Mechanical models for dikes: A third school of thought

Townsend, Meredith; Pollard, David D.; Smith, Richard P.

doi:10.1016/j.tecto.2017.03.008

Cited by 89 publications

(68 citation statements)

References 129 publications

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“…Given the natural variability of intrusion geometry, the physical meaning of simple but widely-used numerical pressure source geometries and linear elastic host-rock rheologies remains subject to vivid scientific debate Rivalta et al, 2015;Townsend et al, 2017;Haug et al, 2018). For instance, such simple elastic analytical and numerical models commonly associate sill-like intrusions with domeshaped ground deformation, while they link vertical dikes with ground deformation patterns that comprise two bulges either side of a central trough -i.e., "bulges-and-trough"-and that are correspondingly M-shaped in cross-section, with the M centered above the dike's upper tip (e.g., Mastin and Pollard, 1988;Lundgren et al, 2013;Sigmundsson et al, 2014Sigmundsson et al, , 2018.…”

Section: Introductionmentioning

confidence: 99%

An Inside Perspective on Magma Intrusion: Quantifying 3D Displacement and Strain in Laboratory Experiments by Dynamic X-Ray Computed Tomography

et al. 2019

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Poppe et al. An Inside Perspective on Magma Intrusion KEYPOINTS -Cutting-edge dynamic wide beam X-ray Computed Tomography and Digital Volume Correlation allows an inside view on the temporal behavior of analog magma intrusion in granular host material in laboratory experiments. -Intrusion-induced 3D displacement and strain can be quantified over time. -Thick cryptodomes form with distributed strain and mixedmode fracturing in weak host materials. -Thin dikes form with localized strain and opening-mode fracturing in strong host materials. -A continuum of cone sheet geometries occurs in between these end-members. Frontiers in Earth Science | www.frontiersin.org

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Section: Introductionmentioning

confidence: 99%

An Inside Perspective on Magma Intrusion: Quantifying 3D Displacement and Strain in Laboratory Experiments by Dynamic X-Ray Computed Tomography

et al. 2019

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“…Such deflections have been interpreted as controlled by the local stress field shaped by the surrounding topography (e.g., Bonaccorso et al, ; Corbi et al, ) and sometimes lead to a transition from vertical to lateral magma migration. The competition between vertical and lateral magma transport has also been studied theoretically considering an a priori fixed dike orientation (Pinel & Jaupart, ; Townsend et al, ). These studies show the influence of the local stress field on the ability of the magma to breach the surface and consequently on vents location.…”

Section: Introductionmentioning

confidence: 99%

“…Given the same ratio ( R ) between the external shear stress acting at the upper tip of the crack ( σ xz ) and the average overpressure of the fluid‐filled crack ( Dp ), the propagation path of a fluid‐filled crack should be affected by the crack length ( L ), as suggested by previous theoretical studies (Cotterell & Rice, ; Mériaux & Lister, ). In addition, recent studies focusing on the condition for lateral versus vertical propagation of magmatic intrusions showed that the height of the crack plays a fundamental role in determining the location of the propagating front of the intrusion (Pollard & Townsend, ; Townsend et al, ). However, the effect of the crack length on the deflection of the intrusion has never been quantified separately from the effect of the internal pressure of the intrusion.…”

Section: Introductionmentioning

confidence: 99%

On the Propagation Path of Magma‐Filled Dikes and Hydrofractures: The Competition Between External Stress, Internal Pressure, and Crack Length

Maccaferri

Smittarello

Pinel

et al. 2019

Geochem Geophys Geosyst

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Mixed‐mode fluid‐filled cracks represent a common means of fluid transport within the Earth's crust. They often show complex propagation paths which may be due to interaction with crustal heterogeneities or heterogeneous crustal stress. Previous experimental and numerical studies focus on the interplay between fluid overpressure and external stress but neglect the effect of other crack parameters. In this study, we address the role of crack length on the propagation paths in the presence of an external heterogeneous stress field. We make use of numerical simulations of magmatic dike and hydrofracture propagation, carried out using a two‐dimensional boundary element model, and analogue experiments of air‐filled crack propagation into a transparent gelatin block. We use a 3‐D finite element model to compute the stress field acting within the gelatin block and perform a quantitative comparison between 2‐D numerical simulations and experiments. We show that, given the same ratio between external stress and fluid pressure, longer fluid‐filled cracks are less sensitive to the background stress, and we quantify this effect on fluid‐filled crack paths. Combining the magnitude of the external stress, the fluid pressure, and the crack length, we define a new parameter, which characterizes two end member scenarios for the propagation path of a fluid‐filled fracture. Our results have important implications for volcanological studies which aim to address the problem of complex trajectories of magmatic dikes (i.e., to forecast scenarios of new vents opening at volcanoes) but also have implications for studies that address the growth and propagation of natural and induced hydrofractures.

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“…Several factors may dictate whether a dike will propagate vertically or laterally. Among these, buoyancy has been proposed as the dominant control (Menand & Tait, ; Taisne & Tait, ; Takada, ; Townsend et al, ); a neutrally buoyant dike may arrest and expand laterally at the Level of Neutral Buoyancy (LNB; Lister & Kerr, ). Moreover, stiffer layers overlying more compliant ones may provide barriers to magma ascent (A. Gudmundsson, ; Kavanagh et al, ; Maccaferri et al, ; Rivalta et al, ).…”

Section: Introductionmentioning

confidence: 99%

What Drives the Lateral Versus Vertical Propagation of Dikes? Insights From Analogue Models

2018

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Volcanic eruptions are usually fed by dikes. Understanding how crustal inhomogeneities and topographic loads control the direction (lateral/vertical) and extent (propagation/arrest) of dikes is crucial to forecast the opening of a vent. Many factors, including buoyancy, crustal layering, and topography, may control the vertical or lateral propagation of a dike. To define a hierarchy between these factors, we have conducted analogue models, injecting water (magma analogue) within gelatin (crust analogue). We investigate the effect of crustal layering (both rigidity and density layering), topography, magma inflow rate, and the density ratio between host rock and magma. Based on the experimental observations and scaling considerations, we suggest that rigidity layering (a stiffer layer overlying a weaker one) and topographic gradient favor predominantly lateral dike propagation; inflow rate, density layering, and density ratio play a subordinate role. Conversely, a softer layer overlying a stiffer one favors vertical propagation. Our results highlight the higher efficiency of a stiff layer in driving lateral dike propagation and/or inhibiting vertical propagation with respect to the Level of Neutral Buoyancy proposed by previous studies.

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Mechanical models for dikes: A third school of thought

Cited by 89 publications

References 129 publications

An Inside Perspective on Magma Intrusion: Quantifying 3D Displacement and Strain in Laboratory Experiments by Dynamic X-Ray Computed Tomography

An Inside Perspective on Magma Intrusion: Quantifying 3D Displacement and Strain in Laboratory Experiments by Dynamic X-Ray Computed Tomography

On the Propagation Path of Magma‐Filled Dikes and Hydrofractures: The Competition Between External Stress, Internal Pressure, and Crack Length

What Drives the Lateral Versus Vertical Propagation of Dikes? Insights From Analogue Models

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