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Volcanic tremor is a crucial indicator for assessing the state and hazard potential of volcanic systems. At Whakaari (White Island volcano, Aotearoa New Zealand), a pulsed tremor signal emerged after a hydrothermal explosion in August 2012. The tremor accompanied the extrusion of a lava dome, before gradually disappearing prior to the onset of renewed hydrothermal activity in January 2013. We interpret this seismic signal to represent discrete gas transfers from a magmatic intrusion toward a permeable cap—possibly a hydrothermal seal—in the upper layers of Whakaari's hydrothermal system. Such tremor may thus be associated with heightened potential for hazardous explosive activity but is difficult to detect using conventional seismic monitoring parameters. To highlight the emergence of subtle periodic signals, we experiment with Lomb‐Scargle periodograms (LS). LS detect the tremor 5 days before it becomes visible in seismograms, thus facilitating the recognition of such elusive seismic patterns. Plain Language Summary: A periodic seismic signal was observed at Whakaari (White Island volcano, Aotearoa New Zealand) in 2012, a few weeks after an explosion took place at the volcano. This signal persisted over more than 3 months and consists of slowly emerging, then slowly disappearing and regularly spaced "pulses." Similar signals have been observed at other volcanic systems, where they are usually linked to rising magma, which then releases gases. Subsequently, gas slugs forming from the magma rise toward the surface and interact with and excite more solid layers of the system, which is visible in the seismic records. Therefore, such seismic signals could indicate increased potential for dangerous volcanic activity. Common techniques applied to track volcano activity struggled to highlight the emergence of this very subtle pattern. Instead, a new visualization approach allowed us to track the emergence and decline of the signal over time. This shows that such subtle patterns can be discovered days before they become recognizable in seismograms. We therefore suggest ongoing testing and validating this approach before adding it to current monitoring techniques. This work helps to identify and better understand the physical processes behind the patterns hidden in the seismic signals of volcanoes. Key Points: An unusually long‐lasting episode of pulsed tremor was recorded at Whakaari volcano during its 2012/13 eruptive unrest episodeThe tremor may reflect discrete gas transfers from a magmatic intrusion toward a permeable cap or sulfuric seal in a hydrothermal systemSubtle, periodic seismic patterns can efficiently be visualized via Lomb‐Scargle periodograms [ABSTRACT FROM AUTHOR]

As a result of generalization of geophysical studies, petro-paleomagnetic and structural-geomorphological analyses, as well as thermodynamic modeling, some features of ore formation in the hydrothermal system of Cape Fiolent (southwestern Crimea) under island arc conditions were revealed.It has been established that the main transformations of rocks of the Middle Jurassic igneous complex of Cape Fiolent occurred under the influence of hydrothermal fluids during the introduction of felsic intrusions during 168–140 Ma. The zones contain sulfide mineralization, the main minerals of which are pyrite, sphalerite, pyrrhotite, galena, chalcopyrite and arsenic pyrite. In the central parts of the hydrothermal alteration zone, massive sulfides are strongly weathered; these zones contain many secondary sulfates. In the marginal parts of hypergenic limonite, yellow-brown goethite prevails in the oxidation zone, yellow jarosite in the center, which is probably due to the large amount of pyrite in the center of the system, which gave more sulfuric acid during oxidation. The presence of native sulfur in the section testifies to the mixing of the acidified hydrothermal solution with seawater. Complex petro-paleomagnetic and magnetometric studies have shown that contact changes and transformation of the contrasting basalt-rhyolite formation occurred along the NNW-trending faults.

The article presents the results of studying changes in the chemical composition of Upper Pleistocene sediments from Hole ODP 1036A drilled in the Middle Valley of the Juan de Fuca oceanic ridge at the Dead Dog hydrothermal field to a depth of 38.50 m, 9 m from a black smoker with a temperature of 268°C. The most significant changes in sediment chemistry occurred in the lower intervals of the hole. In the 20–30.70 m interval, the concentration of a large number of chemical elements increased and, accordingly, the hydrothermal fluid was depleted of these elements. Conversely, in the 30.70–38.5 m interval, the concentration of most chemical elements decreased, which led to significant enrichment of hydrothermal fluid in these elements. [ABSTRACT FROM AUTHOR]

At hydrothermal systems, heat transfer across the final surface layer is driven by permeable convection and conduction, so that soil permeability and thermal conductivity play fundamental roles in controlling heat flux to the atmosphere. We build a Rayleigh-number driven heat transfer model for a bottom-heated surface that uses measurements of heat flux density (radiation and convection to the atmosphere in W/m2), surface temperature, and soil temperature to solve for soil conductivity, density, and permeability for such a bottom-heated surface. At Vulcano in 2019, we measured an ASTER-derived heat flux density of 240 ± 70 W/m2 and a difference between soil and surface temperature of 18 ± 6 °C. The surface layer is a 7.5 ± 2.5 cm thick case-hardened crust across which heat transfer is conduction dominated. We invert our heat transfer model using the temperature (T) gradient derived from a trench dug into the soil: T = − 49.7y2 + 113.6y + 35 (R2 = 0.9997), where y is depth in meters between the surface and 70 cm. The result is a conductivity for the case-hardened surface layer of 1.0 ± 0.3 W/(m K) and a density of 2440 ± 120 kg/m3. Below this case-hardened crust, heat transfer is dominated by permeable convection in a soil comprised of highly altered trachytic blocks in an ash matrix. Our model gives permeabilities of 1–19 × 10−10 m2 for this layer in 2019. In 2021, Vulcano entered a phase of unrest. Our model reveals that this was associated with an increase in permeability to 10−7 m2. However, by 2023 permeabilities had reverted to pre-unrest levels. Using simple measurements of surface and soil temperature, coupled with heat flux density from a satellite overpass, the model can be used as a basis to constrain heat transfer and to assess permeability at any hydrothermal system. [ABSTRACT FROM AUTHOR]

Authigenic dispersed biotite was discovered for the first time in Pleistocene terrigenous sediments of the Central Hill located in the Escanaba Trough in the southern part of the Gorda Ridge (northeastern sector of the Pacific Ocean). It accounts for almost the entire content of fine fractions <1 μm of most samples from ODP Hole 1038B. The authigenic nature of the biotite is associated with the metasomatic effect of hydrothermal solution on terrigenous clay minerals of sediments after the intrusion of basaltic magma in the form of laccolith with a temperature of ~1200°C. The mineral composition of fine fractions of sediments was studied using complex analytical methods, including modeling of their X-ray diffraction patterns. It has been established that the dispersed micaceous mineral (biotite) is trioctahedral, high-iron, does not swell when saturated with glycol, but contracts after heating at 550°C. It is shown that its structure is devoid of foreign layers, the height and composition of which differ from those of micaceous layers. The decrease in the height of micaceous layers upon heating biotite to 550°C is mainly related to a decrease in the height of 2 : 1 octahedra due to the difference in the Fe2+–O and Fe3+–O bond lengths as a result of the oxidation of Fe2+ cations. It has been established that a limit value for the coefficient of variation CV should not exceed 0.10 to characterize the absence of mixed-layering in a regular structure. [ABSTRACT FROM AUTHOR]

Abstract Volcanic tremor is a crucial indicator for assessing the state and hazard potential of volcanic systems. At Whakaari (White Island volcano, Aotearoa New Zealand), a pulsed tremor signal emerged after a hydrothermal explosion in August 2012. The tremor accompanied the extrusion of a lava dome, before gradually disappearing prior to the onset of renewed hydrothermal activity in January 2013. We interpret this seismic signal to represent discrete gas transfers from a magmatic intrusion toward a permeable cap—possibly a hydrothermal seal—in the upper layers of Whakaari's hydrothermal system. Such tremor may thus be associated with heightened potential for hazardous explosive activity but is difficult to detect using conventional seismic monitoring parameters. To highlight the emergence of subtle periodic signals, we experiment with Lomb‐Scargle periodograms (LS). LS detect the tremor 5 days before it becomes visible in seismograms, thus facilitating the recognition of such elusive seismic patterns.

