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Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide (SO2). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO2. Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission. Published version Initial implementation of the network was funded by the EU FP6 NOVAC project (https://cordis.europa.eu/ project/rcn/75513/factsheet/en, last access: 1 October 2020). Recent funding for this work was provided by the Alfred P. Sloan Foundation’s Deep Carbon Observatory programme (https://deepcarbon. net/, last access: 1 October 2020), Chalmers University of Technology, the Swedish National Space Agency (career grant no. 149/18), and the ECMWF CAMS_81 Global and Regional Emissions project. The authors are thankful for the valuable support from the USGS–USAID Volcano Disaster Assistance Program (https: //volcanoes.usgs.gov/vdap/, last access: 1 October 2020) provided to NOVAC since 2015.

The geochemistry of volcanic gases has been fruitfully applied to identify important changes in the volcanic activity. This study reviews the dataset of the volcanic gas survey performed during 2009 and 2010 at Stromboli (Aeolian Islands - Italy). Dry gas collection occurred discontinuously at the crater fumaroles for subsequent chemical and isotopic (δ13C-CO2) analyses in the laboratory.A tailor-made device enabled continuous survey of H2 molar fraction and CO2 flux on the same site. Evaluation of the raw data was performed in accordance with air temperature, atmospheric pressure, wind speed and wind direction dataset. Both MLR (Multiple Linear Regression) and FFT (Fast Fourier Transform) analyses allowed filtering the dataset from the environmental effects. The MLR analysis indicated that wind speed and air temperature affected the CO2 flux. Changes in the atmospheric pressure promoted pumping effect of the fumarole gas and caused changes in the H2 molar fraction. The power spectral analysis revealed daily cycles in both gases. A digital signal filtering procedure enabled minimizing the environmental effects.This study confirmed that gas emissions from the crater fumaroles have both chemical ad isotopic composition similar to the magmatic gas phase. The results of the continuous survey showed that changes of both H2 and CO2 correlated with changes of the volcanic activity. Therefore, H2 and CO2 resulted effective tracers of the dynamics involving the plumbing system of Stromboli. Identification of changes in the gas emissions at open conduit volcanoes offers a great advance over the ground gas survey. The results of the continuous survey at Stromboli showed that H2 could apply as an auxiliary parameter of the CO2 flux in the surveillance programs of active volcanoes.

Magnetic resonance mass spectrometers (MRMSs), developed in the second half of the 20th century at the Ioffe Institute, have still possessed such a complex of parameters that they have no alternative for solving many analytical problems, in particular, in the isotopy of helium. With the resolution of one of the devices several thousand at the base of the 3He+ mass peak, its absolute sensitivity is

The Pico do Fogo volcano, in the Cape Verde Archipelago off the western coasts of Africa, has been the most active volcano in the Macaronesia region in the Central Atlantic, with at least 27 eruptions during the last 500 years. Between eruptions fumarolic activity has been persisting in its summit crater, but limited information exists for the chemistry and output of these gas emissions. Here, we use the results acquired during a field survey in February 2019 to quantify the quiescent summit fumaroles' volatile output for the first time. By combining measurements of the fumarole compositions (using both a portable Multi-GAS and direct sampling of the hottest fumarole) and of the SO2 flux (using near-vent UV Camera recording), we quantify a daily output of 1060±340 tons CO2, 780±320 tons H2O, 6.2±2.4 tons H2S, 1.4±0.4 tons SO2 and 0.05±0.022 tons H2. We show that the fumarolic CO2 output from Pico do Fogo exceeds (i) the time-averaged CO2 release during 2015-type recurrent eruptions and (ii) is larger than current diffuse soil degassing of CO2 on Fogo Island. When compared to worldwide volcanoes in quiescent hydrothermal-stage, Pico do Fogo is found to rank among the strongest CO2 emitters. Its substantial CO2 discharge implies a continuous deep supply of magmatic gas from the volcano’s plumbing system (verified by the low but measurable SO2 flux), that becomes partially affected by water condensation and sulphur scrubbing in fumarolic conduits prior to gas exit. Variable removal of magmatic H2O and S accounts for both spatial chemical heterogeneities in the fumarolic field and its CO2- enriched mean composition, that we infer at 64.1±9.2 mol. % H2O, 35.6±9.1 mol. % CO 0.26±0.14 mol. % total Sulfur (S ), and 0.04±0.02 mol. % H2.

Aerobic lifeforms, including humans, thrive because of abundant atmospheric O2, but for much of Earth history O2 levels were low. Even after evidence for oxygenic photosynthesis appeared, the atmosphere remained anoxic for hundreds of millions of years until the ~2.4 Ga Great Oxidation Event. The delay of atmospheric oxygenation and its timing remain poorly understood. Two recent studies reveal that the mantle gradually oxidized from the Archean onwards, leading to speculation that such oxidation enabled atmospheric oxygenation. But whether this mechanism works has not been quantitatively examined. Here, we show that these data imply that reducing Archean volcanic gases could have prevented atmospheric O2 from accumulating until ~2.5 Ga with ≥95% probability. For two decades, mantle oxidation has been dismissed as a key driver of the evolution of O2 and aerobic life. Our findings warrant a reconsideration for Earth and Earth-like exoplanets., The early Earth’s atmosphere had very low oxygen levels for hundreds of millions of years, until the 2.4 Ga Great Oxidation Event, which remains poorly understood. Here, the authors show that reducing Archean volcanic gases could have prevented atmospheric O2 from accumulating, and therefore mantle oxidation was likely very important in setting the evolution of O2 and aerobic life.

Approximately 700 diamond crystals were identified in volcanic (mainly pyroclastic) rocks of the Tolbachik volcano, Kamchatka, Russia. They were studied with the use of SIMS, scanning and transmission electron microscopy, and utilization of electron energy loss spectroscopy and electron diffraction. Diamonds have cube-octahedral shape and extremely homogeneous internal structure. Two groups of impurity elements are distinguished by their distribution within the diamond. First group, N and H, the most common structural impurities in diamond, are distributed homogeneously. All other elements observed (Cl, F, O, S, Si, Al, Ca, and K) form local concentrations, implying the existence of inclusions, causing high concentrations of these elements. Most elements have concentrations 3–4 orders of magnitude less than chondritic values. Besides N and H, Si, F, Cl, and Na are relatively enriched because they are concentrated in micro- and nanoinclusions in diamond. Mineral inclusions in the studied diamonds are 70–450 nm in size, round- or oval-shaped. They are represented by two mineral groups: Mn-Ni alloys and silicides, with a wide range of concentrations for each group. Alloys vary in stoichiometry from MnNi to Mn2Ni, with a minor admixture of Si from 0 to 5.20–5.60 at%. Silicides, usually coexisting with alloys, vary in composition from (Mn,Ni)4Si to (Mn,Ni)5Si2 and Mn5Si2, and further to MnSi, forming pure Mn-silicides. Mineral inclusions have nanometer-sized bubbles that contain a fluid or a gas phase (F and O). Carbon isotopic compositions in diamonds vary from –21 to –29‰ δ13CVPDB (avg. = –25.4). Nitrogen isotopic compositions in diamond from Tolbachik volcano are from –2.32 to –2.58‰ δ15NAir. Geological, geochemical, and mineralogical data confirm the natural origin of studied Tolbachik diamonds from volcanic gases during the explosive stage of the eruption.

