182W证据证明了早期地幔分化的产品的长期保存
Mathieu Touboul1, Igor S Puchtel, Richard J Walker
1Department of Geology, University of Maryland, College Park, MD 20742, USA. mtouboul@umd.edu
概括
地球的早期地幔可能没有完全混合,古代岩石中的同位素证明了这一点. 科斯托穆克沙科马提石显示出明显的 (182W) 签名,表明一个保存的原始水库.
科学领域:
- 地质化学 地质化学
- 同位素地质学的同位素.
- 行星科学 行星科学
背景情况:
- 地球的地幔可能含有同位素异质,由于晚期积聚,早期分化和核心-地幔相互作用等过程.
- (W) 同位素,特别是182W,是早期行星进化和地幔过程的敏感标志物.
- 以前的研究表明,地球地幔内可能存在保存的原始水库.
研究的目的:
- 为了研究地球地幔中同位素异质的起源.
- 为了确定太阳系历史早期形成的原始水库是否存在于地幔中.
- 通过同位素分析来限制地幔混合的时间和程度.
主要方法:
- 在古代科马提石 (科斯托穆沙和科马蒂) 中分析 (182W) 同位素组成.
- 使用Os (186,187Os) 和Nd (142,143Nd) 系统进行联合同位素分析.
- 来自不同地质样本和时间段的同位素数据的比较.
主要成果:
- 与现代陆地样本相比,Kostomuksha komatiites (28亿年前) 的显著过剩是182W.
- 科马提科马提石 (年龄35亿年) 没有显示出这种182W的过剩.
- 综合的同位素数据表明,Kostomuksha komatiites的地幔源含有原始储库,可能来自早期的金属酸盐平衡或岩分化.
结论:
- 一个原始的水库,可能是在太阳系最初的3000万年内形成的,在地球地幔中持续到至少28亿年前.
- 这个水库的存在和保存表明,地球地幔可能没有经历完全的混合.
- 这些发现对理解陆地行星的早期分化和演化有意义.
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