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Strain‐induced permeability increase in volcanic rock
Author(s) -
Farquharson Jamie I.,
Heap Michael J.,
Baud Patrick
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl071540
Subject(s) - geology , cataclastic rock , permeability (electromagnetism) , andesite , electrical conduit , porosity , strain partitioning , petrology , volcanic rock , volcano , mineralogy , fault (geology) , geotechnical engineering , geochemistry , seismology , mechanical engineering , tectonics , membrane , biology , engineering , genetics
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.