In recent years, the presence of supercritical fluids (T > 400 °C) has for instance gain major attention as they offer significantly more energy potential than conventional geothermal operations. Due to high concentration in elements as Cl and S, the high-T fluids may also carry significant amounts of metals as Cu, Au, Mo, Pb or Se and (supercritical) geothermal production in volcanic systems thus has the potential to become a more sustainable method than traditional mining. Yet, the circulation of hot (100 °C < T < 900 °C) and generally acidic fluids also affects the surrounding rocks mineralogy, porosity, permeability, and mechanical stability, which can trigger seismicity or flank collapse of volcanoes, major hazards in populated and oceanic areas.
The development of numerical simulations for risk mitigation or future operations not only requires a better understanding of fluids, magmas and rocks properties in these complex systems, but also of new formalism adapted to supercritical or CO2/salt-rich conditions.
With this session, we wish to invite petrologists, geochemists, geophysicists, experimentalists and modelers to discuss the conditions of formation, circulation and release of (magmatic)-hydrothermal fluids in volcanic systems and how their interaction with magmas and surrounding rocks may affect the evolution of the geothermal system. Contributions on the properties of the high-T fluids, the extent and timescales of hydrothermal alteration in different settings, rock properties or the development of local to large-scale THMC models are all welcomed.
Geothermal resources at superhot temperatures (T>374°C) offer exceptional energy potential but generally require proximity to active magmatic heat sources. Numerical simulations show that while shallow boiling zones and elevated heat fluxes may persist for tens of thousands of years after an intrusion cools, supercritical conditions are comparatively short-lived, meaning the presence of a high-enthalpy system alone is not diagnostic of supercritical resource potential. Where magmatic heat sources are present, permeability structure and fluid properties such as salinity and gas content are the primary control on resource accessibility. Production modeling of the IDDP-1 well at Krafla indicates near-magma permeabilities of ~10-13 m2, substantially higher than typically assumed for the brittle-ductile transition zone, and likely indicative of efficient stimulation due to cold-water injection during drilling. Yet detecting such conditions from the surface remains challenging. Deep electrical conductors imaged by magnetotellurics are often interpreted as indicators of high-temperature fluids or partial melt, but conductivity depends jointly on temperature, fluid salinity, porosity, and melt fraction, making interpretation of deep conductors ambiguous. Integrated numerical modeling coupling hydrothermal flow simulations with petrophysical forward models offers a pathway to discriminate between these scenarios and develop physics-based exploration guidelines for supercritical geothermal systems.
How to cite: Scott, S. and Gresse, M.: Exploring for supercritical geothermal resources through integrated numerical modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9323, https://doi.org/10.5194/egusphere-egu26-9323, 2026.
Cerro Machín Volcano (Tolima, Colombia) is considered one of the most hazardous volcanic systems in the country due to its eruptive potential and the presence of an active fumarolic field on the central dome. Characterizing these surface manifestations is essential to understand the hydrothermal dynamics and the potential pressurization mechanisms associated with volcanic activity.
In this study, a geoelectrical characterization of the fumarolic field was carried out through the integrated application of Electrical Resistivity Tomography (ERT), Time-Domain Induced Polarization (IP), and Transient Electromagnetic Soundings (TEM). Data acquisition included three ERT+IP profiles using a Schlumberger configuration with 5 m electrode spacing (profile lengths of 255 m, 315 m, and 310 m), together with two TEM soundings performed along two of the profiles.
ERT sections allowed the delineation of the electrical resistivity distribution, revealing a deep high-resistivity body, a laterally extensive low-resistivity and high-chargeability zone surrounding this body, and localized high-chargeability anomalies in the vicinity of the fumaroles. TEM results were consistent with the ERT sections, confirming the presence of the deep resistive body and increasing confidence in the inferred subsurface structure. IP data further complemented the interpretation by identifying electrochemical contrasts associated with altered materials and chargeable minerals.
