The aim of this session is to bridge short‑time, small‑scale observations with long‑time, large‑scale phenomena. By integrating geodynamic investigations, experimental constraints, and theoretical formulations, we seek a unified understanding of the interacting mechanisms that drive geological deformation.
We invite contributions from all disciplines that explore how grain‑scale processes and rheology influence the overall mechanical behavior of geomaterials.
The coupling between deformation, phase transformations, and chemical reactions governs key Earth processes, including mountain building, earthquakes, magma transport, reservoir stability, and glacier flow. Deformation of solids such as rocks, minerals, and ice generates non-hydrostatic stresses, yet fundamental disagreements persist on how stress controls the thermodynamics of solid–fluid equilibria and reactions. This knowledge gap limits our ability to predict the long-term stability of subsurface reservoirs critical to the energy transition, including nuclear waste repositories, CO₂ and hydrogen storage, and geothermal systems.
Thermodynamic equilibrium requires mechanical equilibrium. However, non-hydrostatic thermodynamic frameworks typically rely on simplified conceptual models that assume stresses within deforming solid grains are always homogeneous and equal to the far-field stress [1]. When extended to multigrain assemblages, the assumption of homogeneous stress in the solid matrix violates mechanical equilibrium and creates apparent inconsistencies between conditions of thermodynamic and mechanical equilibrium [2]. Such inconsistencies are often addressed by invoking the presence of fluid phases in rocks capable of sustaining non-hydrostatic stresses, as in pressure-solution theories [3].
Here, we show that atomistic molecular dynamics (MD) simulations provide an independent framework that avoids such assumptions by self-consistently simulating dissolution, precipitation, and stress evolution from atomic interactions [4,5]. By embedding meshes in large-scale MD simulations, we directly compute the continuum Cauchy stress field from atomic forces and velocities. These simulations reveal that stresses within solid phases of deforming multiphase systems are inherently heterogeneous. Stress patterns obtained from atomistic simulations quantitatively match analytical solutions and numerical continuum models, such as finite-element simulations, demonstrating that continuum mechanics accurately captures the stress state in agreement with atomistic descriptions.
MD simulations naturally capture elastic anisotropy, defect nucleation, stress heterogeneity, and interfacial instabilities, allowing mechanical and thermodynamic equilibrium to emerge spontaneously. Our results show that equilibrium in deforming rocks cannot be explained by normal-stress-only models. Instead, they confirm thermodynamic formulations [6,7] in which local equilibrium is governed by the full local stress state, resolving the apparent conflict between thermodynamics and mechanics and suggesting a significant shift in our understanding of deformation–reaction coupling in Earth materials.
References
1. Wheeler J (2020) Contrib Mineral Petrol 175:116
2. Hobbs BE, Ord A (2016) Earth-Sci Rev 163:190–233
3. Gratier J-P, Dysthe DK, Renard F (2013) Adv Geophys 54:47–179
4. Mazzucchelli ML, Moulas E, Kaus BJP, Speck T (2024) Am J Sci 324
5. Mazzucchelli ML, Moulas E, Schmalholz SM, et al. (2025) ESS Open Archive
6. Gibbs JW (1876) Trans Conn Acad Arts Sci 3:108–248
7. Frolov T, Mishin Y (2010) Phys Rev B 82(17), 1–14.
How to cite: Mazzucchelli, M. L., Moulas, E., and Schmalholz, S. M.: From Atoms to Continuum: Stress Control of Thermodynamic Equilibrium in Deforming Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7189, https://doi.org/10.5194/egusphere-egu26-7189, 2026.
The accumulation of microdamage fundamentally controls the rheological behavior and dynamic permeability of the lithosphere. However, quantifying the internal subcritical damage that precedes macroscopic failure remains a challenge even during controlled laboratory experiments. We present a proof-of-concept study using Electron Paramagnetic Resonance (EPR) spectroscopy to bridge the gap between atomic-scale defects and rock-scale failure.
EPR provides a direct, chemically specific measure of unpaired electron spins associated with broken atomic bonds, effectively serving as a proxy of lattice-scale damage. To test this, we subjected quartz-rich sandstone to intermittent mechanical loading (brazilian splitting and uniaxial compression) and thermal treatment (300°C) to track the evolution of paramagnetic defects.
Preliminary results indicate that the EPR signal is highly sensitive to damage accumulation. Heat-treated specimens show a substantial signal increase, likely reflecting microfracturing driven by thermal expansion of mineral grains. Furthermore, under mechanical loading, the spectral intensity scales with the imposed load level. This suggests that the concentration of paramagnetic defects can track the progression of strain accumulation. We conclude that solid-state spectroscopy offers a promising non-destructive method to probe the fundamental microprocesses accompanying rock deformation, shedding light on the atomic-to-granular mechanisms that ultimately govern rock strength and permeability.
How to cite: Bondarenko, N., Altenhof, A., Saar, M., and Kong, X.-Z.: From atomic defects to microcracks: Tracing damage with EPR , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20834, https://doi.org/10.5194/egusphere-egu26-20834, 2026.
The slow creep of glacial ice plays a key role in sea-level rise, yet its transient deformation remains poorly understood. Glen’s flow law, where strain rate is simply a function of stress, cannot predict the time-dependent creep behavior observed in experiments. Here we present a physics-based rheological model that captures all three regimes of transient creep in polycrystalline ice. The key components of the model are a series of Kelvin-Voigt mechanical elements that produce a power-law (Andrade) creep, and a single viscous element with microstructure and stress dependence that represents reorientation in the polycrystalline grains. The interplay between these components produces a minimum in the strain rate at approximately 1% strain, which is a universal but unexplained feature reported in experiments. Due to its transient nature, the model exhibits fractional power-law exponents in the stress dependence of the strain rate minimum, which has been conventionally interpreted as independent physical processes. Taken together, we provide a compact, mechanistic framework for transient ice rheology that generalizes to other polycrystalline materials and can be integrated into constitutive laws for ice-sheet models.
How to cite: Burton, J., Vargas, A., and Ran, R.: A microstructural rheological model for transient creep in polycrystalline ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4267, https://doi.org/10.5194/egusphere-egu26-4267, 2026.
The lithospheric mantle is crucial in influencing the dynamics at plate boundaries and in forming the geophysical signatures observed on the Earth's surface, although it is not directly observable. To comprehend its deformation history, it is necessary to employ methods that connect scales ranging from microstructures to orogenic belts. The Horoman peridotite complex in Hokkaido, Japan, provides an outstanding natural laboratory for such investigations, offering direct access to fragments of the upper mantle with well-preserved structures.
