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颗粒边界扩散不能解释深层地幔的W同位素异质性
Yihang Peng1, Takashi Yoshino2, Jie Deng3
1Department of Geosciences, Princeton University, Princeton, NJ, USA. yhpeng@princeton.edu.
Nature communications
|February 21, 2025
概括
来自地球核心的 (W) 扩散不太可能解释海洋岛基岩中的同位素变异. 分子动力学模拟表明,W扩散在核心-地幔边界太慢,无法影响岩石中的W同位素.
科学领域:
- 地质化学 地质化学
- 地质物理学 地质物理学
- 材料科学 材料科学 材料科学
背景情况:
- 与大质量地幔相比,海洋岛屿玄武岩显示出明显的 (W) 和 (He) 同位素比率.
- 这些异常表明地球核心通过核心-地幔相互作用的贡献.
- siderophile元素的粒度边界扩散被认为是这种相互作用的关键机制.
研究的目的:
- 在核心-地幔边界条件下,研究 (W) 在铁烯酸粒边界和 (Mg,Fe) O液体中的扩散.
- 评估粒度边界扩散作为核心-地幔交换W同位素的机制的可行性.
- 为了确定核心-地幔相互作用对陆地岩石中W同位素组成的潜在影响.
主要方法:
- 采用大规模的分子动力学模拟.
- 利用了初始质量的机器学习潜力,以实现高精度.
- 在ferropericlase粒边界和 (Mg,Fe) O液体中模拟W扩散.
主要成果:
- 在模拟的核心-地幔边界条件下,发现的扩散缓慢.
- 沿铁烯酶粒边界的W扩散速度不足以显著的核心-地幔交换.
- 在 (Mg,Fe) O液体中的W扩散也不支持实质性同位素修饰.
结论:
- 谷物边界扩散W不太可能是核心-地幔相互作用的有效机制.
- 在海洋岛基岩中观察到的W同位素变化并不能通过这种拟议的扩散过程来解释.
- 核心-地幔相互作用可能通过不同的机制发生,或者同位素异常的来源在其他地方.
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