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Radon (Rn) and helium (He) gases from uranium decay form distinct anomalies related to buried uranium deposits. In order to trace the geochemical anomalous sources from the volcanic-related uranium deposits in deeply buried areas, systematical Rn contents and He isotope ratios were analyzed from the Daguanchang uranium deposit. The soil gas Rn concentrations above the deep uranium are ten times higher than those in barren areas, indicating that instantaneous Rn content measurements can be used to detect deeply buried uranium. The helium isotope ratios (3He/4He) of the unmineralized samples from the mineralized drill hole (ZK1) are relatively lower and uniform compared to those of the samples from no-mineral drill hole (ZK2). However, the Th and U contents of the drill core samples from ZK1 are slightly lower than those of the samples from ZK2, indicating that the lower 3He/4He ratios in ZK1 are most likely due to the addition of 4He from underlying uranium intervals. The differences in the instantaneous Rn contents are consistent with the variations in the He isotope ratios of the drill core samples. These results demonstrate that soil gas Rn and 3He/4He ratios are useful tracers and can indicate the existence of deeply buried volcanic-related hydrothermal uranium ores. [ABSTRACT FROM AUTHOR]

On New Year's Day 2024, a magnitude 7.6 event struck the Noto Peninsula in central Japan. Prior to this event, an intense earthquake swarm had persisted beneath the northeastern peninsula for more than five years. Geophysical evidence provides insight into the upwelling of deep fluids from the uppermost mantle that triggers the seismic swarm activity. The noble gases and their isotopes have been used as geochemical indicators to determine the origin of the fluids associated with the swarms and their upwelling. Gas samples collected from boreholes around the seismic source region are characterized by anomalously high 3He/4He ratios (∼3.9 RAcor), indicating infiltration of mantle fluids from the subcrustal lithosphere. Using a steady‐state advection model, we calculated mantle helium fluxes of 1.1–2.4 × 10−15 mol cm−2 a−1, similar to those estimated for other representative fault zones, such as the San Andreas and North Anatolian faults. Plain Language Summary: In the Noto Peninsula, central Japan, a long‐lasting, intense earthquake swarm has continued since May 2018. On 1 January 2024, the largest M 7.6 earthquake to date occurred. Geophysical evidence provides insight into the upwelling of deep fluids from the uppermost mantle that triggers the seismic swarm activity. The origin of fluids associated with earthquake swarms and their upward fluxes were determined using noble gases and their isotopes. We collected gas samples from hot spring wells around the seismic source region of earthquake swarms. The observed 3He/4He ratios several times higher than the atmospheric value. This indicates infiltration of mantle fluids derived from the subcrustal lithosphere. In addition, we calculated mantle helium fluxes of ∼2.4 × 10−15 mol cm−2 a−1, which is consistent with estimates for other major fault zones around the world. Key Points: Before the M 7.6 earthquake that occurred in the Noto Peninsula on 1 January, there was a persistent earthquake swarm for over five yearsElevated 3He/4He ratios in gas samples from hot spring wells suggest the emission of mantle‐derived helium from the seismic source regionThe mantle fluids infiltrate the seismogenic crust and then diffuse in the fault zone, triggering the earthquake swarm [ABSTRACT FROM AUTHOR]

Helium is an irreplaceable ore resource for many applications, such as nuclear magnetic resonance, aviation, semiconductors, and nuclear energy. Extracting helium in a free state from natural gas is currently the only economical approach at the industrial level. In this study, we compiled geochemical data of 719 natural gas samples from 36 oil and gas fields in the Tarim basin that include experimental results and previously reported data. Helium is of primarily crustal origin in the Tarim Basin according to helium isotope characteristics (not exceeding 0.1 Ra), except in the Ake gas field that has not more than 7% of mantle helium. Helium concentrations in diverse tectonic units vary considerably. Oil-type gas, on the whole, has a higher helium concentration relative to coal-type gas. Abundant helium flux, a favorable fault system between the source-reservoir system, no strong charging of gaseous hydrocarbons, and the good sealing capacity are important factors that control the formation of helium-rich gas fields. Considering both the helium concentration and natural gas reserves, helium-rich gas fields located in the Southwest Depression and Tabei Uplift can be regarded as the major favorable zones of further deployment for helium extraction. [ABSTRACT FROM AUTHOR]