In this study, we conducted quantitative microstructural and intracrystalline analyses using EBSD dataset (Matsuyama & Michibayashi, 2024), combined with rheological modeling. The complex exhibits systematic variations from mylonitic to equigranular textures and from E to A to AG type olivine crystallographic preferred orientations (CPOs) upward through the structural sequence. The microstructural parameters (grain size, aspect ratio, and shape factor) of olivine and orthopyroxene showed a fine-grained microstructure and high intracrystalline strain in the E type samples, consistent with deformation dominated by dislocation creep. In contrast, AG type samples displayed polygonal grain shapes and lower intracrystalline strain, suggesting deformation by diffusion creep.
Rheological modeling based on olivine flow laws (e.g., Hirth & Kohlstedt, 2003) indicates that E type CPOs develop through water-assisted dislocation creep involving the activation of specific slip systems, whereas AG type CPOs formed through melt-induced strain partitioning during diffusion creep. Integrating these results and the tectonics of the surrounding metamorphic belt (e.g., Toyosihma et al., 1997), we propose a three-stage deformation history: (1) early high-temperature, dry deformation producing A type CPOs; (2) syn-kinematic melt infiltration leading to AG type CPOs via diffusion creep; and (3) later water infiltration and thrusting generating E type CPOs through hydrous dislocation creep.
Comparison with other orogenic and ophiolitic peridotites suggests that the A–E and A–AG CPO transitions observed in the complex represent general upper-mantle processes involving water and melt. Our study highlights that the coexistence and transition of multiple deformation mechanisms—modulated by fluid and melt interactions—play a fundamental role in controlling mantle rheology and the evolution of lattice-preferred orientations.
How to cite: Matsuyama, K. and Michibayashi, K.: Insights into uppermost mantle deformation and tectonic evolution from the Horoman peridotite complex, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-868, https://doi.org/10.5194/egusphere-egu26-868, 2026.
Ductile deformation is commonly associated with slow and uniform deformation which unfolds over thousands to hundreds of millions of years. Nevertheless, ductile instabilities can result in the localization of deformation into narrow shear zones which operate on much shorter time scales. Mylonites are one example of ductile localization, and events such as slow slip events and deep earthquakes are also associated with fast ductile deformation. The latter are reported up to depths of 700 km and are difficult to reconcile with our understanding of brittle failure which suggests that they are driven by a ductile localization mechanism instead.
One such mechanism is thermal runaway, a feedback loop of shear heating, temperature-dependent viscosity and deformation. Several one-dimensional (1D) studies support the viability of thermal runaway as a driver of deep earthquakes. Here, we present two-dimensional (2D) thermomechanical models of thermal runaway in olivine under simple and pure shear conditions in line with the cold cores of subducting slabs. The models employ a composite visco-elastic rheology including diffusion creep, dislocation creep, and low-temperature plasticity.
The code is written in the Julia programming language and utilizes the package ParallelStencil.jl for GPU parallelization as well as JustPIC.jl for particle-in-cell advection. We employ an accelerated pseudo-transient (APT) solver which makes use of recent developments in automatic tuning of numerical parameters such as pseudo-time steps and damping coefficients. These features enable us to locally employ strong grid refinement (factor 100) without destabilizing the solver which allows us to use model domains spanning tens of kilometers with local grid resolutions of up to one meter.
Our models capture the nucleation and transient propagation of ductile ruptures through a previously intact host rock. The ruptures initiate in zones of reduced grain size and under plate tectonic deformation rates (10 cm yr-1). During propagation, they self-localize and accelerate to reach slip velocities in the range of earthquakes (> 1 mm s-1). The magnitude of maximum slip velocity is strongly coupled to the stress in the host rock prior to rupture nucleation, and the ruptures self-consistently run out in the high-temperature/low-stress areas of the model domain. This behavior is consistent with scaling laws derived from 1D models and the occurrence of deep-focus earthquakes in the cold olivine cores of subducting slabs. As we consider the latent heat of melting, our models demonstrate that the local temperature surge due to thermal runaway is fast enough to completely melt a thin layer of olivine during rupture propagation, indicating a link between deep earthquakes and pseudotachylytes.
How to cite: Spang, A., Thielmann, M., de Montserrat, A., and Duretz, T.: Understanding the physics of thermal runaway and ductile rupture propagation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4193, https://doi.org/10.5194/egusphere-egu26-4193, 2026.
The ongoing energy transition and technological advancements present increasingly complex challenges for numerical modeling, necessitating the development of multi-physics, multi-scale approaches. Recent progress in high-performance computing has catalyzed the rapid evolution of a new generation of numerical codes designed to tackle these complex problems. However, this progress demands revisiting and refining constitutive models to ensure they are rigorous, thermodynamically consistent, and suitable for computational implementation. In this work, we present a thermodynamic framework for coupled thermo-hydro-mechano-chemical processes in porous media undergoing elastic, viscous, and plastic deformation. The formulation is developed in an Eulerian description and assumes local thermodynamic equilibrium for each phase. By enforcing the second law of thermodynamics through non-negative entropy production, we derive a complete and thermodynamically admissible set of governing equations and closure relations for visco-elasto-plastic porous materials with thermal and chemical coupling. A key result is the identification of the conjugate thermodynamic force associated with porosity, which provides a consistent basis for formulating viscous, plastic, and reaction-induced porosity evolution. The equilibrium (elastic) closure relations are derived from the symmetry properties of the thermodynamic potentials, yielding a compliance matrix that unifies poroelastic, thermoelastic, and thermo-porous couplings. Classical limits are recovered naturally, including Biot and Gassmann relations for homogeneous matrices, Brown–Korringa relations for heterogeneous solids, and Darcy’s law as the low-frequency limit of the dynamic momentum balance. The framework also clarifies the role of inertial (added-mass) effects and relates them to pore-scale tortuosity. The derived equations are implemented in a numerical code, and a numerical example illustrating the propagation of a porosity wave in a viscoelastic medium is presented.
How to cite: Yarushina, V. and Podladchikov, Y.: Thermodynamic foundations of coupled thermo-hydro-mechano-chemical processes in geological and geoengineering materials with complex rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3831, https://doi.org/10.5194/egusphere-egu26-3831, 2026.
Hydromechanical coupling in fluid-saturated porous media governs a wide range of geological processes, including compaction-driven fluid flow, strain localization, and fault activation. Many existing numerical approaches rely on non-conservative formulations expressed in terms of fluid and total pressures. While effective for smooth solutions, such formulations become inconsistent in the presence of sharp porosity gradients, compaction fronts, and shock-like structures, which promote strain localization into shear bands, where mass conservation and correct jump conditions are essential.
