Melt Migration and Chemical Differentiation by Reactive Porosity Waves

Bessat, Annelore; Pilet, S.; Podladchikov, Y. Y.; Schmalholz, Stefan M.

doi:10.1029/2021gc009963

Cited by 10 publications

(6 citation statements)

References 79 publications

(132 reference statements)

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“…Numerical thermo-hydro-mechanical–chemical (THMC) models investigate the reaction between a rising melt and a viscous solid coupled with heat transfer. The results indicate a dramatic reduction of effective viscosity upon shear heating, leading to thermal runaway and proving the presence of high-pressure fluid at depth 73 . Furthermore, there is numerical evidence that high-pressure fluids coincide with the degassing of from the Earth’s mantle as a trigger and driver, for example, the entire 2008 Bohemian earthquake swarm 58 , 74 .…”

Section: Methods: Mathematical and Numerical Modelmentioning

confidence: 81%

Dynamics between earthquakes, volcanic eruptions, and geothermal energy exploitation in Japan

Gunatilake

2023

Sci Rep

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Intruding magma brings high temperatures close to the surface, thus offering possibilities for harnessing large amounts of heat for geothermal exploitation. Mount Aso in southern Japan showed frequent volcanic activity during 2016, accompanied by significant earthquake activities with tens of thousands of aftershocks (Kumamoto sequence). Here we investigate the influence of earthquake/volcanic activity on the future productivity of nearby geothermal power plants to determine whether the activity is detrimental or beneficial to energy exploitation. Model results show an increase in $${\text {CO}}_2$$ CO 2 pressure and temperature with a spatio-temporal correlation between modeled earthquake locations and aftershock decay rates along the entire sequence, showing that seismic activity opened pre-existing vertical cracks providing pathways for the ascending magma. Interestingly, the minor but still significant eruption of Mount Aso in October 2021 may have enhanced future geothermal power generation, indicating a vigorous and active system, possibly increasing the future geothermal power production.

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Section: Methods: Mathematical and Numerical Modelmentioning

confidence: 81%

Dynamics between earthquakes, volcanic eruptions, and geothermal energy exploitation in Japan

Gunatilake

2023

Sci Rep

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“…Therefore, our results have important implications for the interpretation of phase transformations observed in deformed or stressed rocks. Moreover, our mathematical model can be elaborated in the future to consider additionally porous flow related to dehydration or melting reactions [26,38].…”

Section: Discussionmentioning

confidence: 99%

Control of nonlinear bulk deformation and large shear strain on first-order phase transformation kinetics

Utkin

Schmalholz

Podladchikov

2023

Preprint

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Phase transformations play a key role for many coupled natural processes and they are important for many industrial applications. However, the kinetics of phase transformations taking place in coupled chemo-mechanical systems undergoing large mechanical deformations still need to be better quantified. Here, we study phase transformation kinetics for two phases having each two chemical components. We couple a Cahn-Hilliard type model with a mechanical model for compressible viscous flow. The bulk compressibility is a nonlinear function of the pressure and the shear viscosity is a nonlinear function of the concentration. The mechanical coupling is done by considering a pressure-dependent mechanical mixing term in the equation for the Gibbs energy. We derive a dimensionless system of equations which we solve numerically with a pseudo-transient method using conservative finite differences for discretisation. We perform 1D and 2D numerical simulations and consider far-field simple shear and pure shear. For a chemo-mechanically coupled system, we show that the velocity of the phase boundary is a linear function of the degree of metastability and, hence, confirm the hypothesis of “normal growth”. A stronger mechanical coupling and a larger volumetric effect of the chemical reaction cause slower phase boundary velocities. The 2D results show a significant impact of the mechanical coupling and the far-field deformation on the orientation and kinetics of the phase transformations. Under far-field simple shear and pure shear, the phase transformations generate string-like patterns. The orientation of these patterns is controlled by the applied far-field deformation and orientations differ by 45 degrees between simple shear and pure shear.

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“…Such coupled models have been applied to study a variety of geodynamic processes, for example, reaction-driven cracking during serpentinization (e.g., Evans et al, 2020), porosity evolution and clogging during serpentinization (e.g. Malvoisin et al, 2021), the impact of dehydration on earthquake nucleation (e.g., Brantut et al, 2011), the impact of shear heating and associated chemical rock decomposition on thrusting (e.g., Poulet et al, 2014) or reactive melt migration (e.g., Aharonov et al, 1997;Baltzell et al, 2015;Bessat et al, 2022;Schiemenz et al, 2011). We apply here an extension of a HMC model that was previously used to model the dehydration reaction: brucite = periclase + water (Schmalholz et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Shear-driven formation of olivine veins by dehydration of ductile serpentinite: a numerical study with implications for transient weakening

Schmalholz

Moulas

Räss

et al. 2022

Preprint

Self Cite

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Serpentinite subduction and the associated formation of dehydration veins is important for subduction zone dynamics and water cycling. Field observations suggest that en-échelon olivine veins in serpentinite mylonites formed by dehydration during simultaneous shearing of ductile serpentinite. Here, we test a hypothesis of shear-driven formation of dehydration veins with a two-dimensional hydro-mechanical-chemical numerical model. We consider the reaction antigorite + brucite = forsterite + water. Shearing is viscous and the shear viscosity decreases exponentially with porosity. The total and fluid pressures are initially homogeneous and in the antigorite stability field. Initial perturbations in porosity, and hence viscosity, cause fluid pressure perturbations. Dehydration nucleates where the fluid pressure decreases locally below the thermodynamic pressure defining the reaction boundary. Dehydration veins grow during progressive simple-shearing in a direction parallel to the maximum principal stress, without involving fracturing. The porosity evolution associated with dehydration reactions is controlled to approximately equal parts by three mechanisms: volumetric deformation, solid density variation and reactive mass transfer. The temporal evolution of dehydration veins is controlled by three characteristic time scales for shearing, mineral-reaction kinetics and fluid-pressure diffusion. The modelled vein formation is self-limiting and slows down due to fluid flow decreasing fluid pressure gradients. Mineral-reaction kinetics must be significantly faster than fluid-pressure diffusion to generate forsterite during vein formation. The self-limiting feature can explain the natural observation of many, small olivine veins and the absence of few, large veins. We further discuss implications for transient weakening during metamorphism and episodic tremor and slow-slip in subduction zones.

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Melt Migration and Chemical Differentiation by Reactive Porosity Waves

Cited by 10 publications

References 79 publications

Dynamics between earthquakes, volcanic eruptions, and geothermal energy exploitation in Japan

Dynamics between earthquakes, volcanic eruptions, and geothermal energy exploitation in Japan

Control of nonlinear bulk deformation and large shear strain on first-order phase transformation kinetics

Shear-driven formation of olivine veins by dehydration of ductile serpentinite: a numerical study with implications for transient weakening

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