Exhalation ore mineralization is developing in the crater part of the active Kudryavy volcano. Lithogeochemical sampling results have revealed that Re, Au, Ag, As, Bi, Cd, Cu, Ge, In, Mo, Pb, S, Sb, Se, Sn, Te, Tl, W, Zn, Rb, and Cs accumulate in solid fumarole formations. These elements are transported by high-temperature volcanic gases and are deposited in mineral phases in the near-surface horizons of fumarole fields under decreasing temperature conditions. The contents of rhenium and other metals in volcanic deposits of fumarole fields locally reach values characteristic of ore deposits. Zoning of lithogeochemical anomalies in ore element associations has been revealed, expressed by the series Re, Mo, W, Au, Cu, Ag, Zn, Cs, Ge → In → Bi, Cd, Pb, Sn, Tl → As, Sb, Se, Te, (Cu, Ag, Au) in the direction from the highest-temperature fumarole fields to less hot, reflecting their temperature zoning. It is demonstrated that lateral geochemical zoning is caused both by the ore element contents in fumarole gases, which depend on temperature, and by differences in the optimal temperature ranges in which various elements precipitate from gases. Signatures for similar exhalation mineral formation processes have been revealed that occurred in the recent geological past at the neighboring extinct Sredny volcano. This suggests the occurrence of similar processes within other volcanic systems of Iturup Island, which increases the prospects for detecting complex exhalation-related manifestations of rare, base, and noble metals.

Measuring the carbon dioxide (CO2) mass flux in a volcanic environment is necessary for volcanic monitoring. CO2 mass flux must be measured continuously and telemetrically to get, almost in real-time, a better understanding of the dynamics of the volcanic degassing processes, contributing to the building, together with other monitoring technics, of a volcano behavior model. This study presents two analytical solutions, 1) a simple diffuse solution and 2) an advective-diffusive solution, which both implement NDIR (Non-Dispersive Infrared Emitter) sensor arrays in an open chamber (diffusion chimney) and an exchange chamber (gas interchanger). The first system, for which the gas speed is negligible, despite being basic (with values reflected in the slope of an equation line), introduces mass flux calculations with a single sensor NDIR. For the second system, where the gas speed is part of the equation, another mathematical solution and three measuring points are required, which demands the system to include a se­cond NDIR sensor for the correct mathematical solution of the equations system. In addition, an embedded system can automate the method by calibrating, controlling an agitation fan, and recording temperature, pressure, and mass flux in volcanic soils at the surface. Since this theoretically proposed method needs to be tested, experimental data are expected to validate the measurement of CO2 mass flux, which will be used as a helpful tool for volcanic monitoring.

Volcanic gases supplied a large part of Earth's early atmosphere, but constraints on their flux are scarce. Here we model how C-O-H outgassing could have evolved through the late Hadean and early Archean, under the conditions that global plate tectonics had not yet initiated, all outgassing was subaerial, and graphite was the stable carbon phase in the melt source regions. The model fully couples numerical mantle convection, partitioning of volatiles into the melt, and chemical speciation in the gas phase. The mantle oxidation state (which may not have reached late Archean values in the Hadean) is the dominant control on individual species' outgassing rates because it affects both the carbon content of basaltic magmas and the speciation of degassed volatiles. Volcanic gas from mantles more reduced than the iron-w\"ustite mineral redox buffer would contain virtually no CO2 because (i) carbonate ions dissolve in magmas only in very limited amounts, and (ii) almost all degassed carbon takes the form of CO instead of CO2. For oxidised mantles near the quartz-fayalite-magnetite buffer, we predict median CO2 outgassing rates of less than approximately 5 Tmol/yr, still lower than the outgassing rates used in many Archean climate studies. Relatively weak outgassing is due in part to the redox-limited CO2 contents of graphite-saturated melts, and also to a stagnant lid regime's inefficient replenishment of upper mantle volatiles. Our results point to certain chemical and geodynamic prerequisites for sustaining a clement climate with a volcanic greenhouse under the Faint Young Sun., Comment: 25 pages, 9 figures, accepted for publication in PEPI

The volcanic surface phenomena (e.g., ground-surface brightness temperature distribution, volcanic gases, and volcanic ashes) provide useful information to evaluate the current status of volcanic activities. We are planning to develop a new observation device called a surface phenomena imaging camera with a cooled longwave infrared camera (SPIC-C (LWIR)). The SPIC-C (LWIR) is a multiband camera (multi-spectral camera) system used to measure the temperature and SO 2 gas concentration. To realize the SPIC-C (LWIR), we prototype cooled LWIR camera (SPIC-C (LWIR) Camera 3) by adopting a VGA ( $640\times 512$ ) cooled T2SL sensor head unit. The performance evaluations indicate that this system can achieve a NETD of approximately 0.1 K. The evaluation of SO 2 measurement accuracy by simulation using the same SO 2 gas concentration distribution conditions as our original airborne hyperspectral sensor's (ARTS) actual observation on Apr. 8 2008 reveals that the developed cooled LWIR camera can detect SO 2 gas concentration distributions ranging approximately 0.2 - 0.4 ppmv in the background conditions at a temperature of 50 °C with errors of ±0.1 ppmv. These results indicate that the developed cooled LWIR camera can be a sensor head unit for the prototype SPIC-C (LWIR) system.

The correlation of allochthonous lithotectonic complexes of the Pacific allows to establish Early Jurassic (Sinemurian-Toarcian) anoxic event (J1-OAE) for time in the Asia-West Kamchatka region. This event is characterized by organic-riched black cherts and shales bearing pyrite that accumulated in the euxinic oceanic deep water basins of the Pacific. Later anoxic regime gradually weakened that was reflected in dominating of Midle-Upper Jurassic red gematite jaspers. J1-OAE in the Pacific was synchronous to global warming induced by planetary magmatic activity. Volcanic gases and hydroterms stimulated euxinic conditions in the deep water basins. The Sinemurian-Toarcian interval of the OAE in the Pacific Ocean is confirmed by data of the numerous World basins.

