Mineral reactions have mechanical effects that may result in the development of pressure variations and thus are critical for interpreting microstructural and mineral composition observations. Such effects may fundamentally influence element transport properties and rheological behavior.
Here, we encourage presentations focused on the interplay between metamorphic processes and deformation on all scales, on the rheological behavior of crustal and mantle rocks, and time scales of metamorphic reactions in order to discuss
(1) how and when up to GPa-level differential stress and pressure variations can be built and maintained at geological timescales and modeling of such systems,
(2) deviations from lithostatic pressure during metamorphism: fact or fiction?
(3) the impact of deviations from lithostatic pressure on geodynamic reconstructions.
(4) the effect of porous fluid and partial melting on the long-term strength.
We, therefore, invite the researchers from different domains (rock mechanics, petrographic observations, geodynamic and thermo-mechanical modeling) to share their views on the way forward for improving our knowledge of the long-term rheology and chemo-thermo-mechanical behavior of the lithosphere and mantle.
The understanding of geodynamic processes such as earthquakes and mountain building requires a deep knowledge of mineral and rock deformation mechanisms (e.g. Karato, 2013). The most used approach to study mineral and rock rheology is by means of experimental investigations. However, they can be significantly challenged by both apparatus corrections and grain-boundary interactions that result in inhomogeneous stress states within deforming samples. Moreover, few experimental data are available for single crystals under tensile stress even if this is a quite common environment in the crust at all scales (e.g. Fossen, 2010). Finally, most of the data that we have on mineral and rock rheology comes from gem quality, often synthetic, crystals, but they are far to represent the bulk of the crust.
In this contribution, a novel approach that aims to overcome some of these difficulties is presented. The rheology of minerals can be explored using natural host-inclusion mineral systems instead of an experimental deformation apparatus on synthetic products. Host-inclusion systems are the simplest natural “rock samples” occurring on Earth because they consist of two mineral grains and one grain boundary. Moreover, because of the contrast in the thermal expansion and compressibility coefficients between the host and the inclusion, host-inclusion mineral couples are pre-stressed under most pressure and temperature conditions. Therefore, by applying pressure and/or temperature to such systems in the laboratory, it is possible to generate tensile and compressive stresses in the host mineral which can be measured in situ using Raman spectroscopy without applying apparatus corrections (e.g. Campomenosi et al. 2024). Finally, mineral flow laws along with the role of grain boundaries can be investigated from the host deformation experiments coupled with numerical simulation modelling (e.g. Zhong et al. 2024). This new methodology can improve our quantitative understanding of mineral strength under different stress state at non-ambient conditions, providing a significant step forward in the quantification of larger scale geodynamic processes.
References
Campomenosi, N., Angel, R. J., Mihailova, B., & Alvaro, M. (2024). Mineral host inclusion systems are a window into the solid-state rheology of the Earth. Communications Earth & Environment, 5(1), 660.
Fossen, H. (2010). Structural Geology. Cambridge University Press, 480 pp.
Karato, S. I. (2013). Rheological properties of minerals and rocks. Physics and Chemistry of the Deep Earth, 94-144.
Zhong, X., Wallis, D., Kingsbery, P., & John, T. (2024). The effect of aqueous fluid on viscous relaxation of garnet and modification of inclusion pressures after entrapment. Earth and Planetary Science Letters, 636, 118713.
How to cite: Campomenosi, N.: Host-inclusion mineral systems as a new probe for in situ mineral rheology at non-ambient conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-978, https://doi.org/10.5194/egusphere-egu25-978, 2025.
Theory suggests the possibility for significant deviations between total pressure (or dynamic pressure) and lithostatic pressure during crustal metamorphism. If such deviations exist, the implications for orogenic reconstruction would be profound. Whether such non-lithostatic pressure conditions during crustal metamorphism are recorded and preserved in the rock record remains unresolved, as direct field evidence for this phenomenon is limited. Here, we investigate the Paleogene Tethyan Himalaya fold-thrust belt in Himachal Pradesh, northwestern India, which is the structurally highest part of the Himalayan orogen and deforms a ~10–15 km thick Neoproterozoic–Cretaceous passive margin stratigraphic section. Field-based kinematic studies demonstrate relatively moderate shortening strain across the Tethyan Himalaya. However, basal Tethyan strata consistently yield elevated pressure-temperature-time (P-T-t) estimates of 7–8 kbar and ~650°C, indicative of deep burial during Himalayan orogeny (ca. 20–45 Ma, 25–30 km depths). These P-T-t conditions can be reconciled by: (1) deep Cenozoic burial along cryptic structures and/or significant flattening of the Tethyan strata; (2) basal Tethyan strata recording metamorphism and deformation related to pre-Himalayan tectonism; or (3) non-lithostatic pressure conditions (i.e., tectonic overpressure).
To test these models, we systematically mapped the Tethyan fold-thrust belt along the Pin Valley transect in northwestern India, a classic site for stratigraphic, paleontological, paleoenvironmental, and structural reconstructions. The Pin Valley region provides an opportunity to study a structurally continuous metamorphic field gradient from the near-surface to structural depths between 10–15 km, which should reflect P conditions ≤4 kbar if lithostatic. We integrate a multi-method approach combining detailed geologic mapping with quantitative analytical techniques (e.g., thermometry, finite strain analyses, thermo/geochronology, and thermobarometry) to quantify the magnitude, kinematics, thermal architecture, and timing of regional deformation, metamorphism, and subsequent exhumation. Results show: (1) throw on shortening structures is moderate to low (≤4 km); (2) temperature-depth relationships record a continuous, but regionally elevated, upper-crustal geothermal gradient of ≥40 °C/km, which is inconsistent with deep burial models (≤25 °C/km); (3) minimal flattening of basal Tethyan strata; (4) upper Tethyan strata yield pre-Himalayan low-temperature thermochronology dates, further refuting deep Cenozoic burial; and (5) basal Tethyan P-T-t estimates confirm elevated mid-crustal conditions of ~7 kbar, 630°C at 10–15 km depths during the Cenozoic. Preliminary volume expansion calculations are minimal; therefore, mechanisms involving non-hydrostatic thermodynamics, deviatoric stresses, rock strength contrasts, and tectonic mode switching are being explored.