The integrated interpretation of ERT, IP, and TEM data supports a geoelectrical model consistent with the fumarolic dynamics of the Cerro Machín dome. This study represents the first geoelectrical characterization of the Cerro Machín fumarolic system and provides a baseline for monitoring and future investigations of its evolution.
How to cite: Angulo Melendez, M. V., Florez Torres, M. A., and Sanabria Gomez, J. D.: Geoelectrical characterization of fumarolic zones in the Cerro Machín volcanic dome, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8131, https://doi.org/10.5194/egusphere-egu26-8131, 2026.
Understanding the physical properties of volcanic rocks is critical for assessing the stability and eruptive behaviour of hydrothermal systems. At Poás volcano, Costa Rica, rock physical and mechanical properties vary dramatically in response to hydrothermal alteration, exerting strong controls on fluid migration, pressurization, the initiation of phreatic and phreatomagmatic eruptions, and instability and collapse. Poás volcano provides an exceptional natural laboratory for examining these relationships due to its persistent unrest, dynamic crater lake and hydrothermal system, and well-documented eruptive activity. In this study, we characterize the physical and mechanical properties of altered rocks from the active crater of Poás, including porosity, P-wave velocity, permeability, thermal properties, and uniaxial compressive strength. Our results demonstrate that hydrothermal alteration at Poás produces highly heterogeneous rock frameworks characterized by contrasting physical properties. Alteration tends to reduce primary porosity while simultaneously generating secondary pore networks through mineral dissolution, resulting in complex changes to permeability. Uniaxial compressive strength is strongly diminished in highly altered rocks, particularly where weak secondary minerals replace the original mineral assemblage, increasing the susceptibility of shallow crustal materials to mechanical failure. The spatial distribution of permeability barriers and mechanically weakened zones thus influences both the location and style of eruptive behaviour and the location and size of failure and collapse. By linking measured rock properties to hydrothermal processes, eruptive mechanisms, and instability and collapse, this work provides a framework for evaluating how alteration modulates hazard at Poás and similar volcanic systems. Our findings underscore the importance of characterizing rock physical properties in active hydrothermal environments to better anticipate the conditions that engender volcanic hazards.
How to cite: Mick, E., Heap, M., Avard, G., Moulin, M., Harnett, C., Walter, T., and Troll, V.: Rock properties within highly active hydrothermal systems, a case study of Poás volcano, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2626, https://doi.org/10.5194/egusphere-egu26-2626, 2026.
The growing worldwide demand for metals for industrial purposes has led to the development of new experimental approaches to quantify the extraction of metals from magmatic sources. This implies calculating metal partition coefficients between fluid and melt phases at high pressure and high temperature conditions. Such constraints are necessary to understand metal mobility and deposition in magmatic-hydrothermal environments. Cu and Zn have recently received particular attention, being among the 5 more demanded metals for energy transition due to their wide use in industrial domains.
Previous Cu-Zn fluid-melt partitioning experiments involved fluid inclusion synthesis in cold seal pressure vessels (CSPV) and internally heated pressure vessels (IHPV) with post-mortem analysis of quenched fluids in equilibrium with felsic melts. These studies showed a high scattering of partition coefficient values (from 0.5 to 433 for Cu and from 0.01 to 136.1 for Zn), which may arise from the different P-T conditions investigated and the compositions of melts and fluids [1,2,3,4]. Yet this scatter also points to potential issues and limitations with the employed methods such as uncertainties while measuring.
To overcome those limitations, an approach combining in situ and ex situ techniques has been employed. The ex situ technique involves an IHPV with quench melt analysis by LA-ICP-MS and quench fluid analysis performed by ion chromatography for cations/anions and solution ICP-MS for trace elements; it was employed for dacite and rhyolite melts [5, 6]. However, this method relies on the analysis of post-mortem samples, which do not preserve HP-HT information. A newly developed experimental method for in situ measurements also is thus presented involving an IHPV provided with transparent windows allowing a laser or Synchrotron X-ray beam to be transmitted through. Both methods have been comparatively applied to calculate Cu-Zn fluid-melt partition coefficients in pure water and a 0.2m NaCl solution with haplogranite-rhyolite-andesite melts (1000 bar – 800-1000 °C). This data allows to discuss the effect of fluid salinity and melt composition. Preliminary analyses show higher contents of Zn in the melts compared to Cu (> 500 ppm against ~45 ppm) suggesting that Zn has a stronger affinity for the melt relative to Cu.
