Description: We show the results of a study on the volatiles dissolved inmineral waters discharged over a 200 km-long transect along the Rodna-Bârgău area and Călimani-Gurghiu-Harghita volcanic chain (Eastern Carpathians, Romania). All of the collected mineral water samples carry dissolved gas with carbon dioxide content up to 1.99 cm3STP/gH2O, and heliumcontent up to 2.3 × 10−5 cm3STP/gH2O. Carbon (δ13CTDIC total dissolved inorganic carbon, ranging from−15.6 to 5.32‰vs. VPDB), He systematics (He isotopes in the range of 0.38–0.99 Ra, Ra=air-normalized 3He/4He ratio) and CO2/3He ratio spanning over four orders ofmagnitude fromMORB-like values of 2.92× 109 to crustal-type values of 3.02 × 1013, coherently indicate the presence of fluids fromdifferent crustal sources (e.g. sediments, hydrocarbon reservoirs) besidesminor, but detectable contributions ofmantle/magmatic-derived fluids (up to 16.45%). Our investigations show that the wide range of chemical and isotopic composition can be explained in terms of mixings among different gas sources feeding the groundwater and the contemporary occurrence of gas-water interactions like degassing and deposition of carbonates, affecting the circulating waters after their infiltration.

Description: Published

Description: 117-128

Description: 6A. Geochimica per l'ambiente

Description: JCR Journal

Description: Methane flux measurements from surface gas manifestations and springs at the Ciomadu post-volcanic area are reported. These data contribute to extend the Romanian data-set on geological emissions of greenhouse gas to the atmosphere. A total of 46 sites were investigated for methane flux, dissolved methane content and stable carbon isotopic ratio of methane. Total methane output is in the order of 102-103 kg/year, comparable to other ancient volcanic systems in Europe. Methane is mainly abiotic in origin, variably mixed with biotic thermogenic components, likely depending on the amount of crustal sediments involved in the volcanic plumbing system

Description: Unpublished

Description: Bucharest

Description: 6A. Geochimica per l'ambiente

Description: We provide the first high-resolution CO2 flux data for the Neogene to Quaternary volcanic regions of the entire Carpathian-Pannonian Region, Eastern-Central Europe, and estimate the CO2 emission of the seemingly inactive Ciomadul volcanic complex, the youngest volcano of this area. Our estimate includes data from focused and diffuse CO2 emissions from soil. The CO2 fluxes of focused emissions range between 277 and 8172 g d−1, corresponding to a CO2 output into the atmosphere between 0.1 and 2.98 t per year. The investigated areas for diffuse soil gas emissions were characterized by wide range of CO2 flux values, at Apor Baths, ranging from 1.7 × 101 to 8.2 × 104 g m−2 d−1, while at Lăzărești ranging between 1.43 and 3.8 × 104 g m−2 d−1. The highest CO2 focused gas fluxes at Ciomadul were found at the periphery of the youngest volcanic complex, which could be explained either by tectonic control across the brittle older volcanic edifices or by degassing from a deeper crustal zone resulting in CO2 flux at the periphery of the supposed melt-bearing magma body beneath Ciomadul. The estimate of the total CO2 output in the area is 8.70 × 103 t y−1, and it is consistent with other long (N10 kyr) dormant volcanoes with similar age worldwide, such as in Italy and USA. Taking into account the isotopic composition of the gases that indicate deep origin of the CO2 emissions, this yields further support that Ciomadul may be considered indeed a dormant, or PAMS volcano (volcano with potentially active magma storage) rather than an inactive one. Furthermore, hazard of CO2 outpourings has to be taken into account and it has to be communicated to the visitors. Finally, we suggest that CO2 output of dormant volcanic systems has to be also accounted in the estimation of the global volcanic CO2 budget.

