Physical and mechanical property relationships of a shallow intrusion and volcanic host rock, Pinnacle Ridge, Mt. Ruapehu, New Zealand

Mordensky, Stanley; Villeneuve, Marlène; Kennedy, Ben; Heap, Michael; Gravley, Darren M.; Farquharson, Jamie; Reuschlé, Thierry

doi:10.1016/j.jvolgeores.2018.05.020

Cited by 62 publications

(72 citation statements)

References 127 publications

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“…This cluster certainly represents an area of weakness outlining the piston structure associated with the repetitive formation of pit craters and caldera collapses in the volcano summit (Lénat et al, 2012;Michon et al, 2013). These intrusions can in turn maintain damages within the edifice due to the associated stress changes and induced hydrothermal alteration (Heap et al, 2015;Mordensky et al, 2018;Pola et al, 2012;Wyering et al, 2014). Such a weakened zone that is prone to failure can facilitate the propagation of magma intrusions.…”

Section: Discussionmentioning

confidence: 99%

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Constraining Spatiotemporal Characteristics of Magma Migration at Piton De La Fournaise Volcano From Pre‐eruptive Seismicity

Duputel

Lengliné

Ferrazzini

2019

Geophysical Research Letters

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Volcano‐tectonic seismicity has been recorded for decades on various volcanoes and is linked with the magma transport and reservoir pressurization. Yet earthquakes often appear broadly distributed such that magma movement is difficult to infer from its analysis. We explore the seismicity that occurred before eruptions at Piton de la Fournaise in the last 5 years. Using template matching and relocation techniques, we produce a refined image of the summit seismicity, demonstrating that most earthquakes are located on a ring structure. However, only a portion of this structure is activated before each eruption, which provides an indication as to the direction of the future eruptive site. Furthermore, we show that the delay between the pre‐eruptive swarm and the eruption onset is proportional to the distance of the eruptive fissures relative to the summit cone. This reveals that the beginning of the intrusion already bears information regarding the future eruption location.

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Section: Discussionmentioning

confidence: 99%

“…Such a weakened zone that is prone to failure can facilitate the propagation of magma intrusions. These intrusions can in turn maintain damages within the edifice due to the associated stress changes and induced hydrothermal alteration (Heap et al, 2015;Mordensky et al, 2018;Pola et al, 2012;Wyering et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

Constraining Spatiotemporal Characteristics of Magma Migration at Piton De La Fournaise Volcano From Pre‐eruptive Seismicity

Duputel

Lengliné

Ferrazzini

2019

Geophysical Research Letters

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“…Depending on the style of alteration, alteration may increase or decrease the Young's modulus of volcanic rock (Frolova et al, 2014). Since porosity exerts a first-order influence on the Young's modulus of a volcanic rock ( Figure 5), pore-and microcrack-filling alteration (porosity decreasing alteration) increases the Young's modulus, while alteration leading to mineral dissolution (porosity J o u r n a l P r e -p r o o f increasing alteration) decreases the Young's modulus (Frolova et al, 2014 Mordensky et al (2018) were 20 mm in diameter and 40 mm in length, and were deformed in uniaxial compression at a strain rate of 1 × 10 -5 s -1 . A subset of their data, showing the intact Young's modulus of unaltered and altered rocks from the same rock unit, is shown in Figure 8a.…”