[1] Bai and Koster van Groos, 1999. GCA 63, 1117-1131
[2] Williams et al., 1995, Contrib. Mineral. Petrol. 121, 388-399
[3] Urabe, 1987, Eco. Geol. 82, 1049-1052
[4] Zajacz et al., 2008, GCA 72, 2169-2197
[5] Iveson et al., 2019, 516, 18-41
[6] Gion et al., 2022, Chem. Geol. 121061
How to cite: Chatelin, T., Testemale, D., Haupt, C. P., Diagileva, D., Freslon, N., Erdmann, S., Iacono Marziano, G., and Louvel, M.: Effect of fluid salinity and melt composition on the fluid-melt partitioning of Cu-Zn evidenced by ex situ and in situ measurements., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9483, https://doi.org/10.5194/egusphere-egu26-9483, 2026.
Brines play a significant role in magmatic hydrothermal systems by controlling metal transport, phase equilibria and the type and degree of ore enrichment. [1, 2, 3] Accurate and precise constraints on the volumetric and compositional properties of the fluids along with the pressure-temperature (P-T) conditions of vapor–liquid (V–L) phase separation in the H₂O–NaCl system are critical to better understand the behaviour of magmatic-hydrothermal fluids in natural systems. [4] From previous work, it is clear that there are gaps in the investigated P-T conditions of the existing experimental studies that show various discrepancies especially at higher pressures and concentrations where the location of the V–L boundary is more complicated to observe. Therefore, semi-empirical thermodynamic models based on existing experimental datasets lack validation and need to be re-evaluated. [5, 6]
In this contribution, we present ongoing in situ experimental work aimed at precisely constraining the onset of V–L phase separation in the H₂O–NaCl system and determining the densities of coexisting phases over a broad range of pressure, temperature, and compositional conditions i.e. 100-800°C, 200-1500 bars and 0.2-4 molal NaCl. Experiments are conducted in-situ using high-pressure, high-temperature vessel [7] combined with techniques such as X-ray radiography and X-ray absorption to visualise the phase separation changes. In addition,we aim at developing a novel image-based density calculation method to extract a density map for each phase directly from the radiographic data based on the Beer-Lambert attenuation law. Once validated by classical transmission measurements, this approach would enable simultaneous determination of phase proportions and densities, avoiding relying on indirect model assumptions. Preliminary results indicate systematic differences in the P-T conditions of V–L separation compared to earlier experimental and modelling studies, highlighting potential uncertainties in commonly used equations of state.
This work is conducted within the framework of the ANR MAGBRINES project, which investigates the role of magmatic brines in mobilizing and concentrating economically valuable metals in magmatic systems of the Lesser Antilles. From a broader perspective, the new experimental dataset will provide improved constraints for development of new equations of state (EOS) and thermodynamic models for H2O-NaCl, with implications for simulating magmatic degassing, hydrothermal circulation, and ore-forming processes in volcanic arcs. Future work will extend this methodology to more complex brine compositions relevant to natural magmatic–hydrothermal systems.
Keywords: Magmatic-hydrothermal fluids; In-situ experimentation; aqueous sodium chloride; high pressure; high temperature
References:
[1] H. CA, Rev.Mineral.Geochem,65(1), 363-87, 2007.
[2] T. Ulrich, D. Günther and C. Heinrich, Nature, 399(6737):676-9., 1999.
[3] B. Yardley, D. Banks, A. Barnicoat and T. Porter, Australian Mineral Foundation, 2000.
[4] S. Geiger, T. Driesner, C. Heinrich and S. Matthäi, JGR: SE.110, B7, 2005.
[5] R. Bodnar, C. Burnham and S. Sterner, GCA, 49, 9, 1861-73., 1985.
