Mud volcanism represents one of the unique natural phenomenon that reflects subsurface processes characterized by movement of large volumes of sediments and fluids in the Earth’s crust. The significant part of world mud volcanoes is concentrated within the on- and offshore Azerbaijan, South Caspian basin (SCB).

The study integrates comprehensive geological, geophysical and geochemical database and presents the results of the analysis of the sedimentary environments in SCB to understand origin and development of mud volcanism in the context of the evolution of the basin. The interpretation of new 2D and 3D seismic data shows that the roots mud volcanoes do not extend below the base of Oligocene-Lower Miocene Maikop Group. The features of sedimentation were studied in details and the sedimentation model of Maikop Group was suggested.

According to the geochemical data and thermobaric conditions Maikop Group considered as the main hydrocarbon source rock within the South Caspian basin. Sedimentary environment during Oligocene-Early Miocene within the territory of Azerbaijan and adjacent Caspian Sea characterized by the complex interaction of various sedimentary processes resulted in the formation of a unique sedimentary complex. The accumulation of Maikop deposits is associated with the beginning of the formation of the folded mountain structures of the Greater Caucasus, the Kopetdag, and the Elbors mountain systems surrounding the SCB, which were the main provenance of clastic material. According to seismic data, the thickness of Maikop sediments currently reaches 3000 m indicating high sedimentation rates over such a relatively short period of geological time. The recent paleontological and geochemical data suggests that Maikop deposits accumulated mainly in the deep marine environment. The rapid burial and subsidence of Maikop sediments occurred because of subsequent intense (avalanche) sedimentation, especially in the Pliocene-Quaternary period. Due to rapid burial, Maikop sediments remain underconsolidated, water-saturated and represent a plastic clay mass, overlapped by thick sequence of denser sediments of the Low Pliocene Productive Series. Thus, as a result of deep subsidence and subsequent catagenic transformations Maikop medium turned into closed physico-chemical system characterized by specific elision processes. The sedimentary environment providing the 20.5 km thick sedimentary filling of the SCB controls mass, fluid and energy transfer within the basin, resulted in formation of mud volcanoes and hydrocarbon accumulations.

Structural interpretation of seismic and geological data, carried out over the past 25 years, indicates that the hydrocarbon deposits discovered in SCB are confined to rootless structures, i.e. injection folds. The formation of injection folds in the sedimentary cover occurs at different stages of basin development due to the alternation of transgressive and regressive series of sediments represented by the layers of clay and sand. All the folds are complicated with mud volcanoes indicating genetic relationship between them, thus the results of paleoreconstructions suggest that mud volcanism in the study area appears to be synchronized in time and space with the growth of anticlinal folds. The mechanism of mud volcano formation based on the gravitational instability has been suggested.

How to cite: Huseynova, S., Yusubov, N., and Guliyev, I.: Impact of sedimentary environment on mechanism of mass, fluid and energy transport in the South Caspian basin , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5963, https://doi.org/10.5194/egusphere-egu24-5963, 2024.

The Arctic seafloor has emerged as a pivotal asset, playing a crucial role in fostering intensified exploitation activities and the incoming deep-sea mining industry, particularly in the so-called "extreme environments" where deep-sourced fluids reach the seafloor at hydrothermal vents and hydrocarbon seeps. Positioned as a promising frontier for resource extraction, exploring the Arctic seafloor is significant with the expanding reach of human exploitation. The ongoing reduction in sea ice coverage in the Arctic region facilitates resource exploration and opens up previously inaccessible areas for scientific investigation.

The paramount importance of comprehending the unique geological and ecological characteristics of the Arctic seafloor becomes evident in the quest for sustainable and responsible exploitation. As a response to this imperative, the integration of seafloor optical and acoustic seafloor and sub-seafloor imaging, and bio-geochemical analyses represents a pivotal approach. This integration allows the reconstruction of comprehensive models delineating geological processes, including the dynamics of hydrothermal and hydrocarbon systems.

