Kyriaki Daskalopoulou

Tectonic structures such as faults and fractures act as preferential pathways for gas ascent and their consequent release into the atmosphere. Magma-derived gases are widespread throughout the western Eger Rift (Czech Republic), an intraplate region without active volcanism but with the occurrence of mid-crustal earthquake swarms. Geogenic CO2 discharges from the Počatky–Plesná fault zone (PPZ), Mariánské Lázně Fault (MLF), Bad Brambach (BB), and a deep local fault (DLF) have been sampled since 2021. Gases were analysed for their chemical (CO2, N2, O2, Ar, He, CH4, and H2) and isotopic contents (noble gases, CO2, and CH4). Results showed that CO2 is the dominant gas species (concentrations > 99.4%), with the remaining gases being present in minor amounts. The He isotopic composition for gas samples from the PPZ and MLF is typical for the subcontinental lithospheric mantle (SCLM - with 3He/4He ratios between 5 and 6 RA), while gases from BB and the DLF show a lower mantle input (3He/4He is 3.2 and 2.4 RA, respectively). δ13CCO2 data reflect a SCLM CO2 signature (-4 to -1 ‰ vs. V-PDB). First CH4 isotopic data present values between -52.0 and -47.1 ‰ vs. V-PDB for δ13CCH4 and between -307 and -284 ‰ vs. V-SMOW for δ2HCH4. With the exception of samples collected from the MLF that show a clear thermogenic CH4 origin, all the other samples present isotopic values and CH4/(C2H6+C3H8) ratios that suggest a likely biogenic origin, with secondary processes playing a crucial role on the gases’ isotopic signature. It should be noted that low CH4concentrations (

The western Eger Rift (Czech Republic) is a non-volcanic rift setting of intraplate seismicity that is characterized by abundant degassing of mantle-derived fluids. Since 2019, gases obtained from the free gas phase and volcanic rock samples of Quaternary age have been collected in order to determine the origin and evolution of volatiles in the system and define the magma chamber p-T conditions. Results of the CO2-dominated gas discharges of the Bublák and Hartoušov mofette fields yield an ~93 % mantle input (considering a subcontinental lithospheric mantle) for He. Ne isotopic ratios range from 9.8 to 11.0 for 20Ne/22Ne and from 0.0282 to 0.0480 for 21Ne/22Ne. Notwithstanding the samples enriched in 20Ne likely due to mass fractionation, many samples show a mixed atmospheric-mantle type source for Ne. However, an additional crustal input cannot be excluded. 40Ar/36Ar ratios also cover a wide spectrum of values (between 300 and 4680). Overall, gas samples typically present a higher-than-atmospheric value with 40Ar likely deriving from the mixing of an atmospheric and deep source. The 4He/40Ar* ratio is moderately constant and falls within the MORB range, suggesting an unfractionated magma that originates from mantle sources.. Results obtained from mineral quantitative analyses and by using thermobarometry of orthopyroxene and clinopyroxene rim pairs of matrix grains yield predominantly temperature and pressure conditions of 700 ±100 °C and 1.1 ±0.5 GPa, respectively, indicating a lithospheric depth that ranges between 40 - 45 km for 1.5 GPa and 20-25km for 0.5 GPa. In addition, pairing cores of mm-sized pyroxenes point to a temperature of 1100 ±100 °C and a pressure of 2.5 ±0.5 GPa that correspond to a lithospheric depth of ~75 km. Those minerals that indicate greater depths are likely the oldest ones as they were able to grow for longer times during their ascent. On the other hand, secondary overgrowths or smaller matrix grains represent younger grains that have grown during magma evolution. Therefore, their diverse chemistry and the wide range of p-T conditions reveal rising (and cooling) of magma.This research is a part of the “MoRe-Mofette Research” and MoCa - “Monitoring Carbon” projects, which were funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 419880416, 461419881.

