Plug flow and brecciation in volcanic conduits can emerge from shear-induced crystal migration in otherwise Newtonian magmas

Vasseur, Jérémie; Wadsworth, Fabian B.; Dingwell, Donald B.; Lavallée, Yan (2024): Plug flow and brecciation in volcanic conduits can emerge from shear-induced crystal migration in otherwise Newtonian magmas. Communications Earth & Environment, 5: 389. ISSN 2662-4435

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.

• Dokumententyp: Artikel (LMU)
• Organisationseinheit (Fakultäten): 20 Geowissenschaften > Department für Geo- und Umweltwissenschaften > Mineralogie, Petrologie und Geochemie
• DFG-Fachsystematik der Wissenschaftsbereiche: Naturwissenschaften
• DFG: Gefördert durch die Deutsche Forschungsgemeinschaft (DFG) - 491502892