The composition of Earth's mantle, continental crust, and oceanic crust continuously evolve in response to the dynamic forces of plate tectonics and mantle convection. The classical view of terrestrial geochemistry, where mid‐ocean ridges sample mantle previously depleted by continental crust extraction, broadly explains the composition of the oceanic and continental crust but is potentially inconsistent with observed slab subduction to the lower mantle and oceanic crust accumulation in the deep mantle. We develop a box model to explore the key processes controlling crust‐mantle chemical evolution. The model mimics behaviors observed in thermochemical convection simulations including subducted oceanic crust separating and accumulating in the deep mantle. We demonstrate that oceanic crust accumulation strongly depletes the mantle independently of continental crust extraction. Slab stalling depths and continental crust recycling rates also affect the extent and location of mantle depletion. We constrain model regimes that reproduce oceanic and continental crust compositions using Markov chain Monte Carlo sampling. Some regimes deplete the lower mantle more than the upper mantle, contradicting the assumption of a more enriched lower mantle. All regimes require oceanic crust accumulation in the mantle. Though a small fraction of the mantle mass, accumulated oceanic crust can sequester trace element budgets exceeding the continental crust, depleting the mantle more than continental crust extraction alone. Oceanic crust accumulation may therefore be as important as continental crust extraction in depleting the mantle, contradicting the paradigmatic complementarity of depleted mantle and continental crust. Instead, depleted mantle is complementary to continental crust plus sequestered oceanic crust.

中文翻译：

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俯冲洋壳在生成中洋脊玄武岩地幔中的作用

地球的地幔，大陆壳和海洋壳的组成不断响应板块构造和地幔对流的动力而不断发展。陆地地球化学的经典观点是，洋中脊采样了先前被大陆壳提取所耗尽的地幔，从广义上解释了海洋和大陆壳的组成，但可能与观测到的板块俯冲到下地幔和深海地壳堆积不一致地幔。我们开发了一个盒子模型来探索控制地幔化学演化的关键过程。该模型模仿在热化学对流模拟中观察到的行为，包括俯冲的洋壳分离和在深地幔中聚集。我们证明，洋壳的积聚强烈地消耗了地幔，而与大陆壳的提取无关。平板失速深度和大陆壳再循环率也影响地幔耗尽的程度和位置。我们限制使用马尔可夫链蒙特卡洛采样法复制海洋和大陆壳成分的模型体制。一些政权使下地幔耗竭比上地幔耗费更多，这与人们认为下地幔更富裕的假设相矛盾。所有制度都要求在地幔中积累洋壳。尽管地壳质量的一小部分，但累积的洋壳可以隔离痕量元素的预算，超过了大陆壳，这使地幔的消耗超过了单独提取大陆壳的消耗。因此，在消减地幔时，洋壳的积累可能与大陆壳提取一样重要，这与枯竭地幔和大陆壳的范式互补性相矛盾。取而代之的是，地幔枯竭补充了大陆壳加上隔离的海洋壳。