This presentation aims to show the effectiveness of a multidisciplinary and multiscale approach in exploring extreme environments through a selection of case studies. Encompassing remote sensing, geochemistry, biology, and a range of seafloor imaging techniques, these studies highlight the complexity and unicity of these environments. Furthermore, we will show how those integrated studies equip both the public and policymakers with essential information, fostering a balanced approach that reconciles economic interests with environmental conservation in the realm of Arctic seafloor exploration.

How to cite: Panieri, G., Argentino, C., Savini, A., Fallati, L., and Ramirez Llodra, E.: Exploring extreme environments at the Arctic seafloor: comprehensive studies integrating science, sustainability, and responsible resource exploitation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16796, https://doi.org/10.5194/egusphere-egu24-16796, 2024.

Tectonic structures such as faults and fractures act as preferential pathways for gas ascent and their consequent release into the atmosphere. Magma-derived gases are widespread throughout the western Eger Rift (Czech Republic), an intraplate region without active volcanism but with the occurrence of mid-crustal earthquake swarms. Geogenic CO₂ discharges from the Počatky–Plesná fault zone (PPZ), Mariánské Lázně Fault (MLF), Bad Brambach (BB), and a deep local fault (DLF) have been sampled since 2021. Gases were analysed for their chemical (CO₂, N₂, O₂, Ar, He, CH₄, and H₂) and isotopic contents (noble gases, CO₂, and CH₄). Results showed that CO₂ is the dominant gas species (concentrations > 99.4%), with the remaining gases being present in minor amounts. The He isotopic composition for gas samples from the PPZ and MLF is typical for the subcontinental lithospheric mantle (SCLM - with ³He/⁴He ratios between 5 and 6 R_A), while gases from BB and the DLF show a lower mantle input (³He/⁴He is 3.2 and 2.4 R_A, respectively). δ¹³C_CO2 data reflect a SCLM CO₂ signature (-4 to -1 ‰ vs. V-PDB). First CH₄ isotopic data present values between -52.0 and -47.1 ‰ vs. V-PDB for δ¹³C_CH4 and between -307 and -284 ‰ vs. V-SMOW for δ²H_CH4. With the exception of samples collected from the MLF that show a clear thermogenic CH₄ origin, all the other samples present isotopic values and CH₄/(C₂H₆+C₃H₈) ratios that suggest a likely biogenic origin, with secondary processes playing a crucial role on the gases’ isotopic signature. It should be noted that low CH₄concentrations (<100 μmol/mol) correspond to low CH₄/³He ratios (around 10⁴) in CO₂-rich magmatic gases, suggesting a possible common origin for these gases. Therefore, multiple origins of CH₄ (biogenic and volcanic-geothermal) cannot be excluded.

This research is a part of the MoCa - “Monitoring Carbon” project and this work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 461419881.

How to cite: D'Alessandro, W., Daskalopoulou, K., Grassa, F., Vieth-Hillebrand, A., Zimmer, M., Niedermann, S., and Woith, H.: First indications on CH4 origin in the CO2-dominated gas discharges of the western Eger Rift (Czech Republic), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12897, https://doi.org/10.5194/egusphere-egu24-12897, 2024.

The Goshogake hydrothermal field in Tohoku, northern Japan, is located on the western flank of the Akita Yakeyama volcano. This N-S elongated field extends over ~20-25 acers and is placed over a tectonic discontinuity that controls the migration of hydrothermal fluids. A variety of surface degassing manifestations can be distinguished including small hydrothermal lakes, clustered bubbling pool fields, active mud erupting gryphons, sulfur-rich fumaroles and localized apparently oil-rich pools. So far it remains unclear if this system and the released gases are purely magmatic or if is also involved the migration of mantle-derived fluids interacting with buried sedimentary deposits. Here we report the result of field observations and fluid samples analyses. The measured temperatures of the active seepage sites range from 33 to 97 °C (in large part higher than 90 °C), while pH is overall low at all sites (i.e. ~2.5).

Gas analyses reveal that all the active sites are CO₂-dominated with slightly higher CH₄ content in the colder and mud seeping sites. While CO₂ has a distinct mantle-derived isotopic signature, the origin of methane is still debated. The apparent d¹³C thermogenic signature of methane, could also be related to an abiotic origin which would be consistent with a CO₂-dominated geothermal system. The presence of oil, if confirmed, could be related to shallow-sourced hydrothermal oil (e.g. similar to that described by Didyk and Simoneit (1989), or, more interestingly, could indicate that this active site is part of a petroleum system potentially linked with deeply buried lacustrine sediments that fill a 1-Ma-caldera formed after a ignimbrite eruption. The possible presence of these deposits in the erupted mud has been suggested by Komatsu et al., (2019) based on mineralogical analyses.