Abstract The thermal activity of a magmatic–hydrothermal system commonly changes at various stages of volcanic activity. Few studies have provided an entire picture of the thermal activity of such a system over an eruptive cycle, which is essential for understanding the subsurface heat transport process that culminates in an eruption. This study quantitatively evaluated a sequence of thermal activity associated with two phreatic eruptions in 2021 at Aso volcano. We estimated plume-laden heat discharge rates and corresponding H2O flux during 2020–2022 by using two simple methods. We then validated the estimated H2O flux by comparison with volcanic gas monitoring results. Our results showed that the heat discharge rate varied substantially throughout the eruptive cycle. During the pre-eruptive quiescent period (June 2020–May 2021), anomalously large heat discharge (300–800 MW) were observed that were likely due to enhanced magma convection degassing. During the run-up period (June–October 2021), there was no evident change in heat discharge (300–500 MW), but this was accompanied by simultaneous pressurization and heating of an underlying hydrothermal system. These signals imply progress of partial sealing of the hydrothermal system. In the co-eruptive period, the subsequent heat supply from a magmatic region resulted in additional pressurization, which led to the first eruption (October 14, 2021). The heat discharge rates peaked (2000–4000 MW) the day before the second eruption (October 19, 2021), which was accompanied by sustained pressurization of the magma chamber that eventually resulted in a more explosive eruption. In the post-eruptive period, enhanced heat discharge (~ 1000 MW) continued for four months, and finally returned to the background level of the quiescent period (

Abstract Inflations at active volcanoes are indicators of overpressure in the subsurface, which is known to be a phenomenon that precedes eruptions. Volcanic overpressure is induced by the injection of magmatic fluids, accumulated magma, or heat supply from greater depths. Azuma volcano (Japan) has experienced several episodes of volcanic unrest with increases in seismicity at the depth of the hydrothermal system, implying a potential increase in phreatic eruptions. The time series of interferometric synthetic aperture radar data, associated with the unrest episodes occurring in 2014–2015 and 2018–2019, revealed spatiotemporal variations of inflation episodes, centered around Oana crater, the most active fumarole of Azuma volcano. The modeled best-fit geometry of the elongated pressure source for the local deformation has the same dip as the overlying topographic slope direction and angle around Oana crater, suggesting the existence of topography-correlated layered structures within the hydrothermal system. In contrast, the broader deformation associated with the 2014–2015 unrest was explained by the overpressure of a horizontal flat source at 360–1500 m below sea level, showing the similar depth of the top as the conductive low-resistivity or low-viscosity body suggested by previous studies. The unrest episodes were thus interpreted as resulting mainly from the supply of magmatic fluids, or the transfer of heat from greater depths. Our study helps in understanding the shallow structure of this volcanic system and contributes to evaluating the potential for forthcoming eruptions in Azuma volcano. Graphical Abstract

In this study, hydrothermal metallurgy technology was used to convert arsenic in the solution into a stable, dense, and granular arsenic-fixing mineral, scorodite (FeAsO4·2H2O), that is conducive to storage. The effect of Na+ on the precipitation rate of arsenic and iron, the phase composition, and the transformation of arsenic residue during the mineralization and arsenic precipitation of hydrothermal scorodite in the H3AsO4-FeSO4-Na2SO4-H2O system were studied. The results show that Fe3+ co-precipitates with As5+ to form scorodite (FeAsO4·2H2O). In the later stage of the reaction, Fe3+ and Na+ combine to precipitate in the form of sodium jarosite [NaFe3(SO4)2(OH)6]. Under the conditions of an initial Na+ concentration of 10 g/L, an arsenic concentration of 10 g/L, a molar ratio of iron to arsenic of 1.5, a pH of 1, a reaction temperature of 160 °C, a stirring speed of 500 r/min, a reaction time of 3 h, and an oxygen partial pressure of 0.6 MPa, the precipitation rates of arsenic and iron were 98.2% and 93.2%, respectively. The phase composition of the arsenic residue is mainly composed of large-grained polyhedral crystal scorodite, and a small amount of irregular, small-grained crystal sodium jarosite is dispersed in it. By controlling the initial molar ratio of iron to arsenic, the concentration of Na+, and prolonging the reaction time, the formation of the sodium jarosite phase can be inhibited, and the transformation of the sodium jarosite phase into the scorodite phase can be promoted, so as to realize the efficient precipitation of arsenic, reduce the amount of arsenic residue, ensure the stability of arsenic residue, and avoid potential environmental pollution risks. [ABSTRACT FROM AUTHOR]

The thermal activity of a magmatic–hydrothermal system commonly changes at various stages of volcanic activity. Few studies have provided an entire picture of the thermal activity of such a system over an eruptive cycle, which is essential for understanding the subsurface heat transport process that culminates in an eruption. This study quantitatively evaluated a sequence of thermal activity associated with two phreatic eruptions in 2021 at Aso volcano. We estimated plume-laden heat discharge rates and corresponding H2O flux during 2020–2022 by using two simple methods. We then validated the estimated H2O flux by comparison with volcanic gas monitoring results. Our results showed that the heat discharge rate varied substantially throughout the eruptive cycle. During the pre-eruptive quiescent period (June 2020–May 2021), anomalously large heat discharge (300–800 MW) were observed that were likely due to enhanced magma convection degassing. During the run-up period (June–October 2021), there was no evident change in heat discharge (300–500 MW), but this was accompanied by simultaneous pressurization and heating of an underlying hydrothermal system. These signals imply progress of partial sealing of the hydrothermal system. In the co-eruptive period, the subsequent heat supply from a magmatic region resulted in additional pressurization, which led to the first eruption (October 14, 2021). The heat discharge rates peaked (2000–4000 MW) the day before the second eruption (October 19, 2021), which was accompanied by sustained pressurization of the magma chamber that eventually resulted in a more explosive eruption. In the post-eruptive period, enhanced heat discharge (~ 1000 MW) continued for four months, and finally returned to the background level of the quiescent period (< 300 MW) in early March 2022. Despite using simple models, we quantitatively tracked transient thermal activity and revealed the underlying heat transport processes throughout the Aso 2021 eruptive activity. [ABSTRACT FROM AUTHOR]

Inflations at active volcanoes are indicators of overpressure in the subsurface, which is known to be a phenomenon that precedes eruptions. Volcanic overpressure is induced by the injection of magmatic fluids, accumulated magma, or heat supply from greater depths. Azuma volcano (Japan) has experienced several episodes of volcanic unrest with increases in seismicity at the depth of the hydrothermal system, implying a potential increase in phreatic eruptions. The time series of interferometric synthetic aperture radar data, associated with the unrest episodes occurring in 2014–2015 and 2018–2019, revealed spatiotemporal variations of inflation episodes, centered around Oana crater, the most active fumarole of Azuma volcano. The modeled best-fit geometry of the elongated pressure source for the local deformation has the same dip as the overlying topographic slope direction and angle around Oana crater, suggesting the existence of topography-correlated layered structures within the hydrothermal system. In contrast, the broader deformation associated with the 2014–2015 unrest was explained by the overpressure of a horizontal flat source at 360–1500 m below sea level, showing the similar depth of the top as the conductive low-resistivity or low-viscosity body suggested by previous studies. The unrest episodes were thus interpreted as resulting mainly from the supply of magmatic fluids, or the transfer of heat from greater depths. Our study helps in understanding the shallow structure of this volcanic system and contributes to evaluating the potential for forthcoming eruptions in Azuma volcano. [ABSTRACT FROM AUTHOR]

