Flow regimes during fluid-filled crack propagation in elastic media: Applications to volcanology and magma flow within dykes

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Janine Lynsey Kavanagh, Thomas J Jones, David JC Dennis


Scaled analogue experiments were conducted to explore the effect of magma flow regimes, characterised by the Reynolds number (Re), on the transit of magma through the lithosphere via fractures. An elastic, transparent gelatine solid (the crust analogue) was injected by a fluid (magma analogue) to create a thin, vertical, and penny-shaped crack that is analogous to a magma-filled crack (dyke). A vertical laser sheet fluoresced passive-tracer particles suspended in the injected fluid, and particle image velocity (PIV) was used to map the location, magnitude, and direction of flow within the growing dyke from its inception to its surface rupture. Experiments were conducted using water, hydroxyethyl cellulose (HEC) or xanthan gum (XG) as the magma analogue. The results suggest that Re has significant impact on the direction of fluid flow within propagating dykes: Re > 0.1 (jet-flow) is characterised by a rapid central rising fluid jet and downflow at the dyke margin, whereas Re < 0.1 (creeping flow) is characterised by broadly uniform velocities across the dyke plane. Re may be underestimated by up to two orders of magnitude if tip velocity rather than internal fluid velocity is used. In nature, these different flow regimes would affect the petrological, geochemical, geophysical, and geodetic measurements of magma movement, key information upon which reconstructions of volcanic plumbing system architectures and their growth are based.




Earth Sciences, Fluid Dynamics, Physics, Tectonics and Structure, Volcanology


Analogue experiments, magma analogue, Reynolds number, volcanic plumbing system, viscosity, magma rheology, magma analogue, Reynolds number, volcanic plumbing system, viscosity, Magma rheology


Published: 2021-12-13 16:31

Last Updated: 2021-12-14 00:31


CC BY Attribution 4.0 International

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