Here, we present a fully conservative hydromechanical formulation based on the conservation of fluid mass, total mass, and an explicit porosity evolution equation. This framework provides a physically consistent description of coupled flow–deformation processes, making it particularly suited for problems involving discontinuities, porosity waves, and localized deformation. We demonstrate that classical solitary porosity waves arise directly from the conservative equations and that fluid overpressure associated with channelized flow can trigger shear band formation through poro-visco-elasto-plastic yielding. We further extend the conservative formulation to two-phase flow with capillary pressure, showing that strain localization fundamentally alters phase pressure evolution and fluid distribution. The formulation is implemented in a GPU-accelerated framework, enabling high-resolution three-dimensional simulations of strongly nonlinear hydromechanical instabilities.
These results establish conservative hydromechanics as a foundation for modeling flow-driven localization, porosity waves, and multiphase transport in deforming geological media, with implications for fluid-induced seismicity and fault mechanics.
How to cite: Alkhimenkov, Y. and Podladchikov, Y.: A Fully Conservative Formulation of Hydromechanical Processes in Deforming Porous Media, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3003, https://doi.org/10.5194/egusphere-egu26-3003, 2026.
Geological carbon storage must simultaneously address two practical challenges: (i) realistic CO₂ streams that contain impurities from capture and transport, and (ii) highly nonlinear subsurface reactions that can modify porosity, permeability, and stress, ultimately controlling injectivity and long-term containment. We present an integrated modeling strategy that links multicomponent thermodynamic evaluation of CO₂-impurity mixtures with fully coupled hydro-mechanical-chemical (HMC) simulations of reactive flow in deformable rocks.
Our framework resolves the mutual feedbacks between fluid migration, chemical re-equilibration, and evolving pore space, capturing localized mineral alteration and the emergence of sharp reaction fronts. A key outcome is that mineral trapping and pH evolution are strongly localized: carbonation and dissolution tend to occur within a narrow front whose migration speed is dictated by the interplay of pressure gradients and evolving permeability. Importantly, we find that simplified chemistry can severely over-acidify predicted fluids, whereas explicit treatment of aqueous speciation and host-rock buffering stabilizes pH at realistic values, even in the presence of acid-forming impurities.
Accurate prediction of rock-fluid equilibria and pH fields demands shock-resolving spatial resolution together with full aqueous speciation. Under-resolved meshes and simplified reaction networks artificially diffuse concentration discontinuities, leading to large errors in acidity, mineral alteration extent, and permeability evolution. Benchmarking against laboratory-scale observations and illustrative field-scale scenarios confirms that GPU-accelerated, fully coupled HMC simulations are essential to capture extreme localization and front propagation dynamics.
In summary, impurity-bearing CO₂ storage is controlled by sharply localized reactive fronts, where pH buffering, mineral alteration, and porosity–permeability evolution are tightly coupled. Only conservative, fully coupled high-performance HMC simulations with explicit multicomponent speciation (neutral and charged species) can resolve this localization and provide robust guidance for impurity-tolerant injection design and long-term containment, delivering the predictive capability required for reliable geological CCS.
How to cite: Podladchikov, Y.: Reactive rock-fluid dynamics under impurity-bearing CO₂ injection: toward predictive geological CCS , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16898, https://doi.org/10.5194/egusphere-egu26-16898, 2026.
Hydration reactions play a key role in controlling fluid transport and deformation in subduction zones. These reactions are associated with changes in material properties (mainly permeability, density and strength) that can strongly influence their propagation in rocks. However, the mechanisms controlling their development remain poorly understood. The granulite-to-eclogite transformation is a striking example of a pressure- and fluid-driven metamorphic reaction and is characterized by a significant increase in density. On the island of Holsnøy (Norway), incipient eclogitization affects continental granulites and forms characteristic finger-like structures. Field observations show that these eclogite fingers are systematically aligned with the pre-existing granulite foliation, and that the orientation of this foliation appears to control the way the eclogite front propagates. However, it remains unclear whether this preferential propagation arises from mechanical anisotropy, permeability anisotropy alone, or a combination of both.
In this study, we investigate the influence of the initial granulite foliation, in terms of permeability only, on the propagation of eclogitization. We use a hydro-chemical numerical model to simulate the evolution of eclogitization in a granulitic matrix where fluid flow and pressure variations govern metamorphic reactions. For this, we solve a fully coupled system of equations (conservation of mass and Darcy's law) using Kozeny-Carman formulation for permeability associated with an equation of state. The eclogite transformation is simulated by a density increase occurring when fluid pressure is higher than the pressure of the reaction.
We propose a parametric study allowing us to assess the role of permeability layering in the initial granulite on the development and propagation of eclogite fingers. Our results are then discussed and compared with field observations from Holsnøy, providing new insights on fluid-mediated metamorphic transformations in subduction-related settings.
How to cite: Cochet, A., Yamato, P., Duretz, T., Schmalholz, S., and Podladchikov, Y.: Eclogitization front propagation in a layered lower crust: Insights from Hydro-Chemical numerical modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7527, https://doi.org/10.5194/egusphere-egu26-7527, 2026.
Fault zones exert first-order control on crustal fluid migration, and fault intersections further enhance permeability both "structurally," via damage, and "geometrically," by partitioning crustal deformation. This study examines how fault intersections affect strain localization and stress regimes during far-field tectonic transpression through two case studies in the Southern Volcanic Zone, Chile (SVZ). Three-dimensional, temperature-dependent, visco-elasto-plastic models simulate the mechanical response of an upper crust segment containing intersecting, pre-existing, weak fault zones set immediatetly above hot, reactive and partially molten domains.
Geometry Type I consists of a margin-parallel vertical fault intersected by a high-angle transverse fault (ATF), while Type II includes two orthogonal, margin-oblique vertical faults; these are inspired by the Puyehue-Cordón Caulle and Nevados de Chillán volcanic complexes (33°S–46°S), respectively. Model results reveal deformation partitioning: NW-striking faults preferentially localize shear strain, whereas NE-trending faults concentrate volumetric strain. In both geometries, fault intersections display local transitions from compressional to strike-slip or transtensional stress regimes within a roughly 2 km radius and down to depths of approximately 2 km. Type I intersections produce nearly twice the dilation of Type II, emphasizing how intersection orientations influence long-term rock damage.
These modeled stress and strain patterns offer a mechanical framework for understanding the spatial distribution of volcanic and hydrothermal features, including the location of the Puyehue stratovolcano and the contrasting alignments of dikes and monogenetic cones at Nevados de Chillán. Further tests incorporating (i) plastic dilatancy and (ii) poro-elasticity illustrate their importance in controlling fluid flow toward the surface. These results provide foundation for future, more evolved self-consistent and coupled fluid-solid rheologies to help understand: (i) why upward magmatic and geothermal fluid migration in the upper crust may not be vertical under transpressional conditions, particularly near fault intersections, and (ii) the link between deformation and geoflluids flow over timescales intermediate between volcanic and geological scales.
