月球岩海洋固化在4.43亿年前完成
Nicolas Dauphas1, Zhe J Zhang1, Xi Chen1
1Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637.
概括
月球在4,429 ± 7600万年前完成了99%以上的结晶,这表明月球形成的年龄较早. 这种结晶发生在早期的行星轰炸期间,受到KREEP丰富的月球岩海洋的影响.
科学领域:
- 月球地质学和行星科学.
- 放射测年法和同位素地质化学
- 太阳系早期的进化过程
背景情况:
- 月球岩海洋 (LMO) 是解释月球化学演变的关键概念.
- KREEP (,稀土元素,) 是由LMO结晶产生的独特化学成分.
- 以前对LMO结晶完成的估计有很大的差异.
研究的目的:
- 为了精确确定月球岩海洋结晶的年龄.
- 为了限制月球的形成年龄.
- 调查KREEP组件的起源和时间.
主要方法:
- 分析月球子中的Lu-Hf衰变系统.
- 月球样本的放射测年测定以确定U-Pb年龄.
- 同位素数据与热和积累模型的比较.
主要成果:
- 月球在4429 ±76万年前实现了>99%的结晶.
- 这表明月球形成年龄大约为4,450万年前或更早.
- 富含KREEP的水库在太阳系形成后约1.4亿年形成,Hf比较低.
结论:
- 月球岩海洋结晶发生在月球历史的早期,与行星积聚重叠.
- 海玄武岩来源的时间可能与撞击事件有关,而不是LMO结晶.
- 对南极-艾特肯盆地样本的进一步分析可以澄清KREEP分布及其早期月球意义.
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