Hydrogen pumps, crafted from proton-conductive ceramic electrolyte and paired with either oxide or metallic electrodes, have been designed for the extraction of hydrogen isotopes from helium gas mixtures containing 0.1 % hydrogen isotopes, particularly within the context of TES for nuclear fusion reactors. This study presents the electrochemical hydrogen permeation research conducted on the perovskite proton conductor materials BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) and BaZr 0.8 Y 0.16 Ni 0.04 O 3-δ (BZYN) under these operational conditions. It was observed that nickel electrodes provided superior performance over SrFe 0.8 Mo 0.2 O 3-δ (SFM) electrodes in terms of hydrogen extraction efficiency. Hydrogen pumps that integrated BZCYYb as the electrolyte with nickel electrodes showed enhanced efficiency, while those utilizing BZYN as the electrolyte coupled with nickel electrodes demonstrated greater stability. Furthermore, the study explored the voltammetric nonlinearity at low hydrogen concentrations and the dependency of concentration polarization efficiency on both voltage and temperature, aiming to establish optimal conditions that balance stability and efficiency for both types of hydrogen pumps. [ABSTRACT FROM AUTHOR]

For decades, superfluid helium has attracted the interest of the scientific community as an extremely pure realisation of a quantum liquid, only accessible at temperatures close to absolute zero. Previously, helium films have only been observed directly using X-rays. However, this method is limited to temperatures above 1 K due to the high levels of energy deposition, and it also suffers from an inability to distinguish between helium isotopes. Here we show that a 3He layer on top of a phase separated mixture film at 170 mK gradually dissolves into the 4He with increasing temperature. We also observe an anomaly in film behaviour near 300 mK and unexpected restoration of the layered structure at 1.5 K which is consistent with a re-entrant phase transition leading to the suppression of superfluidity in the film near 300 mK. Our successful application of neutron scattering to study helium films at ultra-low temperatures opens up new possibilities for future research. Superfluidity, a liquid exhibiting frictionless flow, is so far limited to observations in low-temperature 3He and 4He, where the underlying mechanisms governing the quantum state are complex and different for each isotope, making for a fascinating but challenging phenomenon to study experimentally. The authors use isotope-sensitive neutron reflectometry to investigate mixed 3He/4He superfluid He films on a Si surface, and resolve the structural features and phase transitions that occur with changing temperature. [ABSTRACT FROM AUTHOR]

Pyroxenites, comprising only approximately 2 %–10 % by volume of the upper mantle, are among the most important lithological heterogeneity in the mantle. The formation of pyroxenite veins within peridotites is often attributed to migrating melts which provides an important mechanism for crust-mantle interaction. The Re–Os isotope system provides valuable insight into crust-mantle interaction, as there is a significant contrast in 187Os/188Os between crustal and mantle rocks. Previous Os isotope studies have shown that the forearc mantle wedge mainly consists of highly heterogeneous ancient peridotites. However, limited Re–Os isotope data of forearc mantle pyroxenites exist. Here, two types of mantle pyroxenites from the New Caledonia forearc ophiolite were selected for a comparative study. Contrasting microtextures and geochemical compositions support that these pyroxenites were formed by different processes. The Massif du Sud pyroxenites, hosted in harzburgites, have a cumulate origin and crystallized from boninitic melts generated by remelting of depleted mantle during subduction initiation, whereas the Tiebaghi pyroxenites within the host lherzolites are the products of melt-peridotite reactions. Both types of pyroxenites display highly fractionated highly siderophile element (HSE) patterns. The Massif du Sud pyroxenites are strongly enriched in palladium group platinum-group elements (PPGE) relative to iridium group platinum-group elements (IPGE) with remarkable positive Pt anomalies, which are similar to those of primitive arc lavas and mantle wedge pyroxenite xenoliths. In contrast, the Tiebaghi pyroxenites have flat IPGE but variable PPGE and Re patterns. Compared to the forearc mantle peridotites, the Tiebaghi pyroxenites have higher Os isotope ratios. Ancient basaltic melt percolation followed by long-term (>1 Ga) radiogenic ingrowth can successfully produce the observed correlations of 187Os/188Os with Os or Al 2 O 3 contents. Besides, the oldest Re-depletion model age (T RD) of ∼1.35 Ga has been obtained for the host lherzolites. Therefore, the Tiebaghi pyroxenites and their host lherzolites probably represent a stranded old mantle relict that has undergone ancient partial melting and melt percolation events. Our study supports the presence of highly radiogenic mantle domains in the forearc and provides significant constraints on the role of ancient basaltic melt percolation for generating mantle heterogeneity. [ABSTRACT FROM AUTHOR]