[6] Driesner. T, GCA. 71, 20, 4902-19, 2007.
[7] D. Testemale, R. Argoud, O. Geaymond and J. Hazemann, Review of Scientific Instruments, 76, 4, 2005.
How to cite: Shafqat, A., Louvel, M., and Langerome, B.: Determination of PVT properties and vapor-liquid phase separation in the H2O-NaCl system with in-situ experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9550, https://doi.org/10.5194/egusphere-egu26-9550, 2026.
Volcano unrest associated to ascent of magmatic fluids at shallow depths in the presence of a very active hydrothermal system can promote or enhance extensive hydrothermal rock alteration and form low-strength layers within the edifice. This process can favour flank instability and culminate in partial flank collapse with emplacement of debris-avalanches and pyroclastic-density-currents from potential laterally-directed explosions, engendering significant risks to the surrounding population. In the MYGALE ANR project, we focus on hydrothermal alteration timescales of andesitic rocks to better assess the hazard of volcano flank instability at La Soufrière de Guadeloupe volcano (Eastern Caribbean, France). We characterised the mineral chemistry and the 3D porosity of a suite of unaltered to highly altered andesite samples from the volcanic dome of La Soufrière. Chemical and textural investigation shows the progressive deterioration of plagioclase into kaolinite and Na-alunite, the dissolution of the volcanic glass, and silica precipitation. By comparing the natural products with geochemical computations, we suggest that hydrothermal alteration prevailing at the base of the dome is primarily dominated by the reactive fluid composition (H2O, HCl, and H2SO4) and to a lesser extent by water/rock (W/R) ratio (from 0.5 to 10), pressure close to 100 bars, and temperature (from 150 to 250 °C). We propose that acidic aqueous solutions containing 0.1 mmol/L HCl and 0.15–0.5 mmol/L H2SO4, corresponding to pH of 3.0–3.5, are mandatory to co-precipitate kaolinite, Na-alunite, and silica. We also investigate the alteration of the volcanic dome of La Soufrière under these acidic hydrothermal conditions, using both batch and reactive percolation experiments, combined with kinetic modelling using PHREEQC. The experimental results highlight a strong reactivity of the rhyolitic residual glass and the plagioclase phenocrysts, leading to the formation of clay minerals such as illite, while the pyroxenes and the Fe-Ti oxides remain largely unaltered. Spatial mineralogical heterogeneities develop along the reacted cores, with intense dissolution and secondary mineral precipitation near the fluid inlet and preservation of primary phases toward the outlet. Kinetic simulations of plagioclase dissolution in either pure water or HCl highlight the influence of temperature, W/R ratio, grain-size, and pH on silicon release. Increased temperature and a lower W/R ratio enhance the dissolution rate, while larger grain-sizes reduce the reactive surface area and slow reaction progress. Anorthite dissolution kinetics and alteration extent are also strongly pH-dependent, remaining negligible at pH ≥ 2, becoming rapidly self-limited at pH~1, and evolving continuously under extremely acidic conditions (pH = 0). The alteration sequence simulated following the conditions of the reactivation of La Soufrière since 2018 (i.e., temperature increase, fluid acidification, and rainfall reduction) predicts the preferential formation of Na-alunite and silica precipitation, which reduces the formation of slippery argillic discontinuities and imparts some internal cohesion on the dome rocks. In contrast, an increase in the W/R ratio, as predicted by global warming, would result in preferential formation of phyllosilicates that would serve to increase dome instability. The combined experimental and modelling approach provides a detailed view of the controls on hydrothermal alteration sequence in volcanic systems.
How to cite: Décossin, F., Martel, C., Arbaret, L., Champallier, R., Penhoud, P., Azaroual, M., Muller, F., Heap, M., and Komorowski, J.-C.: Experimental and numerical thermo-kinetic modelling of hydrothermal alteration of volcanic rocks - Example of La Soufrière de Guadeloupe (Eastern Caribbean, France), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11352, https://doi.org/10.5194/egusphere-egu26-11352, 2026.
