Flow systems in the Earth's subsurface represent dynamic interfaces where geological, chemical, and biological processes converge. Driven by pressure gradients, thermal regimes, and tectonic activity, these systems play a crucial role in redistributing elements, forming mineral deposits, and hosting unique microbial ecosystems. Despite their significance, the intricate interactions governing fluid migration, geochemical transformations, and biological adaptations remain incompletely understood. Findings from recent studies in modern microbialites provide valuable insights into the evolution of fluid flow in subsurface environments and its surface expressions.
Investigations along the modern Dead Sea shores have highlighted the critical role of tectonic discontinuities and pre-existing geological structures in controlling vertical fluid migration pathways. These findings emphasize how fault zones can act as conduits or barriers to fluid movement, influencing mineral precipitation, hydrothermal vent activity, and subsurface microbial habitats. The combination of geochemical tracers and detailed sedimentological analyses reveal the temporal and spatial dynamics of fluid-sediment interactions as well as the role of microbial communities. Similarly, studies in recent lacustrine environments in Patagonia, where ongoing microbialite formation occurs, have demonstrated the influence of diverse groundwater sources on the development of carbonate buildups. These findings underscore the role of fluid chemistry and hydrodynamics in shaping microbial communities, and the resulting microbialite structures and carbonate precipitation processes.
These studies highlight the importance of interdisciplinary approaches in deciphering fluid flow dynamics. By integrating geochemistry, sedimentology, and microbiology, we can better interpret modern and ancient fluid-driven systems. Bridging observations from active fluid flow systems with paleo-records enhances our understanding of the long-term implications of fluid flow on Earth's carbon cycle, climate regulation, and biosphere evolution. They further provide potential analogs for extraterrestrial habitable environments.
How to cite: Ariztegui, D.: Fluid flow in the subsurface: Geochemical, sedimentological and microbial interactions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3358, https://doi.org/10.5194/egusphere-egu25-3358, 2025.
The INGV-PROMUD is a 3-years (2023-2025) multidisciplinary project (https://progetti.ingv.it/it/promud), aimed to investigate the indicators of the activity of MVs, with the ultimate goal of individuating possible precursors of paroxysmal events. Its two main target areas, both in Italy, are the ‘Salse di Nirano’ (Northern Apennines) and the ‘Maccalube di Aragona’ (Sicily).
Among the multidisciplinary research activities carried out in the scopes of the project, particular attention is focused on the analysis of the background seismic noise wavefield, and its role in the identification and monitoring of degassing sources and conduits, and of the hydrological regime, and its influence on MVs activity.
Seismic data have been recorded at Aragona, since July 2024, by six seismometers, four of which are part of a seismic array located close to the vents, with the aim of investigating the characteristics of the recorded background seismic noise, e.g., spectral properties, H/V spectral ratios, energy (RMS) and polarization temporal pattern. Preliminary results of data recorded from July to September 2024 show that the main frequency content of the wavefield is below 5 Hz. H/V spectral ratios are almost flat, indicating the absence of amplification effects, at least in the investigated sites. The temporal pattern of the RMS amplitude is affected by some fluctuations, which need to be further investigated to look for evidences of a possible periodic behaviour. The polarization parameters (azimuth, incidence angle and rectilinearity) appear to be stable over the whole analysed time interval. At the array site, in the 0.2-1 Hz frequency band, the noise wavefield is polarized along the NS direction, while polarization azimuths 1-5 Hz band are more disperse.
Seismic monitoring has been coupled to near real time acquisition of meteorological data and temperature, volumetric water content and electric conductivity of soil, integrated by monthly surveys of number and position of active mud emitting vents, and apparent soil moisture content distribution.
First analyses of the acquired data indicate that the hydrological cycle exerts a strong control on both number and distribution of vents, and on the rheological properties of the emitted fluids, playing a potential role in determining pressure accumulation, prodromic to paroxysmal events.
How to cite: Madonia, P., Cusano, P., Petrosino, S., Costanza, A., Fertitta, G., and Gucciardo, D.: Preliminary results from the INGV-PROMUD Project: seismic and hydromorphological monitoring of Maccalube di Aragona Mud Volcano (Sicily, Italy)., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9144, https://doi.org/10.5194/egusphere-egu25-9144, 2025.
The presence of a minimum within the low-frequency range in the average Horizontal (H) to Vertical (V) Spectral Ratios of ambient vibrations has been suggested to be representative of hydrocarbon reservoirs in active oil and gas fields in the Middle East and Europe. Similar evidence has been also found in correspondence of active mud volcanoes in Italy (Antunes et al., 2022; Panzera et al., 2016). In this view, the aim of the study is to explore the possibility of using ambient vibrations to identify and characterize reservoir corresponding to mud volcanoes vents in the Nirano mud volcanoes area (Norther Italy). Seismic surveys carried out in the area so far allowed the seismic characterization of the shallowest part of the subsoil involved in the emission process (Antunes et al., 2022; Brindisi et al., 2023; Carfagna et al., 2024). To extend downward this characterization and understand if the presence of the minimum detected in the Nirano Reserve (Antunes et al., 2022) is confined to the area of emitting vents, an extensive survey of ambient vibrations was performed. In particular, a dense network of velocimetric measurements has been deployed by considering single station and array configurations. Results obtained confirm that measurements with a clear HVSR minimum at around 0.5 Hz only characterize the area of emitting vents. In the assumption that this minimum depends on the characteristics of the reservoir responsible for fluid emissions, the Biot–Gassmann theory (Lee, 2004; Tinivella, 2002) for seismic waves velocities of gas hydrate-bearing sediments has been considered to infer reservoir characteristics from Vs and Vp profiles obtained by the inversion of the HVSR curves. The satisfactory fit of model outcomes with observations testifies one more the effectiveness of ambient vibration measurements to characterize mud volcanoes and relevant subsoil configuration. This opens new possibilities for the study of mud volcanoes and gas reservoirs both onshore and offshore by passive seismic observations.
References
Antunes V., Planès T., Obermann A., Panzera F., D’Amico S., Mazzini A., Lupi M.; 2022: Insights into the dynamics of the Nirano Mud Volcano through seismic characterization of drumbeat signals and V/H analysis. J. Volcanol. Geoth. Res., 431, 107619. https://doi.org/10.1016/j.jvolgeores.2022.107619.
Brindisi A., Carfagna N., Paolucci E., Albarello D.; 2023: Fine structure of seismic emissions from Nirano mud volcanoes (northern Apennines, Italy): a phenomenological study. Bull. Geophys. Oceanogr, 20, 1-12. DOI 10.4430/bgo00437.
