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: 2246804
• 负责人: Ikuko Wada
• 金额: $ 23.42万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard 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=2246804&HistoricalAwards=false
• 关键词: 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 gasses 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.

岩浆活动在将物质和能量从地球内部深处输送到地表的过程中起着至关重要的作用。虽然有些喷发是爆炸性的，但其他喷发没有重大的爆炸行为，导致每种喷发方式的自然灾害不同。这些不同的喷发方式是由岩浆的基本物理性质控制的，特别是粘度和密度。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、压力和溶解气体（如水蒸气）的存在的影响。在这项研究中，研究人员的目标是在与地球内部相关的条件下获得岩浆结构和粘度的基本物理约束。我们将把实验得出的岩浆和流体的物理性质与数值模拟结合起来，预测岩浆如何从地球的俯冲板块迁移。正是这些物质的迁移最终导致了地表的喷发，但在岩浆运输过程中，粘度的复杂作用使得从内部源头到地表的物质追踪变得困难。该项目将为处于职业生涯不同阶段的下一代地球科学家提供培训，包括高中生、本科生、研究生以及博士后学者。尽管已经进行了广泛的研究，以限制流体和熔体在与地球内部有关的条件下的弹性和传输特性，但压力、温度和溶解水的综合影响在这些熔体产生的上地幔条件下仍然很难得到限制。该研究将结合实验室和基于同步加速器的实验数据，在高达20gpa的压力下进行第一性原理分子动力学（FPMD）模拟，目的是确定局部熔体结构，以及高压和高温下的流体和熔体粘度。这项工作将量化溶解钠长石的含水流体的结构和性质，以及钠长石和玄武岩在有水和没有水的情况下的熔体。研究结果将揭示压力、温度和成分如何影响中地幔深度聚合硅酸铝熔体的结构和粘度，并阐明观测到的压力异常对粘度的影响原因。所得的黏度将被整合到两相流模型中，在板块-弧系统和地幔过渡带上方的上升流区域，通过最先进的地球动力学模型来评估熔体迁移的途径。这些模型将评估流体运移模式如何随板块年龄和俯冲速率、板块热结构以及俯冲板块内流体源的分布和体积而变化。由此产生的工作将评估融化造成的流体体积的影响，以及融化本身是否足以将融化集中在火山区域下方的狭窄区域。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。