How to cite: Vlaha, D. R., Zuza, A. V., Guevara, V. E., Haproff, P. J., Webb, A. A. G., Reyes, F., Genge, M. C., Ganbat, A., Wilderman, D., and Singh, B. P.: Mid-crustal overpressure in the Tethyan Himalaya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11961, https://doi.org/10.5194/egusphere-egu25-11961, 2025.
Mid-ocean ridge eruptions and hydrothermal circulation are thought to be fueled by sill-shaped axial melt lenses (AMLs) located a few km below seafloor. Multiple such bodies have now been seismically imaged within lower crustal mush zones. The short recurrence time of eruptions (~10 yrs) at fast-spreading ridges, as well as the considerable heat output of hydrothermal vents (~100 MW) both suggest that AMLs undergo magmatic replenishment at rates that match or exceed long-term rates of oceanic crust accretion. Repeated seismic imaging recently confirmed that AMLs can expand significantly in ~20 years. Lastly, distributed seafloor uplift (~10 cm/yr) indicative of inflation in sub-axial magma reservoirs has now been documented at two magmatically-robust ridge segments.
While observations point to highly dynamic AMLs on decadal time scales, the associated rates of magmatic inflation, and the underlying physics of spontaneous magmatic overpressurization remain elusive. This presentation will review existing and novel constraints on AML inflation dynamics, from the interpretation of seafloor geodetic data to the impact of overpressurization on hydrothermal output. These constraints will then be used to evaluate a range of candidate mechanisms, from volatile exsolution to decompaction below a permeability barrier.
How to cite: Olive, J.-A., Boulze, H., Moutard, K., Chen, J., Barreyre, T., and Aharonov, E.: Overpressure build-up in mid-ocean ridge magma lenses, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15126, https://doi.org/10.5194/egusphere-egu25-15126, 2025.
Evidence from seismological and isotopic studies suggest that fluids released from hydrated lithosphere at great depth in subduction zones can travel upwards through the dry mantle wedge. When they reach the overlying crust, the fluids induce melting which is thought to feed volcanoes on the surface. Many continental collision zones are the result of the closure of an ocean. The suture zone may still contain hydrated rocks. During burial in the continent-continent collision, these rocks may dehydrate, and fluids can travel up through dry overlying crustal rocks. The Western Gneiss Region (WGR) of Norway, a basement window in the Scandinavian Caledonides, is well known for its occurrences of eclogites and peridotites with metamorphic pressures reaching diamond stability field. Often the surrounding felsic gneiss shows evidence for fluid infiltration and partial melting. However, the majority of the protoliths in the WGR consisted of dry felsic magmatic rocks and the source of the fluid for metasomatism and melting remains enigmatic. Like oceanic subduction zones, fluids rising through the overlying dry rocks may be responsible for partial melting in (ultra)-high pressure terrains in continental collision zones. On the way up these fluids react with the rocks and transport mass by carrying chemical elements in solution and metasomatize original continental crust. Fluid focusing may be the reason for the local occurrence of partial melting. This can lead to overpressure due to local volume increasing melting reactions which explains erratic deviations in metamorphic pressure compared to the overall metamorphic field gradient. The newest methodology for calculating aqueous speciation of fluids in the deep earth combined with the latest techniques in numerical modelling of reactive transport is used here to build a quantitative understanding of the processes.
How to cite: Vrijmoed, J. C.: Fluid induced partial melting as a cause for ultra-high-pressure metamorphism, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15420, https://doi.org/10.5194/egusphere-egu25-15420, 2025.
Fluid migration across the lithosphere and mantle, involving aqueous fluids and melts, is crucial to geodynamic processes, including intra-plate volcanism and lithospheric metasomatism. In regions dominated by viscous deformation, porosity waves are a potential mechanism for fluid mass transport. For a constant compaction viscosity, porosity waves initiated by circular perturbations maintain a “blob-like” geometry. However, under decompaction weakening, where compaction viscosity decreases during dilation, these waves adopt a “channel-like” geometry, even when initiated with circular perturbations. While prior numerical studies established that blob-like porosity waves efficiently transport fluid mass, the efficiency of channel-like waves remains unclear. To address this, we present two-dimensional numerical simulations comparing fluid mass transport in blob-like and channel-like porosity waves. Our numerical model integrates tracer transport with varying distribution coefficients to quantify differences in transport efficiency. Preliminary results show that channel-like porosity waves significantly outperform blob-like waves in fluid mass transport. Furthermore, we apply our model to investigate lithospheric metasomatism driven by fluid migration, shedding light on processes underlying intra-plate volcanism, such as petit-spot volcanism.
How to cite: Schmalholz, S. M., Cingari, S., and Khakimova, L.: Impact of Channeling on Fluid Mass Transport by Porosity Waves, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8676, https://doi.org/10.5194/egusphere-egu25-8676, 2025.
Understanding the formation of continental crust, predominantly felsic and rich in silicon and aluminum, remains a key challenge in geoscience. Current models emphasize magmatic differentiation of basaltic magma, produced by partial melting of mantle peridotite induced by fluids from subducting oceanic crust.
However, over 70 years ago, D.S. Korzhinsky proposed the principle of alkali mobility during metamorphism and granitization, emphasizing the significance of alkali (K₂O, Na₂O) and volatile components (H₂O, CO₂) in crust formation [1]. His insights highlighted the role of transmagmatic fluids but lacked a physical framework for describing fluid transport through silicate melts.
Building on Korzhinsky’s concept, we propose a coupled mathematical model that describes the migration of multi-component aqueous solutions at the lithosphere’s base, driven by (de)compaction of fluid-saturated viscoelastic rocks and accompanied by (de)hydration reactions. This model incorporates fluid-rock interactions within vein structures and accounts for changes in density and composition of coexisting phases. Thermodynamic calculations using THERMOLAB [3] reveal that SiO₂ content in fluids significantly influences mineral assemblages. For example, decompression from 2.5 to 0.2 GPa at 700°C transitions a six-mineral system to a three-phase assemblage, increasing the Si/O ratio and priming the mantle protolith for felsic melt generation.