Carfagna N., Brindisi A., Paolucci E., Albarello D.; 2024: Seismic monitoring of gas emissions at mud volcanoes: The case of Nirano (northern Italy). J. Volcanol. Geotherm., 446, 107993. https://doi.org/10.1016/j.jvolgeores.2023.107993.
Lee M.W.; 2004: Elastic velocities of partially gas-saturated unconsolidated sediments. Mar. Pet. Geol., 21(6), 641-650. https://doi.org/10.1016/j.marpetgeo.2003.12.004.
Panzera F., Sicali S., Lombardo G., Imposa S., Gresta S., D’Amico S.; 2016: A microtremor survey to define the subsoil structure in a mud volcanoes area: the case study of Salinelle (Mt. Etna, Italy). Environ. Earth Sci., 75, 1-13. https://doi.org/10.1007/s12665-016-5974-x.
Tinivella U.; 2002: The seismic response to over-pressure versus gas hydrate and free gas concentration. J. Seism. Explor., 11(3), 283-305.
How to cite: Brindisi, A., Paolucci, E., Carfagna, N., and Albarello, D.: Passive seismic measurements to characterize gas reservoirs in a mud volcano field in Northern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10680, https://doi.org/10.5194/egusphere-egu25-10680, 2025.
During the process of fluid transport in the cold seep system at the natural gas hydrate zone, the shallow part of the stratum will be impacted by the fluid, and at the same time, there is a “solid-liquid-gas” transformation of the fluid material in the lower stratum, and the release of energy will lead to vibration events such as fissure collapse and pore rupture, which will produce a series of micro-seismic signals related to the cold seep activity. These microseismic signals can visually and accurately reflect the growth and development status and life cycle of the cold seep system and reveal its fluid escape activity pattern. We use the microseismic data recorded by the ocean-bottom seismometers at two different years, 2014 and 2021, near the “Haima” cold seep in the gas hydrate zone of the Qiongdongnan sea area as the research data. After corresponding preprocessing, a large number of microseismic events related to cold seep activities are identified by using the STA/LTA method. The waveform characteristics, spectral characteristics, and time distribution characteristics of these microseismic signals are then analyzed in order to further understand the characteristics of cold seep microseismic events. The results show that the microseismic events generated by the cold seep activity in the “Haima” cold seep area include short-duration events and typical cold seep microseismic event signals. In these microseismic events, the tail of their waveforms shows a regular decay similar to an exponential pattern, with durations ranging from 0.3s to 2s and the peak frequency distribution in the range of 4-26 Hz, and the occurrence of cold seep microseismic events does not have an obvious tidal temporal distribution pattern but mainly exhibits short-term concentrated distribution characteristics.
How to cite: Hu, G. and Yang, S.: Identification and characteristics analysis of microseismic events in the "Haima" cold seep area, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5553, https://doi.org/10.5194/egusphere-egu25-5553, 2025.
The plate boundary between Africa and Eurasia, ranging from the transform-dominated Gulf of Cadiz in the west to the reverse-faulting Hellenic subduction zone in the east, has been studied to identify mud volcanoes (MVs) of various origins. Different salinity patterns, either freshening or salinization signals, have been identified in different MV fluids through various research expeditions. During the R/V Meteor cruise M149, contrasting fluid signatures were detected at the summit (Cl depletion) and moat/rim (Cl enrichment) of the Ginsburg and Yuma MVs in the Gulf of Cadiz, whereas previous ODP Leg 160 reported similar spatial distributions of Cl concentrations at the Milano MV in the Olimpi MV field on the Mediterranean Ridge. Focusing on three MVs with contrasting fluid signatures, we suggest complex fluid pathways, rarely acknowledged in previous studies, are responsible for fluid expulsion.
By utilizing pore water geochemistry, advection-diffusion modeling, and high-resolution seismic profiles, we trace fluid origins, quantify fluxes, and constrain migration pathways. The Cl-depleted summit fluids originate from clay dehydration and are channeled by central conduits, reaching high advection velocities (up to 50 cm/yr). The Cl-enriched moat fluids exhibit slower advection velocities (0.3-1.5 cm/yr) and show additional evaporite effects. At the Ginsburg MV, one MeBo core of up to 40 m length collected at the moat and high-resolution seismic profiles across the whole MV allow to constrain moat fluid sources and further explain the structural implications behind this spatial variation in chemical and fluid fluxes. Fluid formation temperatures have been calculated using water isotopes and Mg-Li geothermometer. The resulting low temperatures suggest source depths atop the Allochthonous Unit of the Gulf of Cadiz (AUGC) (~0.8 kmbsf), consistent with seismic data across the Ginsburg MV (showing high-amplitude reflections at the same depths) but differently than the summit sites, where the source is deeper within the AUGC (~2.2 kmbsf). We relate moat seepage occurrence to fractures formed due to edifice subsidence, marked by stacked enhanced reflectors. Upon comparing the three MVs with one younger and one inactive MV, we suggest that peripheral seepage of MV edifices is a widespread process that appears at a specific evolutionary stage, during which it represents an important component of the fluid budget.
The findings from this study not only offer insights into the complex mechanisms of fluid circulation within MV structures but also provide a new approach to investigating the role of shallow evaporites in MV fluid dynamics, particularly in regions like the Mediterranean Ridge where evaporites are extensively present. By focusing on rim sites around MVs, the influence of evaporites can be more effectively identified, as peripheral fluids are more susceptible to being overprinted by salinization signals compared to the typically freshening summit fluids.
How to cite: Xu, S., Menapace, W., Urgeles, R., Ford, J., Calahorrano, A., Bartolomé, R., and Kopf, A.: Complex Fluid Pathways and the Role of Shallow Evaporites in Mud Volcano Systems in the Gulf of Cadiz and Mediterranean Ridge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17307, https://doi.org/10.5194/egusphere-egu25-17307, 2025.
The Permian system in northeastern Sichuan is a key natural gas exploration area in the Sichuan Basin. The deeply buried Permian carbonate reservoirs have undergone multiple tectonic events, resulting in complex diagenesis and varying degrees of modification. Fluctuations in temperature and pressure in these deep reservoirs over geological history have shaped the current states of hydrocarbons, reservoir diagenesis, and porosity evolution, all playing significant roles in hydrocarbon migration, accumulation, and preservation.
This study aims to analyze the temperature and pressure distribution characteristics of Permian reservoirs in the Yuanba-Longgang area. It investigates the mechanisms behind overpressure generation and the evolutionary pathway of formation pressure in the Permian Changxing Formation, based on the historical development of the geothermal field.