Description: Published

Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio

Description: JCR Journal

Description: Seeps are the expression of the migration of hydrocarbons from subsurface accumulations to the surface in sedimentary basins. They may represent an important indication of the presence of petroleum (gas and oil) reservoirs and faults, and are a natural source of greenhouse gas (methane) and atmospheric pollutants (ethane, propane) to the atmosphere. Romania is one of the countries with the largest number of seeps in the world, due to the high petroleum potential and active tectonics. Based on a review of the available literature, and on the field surveys performed by the authors during the last 17 years, we report the first comprehensive GIS-based inventory of 470 seeps in Romania (HYSED-RO), including gas seeps (10.4% of the total), oil seeps (11.7%), mud volcanoes (50.4%), gas-rich springs (12.6%), asphalt (solid) seeps (4.3%), unclassified manifestations (4.0%), and uncertain seeps (6.6%). Seeps are typically located in correspondence with major faults and vertical and fractured stratigraphic contacts associated to petroleum reservoirs (anticlines) in low heat flow areas, and their gas-geochemistry reflects that of the subsurface reservoirs. The largest and most active seeps occur in the Carpathian Foredeep, where they release thermogenic gas, and subordinately in the Transylvanian Basin, where gas is mainly microbial. HYSED-RO may represent a key reference for baseline characterization prior to subsurface petroleum extraction, for environmental studies, and atmospheric greenhouse gas emission estimates in Romania.

Description: Published

Description: 39

Description: 6A. Geochimica per l'ambiente

Description: JCR Journal

Description: Hypersaline meromictic lakes are extreme environments in which water stratification is associated with powerful physicochemical gradients and high salt concentrations. Furthermore, their physical stability coupled with vertical water column partitioning makes them important research model systems in microbial niche differentiation and biogeochemical cycling. Here, we compare the prokaryotic assemblages from Ursu and Fara Fund hypersaline meromictic lakes (Transylvanian Basin, Romania) in relation to their limnological factors and infer their role in elemental cycling by matching taxa to known taxon-specific biogeochemical functions. To assess the composition and structure of prokaryotic communities and the environmental factors that structure them, deep-coverage small subunit (SSU) ribosomal RNA (rDNA) amplicon sequencing, community domain-specific quantitative PCR and physicochemical analyses were performed on samples collected along depth profiles. The analyses showed that the lakes harbored multiple and diverse prokaryotic communities whose distribution mirrored the water stratification patterns. Ursu Lake was found to be dominated by Bacteria and to have a greater prokaryotic diversity than Fara Fund Lake that harbored an increased cell density and was populated mostly by Archaea within oxic strata. In spite of their contrasting diversity, the microbial populations indigenous to each lake pointed to similar physiological functions within carbon degradation and sulfate reduction. Furthermore, the taxonomy results coupled with methane detection and its stable C isotope composition indicated the presence of a yet-undescribed methanogenic group in the lakes' hypersaline monimolimnion. In addition, ultrasmall uncultivated archaeal lineages were detected in the chemocline of Fara Fund Lake, where the recently proposed Nanohaloarchaeota phylum was found to thrive.

Description: Published

Description: 2642 – 2656

Description: 6A. Geochimica per l'ambiente

Description: N/A or not JCR

Description: Romania is one of the countries with the largest number of surface hydrocarbon seeps in the world. Seeps may be an important tool for petroleum exploration as they can provide useful information regarding source rock maturity, reservoir quality, and secondary gas alterations. Seeps also represent an important source of methane, ethane, and propane to the atmosphere. To date, the genetic characterization of natural gas in Romania has only been based on molecular composition, without isotopic information. Here, we present an overview of investigations performed over the past 15 years for the main Romanian hydrocarbon seeps, and report the molecular and isotopic compositions of gas, and the fluxes of methane, ethane and propane to the atmosphere. We assessed gas origin and secondary alterations in 17 seeps from several Romanian petroleum systems, and potential source rock types and maturity have been evaluated. As previously inferred, gas within the Transylvanian Basin is largely microbial, but also displays indications of a minor thermogenic component that is likely related to a deep petroleum system. Carpathian Flysch and Foredeep petroleum systems contain thermogenic gas, with clear evidence ofmbiodegradation in some cases. Thermogenic gas generation modelling and maturity plots suggest thatmmost Romanian gases originate from mature type II and III kerogen (%Ro: 2e3). For cases of high flux seeps, gas has the same hydrocarbon molecular composition as the reservoir, while in weaker seeps and some mud volcanoes gas is altered by molecular fractionation (a loss of C2 and C3 during gas migration). Gas seep geochemistry, in general, reflects the different geological and maturity conditions of basins where seeps are located. A vertical sequence of petroleum systems has been suggested in some basins by seeps displaying different maturity and secondary alterations. Measurements of methane flux to the atmosphere from 94 seeps display a wide range of emissions (kilograms to hundreds of tons per year), with a total, conservative estimated methane emission of approximately 3000 t y-1. Microseepage may also release a similar quantity of methane. Consequently, seepage is a substantial contributor to natural emissions of methane on a national level.

