Collaborative Research: Structure and properties of geofluids and their impact on fluid migration in subduction zones

合作研究：俯冲带地流体的结构和性质及其对流体运移的影响

• 批准号: 2246802
• 负责人: Mainak Mookherjee
• 金额: $ 29.35万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2246802&HistoricalAwards=false
• 关键词: Collaborative; Research; Structure; properties; geofluids; Collaborative; Research; Structure; properties; geofluids

Magmatism plays a vital role in transporting matter and energy from the Earth’s deep interior to the surface. While some eruptions are explosive, others erupt without major explosive behavior, leading to different natural hazards for each eruptive style. These distinct eruption styles are controlled by the fundamental physical properties of magma, particularly viscosity, and density. The viscosity of magma is highly dependent on the atomic-scale structure of the magma, influenced by magma composition, temperature, pressure, and the presence of dissolved gases such as water vapor. In this study, the researchers aim to obtain fundamental physical constraints on the structure and viscosity of magma at conditions relevant to the Earth’s interior. We will combine the experimentally derived physical properties of magma and fluids with numerical simulations to predict how magmas migrate from the Earth’s subducting plates. It is the migration of this material that ultimately leads to eruptions at the surface, but the complex role of viscosity in magma transport makes it difficult to trace material from its source in the interior to the surface. The project will provide training for the next generation of Earth Scientists at various stages of their career, including high school, undergraduate, and graduate students, as well as post-doctoral scholars. Although extensive research has been done to constrain the elastic and transport properties of fluids and melts at conditions relevant to the Earth’s interior, the combined effects of pressure, temperature, and dissolved water remain poorly constrained at the conditions of the upper mantle where these melts are produced. This research will couple lab- and synchrotron-based experimental data to pressures up to 20 GPa with first-principles molecular dynamics (FPMD) simulations, with the objective to determine the local melt structure, and fluid and melt viscosity to high pressures and temperatures. This work will quantify the structure and properties of aqueous fluids with dissolved albite, in addition to albite and basaltic melts with and without water. The results will provide insight into how pressure, temperature, and composition affect the structure and viscosity of polymerized aluminosilicate melts at mid-mantle depths and illuminate the causes of observed pressure anomalies on viscosity. The resulting viscosities will be integrated into two-phase flow models in the slab-arc system and the upwelling region above the mantle transition zone to assess the pathways of melt migrations through state-of-the-art geodynamical models. These models will assess how the pattern of fluid migration changes with slab age and subduction rate, slab thermal structure, and the distribution and volume of fluid sources in the subducting slab. The resulting work will assess the impact of fluid volumes due to melting and whether melting alone is sufficient to focus melts into a narrow region beneath volcanic regions.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.

岩浆在将物质和能量从地球深内部运输到表面方面起着至关重要的作用。虽然有些喷发是爆炸性的，但另一些爆发没有重大的爆炸性行为，导致每种喷发风格的自然危害都不同。这些独特的喷发样式受岩浆的基本物理特性控制，尤其是粘度和密度。岩浆的粘度高度依赖于岩浆的原子尺度结构，受岩浆成分，温度，压力以及溶解的气相（如水蒸气）的影响。在这项研究中，研究人员旨在在与地球内部相关的条件下对岩浆的结构和粘度进行基本的物理限制。我们将将岩浆和流体的实验得出的物理特性与数值模拟相结合，以预测岩浆如何从地球俯冲板中迁移。正是这种材料的迁移最终导致了表面喷发，但是粘度在岩浆传输中的复杂作用使得很难从其内部到表面的材料中追踪其材料。该项目将在职业生涯的各个阶段为下一代地球科学家提供培训，包括高中，本科生和研究生以及博士后学者。尽管已经进行了广泛的研究来限制与地球内部相关条件下流体和熔体的弹性和转运性能，但在产生这些熔体的上层地幔条件下，压力，温度和溶解的水的综合作用仍然很差。这项研究将将基于实验室和同步加速器的实验数据与高达20 GPA的压力与第一原理分子动力学（FPMD）模拟相结合，目的是确定局部熔体结构，以及对高压和温度的流体和融化粘度。这项工作还将量化具有硫酸盐溶解的水笛的结构和特性，除了有或没有水的基本熔体外，还可以量化水。结果将提供有关压力，温度和成分如何影响聚合铝硅酸盐在中间深度融化的结构和粘度的洞察力，并阐明了粘度上观察到的压力异常的原因。所得的粘度将集成到平板ARC系统和地幔过渡区上方的上升区域中的两相流量模型中，以评估通过最先进的地球动力学模型的熔体迁移途径。这些模型将评估流体迁移的模式如何随着平板年龄和俯冲率，平板热结构以及俯冲平板中流体源的分布和体积而变化。由此产生的工作将评估由于熔化而引起的流体量的影响，并且单独融化是否足以将元数据集中在火山区下方的狭窄区域。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子和广泛影响的评估来评估来获得的支持。