Silicic volcanic complexes in the Main Ethiopian Rift (MER) system host long-lived shallow magma reservoirs that provide heat needed to drive geothermal systems. Some of these geothermal systems in Ethiopia appear to be suitable for green and sustainable electricity generation. One such prospect is located at the Corbetti volcanic complex near the city of Awassa. High-resolution imaging of the subsurface below Corbetti is of imminent importance, not only because of its geothermal potential, but also due to reported evidence for an ongoing magmatic intrusion. In this study, we present a new subsurface 3-D electrical conductivity model of Corbetti obtained through the inversion of 120 magnetotelluric stations. The model elucidates a magmatic system under Corbetti and reveals that it is linked to a magma ponding zone in the lower crust. Magma is transported through the crust and accumulates in a shallow reservoir in form of a magmatic mush at a depth of |$\gtrapprox 4\, {\rm km b.s.l.}$| below the caldera. The imaged extent and depth of the shallow magma reservoir is in agreement with previous geodetic and gravimetric studies that proposed an ongoing magmatic intrusion. Interpreting our model with laboratory-based conductivity models for basaltic and rhyolitic melt compositions suggests that Corbetti is seemingly in a non-eruptible state with ∼6–16 vol. per cent basaltic melt in the lower crust and ∼20–35 vol. per cent rhyolitic melt in the upper crust. With these observations, Corbetti's magmatic system shares common characteristics with volcanic complexes found in the central MER. Specifically, these volcanic complexes are transcrustal two-stage magmatic systems with magma storage in the lower and upper crust that supply heat for volcano-hosted high-temperature geothermal systems above them. According to the presented subsurface model, a cross-rift volcano-tectonic lineament exerts first-order controls on the magma emplacement and hydrothermal convection at Corbetti. Our study depicts hydrothermal convection pathways in unprecedented detail for this system and helps identify prospective regions for future geothermal exploration. 3-D imaging of both the Corbetti's magmatic and associated geothermal systems provides key information for the quantitative evaluation of Corbetti's geothermal energy potential and for the assessment of potential volcanic risks. [ABSTRACT FROM AUTHOR]

High-definition bathymetry mapping, combined with the measurement of dissolved benthic fluxes and water column biogeochemical properties, allows for a description of new biogeochemical processes around the Panarea Volcanic island. Investigations focused on the CO2 releases from the bottom sea on the east of the Panarea volcanic complex provided insights into the geological setup of the marine area east and south of the Panarea Island. Between the Panarea Island and the Basiluzzo Islet lies a SW-NE-stretching graben structure where a central depression, the Smoking Land Valley, is bounded by extensional faults. Abundant acidic fluids rich in dissolved inorganic Carbon are released on the edges of the graben, along the extensional faults, either diffusely from the seafloor, from hydrothermal chimneys, or at the center of craters of different sizes. The precipitation of iron dissolved in the acidic fluids forms Fe-oxyhydroxides bottom sea crusts that act as a plug, thus preventing the release of the underlying gases until their mounting pressure generates a bursting release. This process is cyclic and results in intermittent gas release from the bottom, leaving extinct craters and quiescent chimneys. The measurement of dissolved benthic fluxes allowed us to estimate the volcanic DIC venting at 15 Mt of CO2 over the past 10,000 years. The fluxes are not distributed homogeneously but rather concentrate along fractures and fault planes, which facilitate their rise to the seafloor. The acidic fluids released affect the chemical properties and structure of the water column through the formation of layers with a lower pH under the pycnocline, which can limit volcanic CO2 release to the atmosphere. Further and continuous monitoring and investigation of the area are needed in order to complete a thorough picture of the variations in fluid releases through time and space. The importance of such monitoring lies in the development of a new method for detecting and quantifying the diffusive dissolved benthic fluxes on a volcanic sea bottom affected by hydrothermal seeps. [ABSTRACT FROM AUTHOR]

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Traditionally, single‐beam echo sounder (SBES) data are used to determine the position of emission structures in the form of a two‐dimensional profile, which may not be straightforward enough to correlate the data of adjacent profiles and determine the exact discharge area. In this study, we develop semiautomatic software to remove noise and select possible flare signals to enhance the speed and precision of the data processing. The program also allows for the transformation of the data into a three‐dimensional point cloud distribution by computing the receiving angle of the data. By applying this method to investigate the distribution and mechanism of gas emission structures in the South Okinawa Trough (SOT), we determine four high flux areas and 22 isolated plumes with roots. Widespread gas flares usually occur in areas with large‐scale volcanic activity or gas‐enriched structures. Isolated gas plumes could be found for a single knoll outcrop and normal faulting structures. The energy of the flares around the knoll area is generally stronger than that observed along the normal faults. Compared with other geophysical data, we find that the widespread distribution of gas flares generally implies a larger hydrothermal potential, which may not be revealed by single‐profile acoustic image observations. We also find that the direction of flares is strongly influenced by tides, and the height of the flare represents the thermocline as a strong boundary for bubbles composited by carbon dioxide. Plain Language Summary: This study introduces a new method using SBES data to analyze gas emission structures in the South Okinawa Trough. By developing specialized software, the researchers enhance the speed and precision of data processing, allowing for the identification of high flux areas and isolated plumes. The study reveals that widespread gas flares indicate significant hydrothermal potential, influenced by tides and thermocline height. This research expands our understanding of gas emissions in the region. Key Points: The precise range and magnitude of gas discharges in the southern Okinawa Trough are determined by processing the SBES dataThe magnitude and intensity of gas discharges can be attributed to volcanic fluid activity or structural faultsThe three‐dimensional flares observed in the water column illustrate the impact of tides on the upward movement of gas plumes [ABSTRACT FROM AUTHOR]

This work considers the occurrence of Hg in a clay strata and pore fluids and conditions of Hg incorporation in sulfides and clay minerals abundant in thermal fields of the Koshelev, Kambalny, and Pauzhetka hydrothermal systems. It is shown that, under physicochemical conditions typical of the studied thermal fields, Hg is mostly incorporated in sulfides (pyrite, marcasite, cinnabar) and clay minerals (kaolinite and montmorillonite) as a result of sorption. Under the conditions of a thermal field, cinnabar is the most stable Hg form, because Fe sulfides are unstable during oxidation. The optimal pH value for Hg sorption by clay minerals (in the absence of chlorides and sulfites) is 3.15. In the presence of Hg-bonding chlorides, sulfites, and other anions, the optimal Hg sorption on layered silicates starts from a pH value of >5. The Hg sorption by clay minerals strongly depends on the local highly dynamic geochemical conditions. [ABSTRACT FROM AUTHOR]