Data from 54 wells in the Yuanba-Longgang area were analyzed, revealing formation pressures in the Changxing Formation range from 53 to 68 MPa in Longgang and 69 to 90 MPa in Yuanba. The pressure distribution shows that Yuanba has higher formation pressures than Longgang. Sealing layers, including the Middle and Lower Jurassic formations, exhibit normal hydrostatic pressures, while the Lower Jurassic base and Upper Triassic Xujiahe Formation constitute the first overpressure system, followed by the Lower Triassic Feixianguan Formation and Upper Mesozoic Permian as the third. Temperatures in the Changxing Formation range from 145°C to 154°C, with Yuanba generally exhibiting higher temperatures than Longgang.
Paleo-heat flow in the Permian of northeastern Sichuan ranged from 55 to 70 mW/m². By analyzing burial and thermal histories, we reconstructed the temperature and source rock maturity evolution in typical wells in the Yuanba-Longgang area. In the Early Triassic, source rocks in the Longtan Formation exceeded the hydrocarbon generation threshold but stagnated. From the Early Jurassic onward, source rocks continued evolving, reaching high maturity by the Late Jurassic and overmaturity by the Early Cretaceous, with peak thermal evolution in the Middle Cretaceous. Oil generation began in the Early Triassic, transitioning to gas generation by the Middle Jurassic, while crude oil cracking started in the Late Jurassic and concluded in the Early Cretaceous.
Gas component analysis in the Feixianguan and Changxing formations shows that the region’s natural gas primarily originates from crude oil cracking. These formations contain abundant asphalt from thermal cracking, with gaseous hydrocarbons forming a significant component of the natural gas. This process also drives overpressure development in the Feixianguan Formation. Basin modeling, using paleopressure values restored from fluid inclusions and current measured pressures, shows that prior to 230 Ma, formation pressures were hydrostatic. From 230 to 91 Ma, overpressure developed, peaking at 91 Ma, and since then, formation and residual pressures have declined.
How to cite: Wang, J. and Qiu, N.: Temperature and Pressure Distribution and Evolutionary Characteristics of Permian Strata in the Yuanba-Longgang Area of Northeastern Sichuan , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21179, https://doi.org/10.5194/egusphere-egu25-21179, 2025.
Electrical methods are widely used to delineate fractured aquifers, still, there are some limitations in their possibility to obtain clear interpretation to simulate resistivity measurements and align the subsurface lithology layer without supplemental data directly. To decrease these limitations, the research integrates electrical measurements with borehole lithological data to explore groundwater potential in fractured basement terrains. In Sudan's Neoproterozoic basement complex, the Orshab watershed provides a suitable example to apply the methods caused by limited groundwater availability in the basement area. Until be approve the depth, thickness, number of layers, and distribution of groundwater-bearing formations, geo-electrical surveys were conducted clothing to productive wells to provide conceptual and enhance the other geophysical interpretation covered in the study area.
Three distinct geo-electrical layers were identified: alluvial deposits with resistivity values ranging from 27 to 1997 Ωm and a thickness of ~5 m; a second layer with thicknesses of 2–10 m; and weathered basement, fractured basement rocks layers reaching 20–45 m and 20–35 m, respectively. Three primary aquifer types were found: alluvial deposits, weathered basement, and fractured basement as unconfined aquifer, with a maximum depth of approximately 65-70 m, as This depth is recommended for drilling new boreholes to ensure a sustainable water supply for the region.
This research expresses that integrating geophysical data with borehole lithological data notably enhances the interpretation of geophysical results. The approach has limited ability to contribute to a reliable understanding of resistivity for groundwater exploration in the region that has similar geological settings
How to cite: M. H. Hassan, M. N. and Buday, T.: Integrating Geophysical Measurements and Borehole Lithological Data Analysis to Assess Groundwater Potential in Fractured Basement Terrains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7118, https://doi.org/10.5194/egusphere-egu25-7118, 2025.
Phosphorus is an essential element of life, as observable in modern life forms that have perfected phosphorus accumulation and recycling. Prebiotic chemistry, on the other hand, was likely challenged by the low abundance and poor solubility of phosphorus minerals on early Earth.
Current experimental approaches to solve this so-called phosphate problem mainly focus on the solubilization of phosphate minerals like apatite or reduced phosphorus species in extraterrestrial schreibersite. However, the possibilities for prebiotic chemistry through magmatic evolution and phosphate enrichment in basaltic melts have not yet been considered.
Here, we show the formation of phosphate-rich glass droplets, driven by liquid immiscibility in basaltic melts, and explore its downstream utilization for prebiotic chemistry. We synthesized two glasses mimicking an average composition of 2.2 – 3.8 Ga old basalts containing more than 0.5 wt.% phosphorus, and doped them with 1 and 10 wt.% P2O5 respectively. In the latter, unmixing lead to the formation of Fe-P-rich droplets in a Si-rich matrix with a partition coefficient of DP ~3.9. Subsequent leaching behavior of the synthesized glass was investigated over a range in pH and organic solvents delivering up to 5 mM dissolved phosphate. The concentration in the experimental leachate was sufficient to form di- and triphosphate afterwards at elevated temperatures and phosphorylation of adenosine was possible.
We further found that our initially produced leachates were able to trigger the synthesis of imidazole phosphate with up to 34 % yield and the downstream phosphorylation of glycerol in wet/dry cycles with up to 17 % yield. Our results thus show an alternative source of phosphate for prebiotic chemistry through its early enrichment in the magma and present an alternative approach to solving the phosphate problem for the origin of life.
How to cite: Weller, D., Matreux, T., Smokers, I. B. A., Schmid, A., Weidendorfer, D., Dingwell, D. B., Mast, C. B., Braun, D., and Scheu, B.: Immiscible basaltic glasses – a prebiotic phosphate source, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19000, https://doi.org/10.5194/egusphere-egu25-19000, 2025.
Geysers are natural hot springs that intermittently erupt with a mixture of water and steam. Geyser eruptions cause hazards but are also valuable resources for potential green energy. Additionally, geyser eruptions share similarities with volcanic eruptions in heat transfer and subsurface fluid dynamics, making them useful analogs for understanding volcanism and aiding hazard mitigation. However, significant gaps remain in our understanding of geyser behavior, particularly regarding the irregular eruption patterns observed in complex geysers like Steamboat. This research aims to address these knowledge gaps by investigating the behavior of geysers with different architectures and heat inputs. To achieve this, we simulate geyser eruption cycles and investigate the factors influencing their periodicity and the evolution within their eruption cycles.
