Eruptive shearing revealed by tomography

Yan Lavallée1, Kai-Uwe Hess2, Jackie E Kendrick1, Kate J Dobson3, Paul A Ashwell4, Ben Kennedy5, Fabian B Wadsworth3, Jeremie Vasseur6 and Donald B Dingwell7, (1)University of Liverpool, Liverpool, United Kingdom, (2)Ludwig-Maximilians-Universität, Department of Earth and Environmental Sciences, Munich, Germany, (3)Ludwig Maximilian University of Munich, Munich, Germany, (4)University of Canterbury, Christchurch, New Zealand, (5)University of Canterbury, School of Earth and Environment, Christchurch, New Zealand, (6)Ludwig Maximilians University of Munich, Munich, Germany, (7)Ludwig Maximilian University of Munich, Earth and Environmental Sciences, Munich, Germany

Contact First Author: Yan Lavallée; ylava@liv.ac.uk

Previously Published Material: this presentation will include a wide dataset, including some of the data presented in the following 2 studies under review- Dingwell D.B., Lavallée Y., Hess K.-U., Flaws A., Marti J.,  Nichols A.R.L., Gilg H.A., Schillinger B., in review. Eruptive shearing in tube pumice: pure and simple. Nature Geosciences.  -Ashwell P.A., Kendrick J., Lavallée Y., Kennedy B.M., Hess K.-U., von Aulock F.W., Wadsworth F.B., Vasseur J., Dingwell D.B., in review. Permeability of compacting porous lavas: no impermeable plugs? Journal of Geophysical Research – Solid Earth.

Abstract ID#: 34804

 

English Abstract:
Magma ascent and eruption dynamics are regulated by changes in deformation mechanisms and the ability of magma to release gas. Recent advances in (neutron and x-ray) tomographic analyses provides us with a mean to image the internal structure of magma (especially its pore phase), allowing 3-D characterisation of sample. Here, we present the result of tomographic reconstruction of natural volcanic rocks (tube pumice, tuffisites and dome rocks) as well as crystal-poor and crystal-rich rocks experimentally deformed at magmatic condition to describe the evolution of the porous permeable network upon eruptive shearing relevant to different volcanic scenarios. The image reconstruction shows how bubble elongation and occasionally coalescence dominate crystal-poor magmas whilst micro-fracture coalescence dominates the permeable network of crystal-rich magmas. The permeable structure is further analysed to derive information regarding shearing conditions (pure vs simple) and fracture distribution depending on deformation modes (ductile vs brittle). We discuss our findings with respect to eruptive shearing during Plinian as well as lava dome eruptions.
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