Description: Published

Description: 130-143

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: Duvalo “volcano” is a site of anomalous geogenic degassing close to Ohrid (North Macedonia) not related to volcanic activity, despite its name. CO2 flux measurements made with the accumulation chamber (321 sites over ∼50,000 m2) showed fluxes up to nearly 60,000 g m−2 d−1, sustaining a total output of ∼67 t d−1. Soil gas samples were taken at 50 cm depth from sites with high CO2 fluxes and analyzed for their chemical and isotope composition. The gas is mainly composed by CO2 (〉90%) with significant concentrations of H2S (up to 0.55%) and CH4 (up to 0.32%). The isotope compositions of He (R/RA 0.10) and of CO2 (δ13C ∼ 0‰) exclude significant mantle contribution, while δ13C-CH4 (∼−35‰) and δ2H-CH4 (∼−170‰) suggest a thermogenic origin for CH4. The area is characterized by intense seismic activity and Duvalo corresponds to an active tectonic structure bordering the Ohrid graben. The production of H2S within the stratigraphic sequence may be explained by thermochemical reduction of sulfate. The uprising H2S is partially oxidized to sulfuric acid that, reacting with carbonate rocks, releases CO2. The tectonic structure of the area favors fluid circulation, sustaining H2S production and oxidation, CO2 production and allowing the escape of the gases to the atmosphere. In the end, Duvalo represents a tectonic-related CO2 degassing area whose gases originate mostly, if not exclusively, in the shallowest part of the crust (〈10 km). This finding highlights that even systems with trivial mantle contribution may sustain intense CO2 degassing (〉1,000 t km−2 d−1).

Description: Published

Description: e2021GC010198

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: We report on the results of an extensive geochemical survey of fluids released in the Vardar zone (central-western Serbia), a mega-suture zone at the boundary between Eurasia and Africa plates. Thirty-one bubbling gas samples are investigated for their chemical and isotopic compositions (He, C, Ar) and cluster into three distinct groups (CO2-dominated, N2-dominated, and CH4-dominated) based on the dominant gas species. The measured He isotope ratios range from 0.08 to 1.19 Ra (where Ra is the atmospheric ratio), and reveal for the first time the presence of a minor (〈20%) but detectable regional mantle-derived component in Serbia. δ13C values range from −20.2‰ to −0.1‰ (versus PDB), with the more negative compositions observed in N2-dominated samples. The carbon-helium relationship indicates that these negative δ13C compositions could be due to isotopic fractionation processes during CO2 dissolution into groundwater. In contrast, CO2-rich samples reflect mixing between crustal and mantle-derived CO2. Our estimated mantle-derived He flux (9.0 × 109 atoms m−2 s−1) is up to 2 orders of magnitude higher than the typical fluxes in stable continental areas, suggesting a structural/tectonic setting favoring the migration of deep-mantle fluids through the crust.