Abstract Hydrothermal systems can generate phreatic and/or phreatomagmatic explosions with little warning. Understanding the temporal and spatial evolution of geophysical and geochemical signals at hydrothermal systems is crucial for detecting precursory signs to unrest and to inform on hazard. Thermal signatures of such systems are poorly defined because data records are often too short or discrete compared to activity timescales, which can be decadal. La Fossa system of Vulcano has been monitored since the 1980s and entered a period of unrest in 2021. We assessed the thermal signature of La Fossa using ground- and satellite-based data with various temporal and spatial scales. While continuously-recording stations provided continuous but point-based measurements, fumarole field vent surveys and infrared images obtained from satellite-flown sensors (ASTER and VIIRS) allowed lower temporal resolution but synoptic records to be built. By integrating this multi-resolution data set, precursory signs of unrest could retrospectively be detected from February to June 2021. Intensity of all unrest metrics increased during summer 2021, with an onset over a few days in September 2021. By September, seismic, CO2, SO2 and other geochemical metrics also indicated unrest, leading Civil Protection to raise the alert level to yellow on October 1. Heat flux, having been 4 MW in May 2019, increasing to 90 MW by September, and peaking at 120 MW in March 2022. We convolved our thermal data sets with all other monitoring data to validate a Vulcano Fossa Unrest Index (VFUI), framework of which can be potentially applied to any hydrothermal system. The VFUI highlighted four stages of unrest, none of which were clear in any single data set: background, precursory, onset and unrest. Onset was characterized by sudden release of fluids, likely caused by failure of sealed zones that had become pressurized during the precursory phase that began possibly as early as February 2021. Unrest has been ongoing for more than 18 months, and may continue for several more years. Our understanding of this system behavior has been due to hindsight, but demonstrates how multiparametric surveys can track and forecast unrest. Graphical Abstract

Abstract Mt. Ontake is an active volcano in central Japan where phreatic eruption activity is prominent. A shallow subsurface structure in the summit region of this volcano has been scarcely studied despite its importance. Our study examines the structure from three seismic analyses: a typical P-wave velocity from the semblance of the vertical propagation of intermediate-depth earthquakes (IDEs), a layered velocity model from P- and S-wave arrival times of shallow volcanic earthquakes, and a pseudoreflection profile from the autocorrelation functions of the IDEs. Our results consistently indicate the presence of three layers, which are interpreted as younger (> 0.1 Ma) and older (0.39–0.78 Ma) eruptive deposits and the basement. A comparison of the structure with hypocentres and deformation sources suggests fluid migration controlled by the structure. Graphical Abstract

The southeastern Korean Peninsula (SeKP) has experienced intense deformation owing to subduction and backarc extension at the eastern continental margin of the Eurasian Plate, leading to the formation of complex tectonic structures. Abnormally high surface heat flux, Cenozoic volcanism, signatures of mantle degassing and hydrothermal alteration, and several active fault systems with extensional sedimentary basins have been identified; however, the major driving forces that promote local seismic events and hydrothermal activities remain enigmatic. Here, we constructed 3-D P -wave velocity of the crust and upper mantle in the SeKP for the first time using a teleseismic traveltime tomography method and an extensive data set obtained from a dense seismic network. Our model revealed three distinct velocity patterns at different depths: (1) in the upper crust (depth ∼0–10 km), a low-velocity anomaly beneath the Cenozoic sedimentary basin exhibiting a prominent lateral velocity contrasts with higher velocities in the Cretaceous sedimentary and plutonic rocks; (2) a N–S trending low-velocity anomaly extending from the lower crust to the uppermost mantle (depth ∼20–35 km) beneath the major active fault systems interpreted as a thermally or mechanically weakened structure that could transfer high surface heat flux and transport mantle-driven gases and (3) a low-velocity anomaly adjacent to the Cenozoic basin in the upper mantle at depths of 35–55 km interpreted as the higher temperature upper mantle. Via a series of geodynamic simulations, we demonstrated that the extensional deformation at the eastern continental margin during the Early to Middle Miocene locally enhanced the temperature of the crust and upper mantle beneath the SeKP. We propose that a hydrothermal system, resulting from the thermally modified lithosphere of the continental margin, has contributed to the enhanced local seismicity and geothermal activities observed in the SeKP region. [ABSTRACT FROM AUTHOR]

We report marine dissolved organic carbon (DOC) concentrations, and DOC Δ14C and δ13C in seawater collected from the West Indian Ocean during the GO‐SHIP I07N cruise in 2018. We find bomb 14C in DOC from the upper 1,000 m of the water column. There is no significant change in ∆14C of DOC in deep water northward, unlike that of dissolved inorganic carbon (DIC), suggesting that transport of deep water northward is not controlling the 14C age of DOC. Variability of DOC ∆14C, including high values in the deep waters, is more pronounced than in other oceans, suggesting that dissolution of surface derived particulate organic carbon is a source of modern carbon to deep DOC in the West Indian Ocean. Low δ13C are present at two of the five stations studied, suggesting a source of low δ13C DOC, or additional microbial utilization of deep DOC. Plain Language Summary: Dissolved organic carbon (DOC) is the most abundant pool of organic carbon in ocean water. It is thought to form primarily from photosynthetic organisms in surface waters, however the radiocarbon (14C) ages of DOC in the Atlantic and Pacific oceans are 4,900–6,400 years old. We find aging of deep DOC in the West Indian Ocean is not similar to that for dissolved inorganic carbon, indicating that transport of deep water northward is not the main control of 14C in DOC. Evidence of young DOC is observed in the deep Indian. Key Points: 14C aging of deep dissolved organic carbon (DOC) northward is not similar to that of deep dissolved inorganic carbon, showing that transport of deep water is not the main control of 14C in DOCVariability of deep DOC 14C indicates heterogeneity in the DOC pool, perhaps by dissolution of surface‐derived, particulate organic CLow DOC δ13C in deep water from two stations may suggest a source of chemosynthetically produced organic matter [ABSTRACT FROM AUTHOR]

Hydrothermal systems can generate phreatic and/or phreatomagmatic explosions with little warning. Understanding the temporal and spatial evolution of geophysical and geochemical signals at hydrothermal systems is crucial for detecting precursory signs to unrest and to inform on hazard. Thermal signatures of such systems are poorly defined because data records are often too short or discrete compared to activity timescales, which can be decadal. La Fossa system of Vulcano has been monitored since the 1980s and entered a period of unrest in 2021. We assessed the thermal signature of La Fossa using ground- and satellite-based data with various temporal and spatial scales. While continuously-recording stations provided continuous but point-based measurements, fumarole field vent surveys and infrared images obtained from satellite-flown sensors (ASTER and VIIRS) allowed lower temporal resolution but synoptic records to be built. By integrating this multi-resolution data set, precursory signs of unrest could retrospectively be detected from February to June 2021. Intensity of all unrest metrics increased during summer 2021, with an onset over a few days in September 2021. By September, seismic, CO2, SO2 and other geochemical metrics also indicated unrest, leading Civil Protection to raise the alert level to yellow on October 1. Heat flux, having been 4 MW in May 2019, increasing to 90 MW by September, and peaking at 120 MW in March 2022. We convolved our thermal data sets with all other monitoring data to validate a Vulcano Fossa Unrest Index (VFUI), framework of which can be potentially applied to any hydrothermal system. The VFUI highlighted four stages of unrest, none of which were clear in any single data set: background, precursory, onset and unrest. Onset was characterized by sudden release of fluids, likely caused by failure of sealed zones that had become pressurized during the precursory phase that began possibly as early as February 2021. Unrest has been ongoing for more than 18 months, and may continue for several more years. Our understanding of this system behavior has been due to hindsight, but demonstrates how multiparametric surveys can track and forecast unrest. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) isotopes in seawater have been proven as an important geochemical tool for tracing ocean Cd circulation in the modern ocean. In this study, we evaluated a new method to separate Cd (~ 60 ng) from seawater using Chelex resin (1.0 g) coupled with AG-MP-1M resin. The results show that the Chelex resin is sufficient to remove Cd from Na and Mg matrix with Cd recoveries at 98.3 ± 3.5 % (2SD, N = 6); while AG-MP-1M resin could separate Cd from the residual Na, Mg, and isobaric inferences. The total Cd recoveries of the method are 96.3 ± 1.5 % (2SD; N = 4) and the salinity of the samples has no significant impacts on Cd recovery. Cd isotope ratios were measured using a Nu Plasma III MC-ICP-MS and 111Cd–110Cd double spike technique. By comparing the δ114/110Cd values (0.00 ± 0.06‰) of synthetic seawaters doped with Cd isotope standard (NIST-3108; treated by Chelex + AG-MP-1M resin) and the reference value (~ 0.00 ‰), no variations were observed. We also analyzed the Cd isotope compositions of three deep seawaters from a column at the Southwest Indian Ocean Ridges (SWIR). The δ114/110Cd values of the column are decreased from 1.05 ± 0.05 ‰ at 3200 m to 0.36 ± 0.05 ‰ at 2800 m, differing from reported δ114/110Cd values of deep seawater in other oceans. Considering the spatial distance between the column and active hydrothermal vents in SWIR (~ 13 km), we propose that such positive δ114/110Cd values of deep seawater were likely contaminated by vent fluids, which could provide heavy Cd isotope to deep seawaters. This study demonstrates that Cd isotope is more sufficient to distinguish the impact of plumes on deep seawater. [ABSTRACT FROM AUTHOR]