The number of explosive eruptions at Shiveluch Volcano has significantly increased over the past years, which requires close volcanic monitoring using all available techniques. In order to implement a new monitoring technique into integrated methods of volcano monitoring, the authors analyze response to the intensity of the vertical component in the atmospheric electrical field (EZ AEF) during the movement of ash clouds. Two eruptions of different intensity that occurred December 16, 2016 and June 14, 2017 at Shiveluch were selected for study. We used a combination of satellite, seismic, and infrasound data to select signals in the EZ AEF field. Signals with negative polarity that accompanied ashfalls in the EZ AEF dynamics were registered for both eruptions within the closest area (< 50 km). In the former case, the ash cloud was “dry” and thus it caused aerial-electrical structure of the negatively charged cloud. In the latter case, a strong explosion sent into the atmosphere the large volume of ash and volcanic gases (98% in form of vapour) that resulted in the formation of a dipolar aerial-electrical structure caused by eolian differentiation within the closest area. At the distance of more than 100 km we registered a positive-going signal that is attributive to the aerial-electrical structure of the positively charged type of the cloud.

Over recent decades, many experimental studies have focused on the effect of CO2 on phase equilibria and melting behaviour of synthetic eclogites and peridotites as a function of pressure and temperature. These studies have been of fundamental importance to understanding the origin of carbonated magmas varying in composition from carbonatitic to kimberlitic. The occurrence of diamonds in natural rocks is further evidence of the presence of (reduced) carbon in the Earth9s interior. The oxygenation of the Earth9s interior (i.e. its redox state) through time has strongly influenced the speciation of carbon from the mantle to mantle-derived magmas and, in turn, to the volcanic gases released to the atmosphere. This paper explains how the knowledge of the oxygen fugacity recorded by mantle rocks and determined through the use of appropriate oxy-thermobarometers allows modelling of the speciation of carbon in the mantle, its mobilization in the asthenospheric mantle by redox partial melting, and its sequestration and storage during subduction by redox freezing processes. The effect of a gradual increase of the mantle fO2 on the mobilization of C is here discussed along with the main variables affecting its transport by subduction into the mantle.

We report new data on trace metal emissions at White Island volcano (2015–2016), the first estimates from Yasur volcano (2016), and a brief review of global volcanic metal fluxes. Bi, Cd, Tl, Se, Sb, Te and Au are the most enriched metals and metalloids in the particulate phase of volcanic plumes. Observations of the particulate phase from the volcanic plumes of White Island, Yasur and Etna reveal abundant silicates and sulfates, sulfuric acid and more interestingly Zn oxide containing variable amounts of Cu. Thermodynamic speciation calculations show chloride species to be very important in terms of gaseous metal transport. Complexation with sulfur, in contrast, appears significant only in S-rich and Cl-poor gases, at high (>700 °C) temperature. Bromine, despite being a minor component of volcanic gases, is very efficient at complexing with metals, and especially with Cu, Pb, Bi, Zn and Cr. Metal emission rates in the study period at White Island are one to two orders of magnitude lower than reported previously, with ~6–10 kg/d of Cu, As, Se and Zn, and

A multi-rotor drone has been adapted for studies of volcanic gas plumes. This adaptation includes improved capacity for high-altitude and long-range, real-time SO2 concentration monitoring, long-range manual control, remotely activated bag sampling and plume speed measurement capability. The drone is capable of acting as a stable platform for various instrument configurations, including multi-component gas analysis system (MultiGAS) instruments for in situ measurements of SO2, H2S, and CO2 concentrations in the gas plume and portable differential optical absorption spectrometer (MobileDOAS) instruments for spectroscopic measurement of total SO2 emission rate, remotely controlled gas sampling in bags and sampling with gas denuders for posterior analysis on the ground of isotopic composition and halogens. The platform we present was field-tested during three campaigns in Papua New Guinea: in 2016 at Tavurvur, Bagana and Ulawun volcanoes, in 2018 at Tavurvur and Langila volcanoes and in 2019 at Tavurvur and Manam volcanoes, as well as in Mt. Etna in Italy in 2017. This paper describes the drone platform and the multiple payloads, the various measurement strategies and an algorithm to correct for different response times of MultiGAS sensors. Specifically, we emphasize the need for an adaptive flight path, together with live data transmission of a plume tracer (such as SO2 concentration) to the ground station, to ensure optimal plume interception when operating beyond the visual line of sight. We present results from a comprehensive plume characterization obtained during a field deployment at Manam volcano in May 2019. The Papua New Guinea region, and particularly Manam volcano, has not been extensively studied for volcanic gases due to its remote location, inaccessible summit region and high level of volcanic activity. We demonstrate that the combination of a multi-rotor drone with modular payloads is a versatile solution to obtain the flux and composition of volcanic plumes, even for the case of a highly active volcano with a high-altitude plume such as Manam. Drone-based measurements offer a valuable solution to volcano research and monitoring applications and provide an alternative and complementary method to ground-based and direct sampling of volcanic gases.

Background The contribution of various volcanic phenomena to immediate soft tissue injury types has received limited attention challenging emergency management planning. This integrative review sought to investigate the immediate types of soft tissue-related injury sustained following volcanic eruptions. Methods A systematic search was conducted in January 2020 across EMBASE, PubMed, and Scopus databases. 718 articles were retrieved, and 15 studies met the final inclusion criteria. Results Injuries acquired, and health impacts were categorized by onset-direct/indirect or immediate/delayed. Health concerns following an eruption were categorised: (1) respiratory; (2) ocular; and (3) skin, including deep tissues. Respiratory concerns were attributed to ashfall, volcanic gases and pyroclastic density currents; most ocular injuries to ashfall; and skin/deep tissues to pyroclastic density currents with mudflows. Conclusions Volcanic eruptions simultaneously present multiple hazards with immediate/short term health consequences across three major levels (i.e., respiratory, ocular, and skin, including deep tissues). Hazard(s) differ by time of onset and associated mostly with the eruptive phenomena. Understanding local volcanic phenomenon is essential to assisting health personnel provide informed and timely care.

Secondary alteration minerals like clays accompanied by volcanic activity can provide an important information on eruption cycle. Representative volcanic tuffs and seabed sediments were collected from the Dokdo volcanic island in East Sea, South Korea, to interpret eruption cycle based on clay mineral characteristics and other geochemical proxies (sulfur isotope composition, Si/Al, K/Al, among others). Tuffs are mainly composed of volcanic glass and hydrothermally altered phenocrysts. Secondary minerals such as clay mineral species in volcanic tuffs mostly were identified as smectite comprising dioctahedral sheets, based on expanding to 15.8 A after treatment with 1 M MgCl2 solution, and 060 reflections near at 1.48 A. Moreover, the results of infrared bands, based on (Al, Al)–OH (904–912 cm−1), (Al, Fe)–OH (865–877 cm−1), (Fe, Mg)–OH (778–798 cm−1) indicate the presence of dioctahedral sheets in clay mineral structure. Partially, occurrence of kaolinite and relatively low pH values and K/Al ratios at the Eolgulbawi tuff support chemical flexibility of clay mineral species. The δ34S value of Dongdo tuff (H2O–S: 15.3‰) is close to water leached sulfate, whereas Seodo tuff II including pyrite and native sulfur (− 5.5‰) shows a value of H2S-bearing volcanic gases. The similarity of chemical compositions between clay fractions and surrounding volcaniclastic rocks suggests that the smectite formed in low-temperature hydrothermal environments, where alkali elements were supplied under reducing conditions. Clay fractions separated from seabed sediments include diatom frustule with higher SiO2/Al2O3 ratios, and clay minerals contain mineral nitrogen originated from organic-rich seafloor sediments. Moreover, the δ34S values of seabed sediments (1.8‰, 8.4‰) indicate that the different origin of clay mineral species between tuffs and seabed sediments. It can be concluded that the alteration types and clay mineral characteristics are similar to the Surtseyan volcano, generally known as shallow-marine phreatomagmatic eruption and deposits. It further suggests that clay minerals sensitive to environmental change will be useful to interpret the volcanic environment characterized by explosive hydrovolcanic activities that occurred at the time of magma in contact with water before erupting into the atmosphere.

