Influence of alteration on the mechanical behaviour and failure mode of andesite: implications for shallow seismicity and volcano monitoring

Mordensky, Stanley; Heap, Michael; Kennedy, Ben; Gilg, H. Albert; Villeneuve, Marlène; Farquharson, Jamie; Gravley, Darren M.

doi:10.1007/s00445-019-1306-9

Cited by 47 publications

(52 citation statements)

References 80 publications

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“…Country rock fracturing would also be increasingly influenced by lithological pressure and more dominated by local tectonics. Ductile deformation is likely to dominate below ~7-9 km (Greenfield and White, 2015), although this may be locally shallower associated with more porous altered rocks (Mordensky et al 2019) and hydrothermal reservoirs and rhyolitic intrusions are commonly found significantly shallower in Iceland (e.g. Weber and Castro 2017).…”

Section: Overview and Implicationsmentioning

confidence: 99%

“…Paterson et al, 1996). In contrast, weak, porous units favour the circulation of hot fluids causing thermal alteration and thermal fracturing, and will undergo significant ductile deformation with shear failure (Delaney et al, 1986;Wong and Baud, 2012;Mordensky et al, 2019). Within the intrusion, small-scale (millimetre) perlitic fracture networks can develop in quenched glassy margins (von Aulock et al, 2013), facilitating significant ingress of external water.…”

Section: Introductionmentioning

confidence: 99%

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Comparative field study of shallow rhyolite intrusions in Iceland: Emplacement mechanisms and impact on country rocks

Saubin

Kennedy

Tuffen

et al. 2019

Journal of Volcanology and Geothermal Research

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Section: Overview and Implicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparative field study of shallow rhyolite intrusions in Iceland: Emplacement mechanisms and impact on country rocks

Saubin

Kennedy

Tuffen

et al. 2019

Journal of Volcanology and Geothermal Research

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“…Alteration affects the physical properties of volcanic rocks [34][35][36][37]. Alteration may drive the loss of porosity and permeability via mineral precipitation in pores and cracks [3,37,38] and/or cementation [39]. Reductions in porosity due to alteration can promote brittle behaviour [39].…”

Section: Introductionmentioning

confidence: 99%

“…Reductions in porosity due to alteration can promote brittle behaviour [39]. Conversely, alteration may drive dissolution and pore creation with measurable porosity and permeability increase [40,41] and promote a ductile failure mode [38,42,43]. Additionally, microcracking is a critical textural consequence of alteration related processes.…”

Section: Introductionmentioning

confidence: 99%

Pressure Controlled Permeability in a Conduit Filled with Fractured Hydrothermal Breccia Reconstructed from Ballistics from Whakaari (White Island), New Zealand

et al. 2020

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Breccia-filled eruption conduits are dynamic systems where pressures frequently exceed critical thresholds, generating earthquakes and transmitting fluids. To assess the dynamics of breccia-filled conduits, we examine lava, ash tuff, and hydrothermal breccia ballistics with varying alteration, veining, fractures, and brecciation ejected during the 27 April 2016 phreatic eruption of Whakaari/White Island. We measure connected porosity, strength, and permeability with and without tensile fractures at a range of confining pressures. Many samples are progressively altered with anhydrite, alunite, and silica polymorphs. The measurements show a large range of connected porosity, permeability, and strength. In contrast, the cracked samples show a consistently high permeability. The cracked altered samples have a permeability more sensitive to confining pressure than the unaltered samples. The permeability of our altered ballistics is lower than surface rocks of equivalent porosity, illustrating that mineral precipitation locally blocked pores and cracks. We surmise that alteration within the conduit breccia allows cracks to form, open and close, in response to pore pressure and confining pressure, providing a mechanism for frequent and variable fluid advection pulses to the surface. This produces temporally and spatially variable geophysical and geochemical observations and has implications for volcano monitoring for any volcano system with significant hydrothermal activity.

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“…The damaged, altered, and heated host rock located near the ascending magma and hydrothermal area should have a low shear modulus and low shear wave velocity of several hundred meters per second (e.g., Agnolin & Roux, 2008;Huang et al, 2018;Lockner et al, 1977;Vanorio et al, 2003). The advanced alteration may cause ductile deformation (Mordensky et al, 2019). A shear wave can propagate in solidifying magmas with high crystallinity at a low velocity of several tens of meters per second (Namiki & Tanaka, 2017).…”

Section: Introductionmentioning

confidence: 99%

A Model Experiment of Fracture Induced Long‐Period Events: Injection of Pressurized Gas Into a Viscoelastic Rock Analog

Namiki

Takahashi

Tsutsui

2019

Geophysical Research Letters

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Low‐frequency events observed in volcanic areas preceding phreatic or phreatomagmatic eruptions may be excited by the injection of pressurized gas into damaged/heated rocks or solidifying magmas. To simulate this process, we conducted a series of gas injection experiments in gels as an analog of such soft rocks. When we inject the pressurized air into a quasi‐Maxwell fluid with higher and lower shear moduli, cracks or a slug appears, respectively. The crack propagation velocity consists of the shear wave velocity of the gel. At the beginning of the crack generation, multiple cracks emerge, causing pulse‐like low‐frequency signals. In contrast, the slug grows faster than the shear wave velocity and excites high‐frequency oscillation. These results show the possibility that the low‐frequency seismicity observed in volcanic regions is the result of not only the resonance of a crack but also the crack propagation in soft rocks.

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Influence of alteration on the mechanical behaviour and failure mode of andesite: implications for shallow seismicity and volcano monitoring

Cited by 47 publications

References 80 publications

Comparative field study of shallow rhyolite intrusions in Iceland: Emplacement mechanisms and impact on country rocks

Comparative field study of shallow rhyolite intrusions in Iceland: Emplacement mechanisms and impact on country rocks

Pressure Controlled Permeability in a Conduit Filled with Fractured Hydrothermal Breccia Reconstructed from Ballistics from Whakaari (White Island), New Zealand

A Model Experiment of Fracture Induced Long‐Period Events: Injection of Pressurized Gas Into a Viscoelastic Rock Analog

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