This approach, validated through numerical simulations [4], advances the understanding of metasomatic processes, offering a robust framework to explore fluid-mediated mechanisms in continental crust formation.
[1] Korzhinskii, D. S. Transmagmatic Fluid Flows of Subcrustal Origin and Their Role in Magmatism and Metamorphism. Crust and Upper Mantle of the Earth (IGC, XXIII Session. Reports of Soviet Geologists, Problem 1), Moscow: Nauka, 1968, pp. 69-74.
[2] Aranovich, L. Y. The Role of Brines in High-Temperature Metamorphism and Granitization. Petrology, 2017, Vol. 25, No. 5, pp. 491-503.
[3] Vrijmoed, J. C., & Podladchikov, Y. Y. Thermolab: A Thermodynamics Laboratory for Nonlinear Transport Processes in Open Systems. Geochemistry, Geophysics, Geosystems, 2022, Vol. 23, No. 4, e2021GC010303.
[4] Khakimova, L., & Podladchikov, Y. Modeling Multicomponent Fluid Flow in Deforming and Reacting Porous Rock. Petrology, 2024, Vol. 32, No. 1, pp. 2-15.
How to cite: Aranovich, L. and Khakimova, L.: Reactive Fluid Flow in Generation of Felsic Crust, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13075, https://doi.org/10.5194/egusphere-egu25-13075, 2025.
Fluid-rock interactions can induce significant chemical changes, resulting in metasomatic rock transformations or the formation of metasomatic fronts when mass transfer is substantial. Among the chemical agents driving metasomatism, magnesium (Mg) plays a critical role, particularly in mafic and ultramafic rock systems. Magnesium's transport not only alters bulk composition but also impacts mineral assemblages in affected rock volumes. Additionally, the large mass difference between 24Mg and 26Mg isotopes enables detectable kinetic fractionation in the rock record.
This study examines a metasomatic reaction zone within the Voltri Massif of the Ligurian Alps (Italy), formed through high-pressure (HP) diffusional metasomatism of a (meta)gabbroic body by Mg-rich fluids (with Ni and Cr) equilibrated with serpentinite. This zone serves as an ideal natural analogue for reactive fluid flow between the downgoing hydrated lithospheric mantle and the overlying mafic crust. The reaction zone features distinct mineralogical changes: a chlorite- and amphibole-rich assemblage near the lithological contact and an epidote-rich assemblage further away.
Evidence for Mg metasomatism includes a continuous MgO gradient, transitioning from serpentinite (~40 wt.%) to metagabbro (~5 wt.%). Isotopic analysis reveals significant fractionation along the transect, with δ26Mg values ranging from +0.09‰ in serpentinite to -1.1‰ in the reaction zone, then increasing to -0.1‰ in metagabbro. This trend indicates kinetic isotope fractionation driven by Mg diffusion.
A reactive transport model incorporating viscous rheology is applied to investigate porosity-permeability evolution and estimate the duration of the process. By integrating bulk rock major element and Mg isotope geochemistry with fully coupled Thermo-Hydro-Mechanical-Chemical (THMC) modeling for reactive transport and phase equilibria, we analyze geochemical and mineralogical transformations across the reaction zone. The model results are validated by fitting field-based geochemical and isotopic data, ensuring consistency with observed MgO gradients and δ26Mg fractionation patterns. Systematic numerical simulations and analyses provide insights into the timescales of Mg metasomatism, shedding light on the dynamics of such metamorphic processes.
How to cite: Antonenko, B., John, T., Dragovic, B., Codillo, E., Scambelluri, M., and Vrijmoed, J.: Thermo-Hydro-Mechanical-Chemical (THMC) reactive transport modeling of Mg isotope fractionation to constrain the timescales of fluid-driven rock transformation in the crust., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18967, https://doi.org/10.5194/egusphere-egu25-18967, 2025.
A key effort in geodynamics is to understand the interplay between localized porous fluid flow and rock deformation. Our primary focus is exploring the effect of brittle deformation and consequent dynamic permeability evolution on localized fluid migration pathways. Such processes are well documented in sedimentary reservoirs and in magmatic systems. The most critical applications include induced seismicity, fault reactivation and associated integrity of cap rocks in siliciclastic reservoirs and dike and sill emplacement with associated seismicity in magmatic systems.
In our models we consider fluid flow in a deformable porous medium. The governing equations are derived from the conservation of mass and momentum in two phases. One phase represents the solid skeleton, which deforms in a poro-(visco-)elasto-plastic manner. The second phase represents low viscosity fluid (water, CH, melt), percolating through the solid skeleton, that is described by Darcy’s law. A special process we will investigate is brittle failure of the matrix due to high fluid pressure (hydro-fracturing, fault reactivation, diking). The system of equations is solved numerically, using the pseudo transient method, that is well suited to solve highly non-linear problems, as solving the global equations and iterating the non-linearities can be done at the same time. Moreover, the algorithm requires large number of local and cheap operations which is ideal for GPU implementation.
We demonstrate that our newly developed numerical codes can resolve important end-member cases of fluid induced fracturing (mode-1 and mode-2). Furthermore, we extract components of seismic moment tensors from the poro-elasto- plastic geomechanical numerical simulation. This approach bridges geomechanical parameters with seismological observables, providing a promising avenue for a more comprehensive understanding of the progressive deformation associated with fluid migration.
How to cite: Kiss, D., Yarushina, V., and Minakov, A.: Hydromechanical modelling of poro-(visco-)elasto-plastic deformation and fluid flow localization , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18320, https://doi.org/10.5194/egusphere-egu25-18320, 2025.
Coupled multiphase flow and poromechanics play a fundamental role in various Earth science applications, from subsurface energy extraction to induced seismicity. However, the inherent complexity of subsurface environments—characterized by fluid compressibility, capillary effects, and heterogeneous permeability—poses significant computational challenges, particularly in high-resolution three-dimensional simulations.
To overcome these challenges, we develop a high-performance computational framework optimized for Graphics Processing Units (GPUs) to simulate two-phase flow in deformable porous media. Our approach introduces a novel formulation of the poro-visco-elasto-plastic equations, explicitly designed for GPU architectures. This framework accounts for compressible fluids with capillary pressure effects and employs a customized iterative solver that enhances computational efficiency. By leveraging modern GPU hardware, we enable large-scale simulations with unprecedented spatial resolution, facilitating faster computations and significantly larger grid sizes than previously achievable.