The origin of methane in hydrothermal fluids has long been a subject of debate – whether it is abiotic or biotic. In this study, we aim to unravel and quantify the sources of CH 4 in active hydrothermal systems by adopting a holistic approach analyzing well characterized high-temperature hydrothermal fluids (∼230–310 °C) in Iceland. We employ a broad variety of geochemical and isotope indicators, encompassing chemical and isotope compositions of the targeted fluids. These signatures are then compared with results from chemical and isotope kinetic models and data from sedimentary-hosted hydrothermal systems. Carbon species in these fluids include CO 2 (2.60–184 mmol/kg), CH 4 (2.39·10−4–0.325 mmol/kg), dissolved organic carbon (4.78·10−3–0.112 mmol/kg), and CO (1.89·10−6–4.16·10−4 mmol/kg). Carbon and helium isotopes suggest a relatively uniform mantle-derived source of CO 2 (δ13C-CO 2 : −4.80 to −1.50 ‰, CO 2 /3He: 1.49·109–4.14·1010 14C-CO 2 : 0.11–2.42 pMC). Methane, in contrast, has multiple sources. Overall, chemical equilibria among carbon species (CO 2 , CH 4 , CO) is not attained, suggesting kinetic controls. Tritium content (<0.8–1.42 TU) and hydrologic constraints indicate relatively short hydrothermal fluid residence times (∼5–200 years), with occasional inputs from older water components. Within this short timeframe, CH 4 concentrations vary from lower, to significantly higher than those calculated using CO 2 reduction kinetics. The isotope composition (δD-CH 4 : −172 to −138 ‰, δ13C-CH 4 : −32.0 to −24.6 ‰; 14C-CH 4 : 0.36–11.54 pMC) and geochemical and isotope modeling suggest that the majority (>80–90 %) of CH 4 originates from a radiocarbon inactive source, i.e. mantle CH 4 , reduction of mantle CO 2 and/or old organic matter, with relatively small contributions from both marine (<20 %) and terrestrial (<10 %) dissolved organic carbon. Measured isotopic compositions of CH 4 do not match those expected for mantle-derived CH 4 as well as values generated from reduction of mantle-derived CO 2. Instead, differences in δD-CH 4 and δ13C-CH 4 values exist between systems fed by meteoric water and those fed by seawater, challenging the assumption of a uniform CO 2 source and invariable reaction mechanisms. Differences between systems are best explained by variable extent of thermal decomposition and primary variations in the isotope composition of marine and terrestrial organic matter. Also, δD-CH 4 and δ13C-CH 4 values in meteoric water-fed systems closely resemble those in the Öxarfjördur sedimentary-hosted systems. In summary, our data supports a predominant thermogenic origin of CH 4 in both seawater and terrestrial hydrothermal fluids in Iceland. The source of organic matter appears to be a combination of modern dissolved organic carbon and older sedimentary deposits. In addition, some of the hydrothermal systems studied (Krafla, Reykjanes, Theistareykir) which are characterized by low CH 4 concentrations, may contain a significant portion of CH 4 that may originate from CO 2 reduction. [ABSTRACT FROM AUTHOR]

Abstract On New Year's Day 2024, a magnitude 7.6 event struck the Noto Peninsula in central Japan. Prior to this event, an intense earthquake swarm had persisted beneath the northeastern peninsula for more than five years. Geophysical evidence provides insight into the upwelling of deep fluids from the uppermost mantle that triggers the seismic swarm activity. The noble gases and their isotopes have been used as geochemical indicators to determine the origin of the fluids associated with the swarms and their upwelling. Gas samples collected from boreholes around the seismic source region are characterized by anomalously high 3He/4He ratios (∼3.9 RAcor), indicating infiltration of mantle fluids from the subcrustal lithosphere. Using a steady‐state advection model, we calculated mantle helium fluxes of 1.1–2.4 × 10−15 mol cm−2 a−1, similar to those estimated for other representative fault zones, such as the San Andreas and North Anatolian faults.

