Turner Simon, Wood Bernard, Johnson Tim, O'Neill Craig, Bourdon Bernard
School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia.
Department of Earth Sciences, University of Oxford, Oxford, UK.
Nature. 2025 Apr;640(8058):390-394. doi: 10.1038/s41586-025-08719-3. Epub 2025 Apr 2.
Although Earth, together with other terrestrial planets, must have had an early-formed protocrust, the chemical composition of this crust has received little attention. The protocrust was extracted from an extensive magma ocean formed by accretion and melting of asteroidal bodies. Both experimental and chronological data suggest that the silicate melt ascending from this magma ocean formed in equilibrium with, or after, metal was extracted to form Earth's core. Here we show that a protocrust formed under these conditions would have had incompatible (with respect to silicate minerals) trace-element characteristics remarkably similar to those of the current average continental crust. This has major implications for subsequent planetary evolution. Many geochemical arguments for when and how plate tectonics began implicitly assume that subduction is required to produce the continental trace-element signature. These arguments are severely compromised if this signature was already a feature of the Hadean protocrust.
尽管地球与其他类地行星一样，必定有一个早期形成的原始地壳，但这个地壳的化学成分却很少受到关注。原始地壳是从由小行星体吸积和熔化形成的广阔岩浆海洋中提取出来的。实验数据和年代学数据均表明，从这个岩浆海洋上升的硅酸盐熔体是在金属被提取以形成地核之后或与之平衡的情况下形成的。我们在此表明，在这些条件下形成的原始地壳会具有（相对于硅酸盐矿物而言）不相容微量元素特征，这与当前大陆平均地壳的特征极为相似。这对随后的行星演化具有重大意义。许多关于板块构造何时以及如何开始的地球化学观点都隐含地假定，俯冲作用是产生大陆微量元素特征的必要条件。如果这种特征在冥古宙原始地壳中就已存在，那么这些观点就会受到严重质疑。
