近日，成都理工大学王达团队研究了地幔现存巨大撞击前成分的钾-40同位素证据。相关论文于2025年10月14日发表在《自然—地球科学》杂志上。
地球的整体组成具有元素和同位素特征，这些特征不能与已知原始陨石组成的混合物完全一致。一种可能的解释是，原地球吸积的物质具有同位素特征，与月球形成大碰撞后吸积的物质不同。
研究组报告了用热电离质谱法对来自地幔和地幔中各种古代和现代地层的陆相岩石进行的高精度质量无关的钾同位素测量，他们认为这与这种解释是一致的。具体而言，他们发现源自冥古宙—始太古代地幔的某些太古宙镁铁质岩石（包括来自伊苏阿、努夫瓦吉图克和卡普瓦尔克拉通的样本）以及部分现代洋岛玄武岩（来自留尼汪岛和夏威夷卡美哈美亚火山）与所有其他已分析的陆地样本相比，平均表现出百万分之65的40K缺失特征。
附：英文原文
Title: Potassium-40 isotopic evidence for an extant pre-giant-impact component of Earth’s mantle
Author: Wang, Da, Nie, Nicole X., Peters, Bradley J., Day, James M. D., Shirey, Steven B., Carlson, Richard W.
Issue&Volume: 2025-10-14
Abstract: Earth’s bulk composition has elemental and isotopic characteristics that cannot be fully reconciled with a mixture of known primitive meteorite compositions1,2,3. One potential explanation for this is that the proto-Earth accreted materials with isotopic signatures distinct from those accreted after the Moon-forming giant impact. Here we report high-precision mass-independent potassium isotopic measurements from thermal ionization mass spectrometry of terrestrial rocks from various ancient and modern sources in the crust and mantle that we argue are consistent with this explanation. Specifically, we found that some mafic Archaean rocks derived from the Hadean–Eoarchaean mantle (including samples from Isua, Nuvvuagittuq and the Kaapvaal Craton) and certain modern ocean island basalts (from La Réunion Island and Kama’ehuakanaloa volcano, Hawaii) exhibit an average 40K deficit of 65 parts per million compared to all other terrestrial samples analysed. The deficit distinguishes these samples from the bulk silicate Earth and any known meteorite group and cannot result from magmatic processes. Therefore, we propose this 40K deficit represents primitive proto-Earth mantle domains that largely escaped mantle mixing after the giant impact and exist in the present-day deep mantle, contributing to some modern hotspot volcanism.
DOI: 10.1038/s41561-025-01811-3
Source: https://www.nature.com/articles/s41561-025-01811-3