Our results reveal that within shear bands, pressure drops occur similarly to single-phase fluid environments. However, in our two-phase flow model, pressure evolves differently due to the influence of strain localization on capillary pressure. This interaction between multiphase flow and mechanical deformation introduces new physical insights, suggesting that strain localization may play a critical role in modifying fluid distributions and capillary effects. These findings offer a deeper understanding of two-phase flow behavior in deforming porous media, with implications for geomechanics, fault stability, and fluid-driven deformation processes.
How to cite: Alkhimenkov, Y. and Juanes, R.: Coupled Multiphase Flow and Poromechanics: Insights into the Effect of Capillarity on Strain Localization from High-Resolution GPU Simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16646, https://doi.org/10.5194/egusphere-egu25-16646, 2025.
During progressive deformation, a strong inclusion in a weaker matrix causes a heterogeneous differential stress field, which not only results in strain localisation nucleating in the compressive quadrants of the clast but potentially also causes local pressure variations. Numerical modelling indicates that especially in a polyphase rock with a clast-in-matrix structure, pressures can locally vary by up to 1 GPa. So far, it is not clear whether and how local tectonically induced pressure changes are reflected in the mineral paragenesis of metamorphic rocks. Here, we present an example of stress-induced mineral replacement from the north Norwegian Caledonides (Finnmark) which is consistent with a local variation in mineral paragenesis due to pressure variations around strong inclusions.
A subvertical metadolerite dyke was rotated to align with the penetrative regional foliation during the emplacement of the overlying nappe. The metadolerite, now reduced to a thickness of approximately 1.4 cm is sandwiched between two quartzite layers and has undergone alteration to a schist comprising biotite, titanite, epidote, garnet, quartz and accessory apatite. The garnets are subhedral and frequently exhibit two growth zones, with inclusions of predominantly titanite and rare amphibole. The surrounding metasedimentary schists contain staurolite, suggesting mid-amphibolite-facies metamorphic conditions (~550 °C and 6 kbar). During later deformation of the altered metadolerite (i.e., biotite schist), some garnets were pushed into the adjacent quartzite, forming prominent ultramylonitic quartz tectoglyphs, while garnets remaining within the biotite schist were rotated to form delta-type structures. In contrast to garnets, epidote and apatite clasts are characterised by a lower aspect ratio and locally appear to have aligned in a stable orientation within the strongly foliated biotite matrix. Such stable clasts show a thin layer (< 25 µm) of phengitic white mica accompanied by nanocrystals of quartz in their compressive quadrants. The phengitic nature of the white mica suggests a pressure value deviating from the accepted regional mid-amphibolite facies conditions (~550 °C and 6 kbar), potentially indicating a local tectonic overpressure around the strong clasts in the weak biotite matrix. This hypothesis, however, still needs to be validated by further quantification of the local variations in pressure and temperature conditions.
How to cite: Rogowitz, A., Goncalves, P., Rice, A. H. N., Hou, Z., and Grasemann, B.: Differential stress induced mineral replacement around strong clasts in a weak biotite matrix, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3241, https://doi.org/10.5194/egusphere-egu25-3241, 2025.
Mechanochemical study have shown that mechanical forces can directly affect chemical bonds and bias reaction pathways.
Quantum chemistry calculations and molecular simulations on the gas generation mechanisms of coals indicated that shear stress can directly affect the six-membered ring structure and cause rupture, resulting in structural defects that are unlikely to occur under thermal activation (Xu et al., 2015; Hou et al., 2017; Wang et al., 2017, 2019, 2021). The results also indicate that the creation of structural defects involves energy absorption and the conversion of mechanical energy into internal energy (Han et al., 2016, 2017). The aromatic rings can rotate more easily than the bond stretching under stress (Wang et al., 2019).
Combined with the Tersoff potential, molecular dynamics simulation on the shear deformation process of two α-quartz crystals show that the crystal model primarily exhibits atoms flowing and changing in the direction of chemical bonds during the steady-state flow stage at 600 K (Sun et al., 2025). The molecular potential energy and stress vary in an oscillating up-and-down curve during shear, indicating that chemical energy can be stored and released during plastic deformation.
Studies from the mechanochemistry and tectonic stress chemistry indicate that the differential stress may influence the metamorphism and also the mechanism of the partial melting of the subduction plate.
References:
- Han, Y., Xu, R., Hou, Q., Wang, J., and Pan, J., 2016, Deformation Mechanisms and Macromolecular Structure Response of Anthracite under Different Stress: Energy & Fuels, v. 30, no. 2, p. 975-983.
- Han, Y., Wang, J., Dong, Y., Hou, Q., and Pan, J., 2017, The role of structure defects in the deformation of anthracite and their influence on the macromolecular structure: Fuel, v. 206, p. 1-9.
- Hou, Q., Han, Y., Wang, J., Dong, Y., and Pan, J., 2017, The impacts of stress on the chemical structure of coals: a mini-review based on the recent development of mechanochemistry: Science Bulletin, v. 62, no. 13, p. 965-970.
- Sun, J., Guo, Q., and Hou, Q. 2025. Molecular dynamics simulation of quartz deformation under slow earthquake background: SCIENCE CHINA Earth Sciences. DOI: https://doi.org/10.1007/s11430-024-1469-0.
- Wang, J., Guo, G., Han, Y., Hou, Q., Geng, M., and Zhang, Z., 2019, Mechanolysis mechanisms of the fused aromatic rings of anthracite coal under shear stress: Fuel, v. 253, p. 1247-1255.
- Wang, J., Han, Y., Chen, B., Guo, G., Hou, Q., and Zhang, Z., 2017, Mechanisms of methane generation from anthracite at low temperatures: Insights from quantum chemistry calculations: International Journal of Hydrogen Energy, v. 42, no. 30, p. 18922-18929.
- Wang, J., Hou, Q., Zeng, F., and Guo, G., 2021, Stress Sensitivity for the Occurrence of Coalbed Gas Outbursts: A Reactive Force Field Molecular Dynamics Study: Energy & Fuels, v. 35, no. 7, p. 5801-5807.