We explore the sensitivity of eruption intervals to a range of geological and thermal parameters, including porosity, the permeability contrast between the geyser conduit and the surrounding rock matrix, basal heat flux, and conduit dimensions (radius and depth). Our results indicate that variations in basal heat flux can influence eruption style and, consequently, periodicity. We classify the observed eruption styles as "regular" and "long-period" geysers, based on the eruption duration and interval reflected in the evolution of the steam saturation profile within the conduit. Changes in permeability and porosity affect the eruption interval, with permeability demonstrating a particularly significant control over periodicity. Conduit dimensions, however, show no significant impact if the heat flux in the unit area unchanged. We compared the observed time intervals from the Steamboat geyser to our model results. The results indicate that the permeability change may reawaken the eruptions at Steamboat since 2018.
Additionally, we analyze the evolution of key parameters within the eruption cycle, including the migration of the boiling front, water and steam mass flux, pressure, and temperature in the conduit. The evolution of those parameters is consistent with the observations from Steamboat providing insights into the pre- and post-eruption dynamics, offering clues about the triggering mechanisms of Steamboat’s eruptions. This research contributes to a refined understanding of the complex interplay of factors governing geyser behavior, potentially offering insights into the dynamics of more complex real-world geysers such as Steamboat.
How to cite: Chan, M. Y. D., Zhan, Y., and Wu, H.: Controls on Geyser’s Eruption Behavior by Numerical Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-749, https://doi.org/10.5194/egusphere-egu25-749, 2025.
Posters on site: Thu, 1 May, 16:15–18:00 | Hall X2
Research on naturally occurring fluid migration within geological systems under higher pressures and temperatures has shown the ability for gas to be released with different physical mechanisms leading to formation of various geological structures (e.g., gas chimneys, volcanic diatremes, hydrothermal vents, salt diapirism). More recently, it has been suggested that such systems could result from fluid injection into the subsurface (e.g., CO2 sequestration, H2 storage as a battery). Focused fluid flow is often transient and self-organizing, occurring within a local area in reaction to changing temperatures and pressures (e.g., overpressure). Once started, a feedback loop between fluid pressure, media deformation, and permeability can occur resulting in a continuous fluid seepage. Geological evidence across a broad swathe of systems highlights that during and after the vertical fluid flow has occurred, there is a significant, localized impact on the geological fabric of the subsurface.
Focused fluid flow is a phenomenon that could manifest within ductile deformation settings at lower fluid pressures than those associated with brittle stress behaviour (i.e., fractures), but higher fluid pressures than what is seen when solely diffusion occurs. As such, the impact on the surrounding media also varies. With higher pressures, fracturing (i.e. failure) of the media occurs. Heterogenous layering roughly parallel with the planetary surface will work to impede vertical propagation resulting in a series of oblique, but often interconnected pathways. With lower pressures, diffusion occurs, potentially resulting in geochemical and minor physical alterations to media with higher transmissibility. However, diffusion lacks the necessary pressure to bypass sections of lower transmissibility. At these intermediate pressures, porosity waves can develop, facilitating the movement of fluids through localized, transient increases in porosity within the medium. These waves enable fluid transport even in regions of relatively low permeability by temporarily enhancing the pore space without causing structural failure. The result is a dynamic interplay between pressure gradients, fluid viscosity, and the mechanical properties of the surrounding media. This interplay leads to significant changes in fluid distribution, mineralization patterns, and the potential for localized geochemical reactions.
Here we utilize analogue and numerical modelling of focused fluid flow in order to better understand the geological and injection engineering principles that could lead to the narrow range of conditions under which porosity waves could breach sections of lower transmissibility without fracturing it. Our modelling identifies key parameters of these systems that could help us better understand both the natural and the geo-engineered, including (1) proximity to surface, (2) strength of the host rock, (3) mechanical anisotropy, and (4) injection rates and amounts. For the analogue modelling we use a Hele-Shaw cell wherein we inject a lower density fluid into a viscoelastic hydrogel. By varying the injection rate we are able to identify the narrow range within which porosity waves occur. For numerical modelling we use a finite difference pseudo-transient methods to simulate coupled fluid flow and mechanical deformation in heterogeneous media. The numerical model is calibrated using results from the Hele-Shaw cell experiments, ensuring consistency between analogue and numerical observations.
How to cite: Johnson, J., Wang, H., and Yarushina, V.: Focused fluid flow: the mechanisms, geological impacts, and insights from analogue and numerical modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4087, https://doi.org/10.5194/egusphere-egu25-4087, 2025.
Global estimates on the number of submarine mud volcanoes are highly uncertain, as well as their role in the deep-sea biosphere and methane budgets. Here, we report the discovery of ten mud volcanoes in the Southwestern Barents Sea (440-480 m depth), where only two had been previously known. The new mud volcanoes form flat-topped mounds which are connected to seismic chimneys rooted within the infilling of a buried Pleistocene mega-slide. High-resolution seafloor imagery, collected with a Remotely Operated Vehicle during the EXTREME24 expedition in May 2024, revealed ongoing methane-rich mud expulsion, including mud pools, flows, and associated chemosynthetic fauna. Biostratigraphic and geochemical (gas and oil) analyses of extruded sediments provided insights into the plumbing system. We will present a formation model for the Polaris Mud Volcano Complex, offering new perspectives on the shallow geodynamics of (paleo)glaciated continental margins in relation to mega-slide events.
We acknowledge the projects Advancing Knowledge on Methane in the Arctic (AKMA) (Research Council of Norway grant No. 287869) and EXTREMES (UArctic UA 06/2024) for supporting this research and EMAN7 (Research Council of Norway grant No. 320100) for financing CA position. The Norwegian Offshore Directorate (NOD) partly funded the expedition and analysis. We are grateful to REV Ocean for support during the EXTREME24 cruise and the use of ROV Aurora.
How to cite: Argentino, C., Mattingsdal, R., Eidvin, T., Ohm, S. E., and Panieri, G.: Unveiling the Polaris Mud Volcano Complex: A Chain of Mud Volcanoes in the Southwestern Barents Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9083, https://doi.org/10.5194/egusphere-egu25-9083, 2025.
Borealis is a newly identified underwater mud volcano located in the Polar North Atlantic, distinct from the many methane emissions previously found in the area. In this study, we present direct observations from a remotely operated vehicle (ROV), documenting the emission of warm (11.5°C) Neogene sediments and methane-laden fluids from a gryphon at Borealis. The seafloor around the mud volcano is covered with extensive carbonate formations, suggesting a long history of diffuse methane flow. Our sampling and imagery indicate that Borealis hosts unique ecosystems adapted to low-oxygen environments near methane seeps. Furthermore, the irregular carbonate formations may provide natural protection against bottom trawling, offer a surface for stationary marine life, and act as breeding grounds for endangered fish species. This finding highlights the ecological importance of cold seep ecosystems in the Polar North Atlantic, emphasizing their contribution to biodiversity by providing refuges for marine life and stressing the importance of their preservation.