Active biomonitoring of mercury (Hg) using non-indigenous moss bags was performed for the first time within and around the former Hg mining area of Abbadia San Salvatore (Mt. Amiata, central Italy). The purpose was to discern the Hg spatial distribution, identify the most polluted areas, and evaluate the impacts of dry and wet deposition on mosses. The exposed moss bags consisted of a mixture of Sphagnum fuscum and Sphagnum tenellum from an external uncontaminated area. In each site, two different types of moss bags, one uncovered (to account for the wet + dry deposition) and one covered (to evaluate the dry deposition), were exposed. The behavior of arsenic (As) and antimony (Sb) in the mosses was investigated to assess the potential relationship with Hg. GEM (Gaseous Elemental Mercury) concentrations were also measured at the same sites where the mosses were exposed, although only as a reference in the initial stages of biomonitoring. The results revealed that the main Hg emissions sources were associated with the former mining area of Abbadia San Salvatore, in agreement with the measured GEM concentrations, while arsenic and antimony were related to soil enriched in As-Sb waste material. The three elements registered higher concentrations in uncovered mosses with respect to the covered ones, i.e., wet deposition was the key factor for their accumulation on the uncovered mosses, while dry deposition was especially important for the covered samples in the mining area. Hg was accumulated in the mosses via GEM adsorption, uptake of particulate Hg, and precipitation via raindrops/snowfall, with almost no loss and without post-deposition volatilization. The results testified that the chosen biomonitoring technique was an extremely useful tool for understanding Hg transport and fate in a contaminated area.

Mofettes are gas emission sites where high concentrations of CO₂ ascend through conduits from as deep as the mantle to the Earth’s surface and as such provide direct windows to processes at depth. The Hartoušov mofette, located at the western margin of the Eger Graben, is a key site to study interactions between fluids and swarm earthquakes. The mofette field (10 mofettes within an area of 100 m × 500 m and three wells of 28, 108, and 239 m depth) is characterized by high CO₂ emission rates (up to 100 t/d) and helium signatures with (³He/⁴He)_c up to 5.8 Ra, indicating mantle origin. We compiled geological, geophysical, geochemical, and isotopic data to describe the mofette system. Fluids in the Cheb basin are mixtures between shallow groundwater and brine (>40 g/L at a depth of 235 m) located at the deepest parts of the basin fillings. Overpressured CO₂-rich mineral waters are trapped below the mudstones and clays of the sealing Cypris formation. Drilling through this sealing layer led to blow-outs in different compartments of the basin. Pressure transients were observed related to natural disturbances as well as human activities. External (rain) and internal (earthquakes) events can cause pressure transients in the fluid system within hours or several days, lasting from days to years and leading to changes in gas flux rates. The 2014 earthquake swarm triggered an estimated excess release of 175,000 tons of CO₂ during the following four years. Pressure oscillations were observed at a wellhead lasting 24 h with increasing amplitudes (from 10 to 40 kPa) and increasing frequencies reaching five cycles per hour. These oscillations are described for the first time as a potential natural analog to a two-phase pipe–relief valve system known from industrial applications.

The new in situ geodynamic laboratory established in the framework of the ICDP Eger project aims to develop the most modern, comprehensive, multiparameter laboratory at depth for studying earthquake swarms, crustal fluid flow, mantle-derived CO₂ and helium degassing, and processes of the deep biosphere. In order to reach a new level of high-frequency, near-source and multiparameter observation of earthquake swarms and related phenomena, such a laboratory comprises a set of shallow boreholes with high-frequency 3-D seismic arrays as well as modern continuous real-time fluid monitoring at depth and the study of the deep biosphere. This laboratory is located in the western part of the Eger Rift at the border of the Czech Republic and Germany (in the West Bohemia–Vogtland geodynamic region) and comprises a set of five boreholes around the seismoactive zone. To date, all monitoring boreholes have been drilled. This includes the seismic monitoring boreholes S1, S2 and S3 in the crystalline units north and east of the major Nový Kostel seismogenic zone, borehole F3 in the Hartoušov mofette field and borehole S4 in the newly discovered Bažina maar near Libá. Supplementary borehole P1 is being prepared in the Neualbenreuth maar for paleoclimate and biological research. At each of these sites, a borehole broadband seismometer will be installed, and sites S1, S2 and S3 will also host a 3-D seismic array composed of a vertical geophone chain and surface seismic array. Seismic instrumenting has been completed in the S1 borehole and is in preparation in the remaining four monitoring boreholes. The continuous fluid monitoring site of Hartoušov includes three boreholes, F1, F2 and F3, and a pilot monitoring phase is underway. The laboratory also enables one to analyze microbial activity at CO₂ mofettes and maar structures in the context of changes in habitats. The drillings into the maar volcanoes contribute to a better understanding of the Quaternary paleoclimate and volcanic activity.