How to cite: Siciliano, A. and Vuilleumier, R.: Charge transport in concentrated magmatic brines from molecular dynamics simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12668, https://doi.org/10.5194/egusphere-egu26-12668, 2026.
The porosity, geometry and permeability of magmatic geothermal systems is important for interpreting geophysical signals at potentially active volcanoes, understanding geothermal production and the concentration of critical metals in fluids. Our case study is the Laguna del Maule volcano (Chile) which is undergoing rapid ground surface uplift that could have a geothermal or magmatic origin. We study porous hydrothermally altered granitic lithic clasts, older than 150ka, from the 17ka rhyolite ignimbrite eruption. There are no outcropping granites, so these lithics provide information on some portion of the subsurface, which has also been extensively studied by multi-parameter geophysics. The lithics vary in composition, crystal sizes and alteration, and those we studied are holocrystalline, fine-grained granodiorites and coarser-grained monzogranites. The latter break more readily, however, all samples contain fractures and miarolitic cavities. Amphibole geothermobarometry indicates crystallization pressures of 0.5-2 (+/- 0.6) kbar (2-8 km depth) at 600-800 (+/- 30)˚C, overlapping with a Magnetotelluric anomaly of >1 S m−1 at 3-5 km depths. We apply diverse techniques to quantify the porosity and pore structure of the lithics. Helium pycnometry data show they have up to 7 vol% connected porosity. SEM analysis reveals millimetre-scale miarolitic cavities, however, image analysis shows that the pore volume is dominantly comprised of a connected network of 5-25 μm-wide pores along grain boundaries, especially, but not exclusively, around quartz grains. We suggest the density increase associated with the beta-to-alpha quartz transition is an important mechanism for generating connected porosity in granites as they cool below ~570˚C, and can generate conductive and permeable regions with relatively low porosity. Calculations reveal the MT anomaly could be generated with a low-intermediate salinity brine (5-25 wt.% NaCl) with a fluid fraction of 0.03-0.06. We propose that the erupted granites were brought to the surface rapidly from an active hydrothermal system beneath the Laguna del Maule volcanic complex.
How to cite: Ellis, H. and Rust, A.: The pore structure of hydrothermally altered granites: insights into the magmatic-hydrothermal system of the Laguna del Maule volcanic complex, Chile., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13779, https://doi.org/10.5194/egusphere-egu26-13779, 2026.
Fluids in volcanic systems (supercritical fluids produced by magma degassing at depth, brines, vapors or mixed geothermal waters) are tremendous vectors of energy and volatiles (CO2, CH4, CO, HCl, H2S, etc…). They may also carry consequent and sometimes toxic amounts of metals, with recent estimates of metal emissions from Masaya, Etna or Iceland even suggesting that short-term metal release associated with volcanic activity may be comparable to anthropogenic emissions from rich industrial countries [1].
While an increasing amount of experimental data is already available to describe the speciation, solubility or fluid-melt partitioning and model the release of metals of economic interest (Cu, Au) in arc settings [2,3,4], how metals as As, Hg, Pb, Cd, Se or Te are extracted from underlying magmas and transferred towards the surface remains poorly constrained. Furthermore, underground reactions between the high-temperature fluids and rocks may favour precipitation, incorporation in sulfosalts or adsorption on mineral surface and thus complicate the interpretation of ‘quenched’ signal from fluid inclusions or fumarole analyses [5]. The development and validation of precise THMC models of fluid-rock interactions and precipitation patterns in volcanic geothermal systems thus requires new experimental data.
Here, we will present two different approaches that have been developed to enable the characterization of Pb, Se and Te behaviour in silicate melts, supercritical fluids, brines and vapors, as a function of P-T conditions, melt and fluids composition, down to the molecular level. They first one relies on the recovery of quenched fluids for detailed chemical analysis by ion chromatography (major elements + Cl or S) and ICP-MS to determine fluid-melt partition coefficients to 800-1200 °C and 2-4 kbar, whether the second one takes advantage of in situ Raman or X-ray Absorption Spectroscopy to assess the speciation and brine-vapor fractionation of the metals to 200-600 °C and 0.5-1.5 kbar. Ultimately, these complementary results will enable estimating the budget of Pb, Se and Te transferred to the geothermal system and the atmosphere and the information it bears about the P-T-X-fO2 conditions and processes at depth.