Unmanned aerial vehicles (UAVs), represented by rotor-based drones, are suitable for volcanic observations owing to the advantages of mobility and safety. In this study, vertical profiles of wind and aerosol concentrations at altitudes up to 1000 m around Mt. Sakurajima, one of the most active volcanoes in Japan, were measured in situ using a drone equipped with an ultrasonic anemometer and aerosol sensor. The drone-measured wind profiles were compared with Doppler LiDAR data and analysis values derived from a meteorological model. Drone-measured vertical profiles collected at a vertical speed of 1 m·s−1 (upward and downward) showed strong agreement with the LiDAR observations, as did the averaged values of hovering drone measurements. Obvious vertical wind shear was found by the drone in the vicinity of Mt. Sakurajima. An aerosol sensor was installed on the drone with the capability to measure fine (PM2.5) and coarse particles (PM10) simultaneously, in this manner, volcanic ash and aerosol pollutants around the volcano could be distinguished. Thus, it was proven that drones could be applied to investigate wind conditions and aerosols in situ, even at dangerous locations near active volcanoes.

The Cape Verde islands are located about 800 km west of Senegal, at 14°-17° latitude and 21°-25° longitude. The archipelago consists of a volcanic chain of 10 major islands and eight minor islands The only currently active volcano in the Cape Verde archipelago is Pico do Fogo, which is located on the island of Fogo. Rising to 2829 m a.s.l., it is the most active volcano of the Cabo Verde Island. We report the results of the geochemical monitoring of the fumarolic discharges at the Pico do Fogo volcano in Cape Verde from 2007 to 2016. During this period Pico do Fogo experienced a volcanic eruption (November 23, 2014) that lasted 77 days. Two fumaroles were sampled, a low (F1~100ºC) and a medium (F2~300ºC) temperature. The variations observed in the δ18O and δ2H in F1 and F2 suggest different fluid source contributions and/or fractionation processes. Although no significant changes were observed in the outlet fumarole temperatures, two clear increases were observed in the vapor fraction of fumarolic discharges during the periods 2008-2009 and 2013-2014. Also, two sharp peaks were observed in CO2/CH4 ratios at both fumaroles, in November 2008 and November 2013, coinciding with significant increases in the emission rate of diffuse CO2 and He, and heat flow measured in the crater of Pico do Fogo volcano. This confirms that gases with a strong magmatic component rose towards the surface within the Pico do Fogo system during 2008 and 2013. Further, F2 showed two CO2/St peaks, the first in late 2010 and the second after eruption onset, suggesting the occurrence of magmatic pulses into the volcanic system. Time series of He/CO2, H2/CO2 and CO/CO2 ratios are low in 2008-2009, and high in 2013-2014 period, supporting the hypothesis of fluid input from a deeper magmatic source. Regarding to the isotopic composition, increases in 3He/4He (R/RA)cor are observed in both fumaroles; F1 showed a peak in 2010 from a minima in 2009 during the first magmatic reactivation onset and another in late 2013, while F2 displayed a slower rise to its maximum in late 2013. The high 3He/4He ratios in both fumaroles are close to the magmatic end-member, indicating that He is predominantly of upper mantle origin. This work supports that monitoring of the chemical and isotopic composition of the fumaroles of the Pico do Fogo volcano is a very important tool to understand the processes that take place in the magmatic-hydrothermal system and to be able to predict future episodes of volcanic unrest and to mitigate volcanic risk.

Summary The spatial variability of gas emissions at Earth’s surface is a proxy for structural discontinuities in the subsurface of geothermal systems. Thus, they provide reliable information on reservoir-scale to reduce the high exploration risk in geothermal projects and contribute to the site selection of costly production wells. In addition, permanent monitoring of geothermal gases at the surface allows to investigate temporal changes related to changing reservoir conditions. This represents an additional application of soil gas studies for a successful reservoir management. Here, we show a summary of selected case studies in geothermal systems worldwide highlighting the successful performance of comprehensive and systematic soil gas studies as a reliable geothermal exploration tool. In our studies we use integrated approaches by analyzing emission rates, concentration, and isotopes of the different volcanic gases and linking them to the deep reservoir. We consider soil gas studies as a complementary technique to well-established geophysical or geochemical exploration methods, which will help to improve conceptual models of geothermal systems. For this purpose, we have developed a mobile soil gas lab for flexible in-situ applications. Fluxtec focuses on the optimization and promotion of this type of survey, which is not yet commonly used in geothermal exploration.

Aerial measurements using unoccupied aerial systems (UAS) transform our ability to measure and monitor volcanic plumes., Volcanic emissions are a critical pathway in Earth’s carbon cycle. Here, we show that aerial measurements of volcanic gases using unoccupied aerial systems (UAS) transform our ability to measure and monitor plumes remotely and to constrain global volatile fluxes from volcanoes. Combining multi-scale measurements from ground-based remote sensing, long-range aerial sampling, and satellites, we present comprehensive gas fluxes—3760 ± [600, 310] tons day−1 CO2 and 5150 ± [730, 340] tons day−1 SO2—for a strong yet previously uncharacterized volcanic emitter: Manam, Papua New Guinea. The CO2/ST ratio of 1.07 ± 0.06 suggests a modest slab sediment contribution to the sub-arc mantle. We find that aerial strategies reduce uncertainties associated with ground-based remote sensing of SO2 flux and enable near–real-time measurements of plume chemistry and carbon isotope composition. Our data emphasize the need to account for time averaging of temporal variability in volcanic gas emissions in global flux estimates.