Molybdenum is used as plasma-facing material in tokamaks and as material for plasma optical diagnostics mirrors. Harsh conditions of neutron irradiation, exposure to hydrogen isotopes and helium ions, and high operating temperatures result in degradation of the molybdenum surface and ultimately limit their lifetime in a fusion power plant. In the current paper, intake and subsequent thermal release of deuterium from self-irradiated by high energy (1 MeV) ions molybdenum as a function of irradiation dose are investigated. Several characteristic temperature regions where deuterium release takes place are identified and attributed to trapping of deuterium in intrinsic and radiation-induced microstructure defects. This attribution is further validated by molecular dynamics modeling, which confirms that increase and saturation of vacancy concentration found in simulations follows increase and saturation of experimentally determined deuterium content. Deuterium inventory and vacancy content saturate at a damage level of around 0.2 dpa (displacement per atom), similar to recent modeling and experimental studies of iron and tungsten. Reflectivity measurements of irradiated molybdenum show that it is only slightly affected by damage up to 1 dpa. [ABSTRACT FROM AUTHOR]

The Three Rivers Lateral Collision Zone (TRLCZ), situated at the southeastern margin of the Tibetan Plateau, is a crucial frontier where materials from the plateau flow southeastward. This study extensively investigated the hydrochemical characteristics and origin of helium and carbon isotopes in 73 thermal springs within the TRLCZ. The analysis revealed dominant processes, including carbonate and silicate interactions, resulting in elevated concentrations of HCO3− and Na+. The impact of Ca/Mg-rich minerals, particularly dolomite, influenced the cation composition. Additionally, gypsum dissolution, notably in the Lancangjiang Fault and Weixi–Qiaohou Fault, was highlighted through Ca/SO4 ratios. The positive correlation between SO42− and Cl− indicated dilution by shallow cold water, explaining the lower SO42− content in the Jingshajiang–Zhongdian Fault and Nujiang Fault compared to the Weixi–Qiaohou Fault and Lancangjiang Fault. The circulation depth of thermal spring water varied, with the northern Weixi–Qiaohou Fault exhibiting the shallowest circulation depth (~3 km), while the Jingshajiang–Zhongdian Fault and southern segments of the Nujiang Fault displayed deeper depths—ranging from 4 to 7 km. A positive correlation between the circulation depth and fault activity was also observed. The Rc/Ra ratios of free gas samples, predominantly indicating crustal origin, varied from 0.01 Ra to 0.53 Ra. Elevated Rc/Ra ratios in the research area suggested potential minor additions of mantle helium through faults and fractures. Crustal limestone was identified as the primary source of CO2-rich samples, with δ13CCO2 values ranging from −1.6‰ to −7.2‰, while trace amounts of mantle CO2 were found. The spatial distribution of the H2 concentration, CO2 concentration, He concentration, and mantle He proportions in gases indicated that higher values of He concentration and mantle He% always occur near sampling points with deeper circulation depths. However, no similar correlation was observed for H2 and CO2. Most earthquakes of magnitude 5 or greater occurred near the regions with high values of mantle source He release, highlighting the critical role of mantle fluids in the occurrence of earthquakes in the region. In this study, a fluid circulation model was developed to describe the process of fluid (water and gas) circulation migration and earthquake generation in the TRLCZ. [ABSTRACT FROM AUTHOR]

