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

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，导致每种喷发类型的自然灾害不同。这些不同的喷发方式是由岩浆的基本物理性质，特别是粘度和密度控制的。岩浆的粘度高度依赖于岩浆的原子尺度结构，受到岩浆成分、温度、压力和溶解气体（如水蒸气）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。我们将结合联合收割机的实验得出的物理性质的岩浆和流体的数值模拟来预测岩浆迁移从地球的俯冲板块。正是这种物质的迁移最终导致了地表的喷发，但岩浆运输中粘性的复杂作用使得很难从内部的来源追踪物质到地表。该项目将为下一代地球科学家在其职业生涯的各个阶段提供培训，包括高中，本科和研究生，以及博士后学者。 虽然已经进行了广泛的研究，以限制弹性和运输性能的流体和熔体在有关地球内部的条件下，压力，温度和溶解水的综合影响仍然很差的限制在上地幔的条件下，这些熔体产生。这项研究将基于实验室和同步加速器的实验数据与压力高达20 GPa的第一性原理分子动力学（FPMD）模拟相结合，目的是确定局部熔体结构，以及高压和高温下的流体和熔体粘度。这项工作将量化的结构和性质的含水流体溶解的钠长石，除了钠长石和玄武质熔体有和没有水。结果将提供洞察压力，温度和组合物如何影响聚合的铝硅酸盐熔体的结构和粘度在中地幔深处，并阐明所观察到的压力异常粘度的原因。由此产生的粘度将被整合到板弧系统和地幔过渡带上方的上涌区域的两相流模型中，以通过最先进的地球动力学模型评估熔体迁移的途径。这些模型将评估流体迁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物集中到火山区域下方的狭窄区域。该奖项反映了NSF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。