Understanding Melt Distribution Beneath Volcanoes: An Experimental Approach

Abstract:

Models of large-scale magmatic systems have developed from simple chambers to more complex systems containing transient, layered structures of fluid, melt and crystal mush. Imaging these subsurface structures therefore can lead to better understanding of the threats posed and assist monitoring programmes, but current imaging techniques provide only limited resolution of magmatic structures, with strong trade-offs between seismic waves sensitive to melt fraction and distribution. Despite this, the commonly used relationships linking melt distribution and seismic velocities rely on either 2D images of synthetically melted rock aggregates or simplified geometrical approximations and are therefore not wholly representative of the volcanic system models.

This project aims to develop a new approach to analyse grain-scale structures at different melt fractions through the manufacture of physical models which can be seismically tested analogously. The initial stage has focussed on testing idealised melt inclusions of chosen aspect ratios and comparing them to effective medium models. The solid crystal material is represented by epoxy resin, which is mechanically stable up to 50^oC, while myristyl alcohol, with a melting point of 38^oC, represents the melt; testing has indicated that these materials have suitable mechanical and acoustic properties for producing physical approximations of melt structures.

Future stages will use a variety of techniques such as 3D printing to develop models of realistic melt structures at varying melt fractions. At completion of the project, a suite of seismic parameters will be determined which will be applied to real-world, active volcanic settings to better describe melt distribution in the crust.