Constraining the style of magma-ocean crystallisation by present-day Earth structure: a coupled thermodynamic-geodynamic approach

当前地球结构限制岩浆-海洋结晶的方式：热力学-地球动力学耦合方法

• 批准号: NE/X000508/1
• 负责人: Maxim Ballmer
• 金额: $ 61.11万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX000508%2F1
• 关键词: Constraining; style; magma; ocean; crystallisation

Earth began life as a globally molten ball, a "magma ocean", following the vast energy release of its accretion. While evidence for such a magma ocean is preserved on the Moon's surface, there is no direct geochemical or geophysical evidence preserved on the Earth's surface.As the magma ocean cooled and froze, crystals settled to form the first solid mantle, and the shrinking magma ocean is thought to have become progressively enriched in iron and e.g. radioactive trace elements. Accordingly, the last droplets of the magma ocean, which ultimately stabilized the first crust on Earth, are thought to be extremely enriched in these elements. The differentiation of the rocky Earth in the magma-ocean stage has far-reaching implications for the long-term evolution of the Earth interior, the dynamics of which sustain life-friendly conditions on its surface. In this project, we propose to address an important, but previously neglected process during magma-ocean crystallization. Recent work has established that the crystal package already undergoes solid-state churning, or convection, while the magma ocean is still in the process of progressive freezing. This convection leads to upwellings of hot material, and the associated pressure decrease will bring about partial melting. However, the consequences of this melting for magma-ocean compositional evolution have not yet been explored. Using newly coupled thermodynamic-geodynamic models, our goal is to quantify these consequences of partial melting of the crystal package, and of related material exchange with the magma ocean. We hypothesize that this exchange completely changes the compositional structure of the first solid mantle and the chemistry of the primary crust. For example, it may reconcile the rather moderate compositional stratification of the present-day Earth mantle, which is not addressed by previous models of magma-ocean crystallization at all. The predictions of our new models will be tested, for example by interrogating the seismic structure of the deep mantle, which may host the remnants of the primary crust.

在其积聚的大量能量释放之后，地球以全球熔融球（岩浆海洋”的身份开始生命。虽然这种岩浆海洋的证据保存在月球表面上，但在地球表面上没有直接的地球化学或地球物理证据。随着岩浆海洋冷却和冻结，晶体凝固以形成第一个固体地幔，并且认为萎缩的岩浆海洋被认为在铁中逐渐富集，例如铁和等等。放射性痕量元素。因此，岩浆海洋的最后一滴最终稳定了地球上的第一个地壳，被认为在这些元素中非常丰富。在岩浆阶段，岩石地球的区分对地球内部的长期演变具有深远的影响，地球内部的长期演变是在其表面上维持生命友好条件的动力。在这个项目中，我们建议在岩浆 - 海洋结晶过程中解决一个重要但以前被忽略的过程。最近的工作已经确定，水晶包已经经历了固态搅动或对流，而岩浆海洋仍在进行性冻结过程中。这种对流导致热材料的上升，相关的压力降低将导致部分熔化。但是，尚未探索这种融化对岩浆形成进化的后果。我们的目标是使用新耦合的热力学 - 地球动力学模型，是量化晶体包装部分熔化以及与岩浆海洋相关的材料交换的这些后果。我们假设这种交换完全改变了第一个固体地幔的组成结构和主要地壳的化学。例如，它可能会调和当今的地球底尔的相当中等的组成分层，这根本没有通过岩浆 - 海洋结晶的先前模型来解决。将测试我们新模型的预测，例如，通过询问深幔的地震结构，这可以容纳主要地壳的残余物。

项目成果

Multi-scale anisotropy in NE China: Evidence for localized mantle upwelling

• DOI: 10.1016/j.epsl.2023.118495
• 发表时间: 2024-01
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Cunrui Han;James O.S. Hammond;M. Ballmer;Wei Wei-Wei;Mijian Xu;Zhouchuan Huang;Liangshu Wang