The 1257 CE eruption of Mount Samalas (Indonesia) is the source of the largest stratospheric injection of volcanic gases in the Common Era. Sulfur dioxide emissions produced sulfate aerosols that cooled Earth's climate with a range of impacts on society. The coemission of halogenated species has also been speculated to have led to wide-scale ozone depletion. Here we present simulations from HadGEM3-ES, a fully coupled Earth system model, with interactive atmospheric chemistry and a microphysical treatment of sulfate aerosol, used to assess the chemical and climate impacts from the injection of sulfur and halogen species into the stratosphere as a result of the Mt. Samalas eruption. While our model simulations support a surface air temperature response to the eruption of the order of -1°C, performing well against multiple reconstructions of surface temperature from tree-ring records, we find little evidence to support significant injections of halogens into the stratosphere. Including modest fractions of the halogen emissions reported from Mt. Samalas leads to significant impacts on the composition of the atmosphere and on surface temperature. As little as 20% of the halogen inventory from Mt. Samalas reaching the stratosphere would result in catastrophic ozone depletion, extending the surface cooling caused by the eruption. However, based on available proxy records of surface temperature changes, our model results support only very minor fractions (1%) of the halogen inventory reaching the stratosphere and suggest that further constraints are needed to fully resolve the issue.

Following the eruption of Hekla in 1845-1846 Bunsen was invited by King Christian VIII of Denmark and Iceland to participate in a geochemical expedition to Iceland together with the geologist Sartorius von Waltershausen and the physiologist Carl Bergmann from Gottingen. The French mineralogist Des Cloizeaux went to Iceland separately and joined the expedition. The eudiometer invented by Bunsen was crucial for his accurate characterization of volcanic gases and determination of the composition of mixtures. His analyses of the chemical compositions of numerous rocks and minerals led him to the classification of two fundamental rock types, the more silica rich (nowadays called felsic) and the less silica rich, more basic (mafic) in agreement with Des Cloizeaux and the Danish scientist J. C. Schythe. Bunsen also formulated the correct mechanism of geyser action and helped disband the theory of connections between geysers, volcanoes and the sea. He disagreed vehemently with Waltershausen over the mechanisms of formation of sal ammoniac and of volcanic rocks and their chemical compositions. He revealed himself as an ardent experimentalist vigorously opposed to hypotheses of any kind, which also made him dismiss the new chemical theories, for example, those of Dumas and Kekule.

In this paper, a state-of the art numerical weather prediction (NWP) model is used to simulate the near-field plume of a Plinian-type volcanic eruption. The NWP model is run at very high resolution (of the order of 100 m) and includes a representation of physical processes, including turbulence and buoyancy, that are essential components of eruption column dynamics. Results are shown that illustrate buoyant gas plume dynamics in an atmosphere at rest and in an atmosphere with background wind, and we show that these results agree well with those from theoretical models in the quiescent atmosphere. For wind-blown plumes, we show that features observed in experimental and natural settings are reproduced in our model. However, when comparing with predictions from an integral model using existing entrainment closures there are marked differences. We speculate that these are signatures of a difference in turbulent mixing for uniform and shear flow profiles in a stratified atmosphere. A more complex implementation is given to show that the model may also be used to examine the dispersion of heavy volcanic gases such as sulphur dioxide. Starting from the standard version of the weather research and forecasting (WRF) model, we show that minimal modifications are needed in order to model volcanic plumes. This suggests that the modified NWP model can be used in the forecasting of plume evolution during future volcanic events, in addition to providing a virtual laboratory for the testing of hypotheses regarding plume behaviour.

co-auteur étranger; International audience; Formation of secondary sulfate minerals during the reaction between volcanic gases and rocks modulates the compositionand flux of gaseous emanations. We report on the sub-surface formation of anhydrous alum (MIMIII(XVIO4)2with MI=-NH4+,Na+,K+;MIII=Al3+,Fe3+and XVI=S6+,Mo6+) in the 330°C fumaroles of the Lascar volcano (Chile). The alumoccurs as a few millimetres thick crust that grew internally by two-way diffusion of reaction gases and diffusive influx of rockcations within the crust. The average growth rate is estimated at ca. 0.3lm/day, based on the 19-year-long activity of thedegassing fracture hosting the crust. The growth rate is controlled by the slow migration of the rock cations and decreasestowards crust rim. The crust selectively concentrates Tl, V and Te (thousands oflg/g) and to a lesser extent Mo (hundredsoflg/g). The uptake of gaseous Tl, V and Mo is due to the possibility for these elements to enter the MI,MIIIand XVIsites ofalum, respectively. The process of Te uptake must be related to the incorporation of Tl and V with which Te tightly correlates.Extensive substitution of Tl, V and Te occurs at the surface of the crust where the supply of rock cations is the lowest. Suchsurface enrichment does not occur for Mo, because Mo substitutes for S, another element from the gas. These findings suggestthat the surface of mature alum crust has a high adsorption capacity for those gaseous metals able to compensate for the lackof rock-derived cations. Based on the composition of gases escaping from the fracture hosting the crust, it is estimated that thepartition coefficients of Tl (3.3107), V (1.1107) and Te (0.6107) between crust surface and gases are two to four ordersof magnitude higher than for other volatile metals and metalloids. It follows that gases equilibrating with anhydrous alumslose between 77 and 95% of their initial Tl content, but less than 1% of Pb. Given the Tl emission rate of Lascar volcano(5 g/day), between 17 and 104 g of toxic Tl would deposit every day if all Lascar gases were to equilibrate with anhydrousalums. This study suggests that anhydrous alums significantly immobilize Tl, V and Te in the ground of quiescent volcanoes,reducing the atmospheric emissions of these three elements.Ó2020 Elsevier Ltd. All rights reserved.

Long-range, high-altitude Unoccupied Aerial System (UAS) operations now enable in-situ measurements of volcanic gas chemistry at globally-significant active volcanoes. However, the extreme environments encountered within volcanic plumes present significant challenges for both air frame development and in-flight control. As part of a multi-disciplinary field deployment in May 2019, we flew fixed wing UAS Beyond Visual Line of Sight (BVLOS) over Manam volcano, Papua New Guinea, to measure real-time gas concentrations within the volcanic plume. By integrating aerial gas measurements with ground- and satellite-based sensors, our aim was to collect data that would constrain the emission rate of environmentally-important volcanic gases, such as carbon dioxide, whilst providing critical insight into the state of the subsurface volcanic system. Here, we present a detailed analysis of three BVLOS flights into the plume of Manam volcano and discuss the challenges involved in operating in highly turbulent volcanic plumes. Specifically, we report a detailed description of the system, including ground and air components, and flight plans. We present logged flight data for two successful flights to evaluate the aircraft performance under the atmospheric conditions experienced during plume traverses. Further, by reconstructing the sequence of events that led to the failure of the third flight, we identify a number of lessons learned and propose appropriate recommendations to reduce risk in future flight operations.

