现代弧形中的古代地幔:在izu-bonin-mariana前弧形中的同位素 peridotites
Parkinson1, Hawkesworth, Cohen
1Department of Earth Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA, UK.
概括
来自伊祖-博宁-玛丽亚纳前弧的地幔矿石中的同位素揭示了古代枯竭事件. 这些发现表明,俯冲区可能保留了早期地幔融化的证据,影响了我们对对流的上层地幔的理解.
科学领域:
- 地质化学 地质化学
- 石化学 石化学是一门学科.
- 同位素地质学的同位素.
背景情况:
- 地幔周周提供了对地球地幔组成和演变的洞察.
- 奥斯 (Os) 的同位素是地幔过程的敏感标记物,这是由于Os的高度 siderophile性质和长寿命的同位素.
研究的目的:
- 为了研究来自伊祖-博宁-马里亚纳前弧的地幔矿中的同位素组成.
- 确定这些同位素特征对理解古代地幔融化事件和潜水区过程的影响.
主要方法:
- 在地幔周石样本中分析同位素比率 (187Os/188Os).
- 基于同位素数据计算原生代模型年龄.
- 与中海基岩 (MORB) 来源的矿组成的比较.
主要成果:
- 桃石表现出非放射性187Os/188Os比率,从0.1193到0.1273.3不等.
- 这些比率给出了原生生态模型的年龄在8.20亿至1.23亿年前之间.
- 这些石所指出的被耗尽的地幔源比MORB源更显著地耗尽了不兼容的元素.
结论:
- 前方弧矿石中的同位素记录了对流的上层地幔中古代的融化事件,早于最近的沉降开始.
- 俯冲区作为古老,枯竭的地幔物质的存储库.
- 对流动的上层地幔的部分可能具有比以前推断的更少的放射性同位素组成.
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