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

岩浆作用在将物质和能量从地球深处输送到地表的过程中发挥着至关重要的作用。虽然有些喷发是爆炸性的，但其他喷发没有重大爆炸行为，导致每种喷发方式的自然危害不同。这些不同的喷发方式受控于岩浆的基本物理性质，特别是粘度和密度。岩浆的粘度高度依赖于岩浆的原子级结构，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对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相结合，以预测岩浆如何从地球俯冲板块迁移。正是这种物质的迁移最终导致了地表的喷发，但粘度在岩浆运输中的复杂作用使人们很难从内部追踪物质的来源到表面。该项目将为处于不同职业阶段的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，在与地球内部相关的条件下限制流体和熔体的弹性和运输性质，但在产生这些熔体的上地幔条件下，压力、温度和溶解水的综合影响仍然很差。这项研究将把基于实验室和同步加速器的实验数据与第一原理分子动力学(FPMD)模拟相结合，以确定局部熔体结构，以及在高压和温度下的流体和熔体粘度。除了钠长石和玄武岩熔体外，这项工作还将量化含有溶解钠长石的水溶液的结构和性质。这些结果将有助于深入了解压力、温度和组成如何影响地幔中层聚合铝硅酸盐熔体的结构和粘度，并阐明观测到的粘度压力异常的原因。由此产生的粘度将被整合到板条-弧系和地幔过渡区上方的上升区的两相流动模型中，以通过最先进的地球动力学模型来评估熔体迁移的路径。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中流体来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，以及仅融化是否足以聚焦到火山区域下的狭窄区域。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.