- Xu, R. T., Li, H. J., Hou, Q. L., Li, X. S., and Yu, L. Y., 2015, The effect of different deformation mechanisms on the chemical structure of anthracite coals: Science China: Earth Sciences, v. 58, no. 4, p. 502-509.
How to cite: Guo, Q. and Hou, Q.: Chemical effect of differential stress and its implication on metamorphism and partial melting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17255, https://doi.org/10.5194/egusphere-egu25-17255, 2025.
How to cite: Ibragimov, I. and Moulas, E.: The Dynamics of Ophiolite Emplacement: Insights from Thermomechanical Modeling and Tethyan-Type Ophiolites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19147, https://doi.org/10.5194/egusphere-egu25-19147, 2025.
Partial melting and melt-solid segregation play a key role in crustal differentiation. However, quantifying the melt proportion and its distribution remains challenging. In this study, we document these processes by a structural-petrological analysis of migmatite samples from the southern margin of the Velay dome (French Massif Central), a region that exhibits a progressive transition from micaschists to migmatites formed during the Variscan orogeny.
We first estimate the melt fraction based on the identification of leucosome and mesosome at the outcrop to sample scale within a variety of migmatites across this metamorphic transition. The melt fraction and its chemical composition are further evaluated based on classical petrological analysis using optical microscopy, and geochemical tools (XRF (X-ray fluorescence) and EPMA (Electron Probe Microanalyser)). These data have been used for thermodynamic modeling of migmatite formation and evolution throughout P-T changes using PERPLE_X. We compare these models with textural-micro structural analysis based on SEM (Scanning Electron Microscope) and EBSD (Electron Back Scatter Diffraction) in order to decipher the former residual and peritectic minerals from the minerals crystallized from the melt.
Field observations show migmatites transitioning from metatexites to diatexites. Within metatexites, a network of texturally continuous leucosome veins concordant and discordant relative to the syn-migmatitic foliation points to grain scale melt segregation and melt migration beyond the grain scale. The mineral paragenesis of metatexite migmatite is Mus + Pl + Qz → Melt + Fdk, which is consistent with the modeled mineral reactions identified by thermodynamic modeling. Textural analysis indicates that part of the leucosome consist of a proportion of residual plagioclase, peritectic K-feldspar and quartz crystallized from the melt. Thermodynamic modeling suggests an estimation of melt fraction ranging from ~14% up to ~29% in the metatexites at temperatures ranging from 570 to 650°C and 6 kbar pressure, which is consistent with the estimate derived from textural analysis and is close to the transition between a partially molten rock and a crystal mush (Vanderhaeghe 2009).
This research provides new insights into the mechanisms driving crustal differentiation across scales by quantifying melt fraction and identifying melt-derived textures in partially molten rocks.
How to cite: Bakouche, M., Vanderhaeghe, O., Duchêne, S., Kaczmarek, M.-A., Walther, P., and Thebaud, N.: Partial melting and melt segregation in migmatites from the Southern margin of Velay dome (French Massif Central, Variscan belt)., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6924, https://doi.org/10.5194/egusphere-egu25-6924, 2025.
In convergence zones, metamorphic transformations that affect the subducting lithosphere as due to changes in pressure and temperature significantly influence the mechanical behavior of rocks. For instance, eclogitization of lower crustal rocks, characterized by a notable densification has been associated with strain localization and seismic activity in several localities around the world. However, the mechanisms governing the propagation of this transformation once initiated remain insufficiently understood. In that prospect, this study investigates the process of eclogitization through thermo-mechanical numerical modeling, focusing on the deformation of an inclusion within a reactive matrix of different viscosity. This matrix-inclusion system is deformed under pure shear boundary conditions, and the physical properties of the initial materials evolve toward those of the transformation product in areas of the model where the pressure of the transformation is reached.
A parametric analysis is conducted to assess the influence of a heterogeneous pressure field generated by mechanical heterogeneities on the initiation and propagation of the transformation. Our results show that pressure overstepping and initial viscosity of the material are key factors to trigger the transformation. Other parameters such as (1) density variations during the transformation, (2) the initial viscosity contrast between the matrix and the inclusion, and (3) the shape/orientation of the inclusion instead enhance or inhibit the propagation of the transformation. Additionally, our results show that the direction of the eclogite propagation is systematically perpendicular to the shortening direction. These results show striking similarities with field observations and structural analyses of finger-shaped eclogite fronts on the island of Holsnøy (Norway).
How to cite: Cochet, A., Yamato, P., Baïsset, M., Labrousse, L., and Duretz, T.: On the role of transformation-induced physical changes on eclogite propagation: insights from thermo-mechanical numerical models., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5144, https://doi.org/10.5194/egusphere-egu25-5144, 2025.
Density and viscosity variations induced by metamorphic transformations can significantly impact rock strength. However, despite their importance, most models still largely overlook these transformations.
The goal of this presentation is to clarify and quantify the rheological effects of each of these changes. To achieve this, we first introduce numerical methods that incorporate the dynamic effects of transformations in models (e.g., volume and viscosity changes). In a second time, we illustrate separately the effects of (1) density changes and (2) viscosity changes when a rock undergoes transformation under stress. The models presented enable the study of the dynamic evolution of strain, stress, and pressure fields as a new phase forms within an initially homogeneous rock undergoing transformation.
Our results reveal that, in certain cases, changes in stress and pressure fields can be significant. These findings are particularly crucial for understanding the brittle behavior of rocks under high-pressure conditions. It consequently provides valuable insights into intermediate-depth seismicity occurring in subduction zones.
How to cite: Yamato, P., Duretz, T., Baïsset, M., and Cochet, A.: Thermo-mechanical impacts of metamorphic transformations on rock deformation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5874, https://doi.org/10.5194/egusphere-egu25-5874, 2025.
Aqueous fluids play an essential role in the distribution of chemical elements in the lithosphere. Together with the biosphere, hydrosphere and atmosphere they form an important part of the geochemical cycles in the Earth System. Calculating the chemical composition of aqueous fluids in equilibrium with minerals involving solid solutions is a prerequisite for predictive modelling of open system processes that occur at depth in the Earth. Here it is shown how to do such calculations with Thermolab (Vrijmoed & Podladchikov, 2022). The focus is on the technical details related to Thermolab where efforts were made to facilitate education and clarification of widely known concepts in aqueous speciation calculations. Technical advancements are proposed and compared with classical methods.
