92Nb-(92)Zr和行星体的早期分化历史
1Zentrallabor für Geochronologie, Mineralogisches Institut, Universität Münster, Corrensstrasse 24, 48149 Münster, Germany. Institut für Planetologie, Universität Münster, Wilhelm Klemm Strasse 10, 48149 Münster, Germany.
概括
-92--92系统揭示了早期的行星分化. 根据同位素数据,地球和月球的酸盐储库在石形成后超过5000万年形成.
科学领域:
- 太空化学 太空化学
- 地质时间学 (Geochronology)
- 行星科学 行星科学
背景情况:
- -92--92 ((92) Nb- ((92) Zr) 灭绝的放射性衰变系统提供了一个用于测年早期太阳系事件的工具.
- 了解早期的行星分化对于重建行星形成和进化至关重要.
- 之前的研究使用了各种同位素系统来限制这些过程的时间.
研究的目的:
- 利用 (92) Nb-(92) Zr衰变系统,在陆地行星和石的早期分化上建立新的时间限制.
- 调查地球和月球相对于早期太阳系材料的酸盐水库形成的时间.
主要方法:
- 在各种地质样本中分析同位素丰度,特别是 (92) Zr.
- 测量来自阿伦德石的富含含量 (CAI) 的 (92) Zr 缺陷.
- 来自地球,月球和石样本的同位素数据的比较.
主要成果:
- 地球和最古老的月球皮表现出 (92) Zr. 的相对丰度.
- 在阿连德石CAI中, (92) Zr的缺陷使太阳系的初始 (92) Nb / 93) Nb比率限制在至少0.001.
- 在陆地和月球样本中没有显著的 (92) Zr异常,这表明大型酸盐储库的形成延迟了.
结论:
- 地球和月球上主要的酸盐储库的形成,如岩海洋残留物或枯竭的地幔,发生在最古老的石形成后的5000多万年.
- (92) Nb-{92) Zr系统为早期行星分化的时间尺度提供了强大的约束,突出了最早的太阳系固体的形成和大型行星天体的分化之间的显著时间差距.
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