Volcanologists have demonstrated that carbon dioxide (CO2) fluxes are precursors of volcanic eruptions. Controlling volcanic gases and, in particular, the CO2 flux, is technically challenging, but we can retrieve useful information from magmatic/geological process studies for the mitigation of volcanic hazards including air traffic security. Existing techniques used to probe volcanic gas fluxes have severe limitations such as the requirement of near-vent in situ measurements, which is unsafe for operators and deleterious for equipment. In order to overcome these limitations, a novel range-resolved DIAL-Lidar (Differential Absorption Light Detection and Ranging) has been developed as part of the ERC (European Research Council) Project “BRIDGE”, for sensitive, remote, and safe real-time CO2 observations. Here, we report on data collection, processing techniques, and the most significant findings of the experimental campaigns carried out at the most hazardous volcanic areas in Italy: Pozzuoli Solfatara (Phlegraen Fields), Stromboli, and Mt. Etna. The BrIdge voLcanic LIdar—BILLI has successfully obtained accurate measurements of in-plume CO2 concentration and flux. In addition, wind velocity has also been retrieved. It has been shown that the measurements of CO2 concentration performed by BILLI are comparable to those carried out by volcanologists with other standard techniques, heralding a new era in the observation of long-term volcanic gases.

Volcanic ash presents a widespread and common hazard during and after eruptions. Complex interactions between solid ash surfaces and volcanic gases lead to the formation of soluble salts that may be mobilized in aqueous environments. A variety of stakeholders may be concerned about the effects of ash on human and animal health, drinking water supplies, crops, soils and surface runoff. As part of the immediate emergency response, rapid dissemination of information regarding potentially hazardous concentrations of soluble species is critical. However, substantial variability in the methods used to characterize leachable elements makes it challenging to compare datasets and eruption impacts. To address these challenges, the International Volcanic Health Hazard Network ( www.ivhhn.org ) organized a two-day workshop to define appropriate methods for hazard assessment. The outcome of this workshop was a ‘consensus protocol’ for analysis of volcanic ash samples for rapid assessment of hazards from leachable elements, which was subsequently ratified by leading volcanological organizations. The purpose of this protocol is to recommend clear, standard and reliable methods applicable to a range of purposes during eruption response, such as assessing impacts on drinking-water supplies and ingestion hazards to livestock, and also applicable to research purposes. Where possible, it is intended that the methods make use of commonly available equipment and require little training. To evaluate method transferability, an interlaboratory comparison exercise was organized among six laboratories worldwide. Each laboratory received a split of pristine ash, and independently analyzed it according to the protocol for a wide range of elements. Collated results indicate good repeatability and reproducibility for most elements, thus indicating that the development of this protocol is a useful step towards providing standardized and reliable methods for ash hazard characterization. In this article, we review recent ash leachate studies, report the outcomes of the comparison exercise and present a revised and updated protocol based on the experiences and recommendations of the exercise participants. The adoption of standardized methods will improve and facilitate the comparability of results among studies and enable the ongoing development of a global database of leachate information relevant for informing volcanic health hazards assessment.

International audience; Radon (222Rn) activity in air was measured for about 6 months at the summit of Mt. Etna Central Crater (Sicily) by integrative radon dosimetry at two different heights above ground level (5 cm and 1 m). This technique for air radon monitoring proved operational in the harsh volcanic environment of Mt. Etna summit with a 94% recovery rate of dosimeters. In the southeast sector exposed to the main gas plume, mean radon activity in free air (height 1 m) is significantly higher than the local background and the ground level activity (height 5 cm). The results strongly suggest that the plume is enriched in radon by ≈550 Bq/m3, which has never been evidenced before. Radon activities also reflect soil degassing occurring in the proximity of the crater, with increased ground level activities in zones of enhanced soil fracturing and degassing. Radon measurements also revealed a hot spot in front of the Voragine vent with extraordinary high levels of air activities (26 kBq/m3 at ground level and 8 kBq/m3 in free air). The temporal variation of radon activity was investigated by replacing a few stations half way through the exposure period. The only significant increase was associated with the site located under the main gas plume and correlated with eruptive unrest within the crater. Finally, air radon levels higher than the recommended threshold of 300 Bq/m3 were detected in several zones on the rim and could generate a nonnegligible radiologic dose for workers on the volcano.

The Geostationary Operational Environmental Satellites (GOES)-R Series observe a significant fraction of the most volcanically active region of Earth, known as the “Pacific Ring of Fire,” which includes the western portions of North and South America, East Asia, Indonesia, Micronesia, and New Zealand. Explosive volcanic eruptions often produce complex clouds composed of volcanic ash, volcanic gases, and sometimes hydrometeors. Volcanic clouds can affect weather and are a major aviation hazard. Thus, routine volcanic cloud monitoring is critical. The Advanced Baseline Imager (ABI) and Geostationary Lightning Mapper (GLM) on the GOES-R Series are extremely valuable for detecting, tracking, and characterizing volcanic clouds, including volcanic ash, which is the constituent that poses the greatest overall hazard. In this chapter, an overview of qualitative and quantitative applications of GOES-R measurements, in support of volcanic cloud monitoring, will be given. In particular, the overview is primarily focused on the volcanic ash component of volcanic clouds.

The disequilibrium combination of abundant methane and carbon dioxide has been proposed as a promising exoplanet biosignature that is readily detectable with upcoming telescopes such as the James Webb Space Telescope. However, few studies have explored the possibility of non-biological CH4 and CO2 and related contextual clues. Here, we investigate whether magmatic volcanic outgassing on terrestrial planets can produce atmospheric CH4 and CO2 with a thermodynamic model. Our model suggests that volcanoes are unlikely to produce CH4 fluxes comparable to biological fluxes. Improbable cases where volcanoes produce biological amounts of CH4 also produce ample carbon monoxide. We show, using a photochemical model, that high abiotic CH4 abundances produced by volcanoes would be accompanied by high CO abundances, which could be a detectable false positive diagnostic. Overall, when considering known mechanisms for generating abiotic CH4 on terrestrial planets, we conclude that observations of atmospheric CH4 with CO2 are difficult to explain without the presence of biology when the CH4 abundance implies a surface flux comparable to modern Earth's biological CH4 flux. A small or negligible CO abundance strengthens the CH4+CO2 biosignature because life readily consumes atmospheric CO, while reducing volcanic gases likely cause CO to build up in a planet's atmosphere. Furthermore, the difficulty of volcanically-generated CH4-rich atmospheres suitable for an origin of life may favor alternatives such as impact-induced reducing atmospheres., Comment: Accepted by Planetary Science Journal on September 15th, 2020 and Published on October 29th, 2020

