Effect of argillic alteration on rock mass stability

Watters, Robert J.; Delahaut, Warren D.

doi:10.1130/reg10-p139

Cited by 26 publications

(27 citation statements)

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“…Other tests on remolded volcanic granular flow materials showed decreases in frictional strength of 3-11% (Samuelson et al 2008). For comparison, extensive acid sulfate-argillic alteration of volcanic rocks, without undergoing large strain, can reduce frictional strength by 30-65% (Watters and Delahaut 1995;Zimbelman et al 2004).…”

Section: Shear Strength Of Dome Rocksmentioning

confidence: 92%

Volcano collapse promoted by progressive strength reduction: new data from Mount St. Helens

et al. 2010

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Rock shear strength plays a fundamental role in volcano flank collapse, yet pertinent data from modern collapse surfaces are rare. Using samples collected from the inferred failure surface of the massive 1980 collapse of Mount St. Helens (MSH), we determined rock shear strength via laboratory tests designed to mimic conditions in the pre-collapse edifice. We observed that the 1980 failure shear surfaces formed primarily in pervasively shattered older dome rocks; failure was not localized in sloping volcanic strata or in weak, hydrothermally altered rocks. Our test results show that rock shear strength under large confining stresses is reduced ∼20% as a result of large quasi-static shear strain, as preceded the 1980 collapse of MSH. Using quasi-3D slope-stability modeling, we demonstrate that this mechanical weakening could have provoked edifice collapse, even in the absence of transiently elevated pore-fluid pressures or earthquake ground shaking. Progressive strength reduction could promote collapses at other volcanic edifices.

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Section: Shear Strength Of Dome Rocksmentioning

confidence: 92%

Volcano collapse promoted by progressive strength reduction: new data from Mount St. Helens

et al. 2010

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“…The second part included the collection of representative samples from which intact rock strengths, joint and infilling material strengths, and the type and intensity of alteration were evaluated. For the geotechnical component, hydrothermal alteration classification was based on visual observations, as described in Watters and Delhaut (1995), which varies from an intensity of zero (no alteration) to four (complete replacement of phenocrysts and matrix). …”

Section: Geotechnical Studiesmentioning

confidence: 99%

“…Of these factors, seismic forces and fluid pressures are generally studied after slope failure or volcanic activity, whereas rock strengths and stabilities can be calculated and evaluated prior to an event. For example, Reid et al (2000), using data from Voight et al (1983) and Watters and Delhaut (1995), concluded that the depth and volume of a failure mass is dependent on the rock strength. A key component in edifice stability, therefore, is the assessment of rock mass strength and its spatial distribution, including within the volcanoes interior.…”

Section: Introductionmentioning

confidence: 99%

Stratovolcano stability assessment methods and results from Citlalt�petl, Mexico

Zimbelman

Watters

Firth

et al. 2004

Bulletin of Volcanology

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CitlaltØpetl volcano is the easternmost stratovolcano in the Trans-Mexican Volcanic Belt. Situated within 110 km of Veracruz, it has experienced two major collapse events and, subsequent to its last collapse, rebuilt a massive, symmetrical summit cone. To enhance hazard mitigation efforts we assess the stability of CitlaltØpetl's summit cone, the area thought most likely to fail during a potential massive collapse event. Through geologic mapping, alteration mineralogy, geotechnical studies, and stability modeling we provide important constraints on the likelihood, location, and size of a potential collapse event. The volcano's summit cone is young, highly fractured, and hydrothermally altered. Fractures are most abundant within 5-20-m wide zones defined by multiple parallel to subparallel fractures. Alteration is most pervasive within the fracture systems and includes acid sulfate, advanced argillic, argillic, and silicification ranks. Fractured and altered rocks both have significantly reduced rock strengths, representing likely bounding surfaces for future collapse events. The fracture systems and altered rock masses occur non-uniformly, as an orthogonal set with N-S and E-W trends. Because these surfaces occur non-uniformly, hazards associated with collapse are unevenly distributed about the volcano.Depending on uncertainties in bounding surfaces, but constrained by detailed field studies, potential failure volumes are estimated to range between 0.04-0.5 km 3 . Stability modeling was used to assess potential edifice failure events. Modeled failure of the outer portion of the cone initially occurs as an "intact block" bounded by steeply dipping joints and outwardly dipping flow contacts. As collapse progresses, more of the inner cone fails and the outer "intact" block transforms into a collection of smaller blocks. Eventually, a steep face develops in the uppermost and central portion of the cone. This modeled failure morphology mimics collapse amphitheaters present at many of the world's stratovolcanoes that have experienced massive failure events.

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“…The diamine putrescine is synthesized from arginine and ornithine via the rate-limiting enzymes arginine decarboxylase (ADC) and ornithine decarboxylase (ODC), respectively. Higher plants and bacteria use both the ADC and ODC pathways for synthesising polyamines, while fungi possess only ODC for polyamine biosynthesis [3,4]. It should be possible, therefore, to control fungal polyamine biosynthesis by specifically inhibiting ODC without affecting plant growth and development [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

First‐report of the inhibition of arbuscular mycorrhizal infection of Pisum sativum by specific and irreversible inhibition of polyamine biosynthesis or by gibberellic acid treatment

et al. 1996

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DFMO (~-DL-difluoromethylornithine), a specific irreversible inhibitor of ornithine decarboxylase (ODC), a polyamine biosynthetic pathway enzyme, strongly inhibits root growth and arbuscular mycorrhizal infection of Pisum sativum (P56 myc +, isogenic mutant of cv. Frisson). This inhibition is reversed when exogenous polyamine (putrescine) is included in the DFMO treatment, showing that the effect of DFMO on arbuscular mycorrhizal infection is indeed due to putrescine limitation and suggesting that ODC may have a role in root growth and mycorrhizal infection. However, treatment with gibbereHic acid (GA3) which increased root titers of polyamines strongly inhibited arbuscular mycorrhizal development. The possible role of polyamines in the regulation of the development of arbuscular mycorrhizal infection is discussed.

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Effect of argillic alteration on rock mass stability

Cited by 26 publications

References 0 publications

Volcano collapse promoted by progressive strength reduction: new data from Mount St. Helens

Volcano collapse promoted by progressive strength reduction: new data from Mount St. Helens

Stratovolcano stability assessment methods and results from Citlalt�petl, Mexico

First‐report of the inhibition of arbuscular mycorrhizal infection of Pisum sativum by specific and irreversible inhibition of polyamine biosynthesis or by gibberellic acid treatment

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