行星核心和地球月球系统从Nb/Ta系统学的演变
Carsten Münker1, Jörg A Pfänder, Stefan Weyer
1Institut für Mineralogie, Corrensstrasse 24, Universität Münster, 48149 Münster, Germany. muenker@nwz.uni-muenster.de
概括
尼奥比 (Nb) 在高压下被发现是中度的 siderophile,挑战以前的假设. 这一发现影响了我们对行星分化和月球形成历史的理解.
科学领域:
- 地质化学 地质化学
- 行星科学 行星科学
- 太空化学 太空化学
背景情况:
- (Nb) 和 (Ta) 传统上被认为是光电元素,这意味着它们优先与酸盐相结合.
- 以前的假设表明,在行星分化过程中没有Nb和Ta的显著分化.
- Nb/Ta的混凝土比率是理解行星组成的关键参考点.
研究的目的:
- 研究Nb和Ta在高压分化过程中的行为.
- 根据高精度同位素测量,重新评估Nb的 siderophile性质.
- 为了限制月球和地球的组成和形成.
主要方法:
- 高精度测量/ (Nb/Ta) 的比率.
- 高精度测量/哈夫 (Zr/Hf) 的比率作为一个比较的代理.
- 在大量酸盐地球,月球,火星和小行星中分析Nb/Ta值.
主要成果:
- 高精度测量显示, (Nb) 在高压下适度 siderophile (爱铁),与此前的信念相反.
- 大量酸盐地球 (14.0 ± 0.3) 和月球 (17.0 ± 0.8) 的Nb/Ta比率明显低于合体比率 (19.9 ± 0.6).
- 火星和小行星的Nb/Ta比率更接近于体价值,这表明它们有不同的分化历史.
结论:
- 观察到的Nb/Ta比率表明,在高压下的行星分化过程中,Nb经历了碎裂成金属核心.
- 月球Nb/Ta比率将月球形成撞击物质的质量分数限制在65%以下.
- 月球形成的撞击事件与地球的最终核心-地幔平衡暂时相关,大约发生在4533亿年前.
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