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

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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.