Magma Permeability Estimates From X-ray Tomography Scans

Volatile pressure build-up and degassing rates within volcano conduit magmas appear to be linked to volcanic explosivity. Magma permeability, established by bubble and fracture networks, in turn, determines volatile degassing rates. Therefore, exploring bubble network and fracture permeabilities within magma contributes to an overall understanding of volcanic eruption processes. While the most accurate representations of magmatic bubble networks are typically found in quenched volcanic ejecta, they unlikely form representative elementary volumes that reflect conduit-scale permeabilities. This difficulty may be alleviated by determining the statistical spatial relationships of bubble inclusions and networks in pumice. Lattice-Boltzmann simulations allow us to then calculate pumice permeability of these numerical bubble networks based on three-dimensional, high-resolution, X-ray tomography scans. However, bubble walls, separating inclusions, may be thinner than the X-ray tomography resolution. In such cases, tomographic scans will omit microscopic characteristics, resulting in a misrepresentation of bubble connectivity and macroscopic permeability. Therefore, it is imperative to accurately define these thin bubble walls during image post-processing. Here we present how pumice permeability is affected when thin bubble walls are re-introduced during post-processing. This approach allows improved inferences of large-scale magma permeabilities.