In its early evolution, the Earth mantle likely experienced several episodes of complete melting enhanced by giant impact heating, short-lived radionuclides heating and viscous dissipation during the metal/silicate separation. After a first stage of rapid and significant crystallization (Magma Ocean stage), the mantle cooling is slowed down due to the rheological transition, which occurs at a critical melt fraction of 40–50%. This transition first occurs in the lowermost mantle, before the mushy zone migrates toward the Earth's surface with further mantle cooling. Thick thermal boundary layers form above and below this reservoir. We have developed numerical models to monitor the thermal evolution of a cooling and crystallizing deep mushy mantle. For this purpose, we use a 1-D approach in spherical geometry accounting for turbulent convective heat transfer and integrating recent and solid experimental constraints from mineral physics. Our results show that the last stages of the mushy mantle solidification occur in two separate mantle layers. The lifetime and depth of each layer are strongly dependent on the considered viscosity model and in particular on the viscosity contrast between the solid upper and lower mantle. In any case, the full solidification should occur at the Hadean–Eoarchean boundary 500–800 Myr after Earth's formation. The persistence of molten reservoirs during the Hadean may favor the absence of early reliefs at that time and maintain isolation of the early crust from the underlying mantle dynamics.

中文翻译：

---

岩浆海洋凝固后超过 500 Myr 的糊状地幔

在其早期演化过程中，地幔可能经历了几次完全熔化的过程，这些事件在金属/硅酸盐分离过程中因巨大的撞击加热、短寿命放射性核素加热和粘性耗散而增强。在第一阶段快速且显着的结晶（岩浆海洋阶段）之后，由于流变转变，地幔冷却减慢，这发生在 40-50% 的临界熔体分数。这种转变首先发生在最下层的地幔中，然后随着地幔的进一步冷却，糊状带向地球表面迁移。在该储层上方和下方形成厚的热边界层。我们开发了数值模型来监测冷却和结晶的深糊状地幔的热演化。以此目的，我们在球面几何中使用一维方法来考虑湍流对流热传递，并结合矿物物理学的最新和固体实验约束。我们的结果表明，糊状地幔凝固的最后阶段发生在两个独立的地幔层中。每层的寿命和深度很大程度上取决于所考虑的粘度模型，特别是固体上地幔和下地幔之间的粘度对比。在任何情况下，在地球形成后 500-800 Myr 的冥界-始太古代边界处都应该发生完全凝固。Hadean 期间熔岩储层的持续存在可能有利于当时没有早期地貌，并保持早期地壳与下伏地幔动力学的隔离。