How to cite: Gerbault, M., Zanartu Torres, G., Cembrano, J., Crempien, J., Torres Bunzli, D., Stanton-Yonge, A., Browning, J., Iturrieta, P., and Saez-Leiva, F.: Deformation partitioning and insights on crustal fluid migration from models of fault intersections in the compressional margin of the Southern Volcanic Zone, Chile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13756, https://doi.org/10.5194/egusphere-egu26-13756, 2026.
Serpentinites are hydrous rocks with a wide pressure-temperature stability field that play a key role in geodynamic settings such as subduction zones and associated seismic regions, and strongly influence the deep-water cycle. Field observations and laboratory experiments indicate that dehydration of serpentinites may be caused locally due to deformation, or conversely that dehydration may induce deformation. However, the mechanical-chemical coupling between serpentinite dehydration and deformation remains poorly constrained.
Metamorphic olivine veins observed in antigorite serpentinites are interpreted as dehydration bands, and similar structures have been reproduced in laboratory experiments under uniaxial shortening and differential stress. These observations raise fundamental questions about the role of deformation in controlling serpentinite dehydration, its influence on reaction kinetics, and the impact of shear bands on fluid transport pathways. In addition to laboratory studies, numerical modelling provides a powerful approach to address these questions and to investigate dehydration processes in deforming serpentinites. However, the numerical coupling of dehydration reactions, fluid flow, and rock deformation remains challenging.
Here, we present a mathematical framework that couples poromechanical deformation, Darcy flow and a thermodynamic model for serpentinite dehydration. Based on this framework, we develop a two-dimensional numerical model using finite-difference discretization and an accelerated pseudo-transient solution method based on an iterative, matrix-free approach. The model simulates dehydration reactions driven by deformation-induced pressure variations in mechanically heterogeneous rocks. We benchmark the numerical algorithm by comparing fluid and total pressure variations around mechanically weak inclusions with results from alternative numerical methods, and by validating numerically-modelled reaction-front propagation against a new analytical solution. We then aim to investigate the relationship between shear band formation and serpentinite dehydration. Shear bands are generated using a nonlinear viscous flow law, a pressure-insensitive von Mises criterion, or a pressure-sensitive Drucker–Prager criterion. Our primary objective is to assess whether shear band-related pressure variations can localize dehydration reactions and promote the formation of fluid pathways. Finally, we incorporate a simplified reaction-kinetics model to explore the potential impact of localized deformation within shear bands on the development of dehydration bands.
How to cite: Gasche, G., Cingari, S., Khakimova, L., Duretz, T., and Schmalholz, S.: Coupling of shear banding and dehydration in serpentinite: a numerical study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10960, https://doi.org/10.5194/egusphere-egu26-10960, 2026.
Mantle convection governs the thermal and mechanical evolution of terrestrial planets and provides the long-wavelength engine for plate tectonics and upper-mantle deformation. While early geodynamic models treated the mantle as an incompressible, isoviscous fluid, realistic predictions require non-linear rheology and, in many settings, an explicit treatment of compressibility. Nevertheless, the Boussinesq approximation remains widely used because it neglects volumetric deformation and retains density variations only in the buoyancy term, simplifying the solution procedure. Recent studies indicate that Boussinesq models can reproduce first-order flow speeds in simple cases, but may introduce non-negligible errors in temperature and energetics, motivating the use of compressible formulations. In parallel, Earth’s mantle is inherently multiphase and reactive: mineral phase transitions and solid-solid reactions exchange latent heat and volume, modify buoyancy forces and dissipation patterns, and can alter the style and vigor of convection. Incorporating reaction effects into compressible mantle convection remains challenging, because governing equations are well established for single-phase fluids, but their upscaling and closure assumptions are not straightforward for polymineralic rocks.
Here we present a model formulation for the convection of a multiphase material with applications to the Earth’s mantle. Starting from classical compressible thermomechanical balance laws, we explicitly state the assumptions leading to several compressible approximations used in geodynamics. We then derive the additional closures required to extend the system to reactive polymineralic rocks under a single-velocity approximation (i.e., without explicit melt/fluid percolation), enabling inclusion of both reaction enthalpy and reaction-induced volume change effects.
We compute new two-dimensional solutions of fully compressible convection on Cartesian grids using a pseudo-transient iterative strategy that stabilizes the strongly coupled, highly non-linear system. The simulations confirm the strongly localized nature of adiabatic and dissipative heating and show that mineral reactions can further amplify this localization. Endothermic reactions generally damp convective vigor and can promote transient layering; however, for realistic mantle compositions, layering tends to be intermittent rather than persistent over long times.
Finally, the same framework can be extended to coupled models of multicomponent aqueous-fluid migration with (de)hydration reactions, where fluid-rock interactions within vein networks are tracked together with density and composition changes of the coexisting phases; thermodynamic calculations show that fluid SiO₂ strongly controls the reacting mineral assemblage, and, for example, decompression from 2.5 to 0.2 GPa at 700 °C can shift a six-mineral system to a three-phase assemblage, increasing the fluid Si/O ratio and pre-conditioning the mantle protolith for felsic melt generation.
How to cite: Aranovich, L., Moulas, E., Khakimova, L., and Podladchikov, Y.: Multiphase сompressible mantle convection – model formulation , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21410, https://doi.org/10.5194/egusphere-egu26-21410, 2026.
The flow of fluids within porous rocks is an important process with numerous applications in Earth sciences. Modeling the compaction-driven fluid flow requires solving coupled nonlinear partial differential equations that account for the fluid flow and the solid deformation within the porous medium. Despite the commonly encountered nonlinear relationshipt between porosity and permeability, natural data shows evidence of channelized fluid flow in layered rock formations. Layers of different rock types often have discontinuous hydraulic and mechanical properties, which influences the distribution of chemical trace elements within these rocks.
We present numerical results [1] obtained by a novel space-time method [2] based on a fixed-point scheme inspired by the mathematical analysis [3], combined with a space-time least-squares formulation. This approach can handle discontinuous initial porosity (and hence permeability) distributions without losing its optimal convergence rate. Furthermore, it enables a straightforward coupling to models of mass transport for trace elements as the entire evolution history stored efficiently. Our results show the influence of different kinds of layering in the development of fluid-rich channels and, consequently, on the subsequent mass transport processes [1].
References
[1] Fluid flow channeling and mass transport with discontinuous porosity distribution, S. Boisserée, E. Moulas and M. Bachmayr, Geoscientific Model Development (2025), https://doi.org/10.5194/gmd-18-8143-2025.
[2] An adaptive space-time method for nonlinear poroviscoelastic flows with discontinuous porosities, M. Bachmayr and S. Boisserée, Journal of Numerical Mathematics (2025), https://doi.org/10.1515/jnma-2024-0150.