The authors thank the projects AKMA (287869), HOTMUD (288299), NCS2030 (331644), WELLFATE (344447), and EMAN7 ( 320100),the Norwegian Offshore Directorate, and REV Ocean.
How to cite: Panieri, G., Argentino, C., Savini, A., Ferre, B., Hemmateenejad, F., H. Eilertsen, M., Mattingsdal, R., P. Ramalho, S., Michel, A. M., Rogers, A., Polteau, S., Mazzini, A., Barrenechea Angeles, I., Buenz, S., and Kalenitchenko, D.: The Borealis Mud Volcano is a sanctuary for vulnerable Arctic species, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13139, https://doi.org/10.5194/egusphere-egu25-13139, 2025.
The Norwegian Continental Shelf (NCS) is a region with 100,000s of active and extinct natural occurring methane seeps (NOMS) that are sustaining oases of unique ecosystems. These emissions are sourced from thermogenic and microbial methane. In addition, vigorous seafloor gas emissions (i.e., gas flares) are also found at, or in the vicinity of numerous wells (i.e. WAMS: well-associated methane seep). The NCS hosts ~10.000 wells, ~2,000 of these are already plugged and abandoned, and 2,245 operating wells heading for decommissioning in the next decades. Here we integrate the results of a multidisciplinary surveys conducted in the Tampen area (western Norwegian Channel) where the highest NOMS and WAMS and related gas flare concentration has so far been observed.
We combine a large (800 km2) multibeam and water column survey with high resolution seismic profiles and gas geochemistry analyses from active seepage sites. A complete mapping of the area reveals the presence of nearly 2000 flares, 175 of which are WAMS. The highest density is observed in the western side of the Tampen region where up to 20 flares per km2 can be mapped. Geochemical analyses show that methane is the main seeping gas with a microbial signature (d13CCH4 as low as -91 ‰) and pore water profiles (sulfate and dissolved inorganic carbon-DIC concentrations and d13CDIC) in gravity cores indicated intense anaerobic oxidation of dissolved methane in the shallow subsurface at 2-4 m bsf. Sediment incubations showed a widespread potential for aerobic and anaerobic MO as well as methane production in the top 20 cm, which was further confirmed by molecular biological analyses. We infer a shallow origin of the gas trapped in the glaciogenic wedge of the west shoulder of the Norwegian Channel. This shallow gas charge has also been observed on the reflection seismic data. Selected profiles have been used to trace back the potential fluid migration pathways from deeper units where reservoirs are sited. We suggest that deeper-sited tectonic discontinuities, clinoforms, and sedimentary interfaces promote the vertical and lateral fluid migration, respectively.
These findings are relevant to understanding the environmental impact of gas flare activity, future CO2 and hydrogen storage planning in depleted reservoirs, and mitigation strategies for gas seepage on the NCS.
How to cite: Polteau, S., Mazzini, A., Mattingsdal, R., Buenz, S., Krueger, M., Thomsen, P., Campos, I., Argentino, C., and Fossan, J.: Tampen, the highest gas flaring region in the North Sea: distribution, characterization and fluid migration mechanisms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11183, https://doi.org/10.5194/egusphere-egu25-11183, 2025.
Many large-scale mud volcanoes (MVs) display kilometer-sized mud breccia flows that extend from the crater. These large-scale flows are assumed to be related to the intermittent episodic eruptive events that characterize MV activity. However, only a few sufficiently long-lasting and voluminous eruptions have been documented and considered to be able to generate such extensive flows. Therefore, the exact mechanisms promoting the formation of such long flows remain so far unclear.
In September 2022, shortly after the 11th of August 2022 Lokbatan MV eruption in Azerbaijan, we carried out fieldwork measurements and observations. Although the eruption was short and produced only a volumetrically small amount of mud breccia circumscribed around the crater site, we observed a horizontal displacement of the whole >1km long pre-existing mud flow. This movement was highlighted by fractures indicating detachment and downslope sliding and was later confirmed by InSAR historical data. These findings suggest that this kilometer-sized mud flow may not result solely from massive eruptions, as previously thought, but instead from by a gradual sliding triggered by 1) the additional weight of freshly erupted material and b) by inflation/deflation of the whole MV. We speculate that this gravitative flow behaves similarly to warm-based glaciers.
To validate this model and assess whether this mechanism is unique to Lokbatan, we analyzed Google Earth™ satellite imagery of other large MVs in Azerbaijan. Here we present data that reveal that a similar behavior was observed for least 20 MVs in the Caspian region (e.g. Koturdag, Goturlug, and Pirsaat Burnu among others). These new observations highlight that this previously overlooked mechanism for the growth of kilometer-sized mudflows is more widespread than previously thought and is indeed common for many large MVs. Understanding this process is critical for better assessing their dynamics and the risks they pose to surrounding infrastructures and settlements. Further, this process is essential for understanding the dynamics of mud volcanoes on Earth and may provide insights into the formation of large-scale flow-like features on other bodies in the Solar System.
How to cite: Brož, P. and Mazzini, A.: Gradual Sliding as a Common Growth Process in Caspian Mud Volcanoes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8429, https://doi.org/10.5194/egusphere-egu25-8429, 2025.
The Schofield groundwater body on the island of Oʻahu is one of the most important freshwater reservoirs yet has enigmatically high hydraulic head as compared to the adjacent basal water bodies. Various hypotheses have been proposed to explain this so-called North Schofield Dam, yet for the most part the Schofield aquifer’s high head remains unexplained. For this study we collected extensive self-potential and seismic ambient noise datasets in an effort to better understand the geologic and fluid flow conditions across the North Schofield Dam boundary. We collected 40 km of interconnected self-potential profiles and seismic ambient noise data recorded by 53 stations (Magseis Fairfield) over 18 consecutive days. As a complementary approach, we performed a basic clustering analysis of our self-potential dataset. Our results revealed two distinct domains with different geophysical signatures, demarcated by a NE-SW-striking boundary. The southeastern area exhibits higher self-potential values and seismic velocities, while the northwestern area has lower values for both data types. This sharp boundary, oriented N25°, separates two hydrogeological domains and precisely highlights the North Schofield dam. We interpret that the NW domain contains buried valley-fill material with low permeability, while lava flows from the Wai‘anae and Koʻolau volcanoes dominate the SE zone. We interpret that the mostly impervious valley-fill material acts as a water flow boundary that may explain the abnormally high groundwater levels observed in the Schofield groundwater unit. We thus provide for the first time, the orientation, underground geometry, and geological nature of the North Schofield Dam. This study helps in understanding the mechanisms associated with forming a large aquifer in the elevated central part of the island of Oʻahu. It also emphasizes the importance of geological complexity of volcanic environments in influencing groundwater storage and flow. Our findings will be key to improving hydrogeological models, and thus fresh groundwater resources management on O‘ahu, and it opens perspectives for further comparative studies on other volcanic islands.