In this paper, we investigate geothermal exploration and production in 189 hydrothermal projects and 42 hot dry rock projects around the world. The hydrothermal fields for a working hydrothermal system to generate electricity should have the elements of heat source, water-saturated porous or fractured reservoir, caprock, heat transfer pathway, and good heat preservation condition and geothermal power energy intensity of 10e20 MW per km² within at least 5 km² area in tectonically active region. The hot water or steam flow rate in this hydrothermal system is normally larger than 40 L/s with temperature of 150 °C or above. The power generated from enhanced geothermal system (EGS) in hot dry rock projects are generally less than 2 MW because the flow rate in most cases is much less than 40 L/s even with the hydraulic fractures using the modern stimulation technology learned from the oil and gas industry. The natural fracture in the subsurface is generally beneficial to the hydraulic fracturing and heat recovery in the hot dry rock. Moreover, the hydraulic fracture parameters, injection rate and well spacing, drilling strategy should be properly designed to avoid the short-circuit between injector and producer and low heat productivity. In the future, CO2 enhanced geothermal recovery associated with CO2 sequestration in the high temperature oil, gas, and geothermal fields maybe a good choice. On the other hand, both nearreal-time seismic monitoring to limit the pumping rate and the closed-loop of the Eavor-Loop style system without hydraulic fracture can contribute greatly to heat recovery of hot dry rocks and mitigate the risks of the hydraulic fracturing induced earthquake. Furthermore, the hybrid solar and geothermal system performs better than the stand-alone geothermal system. [ABSTRACT FROM AUTHOR]

Abstract—First results of the experimental study of a hydrothermal multisystem including lanthanides (Ln) and Fe oxides (magnetite and hematite) are presented. Ln concentrations in solutions and crystals were determined by ICP-MS and LA-ICP-MS, respectively. The Ln partition and cocrystallization coefficients obtained are interpreted as the maximum estimates of "true" values corresponding to structurally bound admixture. It is shown that Ln (except for Eu) are the compatible elements in hydrothermal magnetite; heavy Ln (beginning with Tb) are compatible in hematite. The pronounced tendency of the increase of both coefficients with increasing Ln atomic number beginning from Gd–Tb was established. This is of great importance when light to heavy Ln ratio is used as a typochemical guide for localization of ore source. The Ln-rich phases in association with magnetite and hematite were obtained. These phases have oxychloride (without Fe) and oxyhydroxide (with Fe) composition and exemplify the simultaneous occurrence of light and heavy Ln within a single hydrothermal system due to the co-crystallization of phases selectively accumulating light and heavy lanthanides. [ABSTRACT FROM AUTHOR]

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The Tell Atlas of Algeria has a huge potential for hydrothermal energy from over 240 thermal springs with temperatures up to $$98^\circ$$ 98 ∘ C in the Guelma area. The most exciting region is situated in the northeastern part which is known to have the hottest hydrothermal systems. In this work, we use a high-resolution gravity study to identify the location and origin of the hot water, and how it reaches the surface. Gravimetric data analysis shows the shapes of the anomalies arising due to structures at different subsurface depths. The calculation of the energy spectrum for the data also showcases the depths of the bodies causing anomalies. 3D-Euler deconvolution is applied to estimate the depths of preexisting tectonic structures (faults). These preprocessing steps assist with assessing signal attenuation that impacts the Bouguer anomaly map. The residual anomaly is used in a three-dimensional inversion to provide a subsurface density distribution model that illustrates the locations of the origin of the dominant subsurface thermal systems. Overall, the combination of these standard processing steps applied to the measurements of gravity data at the surface provides new insights about the sources of the hydrothermal systems in the Hammam Debagh and Hammam Ouled Ali regions. Faults that are key to the water infiltrating from depth to the surface are also identified. These represent the pathway of the hot water in the study area.

Abstract In 2018, a phreatic eruption occurred at Mt. Motoshirane, a pyroclastic cone group of the Kusatsu-Shirane Volcano in central Japan. The eruption was abrupt, and no signs of volcanic activity have been observed in recent years, in contrast to the other major pyroclastic cone group, Mt. Shirane, which hosts the active crater lake and has endured repeated phreatic eruptions. To understand the mechanism of the eruption at Mt. Motoshirane, information on the shallow hydrothermal system, which is thought to be the source region of phreatic eruptions, is required; however, few studies have been conducted on this particular cone group. In this study, we conducted an audio-frequency magnetotelluric survey in 2020 to reveal the shallow resistivity structure around the 2018 craters. A three-dimensional resistivity structure model showed generally two layers, with high resistivities at shallow depths overlain by low resistivities underneath. The boundary between the layers corresponded to the top boundary of the Neogene basement rocks. These low resistivities were not found beneath the 2018 craters; therefore, part of the Neogene basement rocks could have been lost by the eruption beneath the 2018 craters. This is consistent with the geochemical study on the mineral assemblage of the erupted deposits, which suggested that the explosions reached the depth of the basement. Graphical Abstract

Southeastern China (SE China) is located in the Pacific tectonic domain and has experienced a series of tectonomagmatic events induced by the subduction of the Paleo‐Pacific Plate since the late Mesozoic. The subduction formed a series of NE‐NNE oriented faults under a NW–SE regional stress field, along which a number of thermal springs occur. Previous studies have focused on the genesis mechanism of specific geothermal fields in SE China, but the general characteristics of hydrothermal systems in SE China remains unclear. In this study, we investigate the correlation between geothermal activity, hydrochemical type and regional faults by studying the distribution of hydrothermal activity and geochemical properties of typical hydrothermal systems in SE China. The hydrothermal systems in SE China have a crustal thermally‐dominated structural origin unique to the specific geological and tectonic conditions of the Eurasian Plate margin. The upwelling of the asthenosphere and the widespread granitoids with high radiogenic heat production in SE China provide major heat sources for regional geothermal anomalies. The NE‐oriented crustal thermally‐dominated faults are critical for the formation of geothermal anomalies and NW‐oriented extensional faults have created favorable conditions for meteoric water infiltration, transportation and the formation of thermal springs. [ABSTRACT FROM AUTHOR]

Mt. Ontake is an active volcano in central Japan where phreatic eruption activity is prominent. A shallow subsurface structure in the summit region of this volcano has been scarcely studied despite its importance. Our study examines the structure from three seismic analyses: a typical P-wave velocity from the semblance of the vertical propagation of intermediate-depth earthquakes (IDEs), a layered velocity model from P- and S-wave arrival times of shallow volcanic earthquakes, and a pseudoreflection profile from the autocorrelation functions of the IDEs. Our results consistently indicate the presence of three layers, which are interpreted as younger (> 0.1 Ma) and older (0.39–0.78 Ma) eruptive deposits and the basement. A comparison of the structure with hypocentres and deformation sources suggests fluid migration controlled by the structure. [ABSTRACT FROM AUTHOR]

Key points The Sr isotopic ratios of hydrothermal fluids from the Okinawa Trough are exceptionally high. The enrichment of 87Sr at Yonaguni Knoll IV cannot be explained without the influence of terrestrial clay minerals in sediments. High Sr isotopic ratios are a common feature of sediment-associated hydrothermal systems.