Vrijmoed, J. C., & Podladchikov, Y. Y. (2022). Thermolab: A thermodynamics laboratory for nonlinear transport processes in open systems. Geochemistry, Geophysics, Geosystems, 23, e2021GC010303. https://doi.org/10.1029/2021GC010303
How to cite: Podladchikov, Y. and Vrijmoed, J. C.: Aqueous fluid speciation calculations with Thermolab for modelling open system processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15422, https://doi.org/10.5194/egusphere-egu25-15422, 2025.
Injecting carbon dioxide (CO2) into deep geological formations is part of the process of carbon capture, utilisation and storage (CCUS). When CO2 is injected into hydrocarbon reservoirs, a double benefit can be achieved. Indeed, injecting CO2 into oil reservoirs can enhance oil recovery (EOR) and also reduce emissions of this greenhouse gas into the atmosphere. This approach (CCUS-EOR) appears promising as it helps achieve climate goals in a cost-effective manner.
At the same time, CO2 flooding can complicate the phase behavior of fluids in the reservoir. For example, when hydrocarbons are mixed with CO2, three-phase liquid-liquid-vapor (LLV) equilibria can occur. This means that the mixture of hydrocarbons and CO2 is separated to form a vapor and two liquid phases that differ in their physical properties (density, viscosity and phase composition, etc.). These differences affect fluid flow in porous reservoir rocks and the ultimate displacement efficiency in CCUS-EOR projects.
We study the phase behavior of hydrocarbon-carbon dioxide mixtures and the effect of LLV separation on fluid flow using numerical simulation. We show how direct minimization of the Gibbs energy can be used to calculate LLV equilibria, which is a necessary step for subsequent numerical simulation of three-phase transport in porous reservoir rocks.
How to cite: Isaeva, A., Khakimova, L., and Podladchikov, Y.: Three-phase fluid flow in porous rocks during CO2 injection into reservoirs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3832, https://doi.org/10.5194/egusphere-egu25-3832, 2025.
Reactive fluid transport through deformable porous rocks drives key geodynamic processes, including flux melting, subduction zone dehydration, and lithospheric melt migration. These thermo-hydro-mechanical-chemical (THMC) processes involve complex couplings that remain poorly understood.
We present a THMC model and numerical algorithm for multicomponent reactive transport in deformable, two-phase porous media. The model captures heat transfer, fluid-rock reactions, viscoelastic deformation, and porosity changes driven by reactions and deformation. Thermodynamic admissibility ensures consistency across poroelastic and poroviscous regimes. Conservative discretization enables resolving sharp reaction fronts, such as magma crystallization or rock hydration.
Validation against analytical solutions highlights robustness, with applications to melting, (de)hydration in the antigorite–olivine system, and feldspar-rich reactive transport involving 5 neutral and 50 charged species. This open-access tool advances the study of THMC processes in Earth's lithosphere.
How to cite: Khakimova, L., Schmalholz, S., and Podladchikov, Y.: Reactive transport model for chemically driven rock (de)hydration in the Lithosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12977, https://doi.org/10.5194/egusphere-egu25-12977, 2025.
Earth’s volatile budget calculations indicate the need for an additional upward flux of water released through subduction processes, beyond what is accounted for by arc magmatism. This excess water may diffuse or be channeled through various mechanisms. Lithospheric mantle metasomatism via reactive hydrous infiltration is investigated as a critical process shaping Earth's magmatic, chemical, and geodynamic evolution. Fluid-driven metasomatism may play a more significant role in subduction zone and intraplate magmatism than traditionally acknowledged, acting as a primary agent of mantle transformation. In subduction zones, volatile-rich fluids released from dehydrating slabs infiltrate the mantle wedge, lowering the solidus temperature and enabling flux melting. These fluids may also function as agents of chemical transport. Similarly, in intraplate settings, hydrous fluids can introduce incompatible elements and hydrous minerals, altering mantle fertility and geochemistry.
Thermodynamic and transport models are integrated to examine metasomatic processes in the Earth's lithospheric mantle, particularly under conditions relevant to intraplate volcanism. Thermodynamic calculations generate lookup tables for essential variables such as phase densities, fluid incorporation into minerals, and fluid concentrations across pressure-temperature-composition (P-T-X) space, using Gibbs Free Energy minimization via the Thermolab tool. The transport model employs continuum mechanics principles for a two-phase system of fluid or melt and solid phases, with numerical implementation using finite difference methods to solve conservation laws.
Key metasomatic reactions, including dunitization, serpentinization, amphibolitization, and phlogopitization, are explored through thermodynamic and reactive transport models, revealing their impacts on mantle porosity and mineralogy. Dunitization enhances porosity, facilitating melt transport and the formation of high-permeability pathways such as dunite channels. Serpentinization reduces porosity, potentially clogging transport pathways, though its reverse reaction releases volatiles critical for arc magmatism. Amphibolitization reduces porosity while stabilizing amphiboles, providing insights into fluid-driven mantle metasomatism in the oceanic lithosphere. Phlogopitization highlights the significance of high-pressure metasomatic processes in modifying thick cratonic lithospheres and generating protoliths for alkaline and potassic magmatism.
This study emphasizes the underestimated role of water in magmatic processes, extending beyond its facilitation of melting to its crucial role in metasomatic enrichment, heat transfer, and compositional modification. The findings provide a framework for understanding magmatism’s multistep progression, from mantle enrichment to intraplate volcanic activity, and lay the groundwork for advanced two-dimensional models incorporating coupled thermo-hydro-mechanical-chemical (THMC) processes, with accurate porosity evolution.
How to cite: Repac, M., Khakimova, L., Podladchikov, Y., and Pilet, S.: Lithospheric Mantle Metasomatism by Reactive Hydrous Infiltration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18520, https://doi.org/10.5194/egusphere-egu25-18520, 2025.
