Michael J. Heap
The permeability evolution of tuffisites and implications for outgassing through dense rhyolitic magma
Heap, Michael J.; Tuffen, Hugh; Wadsworth, Fabian B.; Reuschlé, Thierry; Castro, Jonathan M.; Schipper, C. Ian
Authors
Hugh Tuffen
Dr Fabian Wadsworth fabian.b.wadsworth@durham.ac.uk
Associate Professor
Thierry Reuschlé
Jonathan M. Castro
C. Ian Schipper
Abstract
There is growing evidence that outgassing through transient fracture networks exerts an important control on conduit processes and explosive‐effusive activity during silicic eruptions. Indeed, the first modern observations of rhyolitic eruptions have revealed that degassed lava effusion may depend upon outgassing during simultaneous pyroclastic venting. The outgassing is thought to occur as gas and pyroclastic debris are discharged through shallow fracture networks within otherwise low‐permeability, conduit‐plugging lava domes. However, this discharge is only transient, as these fractures become clogged and eventually blocked by the accumulation and sintering of hot, melt‐rich pyroclastic debris, drastically reducing their permeability and creating particle‐filled tuffisites. In this study we present the first published permeability measurements for rhyolitic tuffisites, using samples from the recent rhyolitic eruptions at Chaitén (2008‐2009) and Cordón Caulle (2011‐2012) in Chile. To place constraints on tuffisite permeability evolution, we combine (1) laboratory measurements of the porosity and permeability of tuffisites that preserve different degrees of sintering, (2) theoretical estimates on grainsize‐ and temperature‐dependent sintering timescales, and (3) H2O diffusion constraints on pressure‐time paths. The inferred timescales of sintering‐driven tuffisite compaction and permeability loss, spanning seconds (in the case of compaction‐driven sintering) to hours (surface tension‐driven sintering), coincide with timescales of diffusive degassing into tuffisites, observed vent pulsations during hybrid rhyolitic activity (extrusive behaviour coincident with intermittent explosions) and, more broadly, timescales of pressurisation accompanying silicic lava dome extrusion. We discuss herein the complex feedbacks between fracture opening, closing, and sintering, and their role in outgassing rhyolite lavas and mediating hybrid explosive‐effusive activity.
Citation
Heap, M. J., Tuffen, H., Wadsworth, F. B., Reuschlé, T., Castro, J. M., & Schipper, C. I. (2019). The permeability evolution of tuffisites and implications for outgassing through dense rhyolitic magma. Journal of Geophysical Research: Earth Surface, 124(8), 8281-8299. https://doi.org/10.1029/2018jb017035
Journal Article Type | Article |
---|---|
Acceptance Date | Jul 26, 2019 |
Online Publication Date | Jul 31, 2019 |
Publication Date | Jan 1, 2019 |
Deposit Date | Aug 2, 2019 |
Publicly Available Date | Jan 31, 2020 |
Journal | Journal of Geophysical Research. Solid Earth |
Print ISSN | 2169-9011 |
Electronic ISSN | 2169-9011 |
Publisher | American Geophysical Union |
Peer Reviewed | Peer Reviewed |
Volume | 124 |
Issue | 8 |
Pages | 8281-8299 |
DOI | https://doi.org/10.1029/2018jb017035 |
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Copyright Statement
Heap, Michael J., Tuffen, Hugh, Wadsworth, Fabian B., Reuschlé, Thierry, Castro, Jonathan M. & Schipper, C. Ian (2019). The permeability evolution of tuffisites and implications for outgassing through dense rhyolitic magma. Journal of Geophysical Research: Solid Earth 124(8): 8281-8299. 10.1029/2018JB017035. To view the published open abstract, go to https://doi.org/ and enter the DOI.
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