OVSICORI The sulfur cycle at convergent margins remains poorly constrained yet is fundamentally important for understanding the redox state of Earth's reservoirs and the formation of ore deposits. In this study we investigate the sulfur isotope composition of high temperature volcanic gases emitted from the Nicaraguan (average of +4.8 ± 1.3‰) and Costa Rican (average of +2.3 ± 1.3‰) arc segments contributing to emissions from the Southern Central American Volcanic Arc (SCAVA; average of +3.8 ± 1.7‰). Along-arc variations in geochemical tracers at SCAVA are widely accepted to reflect variations in subduction parameters and deep fluid sources and correlations between these parameters and gas S isotope compositions are observed. These correlations suggest that gas emissions are sourced from a mixture of mantle S with δ34S ~ 0‰ and isotopically heavy slab-derived sulfur with δ34S ≥ ~ +8‰. We employ Monte Carlo mass balance modeling to constrain S inputs to the subduction zone and relative contributions from mantle and slab to arc sulfur emissions. The models indicate that bulk subduction input in Nicaragua has a S isotope composition of +1.4 ± 0.5‰ compared to −0.2 ± 0.4‰ in Costa Rica, requiring preferential release of isotopically heavy oxidized S from the slab to explain the relatively high δ34S observed in arc outputs. We show that the flux of S from the slab is sufficient to oxidize the entire mantle wedge within the lifetime of the arc, indicating that S is a primary oxidizing agent in subduction zones. Furthermore, the preferential removal of heavy S from the slab requires retention of isotopically light S in the residual slab. Subduction-scale fractionation of S isotopes is fundamentally important in explaining why Earth's bulk surface reservoirs are isotopically positive. The sulfur cycle at convergent margins remains poorly constrained yet is fundamentally important for understanding the redox state of Earth's reservoirs and the formation of ore deposits. In this study we investigate the sulfur isotope composition of high temperature volcanic gases emitted from the Nicaraguan (average of +4.8 ± 1.3‰) and Costa Rican (average of +2.3 ± 1.3‰) arc segments contributing to emissions from the Southern Central American Volcanic Arc (SCAVA; average of +3.8 ± 1.7‰). Along-arc variations in geochemical tracers at SCAVA are widely accepted to reflect variations in subduction parameters and deep fluid sources and correlations between these parameters and gas S isotope compositions are observed. These correlations suggest that gas emissions are sourced from a mixture of mantle S with δ34S ~ 0‰ and isotopically heavy slab-derived sulfur with δ34S ≥ ~ +8‰. We employ Monte Carlo mass balance modeling to constrain S inputs to the subduction zone and relative contributions from mantle and slab to arc sulfur emissions. The models indicate that bulk subduction input in Nicaragua has a S isotope composition of +1.4 ± 0.5‰ compared to −0.2 ± 0.4‰ in Costa Rica, requiring preferential release of isotopically heavy oxidized S from the slab to explain the relatively high δ34S observed in arc outputs. We show that the flux of S from the slab is sufficient to oxidize the entire mantle wedge within the lifetime of the arc, indicating that S is a primary oxidizing agent in subduction zones. Furthermore, the preferential removal of heavy S from the slab requires retention of isotopically light S in the residual slab. Subduction-scale fractionation of S isotopes is fundamentally important in explaining why Earth's bulk surface reservoirs are isotopically positive. Universidad Nacional, Costa Rica University of New Mexico, EEUU Columbia University, EEUU Observatorio Vulcanológico y Sismológico de Costa Rica

Sulphur Springs is a vigorous geothermal field associated with the Soufriere Volcanic Centre in southern Saint Lucia. Intensely altered rocks occur over an area of at least 200 × 400 m, together with bubbling hot pools and fumaroles. The pools are sodium‑calcium-sulphate type, with pHs of 3–7 and temperatures of 41–97 °C. Fumaroles have temperatures up to, and at times above 100 °C. Gases collected from both fumaroles and bubbling pools have high contents of CO2 (601–993 mmol/mol) and commonly high H2S (3–190 mmol/mol). Least-altered host rocks surrounding Sulphur Springs comprise calc-alkaline, feldspar-quartz-porphyritic dacites of near-uniform chemical composition. These rocks, which form massive domes and volcaniclastic units, were emplaced 13–30 ka ago (Lindsay et al., 2013). Within the geothermal field, the dacites have been moderately to highly altered to acid-sulphate assemblages of kaolinite, illite, smectite, alunite, natroalunite, cristobalite, opaline silica, native sulphur, jarosite and amorphous compounds. Muddy sediments from grey to blackish thermal pools additionally contain iron sulphides. Despite intense alteration of the volcanic rocks (and derived volcaniclastic sediments), Zr and Ti have remained essentially immobile, which allows identification of the precursors (dacites) and calculation of mass changes. Many of the altered rocks and sediments show major depletions of Fe, Mg, Ca, Na. Extremely altered samples additionally show notable losses of Al, P, K, REE and Y, implying leaching by highly acidic waters. A few of the highly altered rocks, however, have gained Al, together with P, presumably due to neutralization or evaporation of acidic thermal waters. Also present within the geothermal field are metre-scale zones with very high contents of silica and native sulphur, and Surface thermal waters define a linear trend in a plot of δ18O vs. δD, and reach high levels of isotopic enrichment. The enrichment trend is ascribed to progressive evaporation in the thermal pools. The low slope of the isotopic trend (1.4) is interpreted as being due to surficial mixing between meteoric waters and steam condensates derived at about 230 °C from the deep brine that underlies the geothermal field. The whole-rock O-H-isotopic composition of four highly altered samples (kaolinite-smectite-opal-sulphates) can be accounted for if the alteration fluid was a 50:50 mixture of steam and meteoric water, and alteration occurred at 50–125 °C. Whole-rock δ34S values of samples containing variable amounts of sulphates, sulphides and native S are all notably negative (−5 to −16‰), consistent with derivation of sulphur from volcanic gases such as SO2 and H2S. Altered rocks and thermal pool sediments in the geothermal field are commonly enriched in Hg and Se (up to 50 mg/kg). At Sulphur Springs, primary dacitic rocks have been chemically and mineralogically transformed by reaction with acidic waters that formed when uprising volcanic gases condensed into neutral meteoric waters. In many cases, this has led to substantial mass losses or gains in Al, P and REEs. Regardless of the degree of alteration, however, the precursor rocks can still be identified using Ti-Zr relations.

The two most recent eruptions of Tolbachik Volcano, Kamchatka were used to demonstrate how joint volcanological and crystallochemical studies can make it possible to monitor active volcanoes, as well as to sample the products of their activity and perform joint investigations of these samples, ultimately leading to a better understanding of volcanic processes. In particular, X-ray crystallography and X-ray spectroscopy revealed that many minerals that were formed from volcanic gases contained uncommon cation oxy-centered tetrahedra [OA4] (where A is a metal), e.g., [OCu4]6+, unlike the well-known anion tetrahedra of the [SiO4]4– type. These studies have been conducted for 40 years, with the result that a new line of research has been systematized and generalized, viz., the crystal chemistry of inorganic compounds and minerals with assemblages of oxy-centered tetrahedra, or oxysalts. We set forth the essential principles of this science; in particular, the [OA4] tetrahedra are treated as basic building units of minerals produced from volcanic exhalations, while the assemblages of such tetrahedra are considered to be a basic form of transfer of metals by volcanic gases in the high-temperature oxidizing environment of volcanism.

Author Posting. © The Authors, 2018. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 215 (2018): 713–735, doi:10.1093/gji/ggy313.

