Collaborative Research:From silicate melts properties to the dynamics and evolution of an early basal magma ocean

合作研究：从硅酸盐熔体特性到早期基底岩浆海洋的动力学和演化

• 批准号: 2153925
• 负责人: Dave Stegman
• 金额: $ 20.87万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2153925&HistoricalAwards=false
• 关键词: Collaborative; Research; silicate; melts; properties

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.

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。当最初熔融的地幔开始从中间向外凝固时，基底岩浆海洋就出现了，而向下结晶的基底岩浆海洋被认为是我们星球上早期磁场的动力机制。研究小组将收集目前缺失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底岩浆海洋的动力学和演化，并进一步评估基底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：基底岩浆海的初始深度是多少？基底岩浆海会存在多久？是什么影响了基底岩浆海洋中产生的磁场强度？富铁熔体的演化是否与在地幔底部观测到的地震异常相一致？这项工作代表了实验矿物物理学（动态和静态压缩技术）和计算地球动力学之间新的多学科合作，以促进我们对深部和早期地球过程的理解。这项工作将支持研究生在各种实验方法方面的培训：动态和静态压缩技术、x射线和独特的世界级设施的内部表征工具，以及使用最先进的实验约束开发和完善行星内部模型的建模方法。这项工作还将使用具有多层支持和指导的队列构建模型，为本科生和高中实习生提供研究经验。该项目包括三个关键的合作研究部分：1)动态压缩实验，测量铁的自旋状态和致密熔体的液体结构；2)静态压缩实验在激光加热金刚石砧池测量约束铁分配和熔化温度；3)地球动力学建模，利用实验约束来理解固体地幔-基底岩浆海洋耦合系统的热、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，这些数据代表了早期基底岩浆海洋动力学和演化建模的关键实验约束。这些性质包括铁自旋状态（最近才在高压熔体中可行）和硅酸盐熔体的密度，硅酸盐熔体和下地幔矿物之间的铁分配，以及铁对熔融温度的影响。这些新的测量将提供对基底岩浆海的演化的更深入的了解，从它的初始条件到后期凝固产物的性质和组成，这些凝固产物可能仍然存在于深部地幔中。该小组将进一步调查地球磁场可能是由基底岩浆海洋产生的可能性。评估这种情况可能发生的时间将通过提供新的基底岩浆海洋地球动力学模型和相关的、高压的、高温的组成物质的物理性质测量来完成。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。