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地球和月球系统之间的Nd同位素变化
Shelby Johnston1, Alan Brandon2, Claire McLeod3
1Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA.
地球和月球共享类似的构建块,其 (Sm) / (Nd) 比重高于. 这一发现简化了月球形成模型,并表明在月球形成撞击期间没有Sm/Nd分离.
科学领域:
- 星球科学
- 地质化学
- 宇宙化学
背景情况:
- 了解地球和月球的形成需要重建它们的原始构建块.
- 新 (Nd) 同位素和 (Sm) /Nd比率是这些早期材料的关键标记物.
- 之前的研究将地球的Nd142和Nd144比率的差异解释为核合成变异,这意味着它们的前体具有相似的Sm/Nd比率.
研究的目的:
- 准确地确定地球和月球的前体材料的Sm/Nd比率.
- 重新评估地球构建块的初始比例.
- 澄清地球月球系统形成和月球差异化的含义.
主要方法:
- 对新 (Nd) 和 (Sm) 同位素系统的分析,特别是Sm-142和Sm-143衰变链.
- 地球,月球和各种石群之间的同位素比较.
- 模拟同位素演变以限制初始的Sm/Nd比率和Nd/Nd.
主要成果:
- 地球和月球的 (Sm) / (Nd) 比率大约高于的平均值2.4%.
- 地球前体材料的初始142 Nd/144 Nd比率比以前建议的更类似于恩斯泰特.
- 这些发现挑战了核合成同位素变异作为地球142 Nd异常的唯一解释的概念.
结论:
- 观测到的地球和石之间的Sm/Nd比率差异可能源于内部原行星盘混合期间的矿物学分离.
- 月球的分化可以通过从岩海洋形成到凝固的单阶段过程来解释.
- 在巨大的撞击事件中,原地球和月球之间没有发生显著的Sm/Nd分离.
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