References: [1] Edmonds et al., 2018. Nat. Geosc. 11, 790-794. [2] Frank et al., 2002. GCA 66,3719-3732. [3] Zajacz et al., 2012. GCA 91, 140-159. [4] Pokrovski et al., 2013. Rev. Mineral. Geochem. 76, 165-218. [5] Henley and Berger, 2013. Earth Sci. Rev. 125, 146-170.
How to cite: Louvel, M., Haupt, C., Langerome, B., Hurtig, N., and Slodczyk, A.: Speciation and fractionation of toxic metals (Pb, Se, Te) in volcanic geothermal systems: Insights from partitioning experiments and in-situ spectroscopic measurements to high P-T conditions., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14510, https://doi.org/10.5194/egusphere-egu26-14510, 2026.
In the coming decades, it may be possible to exploit magmatic hydrothermal fluids for geothermal energy and the metals they contain. It is essential to find methods for assessing their location, temperature and composition.
The magnetotelluric method allows us to produce electrical conductivity maps and image the areas where these fluids reside. Electromagnetic waves created by storms and solar winds interact with the earth and produce electrical currents in the rocks, fluids and magma that compose it. These electric currents correspond to the migration of ions under the influence of an electric field. The ion current density is proportional to the electrical conductivity of the medium, which can be very high in magmatic fluids. By recording variations in the electromagnetic field at the surface we can create conductivity maps and thus find potential reservoirs of magmatic fluids.
The conductivity of a heterogeneous medium formed of different components can be deduced from the conductivity of each of these components, their relative proportion and the geometry of the interface. For a porous reservoir filled with connected fluid, the Hashing and Shtrikman formula relates total conductivity to fluid conductivity and porosity.
Thanks to magmatic inclusions and volcanic gases, we have an idea of the elements that can be found in these fluids: Na, K, Ca, Fe, Mg, Al, B, Li, Cu, Zn, Rb, Sr, Mo, Ba, Pb. The objective is then to find the possible compositions that explain the observed conductivity given the pressure and temperature conditions and reservoir geometry.
The conductivity of a complex system can be deduced from the conductivity of simple subsystems. An example of a subsystem is the H2O-NaCl system. It is described by the dissociation reactions of NaCl, HCl, NaOH and H2O. Conductivity depends on the number of charge carriers available and is therefore governed by the equilibrium constants of these reactions. Thanks to conductivity measurements in PT these constants can be determined and the conductivity of the H2O-NaCl system can be predicted for given PTc conditions. To do this, existing theories are used, notably the Debye Huckel Onsager theory.
In an electrolyte solution at equilibrium, the charges are not distributed randomly. They arrange themselves in a way that allows the conductive fluid to be electrically neutral. When the ions are set in motion, this structure slows down their progress, resulting in a frictional force that opposes the electric driving force. Once the ion flow is stationary, the speed of an ion is proportional to the driving force and its mobility, which depends on each ion and the properties of the solvent, such as its viscosity.
We have created a database of PT conductivity measurements for the subsystems of a magmatic brine. Based on this database and existing theoretical models, we are developing a model that predicts the electrical conductivity of brine at a given pressure and temperature. This model can be used to determine the possible compositions of brine based on its conductivity. We plan to use it to characterise brines beneath Mount Pelée, Martinique.
How to cite: Bernard, C., Lassin, A., Le Trong, E., Gaillard, F., Wawrzyniak, P., and Arbaret, L.: On the detection and characterisation of magmatic brines using magnetotellurics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19217, https://doi.org/10.5194/egusphere-egu26-19217, 2026.
