著的变化,其中一些比率高达18ppm低于环境上层地幔.
- 在182W/184W比和3He/4He比之间观察到负相关性.
- 这些同位素变化表明,在太阳系历史上最初的6000万年内形成的地幔领域的参与.
结论:
- OIB系统采样了自地球早期形成以来一直孤立的古老的陆地领域.
- 这些古老的领域以金属的存在为特征,
- 在夏威夷,萨摩亚和冰岛下面的超低速度区域 (ULVZ) 被认为是这些古代水库的最可能的候选人,解释了观察到的同位素异常.
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