The maintenance of power system equipment, specifically, the maintenance of generating units, is implicitly related to the reliability and economic operation of the power system. In this study, we established a new technique for the maintenance scheduling of a hydrothermal power system. Two coordination schemes are analysed. The first scheme can be described as a primal optimisation scheme because it maintains a feasible solution at every iteration. The second coordination scheme is defined as a dual optimisation scheme. Two variants of the second scheme are evaluated. These two variants correspond to the Lagrangian relaxation method and augmented relaxation method. The Lagrangian relaxation method uses space dilation to update the system incremental costs. The space dilation method considers the difference of two successive subgradients and aids the Lagrangian relaxation method in producing better convergence and minimum total cost, to date. By realising convergence, hydro maintenance is scheduled. The methodology of economic dispatch is presented and solved for hydrothermal maintenance scheduling. The proposed methodology is applied to modified version of the IEEE–RTS.

The Comoros archipelago is an active geodynamic region located in the Mozambique Channel between East continental Africa and Madagascar. The archipelago results from intra-plate volcanism, the most recent eruptions having occurred on the youngest island of Grande Comore and on the oldest one of Mayotte. Since 2018, the eastern submarine flank of Mayotte has been the site of one of the largest recent eruptive events on Earth in terms of erupted lava volume. On land, the most recent volcanic activity occurred in Holocene on the eastern side of Mayotte, corresponding to the small Petite Terre Island, where two main and persistent gas seep areas are present (Airport Beach, namely BAS, and Dziani Dzaha intracrateric lake). The large submarine eruption at the feet of Mayotte (50 km offshore; 3.5 km b.s.l.) is associated with deep (mantle level) seismic activity closer to the coast (5–15 km offshore) possibly corresponding to a single and large magmatic plumbing system. Our study aims at characterizing the chemical and isotopic composition of gas seeps on land and assesses their potential link with the magmatic plumbing system feeding the Mayotte volcanic ridge and the recent submarine activity. Data from bubbling gases collected between 2018 and 2021 are discussed and compared with older datasets acquired between 2005 and 2016 from different research teams. The relation between $\mbox {}^{3}\mathrm{He}/\mbox {}^{4}\mathrm{He}$ and $\delta ^{13}\mathrm{C}$-$\mathrm{CO}_{2}$ shows a clear magmatic origin for Mayotte bubbling gases, while the variable proportions and isotopic signature of $\mathrm{CH}_{4}$ is related to the occurrence of both biogenic and abiogenic sources of methane. Our new dataset points to a time-decreasing influence of the recent seismo-volcanic activity at Mayotte on the composition of hydrothermal fluids on land, whose equilibrium temperature steadily decreases since 2018. The increased knowledge on the gas-geochemistry at Mayotte makes the results of this work of potential support for volcanic and environmental monitoring programs.

The Tell Atlas of Algeria has a huge potential for hydrothermal energy from over 240 thermal springs with temperatures up to 98 ∘ C in the Guelma area. The most exciting region is situated in the northeastern part which is known to have the hottest hydrothermal systems. In this work, we use a high-resolution gravity study to identify the location and origin of the hot water, and how it reaches the surface. Gravimetric data analysis shows the shapes of the anomalies arising due to structures at different subsurface depths. The calculation of the energy spectrum for the data also showcases the depths of the bodies causing anomalies. 3D-Euler deconvolution is applied to estimate the depths of preexisting tectonic structures (faults). These preprocessing steps assist with assessing signal attenuation that impacts the Bouguer anomaly map. The residual anomaly is used in a three-dimensional inversion to provide a subsurface density distribution model that illustrates the locations of the origin of the dominant subsurface thermal systems. Overall, the combination of these standard processing steps applied to the measurements of gravity data at the surface provides new insights about the sources of the hydrothermal systems in the Hammam Debagh and Hammam Ouled Ali regions. Faults that are key to the water infiltrating from depth to the surface are also identified. These represent the pathway of the hot water in the study area. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In 2018, a phreatic eruption occurred at Mt. Motoshirane, a pyroclastic cone group of the Kusatsu-Shirane Volcano in central Japan. The eruption was abrupt, and no signs of volcanic activity have been observed in recent years, in contrast to the other major pyroclastic cone group, Mt. Shirane, which hosts the active crater lake and has endured repeated phreatic eruptions. To understand the mechanism of the eruption at Mt. Motoshirane, information on the shallow hydrothermal system, which is thought to be the source region of phreatic eruptions, is required; however, few studies have been conducted on this particular cone group. In this study, we conducted an audio-frequency magnetotelluric survey in 2020 to reveal the shallow resistivity structure around the 2018 craters. A three-dimensional resistivity structure model showed generally two layers, with high resistivities at shallow depths overlain by low resistivities underneath. The boundary between the layers corresponded to the top boundary of the Neogene basement rocks. These low resistivities were not found beneath the 2018 craters; therefore, part of the Neogene basement rocks could have been lost by the eruption beneath the 2018 craters. This is consistent with the geochemical study on the mineral assemblage of the erupted deposits, which suggested that the explosions reached the depth of the basement. [ABSTRACT FROM AUTHOR]

Topusko is the second warmest natural thermal water spring area in Croatia, located at the southwest edge of the Pannonian Basin System. Due to favourable geothermal properties, these waters have been used for heating and health and recreational tourism since the 1980s. Thermal springs with temperatures up to 50 °C are the final part of an intermediate-scale hydrothermal system. However, systematic research on the Topusko spring area has not been conducted to lay the foundation for sustainable resource utilisation. Multidisciplinary research including the hydrogeochemical characterisation of naturally emerging thermal water, an electrical resistivity tomography (ERT) investigation conducted to reconstruct the subsurface geology, and hydrogeological parametrisation of the geothermal aquifer was carried out to refine the existing local conceptual model. The results show Ca-HCO3 facies of Topusko thermal waters, which get heated in a Mesozoic carbonate aquifer. The water equilibrium temperature in the geothermal aquifer is estimated to be 78 °C based on the SiO2-quartz geothermometer. The fault damage zone, which enables the upwelling of thermal water, was identified by ERT investigations. The transmissivity values of the aquifer derived from the results of step-drawdown tests range from 1.8 × 10−2 to 2.3 × 10−2 m2/s. Further multidisciplinary research is necessary to improve the existing conceptual model of the Topusko hydrothermal system. [ABSTRACT FROM AUTHOR]

Link for citation: Poturay V.A. Organic matter in the Paratunka geothermal field (Kamchatka) thermal waters. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 98-109. In Rus. The relevance of the research is determined by the need to obtain actual data on the composition of organic compounds in thermal mineral waters. Hydrothermal systems contain different classes of organic matter, its composition in the Far East thermal waters being poorly investigated. The organic matter study is primarily aimed at elucidating the mechanisms of organic components transformation under high temperatures and pressure. This study contributes to deeper understanding of the processes occurring in the system «water–rock–organic matter». The main aim of the research is to determine the organic compounds composition and genesis in the Paratunka geothermal area (Northern and Karymshin sites) thermal waters; estimation of the hydrocarbons molecular weight distribution; compare the obtained data with that for other hydrothermal systems of Kamchatka. Objects: the Paratunka hydrothermal system (thermal water from deep wells in the Northern and Karymshin areas), the Mutnovka and Uzon hydrothermal systems (steam-water mixture from deep wells in the Dachnoe and North Mutnovskaya thermal fields, and thermal water from shallow wells in the Eastern thermal field). Methods: field routes, solid-phase extraction, capillary gas chromatography-mass spectrometry, calculation of geochemical hydrocarbon distribution indices. Results. In the Paratunka geothermal area thermal waters 40 organic compounds are found, which belong to 11 homological series. Aromatic and aliphatic hydrocarbons of thermogenic (formed as a result of thermocatalytic transformation of organic residues) and bacterial origin reach their maximum distribution. The specific molecular-weight distribution of normal alkanes showing only even low-molecular-weight homologues is characteristic of the Karymshin thermal waters. Comparison of the data with the results of the study of organic matter in Kamchatka (the Paratunka, Mutnovka, and Uzon geothermal areas) demonstrates a great similarity of main organic components composition, all of them showing a sharp predominance of aliphatic and aromatic hydrocarbons.