To further test this hypothesis, we are now conducting multiple analyses on the samples recovered from 6 locations at the Goshogake field, including the isotope analysis of water, gas, oil and mud compositions to unravel the source of these fluids as well as the reactions that took place at this site. If confirmed, Goshogake could potentially be the first example of known sedimentary hosted geothermal system in Japan. We speculate that targeted fieldworks would likely identify other hybrid systems in the country.

How to cite: Mazzini, A., Naizhong, Z., Etiope, G., Jajalla, M. A., Nakagawa, M., and Gilbert, A.: The Goshogake hydrothermal field (northern Japan): purely geothermal or hybrid sediment-hosted?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9133, https://doi.org/10.5194/egusphere-egu24-9133, 2024.

Although not all volcanic unrests lead to eruptions, it is generally accepted that magmatic activity is what causes volcanoes to awake. Alternatively, hydrothermal processes are often invoked to explain inflation and deflation dynamics. Magmatic brines have physical properties in between deep magmas and shallow hydrothermal fluids. Yet, to date we have no physical models accounting for geophysical signals that may be generated by the fluid flow of magmatic brines.

Vulcano, the southernmost island of the Aeolian Volcanic Archipelago, Italy, entered into unrest in September 2021. The island experienced intense ground deformation,  fumarole temperature and gas emissions increases, and a marked augmentation of seismicity.

For the first time since the deployment of broadband stations in 2005, very long period (VLP) seismic events were detected in the seismic records. Certain aspects of the geophysical signals recorded during the unrest are probably not fully compatible with traditional causal models involving fresh magma rising at depth or with a hydrothermal scenario.  In this contribution we discuss alternative scenarios and investigate whether fluid flow of magmatic brines may play a key role in understanding volcanic unrests.

How to cite: Lupi, M., Alparone, S., Palano, M., Ricci, T., Finizola, A., and Ursino, A.: Non-eruptive unrest and the role of magmatic brines, Vulcano, Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21336, https://doi.org/10.5194/egusphere-egu24-21336, 2024.

Submarine hydrothermal systems attract increasing interest from the scientific community, as they emit huge amounts of both elements and energy. However, in relation to their extreme environmental conditions (e.g. high temperature and pressure, low Ph) direct measurements can be challenging to perform.

In this context, passive hydroacoustics may represent a powerful technique for both short- and long-term monitoring as the typical source mechanisms of the hydrothermal fields, directly related to ascending fluids, radiate sound pressure following different acoustic modes.
Here we present preliminary results obtained by using a spectral approach for estimating the gas flow emission rate starting from the acoustic dataset collected between 22nd and 26th August 2022 on a stationary flux vent located at ~1.8 metres depth, inside the shallow hydrothermal field at Baia di Levante in Vulcano island (Aeolian Islands, Italy).

To carry out the estimation of the gas flow emission rate emitted by the hydrothermal vent, we implemented a customised inverse modelling algorithm based on a spectral method founded upon the assumption that the acoustic signature of a single bubble event evolves over time as a sinusoid that exponentially decays. According to this approach, we refined  the formulation of a forward model for the sound radiated by a stationary, high-flux  bubbles’ plume, then the path was backward analysed through the proposed inversion algorithm, which allowed us to obtain the estimated value of the flow emission rate.
High-resolution audio frames were recorded by using hydrophones [1 - 12800] Hz, that were deployed in the proximity of the investigated vent, collecting a total amount of  7  bursts of  ~10 hour-long each. 

Preliminary analyses of the Power Spectral Density (PSD) and Pressure Power Spectrum highlighted the presence of different persistent energetic frequency peaks over the environmental background noise coherently with the dynamics of the hydrothermal field. The most energetic ones, likely due to the acoustic signal radiated by a large, resonant bubble plume, consistently confirmed the coupling of the estimated radius with direct observations. 

