Collaborative Research: From Silicate Melts Properties to the Dynamics and Evolution of an Early Basal Magma Ocean

该项目的目标是了解基底岩浆海洋在影响地球早期磁场过程中的潜在作用。当最初熔融的地幔从中间向外开始凝固时，就会形成基岩浆海洋，向下结晶的基岩浆海洋被认为是为地球早期磁场提供动力的一种机制。研究小组将收集目前缺少的含铁硅酸盐熔体物理性质的关键测量数据，以更好地了解早期基础岩浆海洋的动力学和演化，并进一步评估基础岩浆海洋为早期地球磁场提供动力的情景。要解决的主要问题是：基底岩浆海洋的初始深度是多少？基底岩浆海洋将存在多久？是什么影响了在底部岩浆海洋中产生的磁场的强度？富铁熔体的演化是否与在地幔底部观察到的地震异常一致？这项工作代表了实验矿物物理(动态和静态压缩技术)和计算地球动力学之间的一种新的多学科合作，以促进我们对地球深部和早期过程的理解。这项工作将支持对研究生进行各种实验方法的培训：在独特的世界级设施中使用动态和静态压缩技术、X射线和内部表征工具，以及开发和改进使用最先进实验约束的行星内部模型的建模方法。这项工作还将支持本科生和高中实习生的研究经验，使用具有多层支持和指导的队列建立模型。该项目包括三个关键的协作研究部分：1)动态压缩实验，以测量密集熔体的铁自旋状态和液体结构；2)激光加热钻石压腔中的静态压缩实验，以限制铁的分配和熔化温度；3)地球动力学模型，将使用实验约束条件来理解耦合的固体地幔-基底岩浆海洋系统的热和磁演化。研究小组将收集关于含铁硅酸盐熔体物理性质的新测量数据，这是对模拟早期基底岩浆海洋的动力学和演化的关键实验限制。这些性质包括铁的自旋态(最近才开始适用于高压熔体)和硅酸盐熔体的密度，铁在硅酸盐熔体和下地幔矿物之间的分配，以及铁对熔融温度的影响。这些新的测量将提供对基础岩浆海洋的演化的更深层次的理解，从其初始条件到晚期凝固产物的性质和组成，这些产物可能仍然存在于地幔深处。该团队将进一步调查地球磁场可能是从底部岩浆海洋中产生的可能性。评估这种情况可能发生的持续时间将通过提供新的基础岩浆海洋地球动力学模型和相关的高压、高温组成物质的物理性质测量来完成。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is to understand the potential role of a basal magma ocean in influencing magnetic field processes in the early Earth. A basal magma ocean arises when an initially molten mantle begins solidifying from the middle outwards, and a downward crystallizing basal magma ocean has been proposed as a mechanism to power an early magnetic field in our planet. The research team will collect key, currently missing measurements on the physical properties of iron-bearing silicate melts to better understand the dynamics and evolution of an early basal magma ocean and further evaluate the scenario that a basal magma ocean powered the early Earth's magnetic field. The main questions to be addressed are: What is the initial depth of the basal magma ocean? How long would a basal magma ocean exist? What affects the strength of a magnetic field generated within a basal magma ocean? Would the evolution of iron-enriched melts be consistent with seismic anomalies observed at the base of the mantle? This work represents a new, multidisciplinary collaboration between experimental mineral physics (dynamic and static compression techniques) and computational geodynamics to advance our understanding of deep and early Earth processes. This work will support the training of graduate students in a variety of experimental methods: dynamic and static compression techniques and X-ray and in-house characterization tools at unique world-class facilities, as well as modeling approaches to develop and refine models of planetary interiors that use state-of-the-art experimental constraints. This work will also support research experiences to undergraduate and high school interns, using a cohort-building model with multiple layers of support and mentoring.This project includes three crucial, collaborative research pieces: 1) dynamic compression experiments to measure iron spin state and liquid structure of dense melts; 2) static compression experiments in a laser-heated diamond-anvil cell measurements to constrain iron partitioning and melting temperature; 3) geodynamic modelling which will use the experimental constraints to understand the thermal and magnetic evolution of the coupled solid mantle-basal magma ocean system. The research team will collect new measurements on the physical properties of iron-bearing silicate melts which represent crucial experimental constraints for modeling the dynamics and evolution of an early basal magma ocean. These properties include iron-spin state (which has only recently become feasible for high pressure melts) and density of silicate melt, iron partitioning between silicate melt and lower-mantle minerals, and the effect of iron on melting temperature. These new measurements will provide a deeper understanding of the evolution of a basal magma ocean, from its initial conditions to properties and compositions of late-stage solidification products, which may still be present in the deep mantle. The team will further investigate the possibility that the Earth's magnetic field may have been generated from within the basal magma ocean. Evaluating the duration of time this might have occurred will be accomplished by supplying new geodynamic models of basal magma oceans with relevant, high-pressure, high-temperature physical properties measurements of constituent materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.