Description: Published

Description: e2021GC010017

Description: 9T. Geochimica dei fluidi applicata allo studio e al monitoraggio di aree sismiche

Description: JCR Journal

Description: Interactions between volcanoes and glaciers provide insight to the evolution of a volcanic edifice and may be an indicator for renewed volcanic activity. At Mount St. Helens, Crater Glacier, which has formed in the volcanic crater after the eruption in 1980, is one of the world’s last expanding glaciers and provides a unique opportunity to characterize the evolution of a glacier expanding onto an area of significant thermal flux. We combine photographic documentation and glaciovolcanic cave surveys with remote sensing data from Google Earth, UAS, and LiDAR to analyze the present state of Crater Glacier and reconstruct its development since the emplacement of the 2004–2008 lava dome. Our results show that snow accumulation has caused Crater Glacier to grow from 2009 to 2019 by approximately 13.8 × 106 m3, during which time the glacier toe advanced by several hundred meters. The glacier-dome interface shift toward higher elevations against the 2004–2008 lava dome and subsequent encroachment onto thermally active areas led to glacier modification via extensive subglacial cave system formation. Analysis of subglacial tephra layers revealed the existence of juvenile material from the 2004–2008 eruption cycle, providing insights about glacier subsidence of ~ 40 m since 2004/2005 in spite of net growth. Although the lava dome is cooling, the glacier-dome interface seems to have become increasingly stable in the past few years. Our results suggest that glacier development in the accumulation area adjacent to the dome is now being affected by the thermal characteristics of the lava dome itself, making monitoring internal glacier development via tracking glaciovolcanic cave expansion a potentially important volcano monitoring tool. Zusammenfassung Die Interaktionen von Vulkanen und Gletschern tragen häufig zum Verständnis über die Entwicklung eines vulkanischen Systems bei und können als Indikator für wiederkehrende vulkanische Aktivität dienen. Crater Glacier, der nach der Eruption 1980 im Krater des Mount St. Helens entstanden ist, ist einer der letzten wachsenden Gletscher weltweit und bietet somit eine einmalige Chance, die Entwicklung eines Gletschers in Verbindung mit erheblichen Wärmeflüssen zu charakterisieren. Neben einer fotografischen Dokumentation des Gletschers machen wir uns die Kartierung vulkanischer Gletscherhöhlen zu Nutze. Diese kombinieren wir mit Fernerkundungsdaten von Google Earth sowie Drohnen- und LiDAR-Daten, um den aktuellen Zustand des Gletschers zu charakterisieren und seine Entwicklung seit dem letzten Lavadomwachstum zwischen 2004 und 2008 zu rekonstruieren. Unsere Ergebnisse zeigen, dass die ausreichende Akkumulation von Schnee zum Wachstum des Gletschers mit einem Massenzuwachs von ca. 13,8 x 106 m3 zwischen 2009 und 2019 geführt hat. Neben dem Voranschreiten der Gletscherzunge um mehrere hundert Meter hat sich das Wachstum ebenfalls rund um den neuen Lavadom bemerkbar gemacht. Durch die Verschiebung der Kontaktzone von Gletscher und Lavadom hin zu höheren Bereichen des Doms und der damit verbundenen Interaktion zwischen Gletscher und geothermaler Aktivität ist es zu einer deutlichen Veränderung des Gletschers durch die Ausbildung subglazialer Höhlensysteme gekommen. Analysen von im Gletscher eingebetteten Tephraschichten, die vermutlich der letzten Aktivität zwischen 2004 und 2008 zuzuordnen sind, deuten trotz des allgemeinen Wachstums auf eine Setzung des Gletschers um etwa 40 m seit 2004/05 hin. Obwohl der Lavadom an Hitze verliert, scheint die Kontaktzone von Gletscher und Dom in den letzten Jahren zunehmend konstant geworden zu sein. Unsere Ergebnisse deuten darauf hin, dass der Gletscher in diesem Bereich derzeit vor allem durch die thermalen Eigenschaften des Lavadoms beeinflusst wird. Dadurch kommt dem Monitoring interner Gletscherstrukturen mittels Beobachtung vulkanischer Gletscherhöhlen eine potenziell wichtige Bedeutung bei der Vulkanüberwachung zu.