Section: The Influence Of Alteration On Intact Young's Modulusmentioning

confidence: 99%

Towards more realistic values of elastic moduli for volcano modelling

Heap¹,

Villeneuve

Albino

et al. 2020

Preprint

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Highlights We provide porosity-Young's modulus data for 276 volcanic rock samples. We present a method to upscale these laboratory measurements to the rock mass scale. Young's modulus of a typical volcanic rock mass is 5.4 GPa. We provide methods to estimate depth-dependent rock mass Young's modulus. We provide a Microsoft Excel© spreadsheet with the relevant data and equations. J o u r n a l P r e -p r o o f AbstractThe accuracy of elastic analytical solutions and numerical models, widely used in volcanology to interpret surface ground deformation, depends heavily on the Young's modulus chosen to represent the medium. The paucity of laboratory studies that provide Young's moduli for volcanic rocks, and studies that tackle the topic of upscaling these values to the relevant lengthscale, has left volcano modellers ill-equipped to select appropriate Young's moduli for their models. Here we present a wealth of laboratory data and suggest tools, widely used in geotechnics but adapted here to better suit volcanic rocks, to upscale these values to the scale of a volcanic rock mass. We provide the means to estimate upscaled values of Young's modulus, Poisson's ratio, shear modulus, and bulk modulus for a volcanic rock mass that can be improved with laboratory measurements and/or structural assessments of the studied area, but do not rely on them. In the absence of information, we estimate upscaled values of Young's modulus, Poisson's ratio, shear modulus, and bulk modulus for volcanic rock with an average porosity and an average fracture density/quality to be 5.4 GPa, 0.3, 2.1 GPa, and 4.5 GPa, respectively. The proposed Young's modulus for a typical volcanic rock mass of 5.4 GPa is much lower than the values typically used in volcano modelling. We also offer two methods to estimate depth-dependent rock mass Young's moduli, and provide two examples, using published data from boreholes within Kīlauea volcano (USA) and Mt. Unzen (Japan), to demonstrate how to apply our approach to real datasets. It is our hope that the data and analysis presented herein will assist in the selection of elastic moduli for volcano modelling. To this end, we provide a Microsoft Excel© spreadsheet containing the data and necessary equations to calculate rock mass elastic moduli that can be updated when new data become available. The selection of the most appropriate elastic moduli will provide the most accurate model predictions and therefore the most reliable information regarding the unrest of a particular volcano or volcanic terrain. J o u r n a l P r e -p r o o f J o u r n a l P r e -p r o o fMagma". The experimental data presented in this study are, for the most part, unpublished data that were collected during mechanical studies performed in collaboration with many scientists. Although non-exhaustive, we thank

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“…The distribution and type of porous and mineral phases are key for understanding waves speeds and rock strength. Although igneous volcanic rocks have been studied in terms of their porosity, permeability and seismic character (Adam and Otheim ; Adelinet et al ; Benson et al ; Heap et al ; Rossetti et al ; Vanorio et al ; Vinciguerra et al ), and alteration (Adam et al, ; Christensen & Salisbury, ; Heap et al, ; Kanakiya et al, ; Mordensky et al, ; Navelot et al, ; Pola et al, ; Wyering et al, ), little knowledge involves the effect of rock alteration and fractures on elastic waves speed for volcaniclastic rocks. Here we study at atmospheric and reservoir pressures how rock alteration influences the development of porosity and rock density and its impact on wave speeds for volcaniclastic and intrusive rocks within the Ngatamariki geothermal field, New Zealand (Figure ).…”

Section: Introductionmentioning

confidence: 99%

“…No correlations between physical properties on a set of rocks from the Tahorakuri formation are observed by Wyering et al (), and the data set lacks microstructural or geochemical analysis. Mordensky et al () looked at the physical properties of argillic alteration on volcanic rocks as a result of an intrusion. The presence of smectite and increasing porosity affect wave speeds and strength but only for one of the studied lithologies (brecciated lava margin).…”

Section: Introductionmentioning

confidence: 99%

Mineral Alteration and Fracture Influence on the Elastic Properties of Volcaniclastic Rocks

et al. 2019

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In geothermal environments, the physical properties of rocks, such as porosity and alteration, are highly variable and control the reservoir's elastic and hydraulic properties. Elastic wave velocity in volcaniclastic rocks and their relation to fractures, pore shapes, and mineral alteration is mostly unknown. We measure ultrasonic P and S wave speeds on volcanic rocks from the Ngatamariki Geothermal Reservoir, New Zealand. Data clustering of wave speed versus porosity and density allow us to classify lithotypes of variable propylitic and phyllic mineral alteration. Wave speeds increase first due to porosity reduction as a result of mineral alteration and welding and, second, due to the high elasticity of alteration minerals (epidote, chlorite, and carbonates). We model the rock porosity as composed of equant pores and oblate-spheroidal microfractures following an elastic effective medium model. For our samples, microfracture porosities range from 4% in the volcaniclastic tuffs to less than 1% in the ignimbrites, which we validate with pycnometer porosity data under effective pressure. We quantify that within one geological volcaniclastic formation, wave speeds vary up to 47% due to rock alteration and welding, while the effect of microfractures and changes in effective stress on wave speeds is secondary (up to 11%) but not negligible. From the experimental and numerical results we show that equant pores remain open at reservoir conditions (2,000 m) and can retain considerable porosity (10%). Our analysis has implications for microfracture and pore network characterization in geothermal reservoirs, in particular, in vapor-dominated systems where matrix porosity and permeability play a role.

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Physical and mechanical property relationships of a shallow intrusion and volcanic host rock, Pinnacle Ridge, Mt. Ruapehu, New Zealand

Cited by 62 publications

References 127 publications

Constraining Spatiotemporal Characteristics of Magma Migration at Piton De La Fournaise Volcano From Pre‐eruptive Seismicity

Constraining Spatiotemporal Characteristics of Magma Migration at Piton De La Fournaise Volcano From Pre‐eruptive Seismicity

Towards more realistic values of elastic moduli for volcano modelling

Mineral Alteration and Fracture Influence on the Elastic Properties of Volcaniclastic Rocks

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