The performed analysis allowed us to identify the main features of the vent, characterised by bubbles radii up to 0.03 m that produce the main energetic peak centred at ~100 Hz, along with smaller bubbles generating less energetic peaks up to 2 kHz. Therefore, the algorithm was set to work in a wide frequency range, spanning from 60 Hz to 2060 Hz, in order to estimate all the gas released by the vent.

The estimated flow emission rate  for the investigated period retrieved values spanning from 3.31 to 6.98 litres per minute, with a mean value of 4.97 litres per minute, in good agreement with the direct observations. These results confirm that passive acoustic methods represent a valid and robust tool for both monitoring and research activity in submarine hydrothermal fields, providing a long-lasting instrument able to detect the fluctuations connected to the variations of such natural systems.

How to cite: Lazzaro, G., Semprebello, A., Magazù, S., Caccamo, M. T., Gattuso, A., Traina, D., Morici, S., Caruso, C. G., and Longo, M.: Inverse modelling as a powerful tool for gas flow emission rate estimation from stationary hydrothermal vents  (Vulcano Island, Aeolian archipelago, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18259, https://doi.org/10.5194/egusphere-egu24-18259, 2024.

The Formiche di Grosseto are three islets, of about 1,500 m2, included in the Tuscan Archipelago, Italy. The islets rise abruptly from a seabed approximately 100 meters deep in correspondence of a structural high separating Neogene basins of the Tuscan Shelf. Onshore it is possible to observe hydrothermal breccias and speleothems. Offshore, CO2-rich submarine thermal fluids discharge from several springs with temperatures as high as 41°C. These submarine springs are mainly located along the Northern scarp at depths ranging from 6 to 32 m below the sea level.

To better understand the past and present nature of these fluid-driven systems extending offshore, a multidisciplinary exploration campaign was undertaken in the framework the TEMPEST and MIGRATE projects.

The main islet, offers a superb continuous outcrop of the Liassic carbonate rocks forming the backbone of the island.  Fault and fracture systems have been characterized across different scales to create a representative model. Multiple drone-flights have been performed to obtain an optical image for faults and fractures mapped over the islands. Drone-derived observations have been verified in the field and integrated in the structural model. Fractures and structural key geometries have been captured by means of a 2-D fracture network analysis with a circular sampling window. Connectivity within the fracture network have been parameterized by characterizing the different types of fracture terminations and intersections, which have been used to understand the structural architecture controlling the fluid flow. Rocks, hydrothermal breccias and calcitic precipitates have been analysed with cathodoluminescence and stable isotopes. Furthermore, a surface electrical resistivity (ERT) survey was carried out on the islet of Formica Grande di Grosseto - the main inslet - for the characterization of the subsoil up to 20-25 meters deep. The inversion shows a possible upflow of fluids, centred where the hydrothermal breccia has been found. Finally, CO2 diffuse-degassing soil flux measurements were also performed along these alignments.

The integrated study of the collected data pointed out that the northern part of the major islet is marked by upwelling of hot hydrothermal fluids. This was confirmed by a manual excavation that revealed rising thermal fluids - temperature of about 38°C- which was previously unknown on the island. Geochemical investigations have been conducted on the island's fluids, on the already known submarine thermal discharges as well as on the known thermal springs located inland, in the proximity of the Formiche di Grosseto area. 

The chemical compositions of the Formiche water samples are similar to those of seawater, although marked by significant enrichments of SO4, Ca and B and Mg depletion. These compositional characteristics are likely to be ascribed to the mixing of seawater with hydrothermal fluids. Our preliminary results aim to assess the origin of the discharged fluids and their relation with local and regional tectonics, providing an example of how multidisciplinary integrated exploration can be effectively conducted even in challenging contexts.

How to cite: Del Ventisette, C., Montanari, D., Sciarra, A., Mazzini, A., Bonini, M., Tassi, F., Fischanger, F., Del Ghianda, S., Lanari, R., Begue, F., and Lupi, M.: Multidisciplinary exploration for geofluids in small islands, the case study of the Formiche di Grosseto islets, Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21768, https://doi.org/10.5194/egusphere-egu24-21768, 2024.