How to cite: Barde-Cabusson, S., Mordret, A., Grobbe, N., Dores, D., Lautze, N., Sinton, J., and Wallin, E.: Using Self-Potential and Seismic Ambient Noise Methods on Oʻahu’s Groundwater System, to Uncover the Geological Nature of the North Schofield Dam, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9485, https://doi.org/10.5194/egusphere-egu25-9485, 2025.
We deployed a network of temporary stations to invert passive seismic data to compare the intrinsic attenuation distribution and the S-wave velocity structure of a region of the Kendeng Basin in east Java, Indonesia. This geological domain hosts the Lumpur Sidoarjo, nicknamed Lusi, that is the eruptive centre of the sediment-hosted geothermal system that pierced the Earth's surface in May 2006. To date, Lusi is the youngest onshore hybrid system on Earth. We show that ambient noise and intrinsic attenuation tomographies are complementary tools that should be performed routinely when studying geothermal systems.
Our study highlights that Lusi's plumbing system features two distinct fluid flow regimes, one across the shallow sedimentary units and one developing sub-vertically across the deeper domains of the basin. Historically, this region is considered an hydrocarbon province as shown by the dozens of wells extracting hydrocarbons form the gas reservoirs. However, we show that such a basin is also rich in geothermal resources and the well facilities could be re-purposed for the exploitation of geothermal resources. This is particularly timely since the hydrocarbon extraction of the gas fields is declining and the energy transition is becoming more and more pressing. The high geothermal gradient, the steep topography of the nearby volcanic arc, as well as the well-studied subsurface all combine to make this portion of the Kendeng basin an excellent geothermal site. We strongly recommend that future geothermal operators capitalise on the existing infrastructures and transform the natural disaster of Lusi into a geothermal opportunity.
How to cite: Lupi, M., Cabrera-Perez, I., and Mazzini, A.: Using Ambient Noise Attenuation and Surface Tomographies to investigate Lusi, Indonesia. From a natural disaster to a geothermal opportunity., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12190, https://doi.org/10.5194/egusphere-egu25-12190, 2025.
Located on the western flank of the Akita Yakeyama Volcano lies the Goshogake hydrothermal system of Tohoku, Japan. Goshogake is situated between the magmatic volcanic arc and the hydrocarbon province in the back-arc of Japan. This system exhibits a variety of surface manifestations with temperatures ranging between 33°C to 97°C and low, acidic pH values of approximately 2.5. Seepage sites include sulphur-rich fumaroles, localized possible oil-rich pools, active mud- erupting gryphons, small hydrothermal lakes, and clustered bubbling pool fields, implying along with its geodynamic position, a possible hybrid field.
Hydrothermal emissions emerge at the base of a narrow valley, where a N-S oriented fault system framing the Akita Yakeyama Volcano is suggested to occur. Intense seismicity caused by the active tectonics in the region relates to ongoing deformation. To investigate the interconnection between the emission sites and the reservoir(s) feeding them, a 3D Deep Electrical Resistivity Tomography study was conducted by deploying 25 Iris Fullwavers across the Goshogake system. The results were combined with drone-derived thermal photogrammetry, satellite images and geochemical analyses of the seeping fluids.
The inverted resistivity model reveals a conductive system that enables discrimination of the conduits feeding the vents. Geochemical analyses reveal the presence of H2S and CO2 dominated gas with mantle-derived isotopic signatures; the presence of minor quantities of CH4 in colder seepage sites, whether thermogenic or abiotic,remainunsolved.The detected H2 among the seeping gasses may result from the interaction of hydrothermal fluids with pyroxene andesite lava host-rocks.
Further analyses of the possible oil films aim to distinguish its origin with several potential scenarios. The first scenario involving the presence of shallow oil derived from the alteration of recent organic- rich deposits, or a second scenario involving deep oil originating from the thermo- metamorphism of deep-seated lacustrine deposits hosting the volcanic complex. If the latter is validated, Goshogake could well be Japan’s first example of a sedimentary-hosted geothermal system.
How to cite: Narine, K., Lupi, M., Mazzini, A., Sfalcin, J., and Nuriel, P.: A multidisciplinary approach for subsurface investigations of the Goshogake geothermal field, Japan , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16958, https://doi.org/10.5194/egusphere-egu25-16958, 2025.
Muara Laboh is a geothermal system located in central Sumatra along a sector of the Great Sumatra Fault and neighboring the Kerinci volcano. The area is characterized by diffused surface manifestations, including hot springs and fumarolic activity at various sites along the valley. In this geological context, the fluid migration is expected to be controlled by the lithological and tectonic discontinuities that characterize such a heavily faulted region.
To identify subsurface fluid pathways and reservoirs, a large region of nearly 400 km2 was investigated deploying a network of 212 3-components seismic nodes. 182 instruments were placed within a central 25 km area around the populated centre of Muara Laboh, while 6 external antennas (composed of 5 seismic nodes each) were deployed at 40 km SE from the main network to better constrain the depth within the central region. From the seismic records, we extracted cross-correlation functions and Rayleigh wave group-velocity dispersion curves to perform Nodal Ambient Noise Tomography (NANT). We derived a 3D S-wave velocity model that can be used to identify domains characterized by magmatic, tectonic, sedimentary, structural, hydrothermal, and geothermal features. Empirical Green's Functions (EGFs) were derived from ambient noise cross-correlations for Rayleigh waves using standard data processing methods. Dispersion curves were subsequently determined via the Frequency Time Analysis (FTAN) technique. Nonlinear multi-scale inversion was applied to produce group velocity maps for different periods. Finally, a transdimensional Bayesian approach was utilized for depth inversion, resulting in a 3D S-wave velocity model.
Our S-wave velocity model highlights the occurrence of fast and slow domains, often marked by sharp variations. Transition zones of intermediate-velocity are located at the shoulders of the low-velocity zones and are potentially interpreted as the boundaries of intrusive bodies displaying high shear wave velocities. One of these domains is located below the main Muara Laboh geothermal system. Other similar areas can be identified from the 3D tomography data and represent ideal targets for geothermal energy harnessing.
NANT is a non-invasive and cost-efficient method that provides high-resolution subsurface 3D images of the first 5 km of the upper crust. This approach is ideal to identify subsurface fluid storage and pathways along e.g., seismically active regions where tectonic discontinuities are broadly distributed. These discontinuities are often suggested to control the laterally extensive diffused hydrothermal fluid migration that is targeted for geothermal energy harnessing.