Volcanic flank collapse is a recurrent natural disaster documented at volcanoes worldwide, including Mount St. Helens (1980), Bezymianny (1956), Bandai (1888), and Unzen (1792). These large-scale instabilities are often linked to hydrothermal alteration, in which circulating fluids and heat interact with volcanic rocks, altering their mineral composition and weakening their mechanical properties. However, numerical investigation of mineral alteration and deposit formation in volcanic hydrothermal systems remains largely undeveloped. Current models of magmatically driven hydrothermal systems primarily focus on fluid and heat transport, often neglecting the mechanical response of the host rocks. Additionally, they typically consider the constant physical properties of the host rock, such as porosity and permeability. This limits their usefulness in assessing volcanic stability. In this context, modeling the coupled thermal, hydraulic, mechanical, and chemical processes offers a new way to identify zones prone to alteration and potential flank instability.
We constructed a two-dimensional numerical model of a magmatically driven hydrothermal system using the finite element method (FEM) within the open-source MOOSE framework, which is a multiphysics environment for solving coupled nonlinear problems. The PorousFlow module was used to simulate fluid flow, heat transfer, mechanical behavior, and chemical processes. The model couples heat from a magmatic source with fluid circulation in the surrounding porous medium. Chemical processes are represented through indicators of conditions favorable to species transport rather than through explicit solute tracking. Such indicators are used to update the porosity and the permeability of the host rock.
This new model, still under development, offers insights into the dynamics of magmatically driven hydrothermal systems. Permeability is the main factor determining the driving heat transfer mechanism between conduction and advection. Permeability heterogeneities might cause heat accumulation and vaporization, or, conversely, provide an easy escape route. Similarly, faults or other vertical heterogeneities change the entire dynamic by creating a water freeway from deep within the earth to the surface.
In volcanic edifices, cold meteoric water flows from the head at the center to the toes on the sides. This flow shields the volcanic edifice from the hot mineralized (magmatic) water from deep below. This creates relatively sharp temperature variations underneath and near the sides of the volcanic edifice. This process also facilitates the accumulation of high-temperature areas near the bottom of the volcanic slopes and mineral transport.
The presence of the necessary conditions for the dissolution or precipitation of minerals in the hydrothermal system is used to track the transport of chemical species. Due to the shielding effect of the cold downward flow, the chemical species are not transported to or from the body of the volcanic edifice. Instead, they are transported on the sides at the base of the volcanic edifice’s slopes, closing the pores and decreasing the permeability.
The numerical model is still being developed mechanically to couple the opening of existing faults, the nucleation of faults, and plastic computations with the other physics.
How to cite: Niclaes, J., Poulet, T., Delmelle, P., and Rattez, H.: Alteration-driven permeability evolution in volcanic hydrothermal systems revealed by coupled THM(C) numerical modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20193, https://doi.org/10.5194/egusphere-egu26-20193, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 3
EGU26-15407 | ECS | Posters virtual | VPS25
Temporal evaluation of El Chichon´s geothermal potential in the period of 1983-2025.Thu, 07 May, 15:00–15:03 (CEST) vPoster spot 3
El Chichón is an active volcano in Chiapas, Mexico, that features a hydrothermal system characterized by thermal springs, fumaroles and an acid crater lake. Many studies have focused on tracking the geochemical evolution of its fluids since its last eruption in 1982 and some have specifically aimed to evaluate the geothermal potential. This work assesses the evolution of the geothermal potential through time using published geochemical data (1983-2025). We use geochemical diagrams, temperatures estimated with geothermometers and water-rock interaction analysis to identify the main system changes that influence the geothermal potential estimations. Given that El Chichón has been considered a geothermal prospect since the 1980s, we discuss the possible uses of this resource in terms of its recent active seismicity, the risk scenarios and the local socio-cultural context.
How to cite: Salas Ferman, J. L., Jácome Paz, M. P., Campion, R., Armienta, M. A., and Inguaggiato, S.: Temporal evaluation of El Chichon´s geothermal potential in the period of 1983-2025. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15407, https://doi.org/10.5194/egusphere-egu26-15407, 2026.