High-definition bathymetry mapping, combined with the measurement of dissolved benthic fluxes and water column biogeochemical properties, allows for a description of new biogeochemical processes around the Panarea Volcanic island. Investigations focused on the CO2 releases from the bottom sea on the east of the Panarea volcanic complex provided insights into the geological setup of the marine area east and south of the Panarea Island. Between the Panarea Island and the Basiluzzo Islet lies a SW-NE-stretching graben structure where a central depression, the Smoking Land Valley, is bounded by extensional faults. Abundant acidic fluids rich in dissolved inorganic Carbon are released on the edges of the graben, along the extensional faults, either diffusely from the seafloor, from hydrothermal chimneys, or at the center of craters of different sizes. The precipitation of iron dissolved in the acidic fluids forms Fe-oxyhydroxides bottom sea crusts that act as a plug, thus preventing the release of the underlying gases until their mounting pressure generates a bursting release. This process is cyclic and results in intermittent gas release from the bottom, leaving extinct craters and quiescent chimneys. The measurement of dissolved benthic fluxes allowed us to estimate the volcanic DIC venting at 15 Mt of CO2 over the past 10,000 years. The fluxes are not distributed homogeneously but rather concentrate along fractures and fault planes, which facilitate their rise to the seafloor. The acidic fluids released affect the chemical properties and structure of the water column through the formation of layers with a lower pH under the pycnocline, which can limit volcanic CO2 release to the atmosphere. Further and continuous monitoring and investigation of the area are needed in order to complete a thorough picture of the variations in fluid releases through time and space. The importance of such monitoring lies in the development of a new method for detecting and quantifying the diffusive dissolved benthic fluxes on a volcanic sea bottom affected by hydrothermal seeps.

Now there is a huge variety of scenarios of prebiotic chemical evolution, culminating in the emergence of life on Earth, which demonstrates the obvious insufficiency of existing criteria for a reliable consideration of this process. This article develops the concept of thermodynamic inversion (TI concept) according to which the real succession of the formation of metabolism during the origin of life is fixed in the stages of the exit of a resting bacterial cell from anabiosis (suspended animation), just as the succession of events of phylogenesis is fixed in ontogenesis. The deepest phase of anabiosis considers by us as an intermediate state of a microorganism between non-life and life: it is no longer able to counteract the increase in entropy, but retains structural memory of the previous living state. According to the TI concept, the intermediate state between non-life and life thermodynamically corresponds to the approximate equality of the total contributions of entropy and free energy in prebiotic systems (Sc ≈ FEc). Considering such intermediate state in prebiotic systems and microorganisms as a starting point, the authors use the experimentally recorded stages of restoring the metabolic process when a resting (dormant) bacterial cell emerges from anabiosis as a guideline for identifying the sequence of metabolism origin in prebiotic systems. According to the TI concept, life originated in a pulsating updraft of hydrothermal fluid. It included four stages. 1) Self-assembly of a cluster of organic microsystems (complex liposomes). 2) Activation (formation of protocells): appearance in the microsystems a weak energy-giving process of respiration due to redox reactions; local watering in the membrane. 3) Initiation (formation of living subcells): formation of a non-enzymatic antioxidant system; dawning of the protein-synthesizing apparatus. 4) Growth (formation of living cells—progenotes): arising of the growth cell cycle; formation of the genetic apparatus.

At equilibrium, the D/H isotope fractionation factor between H2 and H2O (αH2O-H2(eq)) is a sensitive indicator of temperature, and has been used as a geothermometer for natural springs and gas discharges. However, δDH2 measured in spring waters may underestimate subsurface temperatures of origin due to partial isotopic re-equilibration during ascent and cooling. We present new experimental data on the kinetics of D–H exchange for H2 dissolved in liquid water at temperatures below 100 °C. Comparing these results with published exchange rates obtained from gas phase experiments (100–400 °C), we derive a consistent activation energy of 52 kJ/mol, and the following rate expressions; lnk=9.186-6298/Tandk1=9764.61[H2O]e-6298/T where T is absolute temperature (K), k is the universal rate constant ([L/mol]/hr), and k1 is a pseudo-first-order constant (hr−1) applicable to water-dominated terrestrial systems by constraining [H2O] as the density of H2O (in mol/L) at the P-T of interest. The density-dependent rate constant accounts for the kinetic disparity of D–H exchange with H2 when dissolved in liquid H2O relative to a gas/steam phase, exemplifed by 1/k1 at 100 °C of ∼2 days in liquid, versus ∼7 yrs in saturated steam. This difference may explain the high variability of δDH2 observed in fumarolic gases. Fluids convecting in the crust frequently reach T > 225 °C, where isotopic equilibrium is rapidly attained (

At equilibrium, the D/H isotope fractionation factor between H2 and H2O (αH2O-H2(eq)) is a sensitive indicator of temperature, and has been used as a geothermometer for natural springs and gas discharges. However, δDH2 measured in spring waters may underestimate subsurface temperatures of origin due to partial isotopic re-equilibration during ascent and cooling. We present new experimental data on the kinetics of D–H exchange for H2 dissolved in liquid water at temperatures below 100 °C. Comparing these results with published exchange rates obtained from gas phase experiments (100–400 °C), we derive a consistent activation energy of 52 kJ/mol, and the following rate expressions; lnk=9.186-6298/Tandk1=9764.61[H2O]e-6298/T where T is absolute temperature (K), k is the universal rate constant ([L/mol]/hr), and k1 is a pseudo-first-order constant (hr−1) applicable to water-dominated terrestrial systems by constraining [H2O] as the density of H2O (in mol/L) at the P-T of interest. The density-dependent rate constant accounts for the kinetic disparity of D–H exchange with H2 when dissolved in liquid H2O relative to a gas/steam phase, exemplifed by 1/k1 at 100 °C of ∼2 days in liquid, versus ∼7 yrs in saturated steam. This difference may explain the high variability of δDH2 observed in fumarolic gases. Fluids convecting in the crust frequently reach T > 225 °C, where isotopic equilibrium is rapidly attained (