The concepts of CO₂ emission, global warming, climate change, and their environmental impacts are of utmost importance for the understanding and protection of the ecosystems. Among the natural sources of gases into the atmosphere, the contribution of geogenic sources plays a crucial role. However, while subaerial emissions are widely studied, submarine outgassing is not yet well understood. In this study, we review and catalog 122 literature and unpublished data of submarine emissions distributed in ten coastal areas of the Aegean Sea. This catalog includes descriptions of the degassing vents through in situ observations, their chemical and isotopic compositions, and flux estimations. Temperatures and pH data of surface seawaters in four areas affected by submarine degassing are also presented. This overview provides useful information to researchers studying the impact of enhanced seawater CO₂ concentrations related either to increasing CO₂ levels in the atmosphere or leaking carbon capture and storage systems.

The Cheb Basin (Czech Republic) is characterized by emanations of magma-derived gases and repeated occurrences of mid-crustal earthquake swarms with small to intermediate magnitudes (M_L < 4.5). Associated intense mantle degassing occurs at the Hartoušov Mofette, a representative site for the Cheb Basin. Here, we performed 14 sampling campaigns between June 2019 and March 2020. Gas samples of fluids ascending in two boreholes (F1, ∼28 m depth and F2, ∼108 m depth) and from a nearby natural mofette were analyzed for their chemical (CO₂, N₂, O₂, Ar, He, CH₄, and H₂) and isotope compositions (noble gases and CO₂). CO₂ concentrations were above 99.1% in most samples, while O₂ and N₂ were below 0.6%. He ranged from 19 to 34 μmol/mol and CH₄ was mostly below 12 μmol/mol. Isotope compositions of helium and carbon in CO₂ ranged from 5.39 to 5.86 R_A and from −2.4 to −1.3 ‰ versus VPDB, respectively. Solubility differences of the investigated gases resulted in fluctuations of their chemical compositions. These differences were accompanied by observed changes of gas fluxes in the field and at the monitoring station for F1. Variations in solubilities and fluxes also impacted the chemical concentration of the gases and the δ¹³C values that were also likely influenced by Fischer-Tropsch type reactions. The combination of (a) the Bernard ratio, (b) CH₄/³He distributions, (c) P-T conditions, (d) heat flow, and (e) the sedimentary regime led to the hypothesis that CH₄ may be of mixed biogenic and volcanic/geothermal origin with a noticeable atmospheric contribution. The drilling of a third borehole (F3) with a depth of ∼238 m in August 2019 has been crucial for providing insights into the complex system of Hartoušov Mofette.

Greece belongs to the most geodynamically active regions of the world and as such, it has to be considered an area of intense geogenic degassing. In terms of carbon, the territory is characterized by the high hydrothermal and volcanic activity of the South Aegean Active Volcanic Arc (SAAVA), and by widespread geological seeps of buried carbon dioxide and methane. In the present work, we investigate the island of Gyali located in the volcanic system Kos-Gyali-Nisyros. Nine gas samples have been collected on the island of Gyali in areas found both on land, in a small lake (~2000 m2) along its beach, and in the sea close to the shore at shallow depths (