1. Plug flow and brecciation in volcanic conduits can emerge from shear-induced crystal migration in otherwise Newtonian magmas
- Author
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Jérémie Vasseur, Fabian B. Wadsworth, Donald B. Dingwell, and Yan Lavallée
- Subjects
Geology ,QE1-996.5 ,Environmental sciences ,GE1-350 - Abstract
Abstract In the Earth, the flow of crystal-bearing magma is thought to be non-Newtonian and shear thinning, but the physical origin for this is poorly understood. We use hydro-granular theory to show that the decoupled migration of crystals toward conduit cores during magma ascent is a tenable microphysical mechanism for plug flow, emergent in an otherwise purely Newtonian crystal-bearing magma. We use a numerical conduit model to define the flow development length beyond which crystal migration dominates and strain localises near conduit margins. Applied to magma ascent scenarios, we show that this crystal-migration strain localisation only develops in high crystallinity magmas or magmas ascending in very narrow cracks/conduits. In all other scenarios, crystals do not contribute to non-Newtonian behaviour and such magmas are usually strictly Newtonian. The ascent of very crystal-rich dome magma could be associated with strain localisation and crystal depletion at the conduit margins, lubricating ascent through the crust.
- Published
- 2024
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