[3] Analysis of nonlinear poroviscoelastic flows with discontinuous porosities, M. Bachmayr, S. Boisserée and L. M. Kreusser, Nonlinearity (2023), https://doi.org/10.1088/1361-6544/ad0871.
How to cite: Boisserée, S., Moulas, E., and Bachmayr, M.: Space-time methods for poroviscoelastic flow and mass transport, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3531, https://doi.org/10.5194/egusphere-egu26-3531, 2026.
Olivine, the most ubiquitous mineral in the upper mantle, is believed to control the mantle’s rheological properties, and its evolution of crystallographic preferred orientation (CPO) is the primary cause of the mantle’s seismic anisotropy. However, tracking microstructural and textural evolution of olivine-rich mediums in a large-scale geodynamic model has proven to be challenging. The mean-field, kinematic modeling algorithm ‘D-Rex’ has been widely used to simulate CPO evolution in geodynamic models of mantle flow. Despite D-Rex being able to successfully simulate the evolution and formation of CPO, it lacks important microstructural properties. A key limitation of D-Rex has been its lack of dimensionalization and inability to predict a dimensional grain size evolution, which yields an unrealistic evolution of grain size, and over-predicting CPO strength when run to strains where steady-state is expected (>5).
Here, we present D-Rex++, a mean-field CPO evolution framework built upon D-Rex and embedded with the large-scale geodynamic model ASPECT, which enables the simulation of the co-evolution of CPO and the dimensionalized grain sizes of olivine aggregates deformed to high strains. Evolution of grain size results from the competition between nucleation of strain-free grains during dynamic recrystallization and subsequent recovery, driven either by strain energy gradients (strain-induced grain boundary migration, SIGBM) or by grain boundary curvature (grain coarsening). The model's prediction is influenced by the choice of two major free parameters: Mb, which represents the grain boundary mobility and controls the degree of grain size evolution during SIGBM, and Δrx, the rate of dynamic recrystallization.
To benchmark the free parameters, Δrx and Mb, we compared the results from simple shear-box models with existing data from laboratory shear experiments. We observe that increasing Mb increases the strength of the predicted pole figure and increases the range of the grain size distribution (GSD). The value of Δrx serves to decrease the strength of the CPO due to the influx of grains whose orientations are dispersed from their parent grain (i.e., recrystallized). Simulations were conducted to assess the model's ability to predict the impact of pre-existing fabric. In addition, models run under tectonic-scale strain rates were able to simulate the natural occurrence of CPO evolution in response to accumulated shear strain.
A key aspect of the new model is its ability to account for the evolution of the GSD in conjunction with the texture and deformation history. This enables the use of a composite diffusion–dislocation creep viscosity formulation with varying evolving grain size within ASPECT and coupling of microstructural evolution with large-scale geodynamic models. To conclude, the dimensional treatment of microstructural parameters provides a physically interpretable framework that enables systematic calibration and direct integration with the prediction of rheology and viscosity evolution in geodynamic models. D-Rex++ thus provides a pathway toward mantle convection models in which grain size and CPO can evolve consistently, and can be progressively grounded in realistic microstructure evolution.
How to cite: Vedavyas, S., Fraters, M., Boneh, Y., and Billen, M.: D-Rex++: A new and improved tool to bridge microstructure evolution in mantle-scale geodynamics models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10421, https://doi.org/10.5194/egusphere-egu26-10421, 2026.
Mid- to lower-crustal shear zones accommodate large strains by high-temperature viscous flow. Yet, strain localization is strongly modulated by transient thermal and chemical perturbations such as the presence of syn-kinematic melts or fluids.
We aim at unravelling the general strain localization behavior, the role of fluid/melt presence on the rheology of polymineralic shear zones, with focus on potential changes from mid- to lower-crustal levels.
For this purpose, we use the Cossato-Mergozzo-Brissago (CMB) and the Pogallo shear zone systems in the Southern Alps, Northern Italy (Handy, 1987) as a natural laboratory. Field observations and targeted sampling were combined with quantitative microstructural analysis of polymineralic mylonites and ultramylonites. Quartz paleopiezometry (monomineralic quartz bands) provides differential stress and Ti-in-biotite (Henry et al., 2005) provides temperature for felsic lithologies. Such data from natural mylonites are used as input for granitoid shear-zone flow laws (Nevskaya et al., 2025b) to derive strain rates and compare rheology across crustal depths.
Field and microstructural observations indicate two endmember microfabric types. Type I (CMB) fabrics occur within a broad (~2-3 km) belt of felsic mylonites (grain size ~50-100 µm). Inside the mylonites, many dykes developed with episodic pulses of melt injection and syn-kinematic back veining (Handy and Streit, 1999). These mylonites commonly contain quartz-feldspars-mica domains with steady-state grain sizes stabilized by pinning and dissolution-precipitation processes. Ti-in-biotite thermometry indicates lower-crustal temperatures of ~680-730 °C.
Type II (Pogallo) fabrics also represent microstructural steady states characterized by fine- to ultrafine-grained ultramylonites (grain size <5 µm). These fabrics developed in narrower (~500 m) shear zones, where dykes are clearly pre-kinematic boudinaged/lenticular, indicating pure solid-state deformation. Recrystallization of hydrous phases (sheet silicates) and the occurrence of syn-kinematic quartz veins indicate presence of aqueous fluids during shearing. Type II fabrics are consistent with deformation at lower temperatures and/or higher strain rates relative to Type I fabrics. New geo-thermobarometry data yields pressure-temperature estimates indicating deformation at ~5-6 kbar and ~550-600 °C.
In sum, both Type I and Type II polymineralic fabrics record microstructural steady states in which grain size is stabilized by cycles of nucleation and growth, grain-boundary pinning by neighbouring phases, and dissolution-precipitation processes. Systematic decreases in steady-state grain size correlate with changing deformation conditions (temperature and differential stress). These observations are consistent with recent deformation experiments on granitoid ultramylonites, in which pinning-controlled dissolution-precipitation creep (pc-DPC) was identified as a dominant deformation mechanism (Nevskaya et al., 2025a, b). By combining our constraints on deformation conditions and microstructural parameters with the granitoid flow law of Nevskaya et al. (2025b), we assess how strain localization and effective rheology evolve from mid- to lower-crustal levels.
How to cite: Kapuri, K., Herwegh, M., Berger, A., Hermann, J., and Rubatto, D.: Strain localization within polymineralic mid- to lower-crustal rocks: from melt injection to fluid-present solid-state flow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5170, https://doi.org/10.5194/egusphere-egu26-5170, 2026.
