Samuel Niedermann

The Woodfjorden area in northwestern Svalbard hosts the world's northernmost onshore thermal springs, extinct Quaternary volcanoes (the Bockfjorden Volcanic Complex), late Miocene lava flows (the Seidfjellet Formation) that overlie a Devonian sedimentary basin, and a long‐lived regional fault zone. To contribute to a better understanding of subsurface fluid flow in this volcanic region, we conducted a 3D magnetotelluric (MT) survey at 12 sites, combined with water and gas sampling at the thermal spring clusters (Trollkjeldene and Jotunkjeldene). While the MT survey has a limited aperture due to the remoteness of the region and complex logistics, the identified structural features put several constraints on the evolution of this poorly studied hydrothermal system. The electrically conductive zones (1–10 m), under Trollkjeldene and the Halvdanpiggen volcanic center, are interpreted as signatures of deep hydrothermal fluids or mineralized zones; the resistive anomalies (1–10 km) at 1–4 km depth under the Sverrefjllet volcano indicate buried magmatic or basement rocks. Stable isotope data indicate both meteoric and crustal components for thermal waters. Carbon and noble gas isotope ratios support a mixed gas source involving crustal, atmospheric, and mantle components. Helium isotope ratios suggest a mantle‐derived fraction of 6%–8%. These findings suggest extinct magmatic activity and ongoing hydrothermal circulation, likely prolonged due to fluid compartmentalization at depth by low‐permeability magmatic or metamorphic rocks.

CO₂ flux measurements have become an essential tool in volcanic monitoring, yet standardized methodologies remain critical for cross-study comparability. Here, we present a newly acquired CO₂ flux dataset from the Escarot mofette field, processed using a partially automated geostatistical web application that minimizes user subjectivity. We calculate a CO₂ emission rate of 810 ± 110 t yr⁻¹, one order of magnitude lower than the 8,100 ± 1,800 t yr⁻¹ reported in 2018. Recalculating the 2018 dataset with the same methodology yields 510 t yr⁻¹, revealing a real increase of ~300 t yr⁻¹ (~60%) over eight years. Air-corrected ³He/⁴He ratios of 5.93–6.38 Rₐ confirm a subcontinental lithospheric mantle (SCLM) signature, while δ13CCO2 values of −1.67 to −1.62‰ suggest secondary chemical and physical fractionation processes potentially driven by enhanced deep-sourced fluid flux. Complementarily, δ13CCH4 values further support an abiotic gas origin. The Escarot system appears to be in geochemical disequilibrium over the past decade, potentially coupled with the contemporaneous regional seismic activity. Thus, it represents an ideal natural laboratory to investigate total CO2 emissions from a dormant, intraplate volcanic system structurally controlled by regional tectonics.

Recent clusters of deep, low-frequency earthquakes southeast of Laacher See in the East Eifel region of Germany suggest the presence of an active magmatic system in the lower crust and upper mantle. Measuring fluid data at the Earth's surface could help identify processes in the deep magma system. Dense and continuous monitoring is required to distinguish between environmental and deep processes, but this is rarely carried out. Here, we present a pilot study of an intracontinental, distributed volcanic field in the Eifel, where twelve measuring stations have been installed since 2020 in decommissioned CO₂ wells, mofettes, CO₂-rich springs, CO₂-rich soil, and a cold-water geyser. For the first time, fluid data is being recorded continuously with a high temporal resolution of up to 1 Hz. Interestingly, seasonal variations in fluid parameters are relatively small, and baseline data was determined within two to three years. Short-term transients were observed at individual network stations and were related to events such as heavy rainfall, atmospheric pressure waves, or local and distant earthquakes. However, over longer periods, we also observed trend changes in important magmatic indicators, such as helium isotope ratios, radon concentration, and water temperature. For instance, one location exhibited notable shifts in helium isotopes from 2021 to 2025, seemingly correlating with earthquake swarms at depth. These examples underscore the importance of establishing a network of fluid measuring stations, conducting continuous monitoring, and jointly evaluating meteorological, hydrogeological, geophysical, and geodetic data. Graphical Abstract

The Philippine Archipelago resulted from a series of subduction events, the most recent being still active, and arc-continent collision, forming today a series of active volcanic fields and ophiolites. As such the Philippine Mobile Belt constitutes a unique place where to study the spatial distribution and origin of mantle degassing fluxes during plate convergence.We present the geochemical composition of 12 gas samples collected from various locations across the Philippine archipelago. These include samples from Luzon Island-specifically five wells from the MakBan volcanic geothermal field- three bubbling springs in the Laguna region (Silva, Hernandez, and Silva 2 springs), and a bubbling seep near a river at Poon Bato in Zambales. Additional samples were collected from three bubbling springs on Palawan Island (Bato Bato, Sta. Lourdes, and Sta. Lucia hot springs).Preliminary results of major compound geochemistry reveal two main fluid families. Samples from the geothermal area are dominated by isotopically heavy CO₂ (-4 to -2‰ VPDB), with concentrations reaching 97%. These samples also contain H₂S (up to 2%) and H₂ (up to 0.6%) with δD_H₂ values ranging from -490 to -440‰ VSMOW. Their composition, coupled with measured ³He/⁴He ratios of up to 6.8 R/Ra, indicates a mantle origin influenced by volatiles from the subduction zone. In contrast, samples from the Laguna springs are characterized by high N₂ concentrations (up to 78%) and CO₂ (up to 15%) with δ¹³C_CO₂ values around -10‰ VPDB, suggesting significant interaction with shallow aquifers that may contain dissolved air (e.g., ASW-like N₂).On Palawan Island, the gas compositions vary: CO₂ (60%) and N₂ (29%) dominate at Sta. Lourdes spring, while N₂ and CH₄ dominate at Bato Bato (N₂ = 68%; CH₄ = 20%) and Sta. Lucia springs (N₂ = 85%; CH₄ = 5%). The Poon Bato seep in Zambales consists mainly of N₂ (75%), H₂ (8%), and CH₄ (4%). The emissions from Bato Bato, Sta. Lucia, and Poon Bato are associated with ultramafic rocks of ophiolite complexes. Factors such as elevated pH values at Bato Bato and Sta. Lucia (pH = 9.5–10), high H₂ concentrations with δD_H₂ = -724‰ at Poon Bato, and the presence of potentially inorganic CH₄ (δ¹³C_CH₄ = -40 to -20‰ VPDB) suggest that serpentinization is a likely origin for these fluids.Further interpretation of gas origins will benefit from ongoing analyses of noble gas data, which are currently in progress.