The results of the study of the behavior of redox-dependent sulfur and chlorine compounds in sediments of water bodies of the Pymvashor natural boundary (PNB) located in the Bolshezemelskaya Tundra (the Polar Cis-Ural Region, Nenets Autonomous Okrug, Russian Federation) are presented. Currently, the Pymvashor is the only known location in Continental Europe where hydrothermal springs function in the polar territories. Data on the quantitative characteristics of the geochemical parameters of bacterial sulfate reduction (reduced sulfur compounds, reactive iron forms, and organic matter) in the sediments of all studied Pymvashor water bodies have been obtained. It has been established that the revealed differences in the distribution and transformation of these parameters, in addition to the main reasons affecting the course of redox processes, were also caused by the thermal factor (warming effect of thermal waters on all ecosystems of the natural boundary). Thus, iron monosulphides dominated in the upper sediment layers of non-freezing watercourses, which distinguished them from the sediments of seasonally frozen lakes, where sulfur associated with organic matter dominated along the entire length of the sediment cores. The presence of chlorophenols (CPs) and their derivatives, including pentachlorophenol as a persistent organic pollutant, in the sediments of studied Pymvashor water bodies was established. It is shown that the chlorophenol composition is mainly induced by the occurrence of natural enzymatic and biochemical processes. The influence of microclimatic conditions of the subarctic hydrothermal system on the composition, levels, and distribution of chlorophenolic compounds in the sediments was revealed. [ABSTRACT FROM AUTHOR]

Current-day volcanic activity in the Azores archipelago is characterized by seismic events and secondary manifestations of volcanism. Remote sensing techniques have been widely employed to monitor deformation in volcanic systems, map lava flows, or detect high-temperature gas emissions. However, using satellite imagery, it is still challenging to identify low-magnitude thermal changes in a volcanic system. In 2010, after drilling a well for geothermal exploration on the northern flank of Fogo Volcano on São Miguel Island, a new degassing and thermal area emerged with maximum temperatures of 100 °C. In the present paper, using the ASTER sensor, we observed changes in the near-infrared signals (15 m spatial resolution) six months after the anomaly emerged. In contrast, the thermal signal (90 m spatial resolution) only changed its threshold value one and a half years after the anomaly was recognized. The results show that wavelength and spatial resolution can influence the response time in detecting changes in a system. This paper reiterates the importance of using thermal imaging and high spatial resolution images to monitor and map thermal anomalies in hydrothermal systems such as those found in the Azores. [ABSTRACT FROM AUTHOR]

The article presents the results of studying changes in the chemical composition of Pleistocene sediments from Hole 858B (depth 38.6 m, temperature gradient 10‒11°C/m) drilled in the Middle Valley, Juan de Fuca mid-ocean ridge (Northeast Pacific) in the Dead Dog hydrothermal field 20 m away from a "black smoker" (temperature 276°C). The content of macroelements in these sediments was studied by the XRD method. For the first time, data on a large set of trace elements were obtained from this object using the ICP-MS method. The chemical composition of sediments changed in the process of solution–sediment interaction during a rapid downsection increase of temperature. In the upper part of Sequence I (1.97‒10.41 m), the sediments are commonly altered slightly at a temperature of about 17°C. Changes in the content of macro- and trace elements are prominent in the lower part of Sequence I (12.70‒25.31 m, average temperature 112‒197°C). The chemical composition of sediments is most altered in Sequences IIB and IID (25.31‒38.6 m, temperature from 112‒197 to 320‒330°С). Changes in the content of the majority of macro- and trace elements in the sediments of Sequences IIB and IID are similar, except for a stronger decrease of chemical elements in the sediments of Sequence IID, which is marked by a significantly lower content of Cu, Zn, Ga, Rb, Sr, Ag, Cd, Sb, Cs, Ba, Tl, and Bi (i.e., the majority of detected elements except U) than in background sediments. Sediments in Sequence IID, as in Sequence IIB, contain less Ca, Na, K, and P, but more Mg. A lower content of the above-listed elements in these sediments can be attributed to their evacuation during the solution–sediment interaction and concentration in the solution, whereas a higher content of these elements is likely related to their input into sediments from the solution and, accordingly, their depletion in the solution. The results of studying the chemical composition of metalliferous sediments (Sequence III, 0‒1.97 m) and sulfide layer IV (10.41‒12.70 m), as well as the chemical composition of unaltered background sediments from Holes 855A, 855C, and 855D are presented. [ABSTRACT FROM AUTHOR]

Lake Kipyashchee ~4.6 ha in area whose greatest depth is 25 m fills an explosion crater near an extrusive dome in the Golovnin caldera. The lake water is ultra acid (рН 2.2–2.5), is of the chloride–sulfate type with a salinity of 2.0–2.2 g/L. The water temperature varies between 30 and 100°С at the surface, with the mean value being 37°С. The lake emptied itself via Protoka into Lake Goryachee at a rate of 120 L/s in August 2021. The hydrothermal drainage of magmatic Cl and S (in the form SO4) from Lake Kipyashchee is 10 and 5.4 t/day, respectively. The first ever estimate of the total diffusion output of carbon dioxide from the surface of Lake Kipyashchee is over 5.4 t/day. The geochemical data acquired during the 2020–2021 field surveys indicate an increase (compared with 2015) in the hydrothermal activity in the Golovnin caldera. [ABSTRACT FROM AUTHOR]

Introduction: Continental hydrothermal systems (CHSs) are geochemically complex, and they support microbial communities that vary across substrates. However, our understanding of these variations across the complete range of substrates in CHS is limited because many previous studies have focused predominantly on aqueous settings. Methods: Here we used metagenomes in the context of their environmental geochemistry to investigate the ecology of different substrates (i.e., water, mud and fumarolic deposits) from Solfatara and Pisciarelli. Results and Discussion: Results indicate that both locations are lithologically similar with distinct fluid geochemistry. In particular, all substrates from Solfatara have similar chemistry whereas Pisciarelli substrates have varying chemistry; with water and mud from bubbling pools exhibiting high SO42- and NH4+ concentrations. Species alpha diversity was found to be different between locations but not across substrates, and pH was shown to be the most important driver of both diversity and microbial community composition. Based on cluster analysis, microbial community structure differed significantly between Pisciarelli substrates but not between Solfatara substrates. Pisciarelli mud pools, were dominated by (hyper)thermophilic archaea, and on average, bacteria dominated Pisciarelli fumarolic deposits and all investigated Solfatara environments. Carbon fixation and sulfur oxidation were the most important metabolic pathways fueled by volcanic outgassing at both locations. Together, results demonstrate that ecological differences across substrates are not a widespread phenomenon but specific to the system. Therefore, this study demonstrates the importance of analyzing different substrates of a CHS to understand the full range of microbial ecology to avoid biased ecological assessments. [ABSTRACT FROM AUTHOR]

Asal rift is an aerial rift segment resulting from the westward propagation of the Aden ridge into the Afar Depression. Geothermal manifestations such as hot springs and fumaroles, fault creep, conductivity anomaly, and high geothermal gradient were observed both at the surface and in the subsurface. Despite many scientific works conducted in Asal to understand the rifting mechanisms, the hydrothermal fluid circulation still needs to be evaluated since it is based on simplified conceptual models. To further contribute and progress toward a quantitative evaluation of fluid circulation, a 2D numerical model perpendicular to the rift axis was developed with the objective of better understanding the role of subsurface anisotropy in fluid flow and heat transfer in the Asal rift. Numerical modeling of multiphase flow and heat transfer was carried out with an equivalent porous medium intersected by fault zones having greater permeability. Horizontal anisotropic permeability and magmatic fluid release were taken into account with different simulation scenarios. The results indicate that fault zones act as recharge/discharge areas depending on their location, permeability, and number. Simulations considering horizontal anisotropic permeability allowed the reproduction of the thermal state observed in geothermal wells with the expected general pattern of fluid circulation in the Asal rift. Comparing our result with a recent study made with a 2D numerical modeling parallel to the rift axis, we suggest the presence of a saddle point where fluid flow is both to the northeast and to the southwest direction of the rift. Moreover, magmatic fluid release assumed in two simulation scenarios showed to have an impact on the hydrological behavior of fault zones and facilitate the development of super-critical flow at the center of the rift. [ABSTRACT FROM AUTHOR]