A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography

Fabian B. Wadsworth, Jérémie Vasseur, Jenny Schauroth, Edward W. Llewellin, Katherine J. Dobson, Tegan Havard, Bettina Scheu, Felix W. von Aulock, James E. Gardner, Donald B. Dingwell, Kai Uwe Hess, Mathieu Colombier, Federica Marone, Hugh Tuffen, Michael J. Heap

Research output: Contribution to journalArticle

Abstract

Welding occurs during transport and deposition of volcanic particles in diverse settings, including pyroclastic density currents, volcanic conduits, and jet engines. Welding rate influences hazard-relevant processes, and is sensitive to water concentration in the melt. We characterize welding of fragments of crystal-free, water-supersaturated rhyolitic glass at high temperature using in-situ synchrotron-source X-ray tomography. Continuous measurement of evolving porosity and pore-space geometry reveals that porosity decays to a percolation threshold of 1–3 vol.%, at which bubbles become isolated and welding ceases. We develop a new mathematical model for this process that combines sintering and water diffusion, which fits experimental data without requiring empirically-adjusted parameters. A key advance is that the model is valid for systems in which welding is driven by confining pressure, surface tension, or a combination of the two. We use the model to constrain welding timescales in a wide range of volcanic settings. We find that volcanic systems span the regime divide between capillary welding in which surface tension is important, and pressure welding in which confining pressure is important. Our model predicts that welding timescales in nature span seconds to years and that this is dominantly dependent on the particle viscosity or the evolution of this viscosity during particle degassing. We provide user-friendly tools, written in Python™ and in Excel®, to solve for the evolution of porosity and dissolved water concentration during welding for user-defined initial conditions.

LanguageEnglish
Article number115726
Number of pages9
JournalEarth and Planetary Science Letters
Volume525
Early online date19 Aug 2019
DOIs
Publication statusPublished - 1 Nov 2019

Fingerprint

Ashes
welding
ashes
tomography
Tomography
volcanology
Welding
ash
X rays
x rays
porosity
Water
Porosity
surface tension
confining
water
confining pressure
Surface tension
pressure welding
interfacial tension

Keywords

  • jet engine
  • obsidian
  • porosity
  • sintering
  • surface tension
  • tuffisite

Cite this

Wadsworth, Fabian B. ; Vasseur, Jérémie ; Schauroth, Jenny ; Llewellin, Edward W. ; Dobson, Katherine J. ; Havard, Tegan ; Scheu, Bettina ; von Aulock, Felix W. ; Gardner, James E. ; Dingwell, Donald B. ; Hess, Kai Uwe ; Colombier, Mathieu ; Marone, Federica ; Tuffen, Hugh ; Heap, Michael J. / A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography. In: Earth and Planetary Science Letters. 2019 ; Vol. 525.
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Wadsworth, FB, Vasseur, J, Schauroth, J, Llewellin, EW, Dobson, KJ, Havard, T, Scheu, B, von Aulock, FW, Gardner, JE, Dingwell, DB, Hess, KU, Colombier, M, Marone, F, Tuffen, H & Heap, MJ 2019, 'A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography' Earth and Planetary Science Letters, vol. 525, 115726. https://doi.org/10.1016/j.epsl.2019.115726

A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography. / Wadsworth, Fabian B.; Vasseur, Jérémie; Schauroth, Jenny; Llewellin, Edward W.; Dobson, Katherine J.; Havard, Tegan; Scheu, Bettina; von Aulock, Felix W.; Gardner, James E.; Dingwell, Donald B.; Hess, Kai Uwe; Colombier, Mathieu; Marone, Federica; Tuffen, Hugh; Heap, Michael J.

In: Earth and Planetary Science Letters, Vol. 525, 115726, 01.11.2019.

Research output: Contribution to journalArticle

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T1 - A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography

AU - Wadsworth, Fabian B.

AU - Vasseur, Jérémie

AU - Schauroth, Jenny

AU - Llewellin, Edward W.

AU - Dobson, Katherine J.

AU - Havard, Tegan

AU - Scheu, Bettina

AU - von Aulock, Felix W.

AU - Gardner, James E.

AU - Dingwell, Donald B.

AU - Hess, Kai Uwe

AU - Colombier, Mathieu

AU - Marone, Federica

AU - Tuffen, Hugh

AU - Heap, Michael J.

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KW - jet engine

KW - obsidian

KW - porosity

KW - sintering

KW - surface tension

KW - tuffisite

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