How to cite: Mazzini, A., Jiwani Brown, E. A., Cabrera-Pérez, I., Sfalcin, J., Azis, H., Nugroho, I., Zaizen, T., and Lupi, M.: An innovative and fluid-sensitive prospection method: Deployment of Nodal Ambient Noise Tomography (NANT) in Muara Laboh geothermal system, Sumatra, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10460, https://doi.org/10.5194/egusphere-egu25-10460, 2025.
Deep Electrical Resistivity Tomography (DERT) has proven to be a versatile geophysical method to investigate fluid migration systems and to explore metalliferous deposits. We present the survey conducted at Calamita iron skarn deposit, located in Tuscany, Italy. The site, though no longer actively exploited, presents unique opportunities to evaluate the application of DERT in mineral exploration. The goal is to detect causative magmatic intrusions and map the associated mineralized structures at depth.
The DERT survey conducted at Calamita allowed us identifying several features that are part of a complex paleo-geothermal system. The anomaly beneath the Vallone skarn at a depth of -150 m.a.s.l is interpreted as either an altered granitic body or a pathway for the migration of magmatic fluids that are linked to mineralized surface zones. The resistivity model also highlights the presence of extension faults and a southward dip of the deposits which is consistent with the hypothesized location of the magmatic intrusion. Induced Polarization (IP) measurements further indicate widespread pyritization of schists, following their epidotization, at depths ranging from -50 to -200 m.a.s.l.
Integrated resistivity and chargeability data illustrate the potential of DERT to investigate skarn deposits and support decision-making in mineral exploration. This approach is particularly effective to define hidden ore bodies and to understand the tectonic control on mineralization and could significantly reduce the uncertainty associated with drilling programs.
How to cite: Sfalcin, J., Braize, D., Dini, A., Kouzmanov, K., and Lupi, M.: Deep Electrical Resistivity Tomography (DERT): a versatile method to investigate fluid migration systems and to identify ore deposits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18035, https://doi.org/10.5194/egusphere-egu25-18035, 2025.
La Soufriere is an active stratovolcano located in the South of Basse-Terre island, Guadeloupe, and is part of the Lesser Antilles volcanic arc. Eruptions are usually characterised as peléan with the most recent magmatic eruption occurring approximately in 1530 A.D. Since then, activity at La Soufrière has consisted of phreatic eruptions, the last being in 1976. Present-day activity appears to be related to surface fumaroles and shallow-subsurface seismic activity. In 1992, the alert level was updated from green to yellow and the recorded activity began to slowly increase. Since 2018, the hydrothermal system has been subject to overpressure and overheating processes, resulting in a change to the usual fumarole activity and an increase in volcano seismicity.
We analyze the continuous passive seismic record from one month of data recorded on 47 3-component 5Hz nodal stations, deployed around the volcanic summit. We locate emergent seismic signals, including tremors, to have a better understanding of the subsurface structure of the plumbing system, and reveal more information pertaining to the hydrothermal system.
We use the Python package Covseisnet, which uses a network Covariance Matrix Analysis to detect and locate seismic signals that are typically induced by the geothermal systems and volcanic unrest. This method is based on the decomposition of the matrix into eigenvectors and eigenvalues. Our results are also compared against two complementary methods derived from the same seismic dataset to obtain a more comprehensive interpretation of the subsurface architecture and reduce the uncertainty of our analyses. The combination of our Covariance Matrix analysis, Ambient Noise Tomography, and Local Earthquake Tomography provides an updated image of the shallow plumbing system of the Soufrière Volcano plumbing’s system.
How to cite: Chatelain, U., Munoz Burbano, F. J., Jiwani-Brown, E. A., and Lupi, M.: Detection, classification, and localization of seismic signals at the Soufrière geothermal system, Guadeloupe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12186, https://doi.org/10.5194/egusphere-egu25-12186, 2025.
The Izu-Oshima volcano has been dormant for 38 years since its last eruption in 1986. Historical records indicate an average eruption interval of ~30 years, highlighting the importance of predicting changes in volcanic activity in the near future.
The water table of the Izu-Oshima volcano is at sea level, with a vadose zone about 500 meters thick in the summit caldera. Prior to the 1986 eruption, thermal and electromagnetic signals associated with volcanic fluids ascending through this vadose zone were observed (Kagiyama, 2018). We conducted numerical simulations of the hydrothermal system, based on electromagnetic and thermal observations, to analyze self-potential (SP) signal variations associated with fluid flow through the vadose zone.
Electromagnetic observations were conducted at 32 sites inside and outside the caldera using the Audio-Magnetotellurics (AMT) method in 2006, 2007, 2009, and 2022. A 3D resistivity structure was obtained using inversion analysis with the WSINV3DMT code. The results revealed low resistivities (1–10 Ω·m) below sea level, suggesting the presence of hot water containing dissolved components or altered minerals. In contrast, high resistivities (1,000–10,000 Ω·m) were observed above sea level, except beneath the crater, indicating unsaturated scoria or lava layers. The resistivity structure suggests that relatively stable hydrothermal activity has persisted below sea level through past eruptions.
Numerical simulations were conducted to investigate the effects of rainwater infiltration into the vadose zone and water vapor rising from a deep source. Hydrothermal convection was found to depend on the flow rate of the source. At low flow rates, water vapor condensed, limiting fluid flow to below sea level, which aligns with the observed low-resistivity structures. The SP distribution was calculated from fluid flow and compared with observed SP distributions from 2006 and 2018. While accounting for spatial heterogeneities in some areas is necessary, the observed SP distributions are generally reproduced by incorporating rainwater infiltration and resistivity structure (Onizawa et al., 2009).
Simulations indicated that hydrothermal convection below sea level is difficult to detect through SP distribution alone. However, if the flow rate of water vapor from the source increases, water vapor can rise to near-surface levels, crossing the water table. In such cases, the SP distribution exhibits a negative anomaly at the summit due to the counterflow of water vapor and condensed water in the vadose zone.
Continuous SP monitoring at 20 sites has been conducted since 2006, with data recorded at 1-minute intervals and transmitted to our institute daily. To date, the long-term trends have remained unchanged at most locations. We continue SP monitoring to detect signal changes anticipated by the simulations, which may provide critical insights into future volcanic activity.
How to cite: Matsushima, N. and Gresse, M.: Hydrothermal system of Izu-oshima volcano inferred from numerical simulation and field observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3414, https://doi.org/10.5194/egusphere-egu25-3414, 2025.
