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

Abstract : Mixed ‐ mode fl uid ‐ fi lled cracks represent a common means of fl uid 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 fl uid 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 fi eld. 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 ‐ fi lled crack propagation into a transparent gelatin block. We use a 3 ‐ D fi nite element model to compute the stress fi eld 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 fl uid pressure, longer fl uid ‐ fi lled cracks are less sensitive to the background stress, and we quantify this effect on fl uid ‐ fi lled crack paths. Combining the magnitude of the external stress, the fl uid pressure, and the crack length, we de fi ne a new parameter, which characterizes two end member scenarios for the propagation path of a fl uid ‐ fi lled 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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Journal articles
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https://hal-clermont-univ.archives-ouvertes.fr/hal-02135359
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Submitted on : Tuesday, May 21, 2019 - 11:27:04 AM
Last modification on : Tuesday, June 11, 2019 - 2:14:02 PM

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F. Maccaferri, D. Smittarello, V. Pinel, Valérie Cayol. On the Propagation Path of Magma‐Filled Dikes and Hydrofractures: The Competition Between External Stress, Internal Pressure, and Crack Length. Geochemistry, Geophysics, Geosystems, AGU and the Geochemical Society, 2019, 20 (4), pp.2064-2081. ⟨10.1029/2018GC007915⟩. ⟨hal-02135359⟩

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