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.

该项目的目的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开始凝固时，就会出现一个基底岩浆海洋，并提出了向下结晶的基底岩浆海洋作为一种机制来为我们星球上的早期磁场提供动力。研究团队将收集钥匙，目前缺少对铁硅酸盐融化的物理特性的测量，以更好地了解早期基底岩浆海洋的动态和演变，并进一步评估了基底岩浆海洋为早期地球磁场提供动力的情况。 要解决的主要问题是：基底岩浆海洋的初始深度是什么？基底岩浆海洋存在多长时间？是什么影响基底岩浆海洋中产生的磁场的强度？富含铁的熔体的演变是否与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理学（动态和静态压缩技术）与计算地球动力学之间的新的多学科合作，以促进我们对深层和地球过程的理解。这项工作将支持各种实验方法的研究生培训：动态和静态压缩技术以及独特的世界一流设施的X射线和内部表征工具，以及建模方法，以开发和完善使用最先进的实验性约束的行星内部模型。这项工作还将使用具有多层支持和指导的队列构建模型来支持本科和高中实习生的研究经验。本项目包括三个至关重要的协作研究文章：1）衡量浓密融化的铁旋转状态和液体结构的动态压缩实验； 2）在激光加热的钻石 - 大小细胞测量中进行静态压缩实验，以限制铁分配和熔化温度； 3）将使用实验约束来了解耦合固体地幔岩体岩浆海洋系统的热和磁性演化的地球动力模型。研究团队将收集有关铁硅酸盐融化的物理特性的新测量，这些硅酸盐融化代表了对早期基底岩浆海洋的动力学和演变进行建模的至关重要的实验约束。这些特性包括铁旋转状态（直到最近才对高压熔体变得可行）和硅酸盐熔体的密度，硅酸盐熔体和下层矿物质之间的铁分配以及铁对熔化温度的影响。这些新的测量结果将为基底岩浆海洋的演变提供更深入的了解，从其初始条件到晚期凝固产物的特性和组成，这些物质可能仍然存在于深幔中。该小组将进一步研究地球磁场可能是从基底岩浆海洋中产生的。 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.