Paul A. Ashwell
Permeability of compacting porous lavas
Ashwell, Paul A.; Kendrick, Jackie E.; Lavallée, Yan; Kennedy, Ben M.; Hess, Kai-Uwe; von Aulock, Felix W.; Wadsworth, Fabian B.; Vasseur, Jeremie; Dingwell, Donald B.
Authors
Jackie E. Kendrick
Yan Lavallée
Ben M. Kennedy
Kai-Uwe Hess
Felix W. von Aulock
Dr Fabian Wadsworth fabian.b.wadsworth@durham.ac.uk
Associate Professor
Jeremie Vasseur
Donald B. Dingwell
Abstract
The highly transient nature of outgassing commonly observed at volcanoes is in part controlled by the permeability of lava domes and shallow conduits. Lava domes generally consist of a porous outer carapace surrounding a denser lava core with internal shear zones of variable porosity. Here we examine densification using uniaxial compression experiments on variably crystalline and porous rhyolitic dome lavas from the Taupo Volcanic Zone. Experiments were conducted at 900°C and an applied stress of 3 MPa to 60% strain, while monitoring acoustic emissions to track cracking. The evolution of the porous network was assessed via X‐ray computed tomography, He‐pycnometry, and relative gas permeability. High starting connected porosities led to low apparent viscosities and high strain rates, initially accompanied by abundant acoustic emissions. As compaction ensued, the lavas evolved; apparent viscosity increased and strain rate decreased due to strain hardening of the suspensions. Permeability fluctuations resulted from the interplay between viscous flow and brittle failure. Where phenocrysts were abundant, cracks had limited spatial extent, and pore closure decreased axial and radial permeability proportionally, maintaining the initial anisotropy. In crystal‐poor lavas, axial cracks had a more profound effect, and permeability anisotropy switched to favor axial flow. Irrespective of porosity, both crystalline samples compacted to a threshold minimum porosity of 17–19%, whereas the crystal‐poor sample did not achieve its compaction limit. This indicates that unconfined loading of porous dome lavas does not necessarily form an impermeable plug and may be hindered, in part by the presence of crystals.
Citation
Ashwell, P. A., Kendrick, J. E., Lavallée, Y., Kennedy, B. M., Hess, K., von Aulock, F. W., …Dingwell, D. B. (2015). Permeability of compacting porous lavas. Journal of Geophysical Research. Solid Earth, 120(3), 1605-1622. https://doi.org/10.1002/2014jb011519
Journal Article Type | Article |
---|---|
Acceptance Date | Feb 1, 2015 |
Online Publication Date | Mar 31, 2015 |
Publication Date | Mar 31, 2015 |
Deposit Date | Mar 20, 2018 |
Publicly Available Date | Mar 29, 2024 |
Journal | Journal of Geophysical Research. Solid Earth |
Print ISSN | 2169-9313 |
Electronic ISSN | 2169-9356 |
Publisher | American Geophysical Union |
Peer Reviewed | Peer Reviewed |
Volume | 120 |
Issue | 3 |
Pages | 1605-1622 |
DOI | https://doi.org/10.1002/2014jb011519 |
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Copyright Statement
Ashwell, P. A., J. E. Kendrick, Y. Lavallée, B. M. Kennedy, K. ‐U. . Hess, F. W. von Aulock, F. B. Wadsworth, J. Vasseur, and D. B. Dingwell (2015), Permeability of compacting porous lavas. Journal of Geophysical Research: Solid Earth, 120, 1605-1622. doi: 10.1002/2014JB011519. To view the published open abstract, go to https://doi.org/ and enter the DOI.
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