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 multifaceted problems. However, this progress demands revisiting and refining constitutive models to ensure they are rigorous, thermodynamically consistent, and suitable for computational implementation. A critical aspect of these models is addressing the coupling between fluid flow, rock deformation, chemical reactions, and heat exchange. Specifically, the influence of chemical reactions on porosity evolution and mechanical closure relations requires robust theoretical frameworks. Reservoir rocks experience elastic deformation when subjected to the small pressure changes caused by fluid injection. Elastic deformation affects the reservoir's pore space and permeability, influencing fluid migration and storage capacity. Viscous deformation occurs over time as rocks like salt, shale, or certain clays flow plastically under subsurface conditions. During prolonged CO₂ or H₂ storage, viscous creep can change reservoir geometry, potentially altering caprock integrity and leakage risks. Plastic deformation occurs when the rock is subjected to stresses beyond its yield strength, leading to permanent changes in the reservoir structure. Elevated injection pressures can cause shear failure, inducing fractures or reactivating pre-existing faults, which may compromise containment and pose seismic hazards. This necessitates incorporating elastic, viscous, and plastic rheological behavior into the model. Multiple fluid phases within pore spaces add additional layers of complexity, demanding meticulous attention to thermodynamic consistency in governing equations. This work investigates the thermodynamic admissibility of a multi-phase, coupled thermo-hydro-mechano-chemical model that integrates viscoelastoplastic deformation. Using established thermodynamic principles, we derive closure relations and develop a comprehensive set of governing equations. These equations are formulated to maintain thermodynamic rigor while being optimized for computational efficiency and implementation.
How to cite: Yarushina, V., Podladchikov, Y., and Alkhimenkov, Y.: Thermodynamic modeling of multiphase thermo-hydro-mechano-chemical models with viscoelastoplastic rheology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16518, https://doi.org/10.5194/egusphere-egu25-16518, 2025.
Transitioning to low-emission energy systems involves subsurface activities such as carbon capture and storage (CCS), geological hydrogen storage, and the sealing and abandoning old hydrocarbon wells. Whether tracking the natural transportation of fluid in the subsurface or injecting CO2 or H2, these phenomena are primarily determined by multiphase fluid flow, the deformation of the rock matrix, and chemical fluid-rock interactions. Developing a comprehensive understanding of these processes is essential for reliable assessment of the potential of future storage sites. Here we present newly developed numerical models and validate them with the results of laboratory experiments in transparent microfluidics cells.
Over the last decade, the computational power of Graphics Processing Units (GPUs) showed remarkable growth in absolute terms, per unit cost, and per unit power. At the same time, novel parallel algorithms and efficient and concise high-level packages (e.g., ParallStencil.jl) significantly reduced the difficulty of code development. Therefore, we build a new, robust numerical model to simulate two-phase flow in porous media. The governing equations are derived from the conservation of mass and momentum, which, in the simplest case, results in a coupled system of an elliptic (fluid pressure) and nonlinear advection (saturation) equation, known as the Buckley-Leverett equation. The system of equations is solved with the pseudo-transient method, using staggered grid finite element discretization with a first-order advection scheme (upwind). The model is written in Julia language using GPU-ready algorithms, well suited to exploit the parallel computational efficiency of modern GPU platforms. This will allow detailed simulations of sophisticated subsurface processes. In our presentation, we will briefly discuss the numerical strategies used to apply the pseudo-transient method, traditionally used for elliptic equations, to coupled elliptic-advective systems. We will demonstrate that the numerical method is able to resolve shock fronts with reasonable accuracy.
The numerical results are compared with laboratory experiments in transparent microfluidics cells. The experiments conducted utilizing the microfluidics cell were developed to reproduce the pore-scale behavior of subsurface reservoirs. The experimental setup modeled the injection and displacement of a gas phase (representing H₂ with N₂) inside a medium similar to inert sandstone. Different injection rates were studied to assess the influence on gas distribution and preservation during injecting and backflow mechanisms. Capillary forces, pore-scale interactions, and gas bubble dynamics were analyzed comprehensively by visualization of gas flow pathways. Results from the experiments provide a benchmark for validating the numerical models, mainly in obtaining the impact of injection rate on gas emplacement, efficiency of displacement, and retention of residual gas in porous media.
How to cite: Huseynov, F., Kiss, D., Johnson, J., and Yarushina, V.: Numerical modeling and experimental validation of two-phase flow in porous media., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18932, https://doi.org/10.5194/egusphere-egu25-18932, 2025.
The IODP 392-U1581B borehole was drilled in 2022 about 300 km from the South African coast, at ~4500 m water depth in Transkei Basin. The recovered stratigraphic section includes Cenozoic, mostly carbonaceous, rocks and upper Cretaceous (Maastrichtian and Campanian) siltstones with a low calcium carbonate content (<5 wt%). The lowermost part of the recovered Campanian strata, located between 870 and 1000 m below the seafloor, includes 5-10 cm thick beds of stiff low-porosity (<10%) mudstones. In these beds, we observed enigmatic zebra-like textures including subparallel light-coloured bands (1-5 mm wide) and feather-shaped criss-crossing veins.
Here we present a set of multidisciplinary investigations aiming to define the origin of these enigmatic structures. The SEM-EDS and XRD analyses indicate that the light-coloured bands and veins mainly consist of calcium carbonate, with 10-20% of quartz, clay minerals, siderite, and pyrite. The SEM images reveal microstructures of shear deformation within the bands. The shear plane and transport direction identified based on flow indicators, implies a displacement of ~0.1 mm. In thin sections, the narrow axial zone of the band appears like a void filled with siliciclastic matrix indicating that the crystallization front developed from the fracture wall inwards. The XRD analysis shows that the matrix is composed of quartz, muscovite/illite, kaolinite and some scarce detrital minerals, including siderite, pyrite, plagioclase and others. The siderites grains range in size from 10 to 15 μm, while framboidal pyrite forms small aggregates with a diameter of ~1 μm, often nucleating on top the siderite crystals. Inside the veins, the grain size of the calcite filling is smaller than 1 μm indicating a short crystallization time.