A comprehensive three-dimensional numerical model for the modulation of cosmic rays in the heliosphere is applied to investigate the relative roles of the time dependence of the elements of the diffusion tensor on the proton to total Helium (p/He) and Helium-3 to Helium-4 (3He 2 /4He 2) ratios at rigidities below 3 GV. At these rigidities the ratios have been observed by both PAMELA and AMS-02 detectors to have a time variation in response to changing solar activity. We found that the contribution of the time dependence of the perpendicular diffusion in the radial direction of the heliosphere is the dominant cause of this observed time variation, especially in the A < 0 magnetic field cycle, and not any fundamental difference between the solar modulation of galactic protons and He-isotopes. It follows that neglecting this time dependence from numerical models, both in value and its rigidity dependence, would produce time trends in the mentioned ratios that are incompatible with observed trends at the Earth. Furthermore, we found differences in the computed time trends of p/He and 3He 2 /4He 2 ratios at rigidities below 1.5 GV. This is mainly a consequence of an interplay between perpendicular diffusion in the radial direction and adiabatic energy losses which begin to influence modulated spectra at a higher rigidity for 3He 2 than for 4He 2 , and for total He than for protons. [ABSTRACT FROM AUTHOR]

The detection of hydrogen isotopes is not only the premise of ensuring safety of hydrogen energy, but also has very important application value and scientific significance in the field of fusion energy. Therefore, it is imperative to develop efficient and reliable hydrogen isotope sensors. Herein, a thermal-assisted resistive sensor is constructed based on the hydrogen isotope effect of PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere. The permeation of hydrogen isotopes in palladium lattice is facilitated through thermal effect to improve the dynamic response capability of sensor. The research results show that the response time of sensor to hydrogen and deuterium is reduced from 192 s to 113 s–17 s and 10 s respectively. However, the sensitivity deteriorated by about 40% at 110 °C compared with room temperature. Meanwhile, the PdCr alloy thin film resistive sensor represents a remarkable linear response in a range of 0.1%–4% hydrogen and deuterium, with correlation coefficients of 0.9971 and 0.9998 respectively. And the response difference of hydrogen and deuterium may be utilized to discriminate hydrogen isotopes. Furthermore, the sensor exhibits prominent selectivity, extraordinary working stability and a wide range of 100ppm-100%. Therefore, this work presents a feasible approach to design high-performance resistive hydrogen isotope sensors for the development of hydrogen energy and fusion energy. Schematic illustrations of the PdCr alloy thin film resistive sensor (a), dynamic sensitivity curve to H 2 /He and D 2 /He (b) and the influence of thermal effect on hydrogen isotope permeation process (c). [Display omitted] • A thermal-assisted resistive sensor based on the PdCr alloy thin film is constructed. • The sensor exhibits rapid response/recovery performances and reversible characteristics. • The response difference of hydrogen and deuterium may be utilized to discriminate hydrogen isotopes. • This work presents a feasible approach to design high-performance hydrogen isotope sensors. [ABSTRACT FROM AUTHOR]

A previously undocumented shallow water hydrothermal field from Sicily (Southern Tyrrhenian Sea, Italy) is here described, based on a multidisciplinary investigation. The field, covering an area of nearly 8000 m2 and a depth from the surface to -5 m, was explored in June 2021 to characterise the main physico-chemical features of the water column, describe the bottom topography and features, and identify the main megabenthic and nektonic species. Twenty sites were investigated to characterise the carbonate system. Values of pH ranged between 7.84 and 8.04, ΩCa between 3.68 and 5.24 and ΩAr from 2.41 to 3.44. Geochemical analyses of hydrothermal gases revealed a dominance of CO2 (98.1%) together with small amounts of oxygen and reactive gases. Helium isotope ratios (R/Ra = 2.51) and δ13CCO2 suggest an inorganic origin of hydrothermal degassing of CO2 and the ascent of heat and deep-seated magmatic fluids to the surface. Visual census of fishes and megabenthos (mainly sessile organisms) allowed the identification of 64 species, four of which are protected by the SPA/BIO Protocol and two by the International Union for Conservation of Nature. The macroalgae Halopteris scoparia and Jania rubens and the sponge Sarcotragus sp. were the dominant taxa in the area, while among fishes Coris julis and Chromis chromis were the most abundant species. This preliminary investigation of San Giorgio vent field suggests that the site could be of interest and suitable for future experimental studies of ocean acidification. [ABSTRACT FROM AUTHOR]