Serpentinites are hydrous rocks with a wide pressure-temperature stability range and play a key role in subduction zone dynamics and fluid transfer within the downgoing slab. During subduction, progressive metamorphic reactions transform hydrous mineral assemblages into anhydrous phases. For example, the breakdown of brucite through reactions with antigorite, followed by the terminal breakdown of antigorite to olivine and enstatite, releases aqueous fluids that influence the deep-water cycle and induce major changes in rock density, porosity, permeability, and mechanical strength. Field observations and numerical studies suggest that chemical heterogeneities and variations in fluid composition can localize dehydration reactions and generate fluid pathways. The mechanical-chemical coupling during such fluid pathway generation can be studied with hydro-mechanical-chemical (HMC) numerical models, however, such HMC modelling remains challenging.
Here, we present a HMC model that couples poromechanical deformation and Darcy flow with a thermodynamic model for chemically driven serpentinite dehydration. We develop a two-dimensional numerical HMC model using finite-difference discretization and an accelerated pseudo-transient solution method based on an iterative, matrix-free approach. A particular focus is to make the HMC model conservative to guarantee accurate mass conservation during chemical transport. The numerical implementation integrates thermodynamically constrained look-up tables that relate chemical concentrations with solid and fluid densities to simulate the temporal and spatial evolution of reaction-induced density changes.
We use a new analytical solution for chemically driven reaction-front propagation to test the numerical model. This analytical solution has been validated with laboratory experiments. Initial applications focus on simplified configurations in which a homogeneous medium with a characteristic chemical composition is infiltrated by a fluid with a different silica content, thereby controlling the initiation and propagation of dehydration reactions. The first numerical experiments investigate how dehydration reaction fronts evolve in response to chemical variations. A primary objective of this contribution is to quantify the fundamental controls of chemical heterogeneity on dehydration dynamics and reaction-front propagation as well as the impact of mechanical deformation on such dehydration.
How to cite: Cingari, S., Gasche, G., Khakimova, L., Yarushina, V., and Schmalholz, S.: Mechanical-chemical coupling during chemically driven dehydration in serpentinite: numerical and analytical solutions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10961, https://doi.org/10.5194/egusphere-egu26-10961, 2026.
In recent decades, Digital Rock Physics (DRP) has gained significant attention as an alternative to traditional experimental core analysis. Within the DRP workflow, the absolute permeability of a digital rock sample, reconstructed from micro-computed tomography data, is determined through direct numerical simulation (DNS) by solving the Navier-Stokes equations within the pore space. However, performing full-scale DNS on large digital rock models can demand prohibitive computational resources [1]. A common strategy to mitigate this is to simulate fluid dynamics in smaller subdomains, assuming they constitute a Representative Elementary Volume (REV). But, this is challenging for tight sandstones, an important type of unconventional reservoirs characterized by complex pore structures, narrow and tortuous flow channels, and pronounced heterogeneity. For such digital models, the adequate REV size often becomes so large that its direct simulation exceeds available computational capacities. This limitation necessitates the use of robust numerical upscaling methods to bridge the gap between detailed pore-scale simulations and the macro-scale flow properties of the entire rock.
This work implements and compares two upscaling approaches to predict the effective permeability of full-scale digital rocks: hierarchical homogenization and an analytical method based on an analogy between porous media and electrical resistor networks. Both methods are based on the domain decomposition into smaller subdomains and subsequently calculating local permeability via high-resolution pore-scale DNS. The pore-scale flow simulations are performed using an efficient GPU-accelerated finite difference solver based on the matrix-free relaxation method [2, 3]. The key distinction between the approaches lies in the integration step for obtaining the effective permeability: hierarchical homogenization estimates the overall permeability by considering the rock as a composite medium of homogenized cells, governed by upscaled parameters, while the resistor-network method employs analytical summation based on resistor-network summation rules.
This work is supported by the Russian Science Foundation under grant 24-77-10022.
1. Yakovlev, M., & Konovalov, D. (2023). Multiscale geomechanical modeling under finite strains using finite element method. Continuum Mechanics and Thermodynamics, 35(4), 1223–1234.
2. Räss, L., Utkin, I., Duretz, T., Omlin, S., & Podladchikov, Y. Y. (2022). Assessing the robustness and scalability of the accelerated pseudo-transient method towards exascale computing. Geoscientific Model Development, 15(14), 5757–
3. Alkhimenkov, Y., & Podladchikov, Y. Y. (2025). Accelerated pseudo-transient method for elastic, viscoelastic, and coupled hydro-mechanical problems with applications. Geoscientific Model Development, 18(2), 563–583.
How to cite: Akmanov, I., Lutsenko, P., Yakovlev, M., and Khakimova, L.: Upscaling methods for effective permeability estimation of large digital rock models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11705, https://doi.org/10.5194/egusphere-egu26-11705, 2026.
Geothermal energy is gaining increasing attention as a promising alternative to fossil fuels. The advantage of geothermal power plants over thermal power plants that operate by burning fossil fuels is considered to be the low level of greenhouse gas emissions, primarily carbon dioxide. Another advantage of geothermal power plants is their stable electricity generation, unaffected by time of day or seasonal fluctuations. This distinguishes the use of geothermal resources for electricity generation from solar or wind energy.
At the same time, implementing geothermal energy projects is fraught with a number of challenges. A common problem with geothermal power plants is the precipitation of solids from hydrothermal solutions. Hydrothermal solutions are aqueous solutions that are chemically rich in various substances. When temperature or pressure changes, when minerals dissolve further, or when pH changes, solid precipitates may fall out of such solutions. These processes can have a negative effect and occur in production and reinjection wells, in surface equipment and heat exchangers, as well as in the porous rocks of the geothermal reservoir. Since all of this affects the ultimate efficiency of geothermal energy projects, it is important to study these geochemical processes, including through numerical modeling.
We discuss a mathematical model that can describe the process of solid precipitation from multicomponent hydrothermal solutions moving under the action of a pressure gradient (in a wellbore or in a porous reservoir rock). We show that the considered mathematical model allows us to draw correct conclusions about the growth of solid deposits in wells of a geothermal field in Kamchatka (Russia), consistent with empirical data.
This work is supported by the Russian Science Foundation under grant 24-77-10022.
How to cite: Isaeva, A., Khakimova, L., and Podladchikov, Y.: Numerical modeling of solid precipitation from multicomponent hydrothermal solutions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12734, https://doi.org/10.5194/egusphere-egu26-12734, 2026.
Ice is a polycrystalline material whose microstructure can induce strong viscoplastic anisotropy. Ice fabric (i.e preferred crystal orientations) and ice flow are closely linked: strong anisotropy of a polycristal develops as a result of its deformation history. Strong fabrics have indeed been observed both in nature and in laboratory experiments. In a glacier flow, such anisotropy can modify the directional viscosity of ice, making it locally harder or softer. Preferred crystal orientations may therefore influence glacier flow at large scale.