La Soufrière volcano, located in the volcanic island of Guadeloupe, has virtually unlimited geothermal resources. The intense seismic activity of the volcanic system allows the application of passive seismic methods to explore the geothermal potential in the area. The high seismic activity in the volcano, together with the well-developed network of tectonic faults mapped at La Soufriere facilitates the upwelling of geothermal fluids in the upper crust.
This study aims to image the shallow seismic velocity structure of the volcano by deriving a Local Earthquake Tomography with data from a dense network of 48 three-component short-period nodal geophones deployed in October 2023 around the volcanic massif, complemented by 8 permanent seismic stations operated by the IPGP.
We first built a seismic catalogue by applying a machine-learning seismic phase picker PhaseNet, for which we initially obtained 551,383 P- and S-wave phases. We detected 339 seismic events with PyOcto and successfully located 145 events with NonLinLoc. The seismic catalogue was the input of a Local Earthquake Tomography using our relocated catalogue to develop a high-resolution model of the volcanic system. We produced an interpretation of the subsurface structure based on the distribution of Vp, Vs and Vp/Vs ratio velocity anomalies. This model will highlight fractures and conduits that enable the circulation of hydrothermal fluids, and the different volcanic structures. Our results will be compared with ongoing studies of the volcanic system, such as Ambient Noise Tomography and Tremor relocation, to refine our interpretation of the shallow plumbing system of this active volcano. This work will contribute to the monitoring of the volcano and support geothermal exploration efforts in the region.
How to cite: Gatein, H., Porras Loria, J. L., Jiwani-Brown, E. A., and Lupi, M.: Geothermal survey using earthquake seismic tomography in La Soufrière, Guadeloupe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18483, https://doi.org/10.5194/egusphere-egu25-18483, 2025.
The Oslo Rift formed about 300 million years ago and is characterized by emplacement of subaerial lavas and an extensive sub-volcanic system of sills, dykes, and plutons. The earliest stages of volcanism were dominated by fissure-fed plateau basalts, trachytes and latites (including rhomb porphyries), followed by later stage caldera-related basalts, rhyolites and ignimbrites. More than 1.5 kilometer of rhomb porphyry stratigraphy is preserved in the ca 250 km long subaerially exposed rift system, but primary igneous minerals are usually completely altered except from apatite and rare zircons. Interestingly, the sedimentary rocks that form the substrate for the lavas remain unaffected by hydrothermal alteration, questioning conventional models for fluid flow and temperature evolution in rifts.
Here we use new boreholes and cores from the Oslo Rift to characterize and further understand rift-scale pervasive alteration of lava flows. We focus on two cores, where the first includes 350 meters of interbedded sandstones and lava flows, and the second is 50 meters long and drilled through a fault zone in the two lowermost flow units. We present wireline logs, geochemical data and petrography in order to further understand the hydrothermal alteration and porosity-generation in these rocks. Overall, the primary igneous minerals (e.g. pyroxene, feldspar, ilmenite) are hydrated and replaced by assemblages including chlorite, albite, K-feldspar, quartz, calcite, rutile, monazite, and magnetite. Vesicle-rich horizons in the lavas (flow bases and tops) are filled by chlorite and calcite, with minor dolomite, epidote, fluorite, barite, and bitumen. Vein minerals includes calcite, quartz, and epidote. In the presentation we also show the carbon and oxygen isotope systematics of the carbonates.
Our results shed light on the complex history of fluid-rock interactions in a continental rift. Lavas have acted as reactive lids, trapping water and light and mobile elements such as carbon and alkalies, whereas apatite-hosted REE still preserve igneous geochemical signatures. Hydrothermal circulation took place across a large temperature range, where the maximum temperature is recorded by quartz plus epidote assemblages (ca. 300 C). Conceptual models need to include the variability of fluid sources during rift progression, including igneous/mantle, contact metamorphic, basinal brines, meteoric and seawater sources. Finally, the pervasive hydrothermal alteration resulted in high porosity in the lavas that still has a significant influence on the content and flow of ground water.
How to cite: Svensen, H. H., Callegaro, S., Midtkandal, I., Millett, J., Whattam, J., Dalslåen, B. H., Kjøll, H. J., Neumann, E.-R., and Planke, S.: Continental rifts and reactive lids: Pervasive hydrothermal alteration and carbonation of volcanic rocks in the Oslo Rift , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16966, https://doi.org/10.5194/egusphere-egu25-16966, 2025.
Posters virtual: Tue, 29 Apr, 14:00–15:45 | vPoster spot 1
EGU25-21421 | Posters virtual | VPS22
Chemical mapping of methane in the Northern Guaymas Basin hydrothermal fieldTue, 29 Apr, 14:00–15:45 (CEST) | vP1.8
The Guaymas Basin is a large marginal rift basin in the Gulf of California with ongoing seafloor spreading and strong hydrothermalism centered around two axial troughs. Extremely high concentrations of methane are discharged from diffuse hydrothermal flow, black smokers, and cold seeps. A thick sediment layer across the basin allows for thermocatalytic production of methane in the hot subsurface, resulting in the discharge of hydrothermal fluids from powerful black smokers with temperatures exceeding 300°C. The cooler surface sediments additionally support methanogenesis, providing a complex interplay between the biogenic and abiogenic systems. The dynamism of the Guaymas Basin means that the flux and distribution of hydrothermal vents in this region can change rapidly, impacting the wider oceanography of the region.
We present here results from a 2024 study of hydrothermalism in the Guaymas basin using a new optical sensor, developed at the Woods Hole Oceanographic Institution. SAGE – the Sensor for Aqueous Gases in the Environment – utilizes laser absorption spectroscopy through a hollow core optic fiber to quantify the partial pressure of dissolved methane extracted from the deep sea. This in situ sensor, deployed during a cruise on the R/V Atlantis allows continuous measurement of methane concentrations with high spatiotemporal resolution, with a sampling rate of 1Hz and a stable response time of 1-5 minutes. This new sensing technique facilitated analysis of the relationships between microbial communities and hydrothermalism and guided dives towards hydrothermal vents based on the real-time methane concentration. It also allowed the comprehensive in situ analysis of a rapidly evolving black smoker vent site in the northern axial trough, allowing the methane export to the water column to be characterized with high spatiotemporal resolution. The low detection limit of SAGE – down to ~10 ppm – allows the analysis of the broader impact of these dynamic methane-based systems into the wider oceanography of the region.
How to cite: Michel, A., Burkitt-Gray, M., Marquardt, S., Youngs, S., Remar, J., Joye, S., and Kapit, J.: Chemical mapping of methane in the Northern Guaymas Basin hydrothermal field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21421, https://doi.org/10.5194/egusphere-egu25-21421, 2025.
