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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.

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Authors

Paul A. Ashwell

Jackie E. Kendrick

Yan Lavallée

Ben M. Kennedy

Kai-Uwe Hess

Felix W. von Aulock

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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