To better characterize this influence, several models have been developed to predict fabric evolution coupled with glacier flow. However, the impact of fabric under near-melting temperature remains poorly quantified. In such conditions, dynamic recrystallization (DRX) is expected to strongly affect fabric evolution. Moreover, field observations that could constrain and validate fabric-evolution models in warm and highly dynamic flow are still scarce, leaving the role of ice textures in glacier dynamics unconstrained. As a result most large-scale glacier simulations still rely on isotropic rheologies combined with enhancement factors, which cannot adequately represent local anisotropy induced by evolving fabrics.
R3iCe [1] is a full-field model using a finite element method that couples both the mechanical behavior and the texture evolution of polycrystalline ice. It was recently developed to predict the evolution of crystal orientations under constant strain rate or deviatoric stress, driven by viscoplastic deformation and dynamic recrystallization. R3iCe has been validated against different laboratory creep experiments, where it successfully reproduces both texture evolution and the associated mechanical softening during tertiary creep. However, the model remains untested under more complex deformation cases, such as those experienced by ice particles within real glacier flows.
In this contribution, we extend the validated R3iCe model toward glacier-scale applications by constructing a R3iCe Flow Line (RFL) approach. It extracts the deformation history of Lagrangian ice parcels from large-scale glacier flow simulations, such as Elmer/ice, and provides the kinematic inputs required to drive R3iCe along glacier flow lines. The scheme is first validated using torsion experiments, which allow us to quantify the errors involved in predicting fabric evolution along a flow line in this controlled setting.
R3iCe Flow Line is then applied to Argentière Glacier (French Alps), which is a temperate glacier. Near-surface samples collected in the ablation area are assumed to represent end-of-flow line fabrics, and are compared with RFL predictions driven by a transient Elmer/Ice flow simulation.
By combining R3iCe Flow Line, a state-of-the-art Elmer/Ice simulation of Argentière Glacier flow, and field observations, this work aims to demonstrate the importance of accounting for fabric and its evolution under temperate, highly deforming conditions, where DRX is at play.
[1] T.Chauve; M. Montagnat; V. Dansereau; P. Saramito; K. Fourteau; A. Tommasi. Comptes Rendus. Mécanique, Volume 352 (2024), pp. 99-134. doi: 10.5802/crmeca.243
How to cite: Hilzheber, A., Chauve, T., Montagnat, M., and Gimbert, F.: A full-field flowline framework including dynamic recrystallization to predict viscoplastic anisotropy in temperate glacier, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12637, https://doi.org/10.5194/egusphere-egu26-12637, 2026.
Many geodynamic processes on Earth occur with a certain periodicity, which can range from decades to centuries for earthquake cycles to hundreds of millennia for glacial cycles and up to hundreds of millions of years for plate tectonic cycles. From the simplified view of a rock, all of these geodynamic cycles induce a deformation during a loading/opening phase followed by deformation in the opposite direction during the unloading/closing phase. These periodic cycles thus produce deformation without any net strain on the rock.
In this work, we use simple models to determine the types of rock texture that can develop within mantle rocks after multiple cycles of dynamic processes, and to understand how such textures can influence the effective viscosity of the mantle.
Our simplified setup consists of an olivine polycrystal aggregate ( = our mantle rock) that has an initial (either isotropic or anisotropic) texture at the start of the model. We impose a velocity gradient representing either simple or pure shear in a given direction. The aggregate is sheared with the given velocity gradient for a prescribed amount of strain and then the deformation is reversed. To be impartial, we test the same setting with multiple texture evolution models, including the MDM, the D-REX, the SpecFab and the VPSC models.
Our results show that the frequency of deformation cycling and the magnitude of the deformation (in the measure of strain) can dramatically impact both the stability and the type of texture that forms after a few or many deformation cycles. Because these textures are viscously anisotropic, the strain achieved in a deformation cycle thus greatly influences how the mechanical anisotropy of the mantle evolves, and in turn, influences different geodynamic processes.
As an example, during glacial cycles one expects small amounts of strain in the mantle ranging from 0.0001 to a maximum of 0.01 units of strain during loading and unloading of ice on the surface. Our results suggest that i) a given piece of mantle needs to experience the same glacial-interglacial cycles hundreds to thousands of times to experience enough strain cycles to develop a significant texture, and ii) when this happens the developed texture is very different than what one would get for continuously deforming the mantle in the same direction. Instead of developing a point maximum in the shear direction, we observe a girdle-type texture with a small maxima normal to the shear plane that remains stable once developed. At lower frequencies, for which shear direction reversals occur less frequently and with larger amounts of strain, the texture does not stabilize. Instead, the texture initially develops toward a point maxima that becomes partially destroyed by the subsequent reverse deformation.
Given these trends, we conclude that periodic geodynamic processes may significantly influence the formation of upper mantle rock textures, and that the deformation frequency exerts a particularly important control on the eventual rock texture.
How to cite: Király, Á., Häußler, T., and Conrad, C. P.: Modelled mantle texture evolution during periodic geodynamic cycles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13314, https://doi.org/10.5194/egusphere-egu26-13314, 2026.
We present a thermodynamically admissible modelling and simulation framework for hydro-mechanical-chemical (HMC) processes in deformable porous rocks undergoing mineral reactions. The approach targets regimes with extreme localization in time and space, where sharp reaction fronts (shocks) propagate and where reaction-induced property contrasts (e.g., density, porosity, permeability) strongly impact flow.
The model couples multicomponent reactive transport to local equilibrium thermodynamics and is designed to remain robust under large reaction-driven density changes typical of (de)hydration/(de)carbonation, and impurity-driven acidification during CO₂ storage. The numerical algorithm is conservative, ensuring stable solutions in the presence of discontinuities and steep gradients, and is implemented using accelerated solvers with GPU-optimized kernels for high throughput in memory-bound reactive transport problems.
We provide a suite of verification benchmarks for the numerical scheme, including comparisons against analytical solutions for chemically driven metamorphic fronts, as well as compaction-driven infiltration scenarios. Demonstration cases cover: (i) compaction-driven fluid focusing, (ii) (de)carbonation waves, and (iii) multicomponent aqueous systems relevant to CCS, including more than 50 charged species. For CO₂ storage applications, we explicitly evaluate impurity-bearing injection streams and show how buffering by mineral assemblages controls pH and limits unrealistic acidification predicted by reduced-chemistry models.
Overall, the framework enables high-resolution, physically consistent HMC simulations that resolve steep fronts without numerical errors and provide a basis for predictive assessment of injectivity evolution, reaction localization, and trapping efficiency for impurity-tolerant CO₂ injection strategies.
How to cite: Khakimova, L. and Podladchikov, Y.: Rock-fluid dynamics under impurity-bearing CO₂ injection: conservative shock-capturing simulations of reactive fronts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18952, https://doi.org/10.5194/egusphere-egu26-18952, 2026.