Dating alluvial-fan or river-terrace surfaces that are more than several tens of kyr old is challenging in many environments. Depth profiles of samples can be difficult to extract in the field, time consuming to process in the lab, and expensive to analyze. Even under idealized sampling conditions, the difficulty of constraining possible surface erosion or inflation can lead to large uncertainties in the surface exposure age. Alternatively, sampling individual boulder surfaces or cobbles may be logistically simpler, but large scatter in ages can be difficult to explain, given the possibility that the boulders/cobbles have rotated from their original position, surfaces experienced erosion, or the clasts may have some inherited concentration of cosmogenic nuclides. All of these problems are exacerbated in surfaces that have been exposed for hundreds of kyr.In the Toro Basin of NW Argentina, a set of alluvial-fan surfaces has recently been interpreted to comprise two generations, one likely spanning from ca. 500 to 800 ka, and another less than 100 ka, based on 10Be exposure ages of individual boulder surfaces and one depth profile. Here, we report 21Ne data from a subset of the boulder surfaces with the aim of better constraining the ages.Despite the apparently simple geomorphic setting of the fans, dual-nuclide (“banana”) plots of 21Ne and 10Be data reveal that most of the boulders have a complex burial history, with inferred burial times up to ca. 750 kyr. This finding implies that the boulders were not simply transported from nearby bedrock hillslopes and exposed on the fan surfaces. Instead, the boulders must represent exhumed rocks from an earlier generation of basin filling, which is constrained to between 4.5 and 0.85 Ma in the vicinity of the fans from U-Pb zircon dating of intercalated ashes (Pingel et al., 2020). We use a Monte Carlo approach to explore what possible range of initial exposure times, burial times, and final exposure times are consistent with the 10Be and 21Ne data on any given surface. For several surfaces, parameters trade off such that a wide range of exposure ages is possible. However, if we also take into account the stratigraphic relationships among the surfaces (higher surfaces must be older), and we consider that boulders exposed in the highest surface must have burial times that are shorter than boulders exhumed from lower elevations, relatively tight constraints on exposure ages, inherited nuclide concentrations, and boulder-surface erosion rates are possible on some of the surfaces.

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.

The rapid response of Patagonian topography to ice-mass changes, facilitated by the presence of a slab-window, offers an ideal setting for investigating the interplay between surface processes, climate dynamics, and solid Earth rheology. This study focuses on glacio-fluvial terrace sequences of the Río Santa Cruz and Río Shehuen (50ºS), which are fed by glacial meltwater from the Southern Patagonian Icefield and extend for over 200 km along the entire length of the river. Recent research in Patagonia demonstrates that glacio-fluvial gravels from terraces formed in the vicinity of glacier outlets can be reliably correlated to glacial terminations. Thus, these cut-and-fill terrace sequences provide a geomorphic archive uniquely positioned to directly correlate landscape responses with periodic climate forcing. Yet, the spatially extensive preservation of these terraces over 100s of kilometers likely reflects the influence of geodynamic processes active over continental length-scales. Radiometric dating of basalts overlying the oldest terrace generations documents eastward-draining paleo-valleys by 3.2 Ma. New surface exposure-dating of terraces using in situ cosmogenic 10Be and 21Ne reveal onset of net incision at ~1 Ma, with individual terrace ages well-correlated to Patagonian glaciations and global cold periods. We attribute terrace abandonment and incision following glacial cycles to a drop in sediment supply relative to water discharge, likely influenced by the formation of a proglacial lake (Lago Argentino). While the onset of net incision aligns with the decline of the greatest ice extent in Patagonia and the Mid-Pleistocene Transition (MPT), terrace ages and geometry underscore the need to link net incision to regional geodynamic processes. Sub-parallel, vertically offset terrace profiles require a regional base-level fall of 100 m since 1 Ma, while terrace age-elevation relationships show a temporally non-uniform regional incision history. These observations cannot be explained by climatically-forced sediment supply variation, but likely relate to the evolution of the mantle underlying the slab window. Our study highlights the complex interplay between climate-driven factors and regional geodynamics in shaping the fluvial landscape of southern Patagonia.