Chemical denudation rates during the 2014–15 Barðarbunga eruption, calculated using river chemical fluxes, increased substantially confirming that volcanic activity and its products such as fresh lava, and acidic volatiles accelerates these rates. Although the long-term net effect of the combined input of volcanic gases and basalt from the eruption appears to be the overall net drawdown of CO 2 , it is found that the rapid release of acid gases to surface waters once the basaltic lava comes in contact with surface waters will lead to a short-term release of CO 2 from these waters.

International audience; Hydrogen (H2)-rich fluids are observed in a wide variety of geologic settings including gas seeps in serpentinized ultramafic rocks, sub-seafloor hydrothermal vents, fracture networks in crystalline rocks from continental and oceanic crust, and volcanic gases. Natural hydrogen sources can sustain deep microbial ecosystems, induce abiotic hydrocarbons synthesis and trigger the formation of prebiotic organic compounds. However, due to its extreme mobility and small size, hydrogen is not easily trapped in the crust. If not rapidly consumed by redox reactions mediated by bacteria or suitable mineral catalysts it diffuses through the rocks and migrates toward the surface. Therefore, H2is not supposed to accumulate in the crust. We challenge this view by demonstrating that significant amount of H2may be adsorbed by clay minerals and remain trapped beneath the surface. Here, we report for the first time H2content in clay-rich rocks, mainly composed of illite, chlorite, and kaolinite from the Cigar Lake uranium ore deposit (northern Saskatchewan, Canada). Thermal desorption measurements reveal that H2is enriched up to 500 ppm (i.e. 0.25molkg−1of rock) in these water-saturated rocks having a very low total organic content (

The data about connection between mud volcanous of the Kerch Peninsula and earthquakes are presence. Influence of the earthquakes on state of the mud volcanoes, correlations main component mud volcanic gases, debet mud volcanic water and the volume of the eruptet mud vulcanic breccia are established. The correlative relationship between change of the concentrations CO 2 , He and earthquakes are revealled.

The Kuril Island arc extending for about 1,200 km from Kamchatka Peninsula to Hokkaido Island is a typical active subduction zone with ∼40 historically active subaerial volcanoes, some of which are persistently degassing. Seven Kurilian volcanoes (Ebeko, Sinarka, Kuntomintar, Chirinkotan, Pallas, Berg, and Kudryavy) on six islands (Paramushir, Shiashkotan, Chirinkotan, Ketoy, Urup, and Iturup) emit into the atmosphere > 90% of the total fumarolic gas of the arc. During the field campaigns in 2015–2017 direct sampling of fumaroles, MultiGas measurements of the fumarolic plumes and DOAS remote determinations of the SO2 flux were conducted on these volcanoes. Maximal temperatures of the fumaroles in 2015–2016 were 510°C (Ebeko), 440°C (Sinarka), 260°C (Kuntomintar), 720°C (Pallas), and 820°C (Kudryavy). The total SO2 flux (in metric tons per day) from fumarolic fields of the studied volcanoes was measured as ∼1,800 ± 300 t/d, and the CO2 flux is estimated as 1,250 ± 400 t/d. Geochemical characteristics of the sampled gases include δD and δ18O of fumarolic condensates, δ13C of CO2, δ34S of the total sulfur, ratios 3He/4He and 40Ar/36Ar, concentrations of the major gas species, and trace elements in the volcanic gas condensates. The mole ratios C/S are generally 7RA (where RA is the atmospheric 3He/4He). The highest 3He/4He ratios of 8.3RA were measured in fumaroles of the Pallas volcano (Ketoy Island) in the middle of the arc.

co-auteur étranger; International audience; Thermal infrared (TIR) imaging is a common tool for the monitoring of volcanic activity. Broadband cameras with increasing sampling frequency give great insight into the physical processes taking place during effusive and explosive event, while Fourier transform infrared (FTIR) methods provide high resolution spectral information used to assess the composition of volcanic gases but are often limited to a single point of interest. Continuing developments in detector technology have given rise to a new class of hyperspectral imagers combining the advantages of both approaches. In this work, we present the results of our observations of volcanic activity at Stromboli volcano with a ground-based imager, the Telops Hyper-Cam LW, when used to detect emissions of sulfur dioxide (SO2) produced at the vent, with data acquired at Stromboli volcano (Italy) in early October of 2015. We have developed an innovative technique based on a curve-fitting algorithm to quickly extract spectral information from high-resolution datasets, allowing fast and reliable identification of SO2. We show in particular that weak SO2 emissions, such as inter-eruptive gas puffing, can be easily detected using this technology, even with poor weather conditions during acquisition (e.g., high relative humidity, presence of fog and/or ash). Then, artificially reducing the spectral resolution of the instrument, we recreated a variety of commonly used multispectral configurations to examine the efficiency of four qualitative SO2 indicators based on simple Brightness Temperature Difference (BTD). Our results show that quickly changing conditions at the vent – including but not limited to the presence of summit fog – render the establishment of meaningful thresholds for BTD indicators difficult. Building on those results, we propose recommendations on the use of multispectral imaging for SO2 monitoring and routine measurements from ground-based instruments.

Technical progress is impossible without the creation of new devices, the quantitative and qualitative indicators of which radically differ from the known ones, which in turn requires new technologies and materials. In the creation of new materials, rare and rare-earth metals are increasingly used, the reserves of which are very limited. Therefore, the development and implementation of new methods of mining such metals are a timely and urgent task.Prospective methods of mining mineral deposits from volcanic gases are considered. The proposed model makes it possible to reveal the composition of volcanic gas, to experimentally prove its dynamic properties, to develop a model that allows one to trace the behavior of gas, on its basis to develop a principle scheme for extracting rare-earth elements (REE) and to present the hardwaretechnological scheme for obtaining REE from fumaroles (types of gas) in the form fumarolic metallurgical plant.On the basis of a model system with heavy metal solutions in a liquid, the possibility of studying the behavior of gas particles is shown. Such a model system is converted to volcanic gas and allows interpretation of the results for a fumarolic metallurgical unit (FMU) by determining the critical dimensions of the elements of such an installation (dome sizes, parameters of connecting hoses).

Subvolcanic hydrothermal alteration often leads to volcanic hazards, such as edifice collapse and phreatic eruption. The 1926 eruption of Tokachidake volcano caused a pyroclastic cone to collapse, and phreatic eruptions have occurred repeatedly. Here, we investigate the hydrothermal system of Tokachidake volcano by examining the characteristics of hydrothermally altered rocks and discuss the effects of the hydrothermal system on volcanic hazards. Beneath the crater area, the dense Tairagadake lavas (Ta lava) at the basement of Tokachidake volcano form piles that are >500 m thick. The Ta lava constrains the flows of volcanic gases and thermal water in the subsurface, and strong hydrothermal alteration occurs in both the underlying and overlying deposits that are more permeable. Above the Ta lava, Tokachidake ejecta are altered in low-temperature acidic environments (