The macroscopic properties of porous rocks are governed by their complex microstructure and the constitutive behavior of the solid matrix. Traditional effective media models, often based on analytical solutions for isolated cavities or inclusions, are typically limited to linear elastic or viscous rheologies. However, the elastic-plastic response characteristic of rocks is rarely captured by these approaches. Building on our previous work [1], which provided an analytical solution for elastoplastic compaction and revealed how the effective bulk modulus depends on both elastic properties and yield strength, we extend the framework to include shear effects. Our model demonstrates that plastic yielding couples shear and volumetric responses, leading to phenomena such as shear-enhanced compaction and significant deviations from traditional linear predictions.
Here, we extend this framework [1] by deriving the effective shear modulus and exploring how plastic yielding jointly controls both bulk and shear responses [2]. We systematically test the limits of the analytical solution against high-resolution numerical models of multiple interacting voids, in both 2D (cylindrical/elliptical voids) and 3D (spherical voids) geometries. Our results show that the elastoplastic analytical solution remains valid for rocks with higher porosities of up to 20%, extending beyond typical dilute-distribution assumptions. For cylindrical voids in the 2D case, the merging of plastic zones leads to a sharp decrease in the effective bulk modulus and the onset of full pore collapse. The analytical solution for the critical pressure at which full pore collapse occurs agrees well with the numerical results. For spherical voids arranged in 3D configurations, plastic zone merging leads to a more gradual reduction in the effective bulk modulus. Furthermore, under the influence of shear stresses, the development of aligned plastic zones leads to stress-induced anisotropy in initially isotropic materials.
For numerical homogenization, we employ two complementary approaches: a GPU‑accelerated finite‑difference solver (dynamic relaxation method) and a finite/spectral‑element solver (based on CAE Fidesys [3] computational kernel). To ensure the reliability of the calculated effective moduli, we implement periodic boundary conditions, which we find essential for minimizing spurious boundary effects in both 2D and 3D simulations. The developed numerical tools are capable of handling complex rock microstructures, broadening the potential applications of this modeling approach.
MY acknowledges the support by the Russian Science Foundation under grant 24-77-10022.
1. Yarushina, V.M., Podladchikov Y.Y., & Wang L.H. (2020). Model for (de)compaction and porosity waves in porous rocks under shear stresses. Journal of Geophysical Research: Solid Earth, 125(8), e2020JB019683.
2. Yakovlev, M.Ya., Yarushina, V.M., Bystrov, I.D., Nikitin, L.S., & Podladchikov, Yu.Yu. (2025). Benchmarking effective moduli in porous elastoplastic materials. International Journal of Mechanical Sciences, 306, 110854.
3. https://cae-fidesys.com/
How to cite: Yakovlev, M., Yarushina, V., Bystrov, I., Nikitin, L., and Podladchikov, Y.: Effective moduli of porous elastoplastic rocks: micromechanical modeling and numerical verification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19655, https://doi.org/10.5194/egusphere-egu26-19655, 2026.
The advent of inverse diffusion modelling in minerals has allowed the quantification of effective timescales and cooling rates of metamorphic assemblages. Such information can be proven very useful if combined with information from conventional thermobarometry. This is because, cooling rates at various geologic conditions can provide essential constraints on the temporal character of geodynamic models. Constraining the temporal character of metamorphic processes from natural data provides us with non-unique solutions because of the nature of the data examined. However, considering additional constraints from geophysical/geodynamic models helps reducing the uncertainty of the results since it allows the incorporation of additional (and independent) constraints. Additional constraints include, but are not limited to, erosion rates, maximum topography and maximum surface heat flux.
In this work I present a systematic study from thermo-kinematic and thermo-mechanical models that aims in identifying the key parameters responsible for the preservation of steep compositional gradients in minerals. Results show that in active tectonic environments, fast advection is essential for the rapid transient cooling of metamorphic assemblages. However, for the same type of data, less extreme velocity values can be used if the effects of dissipative heating are included. Therefore, apart from the thermodynamic consistency, the consideration of dissipative heating during geological deformation allows the use of more realistic parameters in geodynamic models.
How to cite: Moulas, E.: Metamorphic evidence of rapid heat production during geological deformation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14416, https://doi.org/10.5194/egusphere-egu26-14416, 2026.
Earth is unique in that it exhibits plate tectonics, where weak localised zones of deformation enable the relative movement of rigid plates. At depth, shear deformation predominantly occurs on narrow zones of fine-grained ultramylonites thought to be both a product of, and contributor to, localisation. In natural rocks, most shear localisation is linked to grain-size sensitive creep, which is facilitated by grain-size reduction and phase mixing. However, the mechanisms of strain localization in large crystals or monomineralic materials (e.g., glaciers, quartz veins, the mantle) are less clear. We deformed nominally dry, synthetic single-crystals of quartz, a major component of the continental crust, at a pressure of 1.5 GPa and temperature of 900°C using a solid salt assembly (SSA) Griggs apparatus at Texas A&M University to examine the mechanisms of strain localization in monomineralic materials. Quartz crystals were cored parallel to <m1> to promote slip of <a> on {m}, that is, prism-<a> slip. Slices of quartz were then cut at 45° to the long axis of the cylinder and deformed in general shear at an approximate shear strain rate of 10−5 s−1. To explore how strain varied both throughout the sample and with progressive deformation, a gold foil was inserted into the centre of the quartz slice perpendicular to the shear direction prior to sample assembly to act as a passive strain marker. We stopped experiments at a variety of macroscopic shear strains ranging from 1.5 to 5.4. Despite being nominally dry, samples deformed pervasively by dislocation creep with extensive recrystallisation. After a critical strain threshold (Ɣ = ~ 1), deformation progressively localised to the central region of the sample with increasing strain. The highest strain experiments (Ɣ ≥ 4.4) display local variations in strain of over two orders of magnitude. Although yield stress varied greatly between experiments, the sample fabric consistently evolved with increasing strain, with more deformed samples evolving ever finer grain sizes and a fabric orientation (defined by elongate grains or ribbons of quartz) which progressively rotated towards the shear plane. Interestingly, grain size seems to evolve as a function of strain rather than stress in these experiments. Our study provides a critical new dataset for exploring shear strain evolution, demonstrating that strain rates are non uniform in general shear experiments (like natural shear zones) following a critical strain threshold. Studies which assume a single steady-state experimental strain rate (e.g., flow laws, experimental studies of microstructural development in rocks) may need to be re-evaluated.
How to cite: Goddard, R., Phillips, N., Kronenberg, A., Ryan, M., V. Dyck, B., Hein, D., and Hollings, P.: Shear-zone development in nominally anhydrous single-crystals of quartz, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15601, https://doi.org/10.5194/egusphere-egu26-15601, 2026.