Mantle‐derived volatile degassing lacks quantitative evaluation in continental regions without active magmatism, such as the Tibetan Plateau. Ten new gas abundance and helium isotope data points combined with 286 hydrothermal volatile literature data points in India–Asia continental collision settings demonstrate widespread mantle‐derived volatiles across the thick (∼70 km) crust. The mantle‐derived 3He is best explained by direct mantle volatile input from subcontinental lithospheric mantle (1%–36.5%) or the asthenospheric wedge (1%–27.8%) instead of fossil residual magmatic fluids or Quaternary mantle‐derived melt intrusion into crustal depth. Mantle‐derived 3He is transported from the deep mantle to the surface at an upflow rate of 30–11,700 mm/year based on a newly developed steady‐state one‐dimensional flow model, corresponding to a mantle‐derived 3He flux of 17 to 1.5 × 107 atoms m−2 s−1 (81.7%–99.4% of the total 3He flux) and a mantle‐derived 4He flux from 2.0 × 106 to 1.8 × 1012 atoms m−2 s−1 (1.4%–36.5% of the total 4He flux). The mantle‐derived helium fluxes in the study area are comparable to those of other nonvolcanic hydrothermal systems in the tectonically active regions but lower than those of volcanic fields. The helium transit time ranges from 5.3 ka to 2.3 Ma, indicating that the spatial pattern of 3He/4He ratios in the India‐Asia continental collision settings can provide a snapshot of the state of the Indian mantle lithosphere between those revealed by potassic‐rich mafic rocks (25–8 Ma) and seismic methods (present). Key Points: 3He is derived directly from mantle depths instead of residual magmatic fluids or Quaternary mantle‐derived melt in the shallow crustThe vertical flow rate, flux and transit time of mantle‐derived 3He were systematically calculatedThe state of the Indian mantle lithosphere revealed by mantle‐derived 3He is between that revealed using petrologic and seismic methods [ABSTRACT FROM AUTHOR]

A common technique for determining the mass accumulation rates of marine sediments is through measurements of constant flux proxies. These proxies, like unsupported 230Th and extraterrestrial 3He, are buried at a known rate at the seafloor, and thus their concentration in sediments is inversely proportional to the vertical mass accumulation rate of ambient sediments. These two proxies have varied assumptions regarding their behavior that have been difficult to test, particularly in regions of very low sedimentation. We present new measurements of helium and thorium isotopes in coretop sediments from the South Pacific Gyre. Our main finding is that 230Th- and 3He-derived mass accumulation rates of these sediments differ by a factor of 2–10, with 230Th-based mass accumulation rates systematically higher than those derived from 3He. While the final cause of the discrepancy is difficult to elucidate, we suggest that up to a factor of 2 worth of the sedimentary 230Th deficit can be explained by lateral transport of 230Th, while the remainder must be explained by other processes, such as ancient coretops undercorrected for post-depositional 230Th decay. Regardless of the mechanism, our findings have critical implications for the application of constant flux proxies in the South Pacific Gyre, with one example being the calibration of dust deposition models in this region. Ultimately, additional testing is required to determine the accuracy of the 3He and 230Th techniques for estimating sediment accumulation rates in regions of the open ocean with extremely low sedimentation rates. [ABSTRACT FROM AUTHOR]

This study focus on the Mt Etna December 2018 eruption with the aim of investigating the geochemical characteristics of the feeding magma. New data on major and trace element geochemistry of olivine-hosted melt inclusions (MI) in volcanic products are presented together with the noble gas geochemistry of fluid inclusions (FI) in olivines. The noble gas geochemistry of fluid inclusions (FIs) in olivines was also investigated. The major element composition of MIs is variable from tephrite/trachybasalt to phonotephrite/basaltic trachyandesite, with SiO2 = 45.51-52.72 wt%, MgO = 4.01-6.02 wt%, and CaO/Al2O3 = 0.34-0.72. Trace element patterns of MIs present a typical enrichment in LILE and LREE, depletion in HFSE, and relatively fractionated REE patterns: (La/Lu) N= 18.8-41.08, with Eu/Eu* = (0.5-1.8). Positive anomalies in Sr (Sr/Sr* = 0.8-2.3) and Ba can be ascribed to the assimilation of plagioclase-rich cumulates in the magmatic reservoir. The variable Ba/La (9.8-15.8), K/Nb (260-1037), Ce/Nb (1.9-3.4), Rb/La (0.4-1.6), and Ba/Nb (10.8-25.8) ratios reveal mixing between two types of end-member magmas comparable to those emitted from 1) the 2001 Upper Vents and 2002-03 Northern Fissures (Type-1) and 2) the 2001 Lower Vents and 2002-03 Southern Fissures (Type-2), respectively. Type-2 represents a magma that was under the influence of a crustal component, whereas Type-1 is compatible with a HIMU-MORB-type heterogeneous mantle source. It appears that the 2018 MIs have captured the two different types of magmas, and the lack of homogenization may imply a very fast ascent (a few months). Compatible with the contemporary presence of primordial HIMU-MORB and crust-contaminated end-members are the data on noble gases from FI that highlighted an ³He/[sup 4]He value of 6.5-6.6Ra. The hypothesis of two different types of magmas, identified by the trace element geochemistry in MIs, is, thus, reinforced by helium isotopic data on FI of the 2018 eruption together with data from other Etnean eruptions and allows the inference of a bicomponent magma mixing. [ABSTRACT FROM AUTHOR]

