The depleted mantle reservoir is that part of Earth's mantle from which crust has been extracted, leaving the remaining mantle depleted in incompatible elements. Knowing how and when it formed is essential for understanding the chemical evolution of Earth, including formation of continental crust. The best-constrained Hf isotope data presented here indicate that the mantle does not become significantly depleted until as late as 700 million years after Earth's accretion. This onset of mantle depletion coincides with the first appearance of substantial volumes of continental crust in the geological record. These data compel a revision to the reference depleted mantle parameters used in Hf isotope studies of planetary evolution. This new reference line follows chondritic evolution until 3.8 Ga and then describes a linear trajectory to a present-day depleted mid-ocean ridge basalt source mantle composition (εHf = +18). We infer that stabilization of continental crust only occurred in earnest on Earth after 3.8 Ga. ▪ Hf isotopes show that Earth's mantle does not become significantly depleted until 700 million years after planetary accretion. ▪ Most of Earth's oldest rocks formed from mantle sources that had radiogenic isotope compositions similar to those of chondritic meteorites. ▪ Isotope evidence shows that Hadean (>4.0-billion-year-old) crust was not essential for formation of younger crust in Archean terranes. ▪ Growth of Earth's continents only began in earnest after 3.8 Ga.

中文翻译：

---

贫瘠地幔的同位素演化


枯竭的地幔储层是地幔的一部分，从中提取了地壳，留下剩余的地幔在不相容的元素中枯竭。了解它是如何以及何时形成的，对于理解地球的化学演变（包括大陆地壳的形成）至关重要。这里提供的最佳约束 Hf 同位素数据表明，地幔直到地球吸积后 7 亿年才显著耗尽。地幔枯竭的开始与地质记录中大量大陆地壳的首次出现相吻合。这些数据迫使对行星演化的 Hf 同位素研究中使用的参考耗尽地幔参数进行修订。这条新的参考线跟踪软骨演化，直到 3.8 Ga，然后描述了到当今枯竭的洋中脊玄武岩源地幔成分 （εHf = +18） 的线性轨迹。我们推断，大陆地壳的稳定仅在 3.8 Ga 之后才真正发生在地球上。 ▪ Hf 同位素表明，地球的地幔直到行星吸积后 7 亿年才显著耗尽。 ▪ 地球上最古老的岩石大多是由地幔源形成的，这些地幔源的放射性同位素组成与软骨陨石相似。 ▪ 同位素证据表明，Hadean（x3E4.0 亿年）地壳对于太古宙地层中年轻地壳的形成并不是必需的。 ▪ 地球大陆的增长是在 3.8 Ga 之后才开始的。