Determining Large-Scale Permeability of Magma From its Bubble and Crystal Microstructure - A Multiphase Percolation Theory Approach

大规模的岩浆渗透率和相关的挥发性脱气率知之甚少，即使通过气泡网络的气体流动是了解广泛的岩浆性质和过程的核心。这些包括气泡和晶体含量和相关的岩浆流变学，火山气体的排放，导管塞的加压和破坏，岩浆破碎和随后的扩张，以及喷发动力学的转变以及熔岩流侵位特征等。这项建议的目的是在数字上确定挥发物的岩浆渗透性，使用小规模的喷发产品的微观结构分析作为输入参数，以净化理论为基础的计算机模型。目标是在大尺度上重建与所讨论的过程相关的平均喷发前微观结构（例如，喷发动力学的导管尺度）。具体而言，该建议解决了以下三个主要问题：1）在何种（气泡和晶体）微观结构条件下，气泡网络预计将存在于岩浆和熔岩中; 2）气泡网络的宏观渗透率是什么;以及3）这种渗透途径如何影响挥发性脱气速率和岩浆/熔岩流变学（反馈渗透率发展）。多相渗流的计算机代码，这是这个建议的一部分，从这项研究的结果也可以用来描述泡状颗粒悬浮液的行为一般遇到在许多物理科学和工程。

Large-scale magma permeabilities and associated volatile degassing rates are poorly understood even though the flow of gases through bubble networks is central to understanding a wide range of magmatic properties and processes. These include bubble and crystal content and related magma rheology, emissions of volcanic gases, pressurization and destruction of conduit plugs, magma fragmentation and subsequent expansion, and transitions in eruption dynamics as well as lava flow emplacement characteristics among others. This proposal aims at numerically determining the permeability of magmas for volatiles using microstructure analyses of small-scale eruption products as input parameters to percolation-theory-based computer models. The goal is to reconstruct the average pre-eruptive microstructure over a large scale that is relevant to the process in question (e.g., conduit scale for eruption dynamics). Specifically, this proposal addresses the following three main questions: 1) under which (bubble and crystal) microstructure conditions are bubble networks expected to exist in magmas and lavas; 2) what are the bubble networks' macroscopic permeabilities; and 3) how do such permeable pathways affect volatile degassing rates and magma/lava rheologies (with feedback to permeability development). The multiphase percolation computer code that is part of this proposal and results from this study may also be used to describe the behavior of vesicular particle suspensions in general as encountered in numerous physical sciences and in engineering.