We constrained the origin of the calcium carbonate deposited in the veins using isotopic analyses. 87Sr/86Sr = 0.708-0.709 is close to the isotopic composition of modern seawater. Depletion of 18O (δ18O = -9‰ to -11‰) implies deposition at elevated temperatures. The negative δ13C = -11‰ to -13‰ remains unclear but could be associated with oxidation of methane. Since no evidence of recrystallization was observed in the Campanian strata, these isotopic ratios would rule out that the zebra textures were formed during burial.
The deformation microstructures indicate that calcite precipitated concurrent to dilatant shear fractures. There is no evidence of post-Campanian tectonic events in the Transkei Basin. If such deformation had existed, some deformation indicators outside the siderite-rich layers should be visible. It is well known that extensional disc fractures and other deformation structures can form in core samples during drilling and core recovery. The geometric relations of fractures to core irregularities also imply that the zebra textures can be induced. However, the precipitation of calcium carbonate in the induced fractures would require super-saturation of the fluid, high reaction rates, the source of calcium and carbon. An elevated pH and temperature conditions, mixed oxidizing and reduced fluids, and rapid decompression on core retrieval could potentially drop the solubility of calcite but it is unknown what would drive precipitation calcite on a time scale of minutes to hours.
How to cite: Minakov, A., Yarushina, V., Bohaty, S., Childress, L., Johansen, I., Kihle, J., Mazzini, A., Nooraiepour, M., Polteau, S., Silkoset, P., and Uenzelmann-Neben, G.: Rapid Deformation-Induced Calcite Precipitation in Siltstone from IODP Hole U1581B, Transkei Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6579, https://doi.org/10.5194/egusphere-egu25-6579, 2025.
The expected depth of dehydration reactions in subducted slabs shows correlation with the hypocenters of intermediate-depth earthquakes, suggesting that dehydration embrittlement may be a key mechanism of earthquake nucleation. However, it is still unclear how dehydration embrittlement occurs during mineral reactions. This uncertainty is mainly rooted in the complex interactions between reaction progress, evolution of effective stresses, and deformation, which are challenging to quantify. Here we present 2D hydro-mechanical-chemical numerical models of antigorite dehydration (antigorite --> enstatite + forsterite + H2O) to quantify these interactions. We investigate how deformation may lead to dehydration and whether the reaction causes significant stress perturbations, potentially leading to earthquakes. Results show that dehydration may be triggered by fast deformation. Initially, deformation induces fluid overpressure (fluid pressure > total pressure) zones. Fluid overpressure is then relaxed by the onset and progress of the dehydration reaction, decreasing the chance of fracturing. This behavior is explained by the negative total volume change during the reaction, meaning that the solid and fluid reaction products occupy a smaller volume than the original reactant antigorite. The reaction zone is the least likely to fracture due to reaction-induced weakening and the locally larger increase of total pressure compared to fluid pressure. However, the weakening of the reaction zone also generates rheological contrasts with respect to the intact domain. As the reaction progresses, rheological contrasts induce the development of fluid overpressure zones along the sides of the reaction zone, which may lead to brittle deformation. Furthermore, reaction-induced weakening may also lead to strain localization/runaway processes, potentially causing brittle failure.
Acknowledgements
The reported investigation was financially supported by the National Research, Development and Innovation Office, Hungary (PD143377).
How to cite: Porkoláb, K., Moulas, E., and M. Schmalholz, S.: Modelling antigorite dehydration: links between reaction progress, deformation and stress field evolution , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3065, https://doi.org/10.5194/egusphere-egu25-3065, 2025.
Continental rifting and breakup as well as plate convergence and collision create specific geophysical configurations with characteristic thermal fields which in turn lead to characteristic rheological settings. Three-dimensional data-integrated models demonstrate how thermal fields and rheological configurations of the Earth’s crust and uppermost mantle are characteristic depending on the tectonic setting. While the spatial variation of thermal conductivities, variable contributions of radiogenic heat in response to crustal thickness and composition, and variable average geothermal gradients in response to lithosphere thickness are the main controlling factors, their superposed effects may result in a variety of thermal and rheological configurations. We present examples illustrating that rifts can be hot or cold depending on the rifting mode, the amount of stretching and the time since rift initiation. Passive continental margins can be hotter on their oceanic or continental side depending on the age of the adjacent ocean. The crust is hotter in orogens than in their forelands due to its thickened radiogenic felsic units compounded by a superposed topographic effect. This hotter orogenic crust is rheologically weaker -a finding consistent with the absence of deep crustal seismicity in orogens as the Andes or the Alpine Himalayan Chain.
How to cite: Scheck-Wenderoth, L., Cacace, M., Bott, J., Ajay Kumar, A. K., and Anikiev, D.: Deep thermal field and rheology in different plate tectonic settings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12030, https://doi.org/10.5194/egusphere-egu25-12030, 2025.
The risk assessment of injection-induced seismicity usually combines a poroelastic framework with a rate-and-state seismicity model. This allows for prediction of the stress changes caused by the injection and enables estimation of the frequency of (micro)seismic events in response to these changes. However, this constitutive framework neglects the time-dependent deformation, which is essential at subcritical stress regime. This work presents the laboratory brittle creep experiments on crystalline and sedimentary rock from the Illinois Basin, where microseismic activity was recorded during CO2 storage operations. The specimens are instrumented with strain gauges and LVDT sensors to monitor their deformation over time, as well as acoustic emission sensors to capture the microcracking activity. The shear viscosity associated with the time-dependent response appears to be exponentially sensitive to the applied deviatoric stress and is measured in the range between 1017-1015 Pa·s for the secondary creep stages, and on the order of 1014 Pa·s during the initiation of the tertiary stage. Locally, the state of stress at the injection site is influenced by stratigraphy and heterogeneity of geologic formations, causing variations in acting deviatoric stress of about 1–2 MPa. Because of the exponential dependence of the shear viscosity on applied deviatoric stress, even small stress variations (on the order of a few MPa) can significantly affect the localization of the time-dependent deformation and shorten the time to failure in critically stressed zones, which cannot be accounted for within the poroelastic framework.
How to cite: Bondarenko, N., Ding, S., Podladchikov, Y., and Makhnenko, R.: Role of visco-elasto-plastic deformation in localization of injection-induced microseismic response, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17901, https://doi.org/10.5194/egusphere-egu25-17901, 2025.
