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Strain-induced permeability increase in volcanic rock

Abstract : The extrusion of dense, viscous magma typically occurs along pronounced conduit-parallel faults. To better understand the evolution of fault permeability with increasing strain, we measured the permeability of low-porosity volcanic rock samples (basalt and andesite) that were deformed in the brittle regime to various levels of inelastic strain. We observed a progressive increase in sample permeability with increasing inelastic strain (i.e., with continued sliding on the fault plane). At the maximum imposed inelastic strain (0.11), sample permeability had increased by 3 orders of magnitude or more for all sample sets. Microstructural observations show that narrow shear fractures evolve into more complex fracture systems characterized by thick zones of friction-induced cataclasis (gouge) with increasing inelastic strain. These data suggest that the permeability of conduit-parallel faults hosted in the rock at the conduit-wall rock interface will increase during lava extrusion, thus facilitating outgassing and hindering the transition to explosive behavior.
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Submitted on : Tuesday, June 28, 2022 - 4:53:31 PM
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Jamie I. Farquharson, Michael J. Heap, Patrick Baud. Strain-induced permeability increase in volcanic rock. Geophysical Research Letters, 2016, 43, pp.11,603-11,610. ⟨10.1002/2016GL071540⟩. ⟨insu-03707560⟩

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