This article presents the results of a comparative analysis of the isotopic–geochemical composition of gases from igneous/hydrothermal and sedimentary volcanic systems in various regions of the world based on a large amount of literature data and the results of the author's own research. The purpose of the study is to evaluate the nature of gases of various volcanic systems using known genetic criteria developed as a result of many years of research by a number of scientists from around the world. Data processing for the purpose of comparative analysis and corresponding graphical constructions have been performed using standard computer programs. A comprehensive analysis of the isotopic composition of carbon-rich gases and the isotopic ratio of helium (R/Ra) allows us to draw the following main conclusions: (1) hydrocarbon (HC) gases of the studied volcanic systems have different genetic sources: (a) abiogenic in igneous and carbonic sedimentary volcanic systems, (b) predominantly abiogenic–biogenic in the hydrothermal system, and (c) biogenic (thermogenic–microbial) in sedimentary volcanoes; (2) the content of abiogenic methane in the magmatic/hydrothermal system is insignificant and does not exceed 1%; (3) the isotope composition of CO2 and the ratio of isotopes of radiogenic and air argon (40Ar/36Ar) in igneous volcanoes varies within very narrow limits when compared with sedimentary volcanoes. However, the use of these parameters as an unambiguous genetic criterion is not possible. [ABSTRACT FROM AUTHOR]

Using a specially designed time-of-flight mass reflectron with a heating element inside the device, which makes it possible to heat solid samples and analyze the gases released from them, protective graphite tiles covering almost the entire plasma-facing surface of the Globus-M2 tokamak vacuum chamber were studied. Mass spectrometric analysis made it possible to determine the composition of the released gases to estimate their quantities, and thus to quantitatively characterize the quality of cleaning and degassing of tiles. It is shown that as a result of the applied method for processing tiles, the content of the light hydrogen isotope— protium, water, carbon monoxide and dioxide decreased several times, and the content of deuterium and helium isotopes decreased almost to zero. [ABSTRACT FROM AUTHOR]

Geothermal energy resources are abundant in the Qinghai Gonghe Basin. Helium isotope evidence indicates that the heat source of the high-temperature geothermal system of the basin is the crustal overlying melt, but the genesis of the melt is still unclear. The composition of 87Sr/86Sr, δ2H, and δ18O confirms that the hot water in the basin is recharged by atmospheric rainfall from the surrounding peaks at an elevation of 3500–5500 m. Based on a comparison with typical mantle-source thermal areas such as Yellowstone Park and Yangbajing, we found that the hot spring water of the Gonghe Basin is peripheral, not steam-heated or mantle-source. Na, K, and Mg composition shows that the reservoir temperature ranges from 140 to 240 ℃, indicating great resource potential. Rare gas isotopes indicate that only about 5% of the basin heat comes from the mantle. The numerical simulation found that the rapid uplift in local areas of the basin made the granite with high thermal conductivity exposed to the surface, resulting in a thermal refraction effect and local thermal anomaly. According to the results of this study, the high-temperature geothermal resources in the Gonghe Basin may not be evenly distributed throughout the whole basin, but in stripes concentrated in areas associated with tectonic uplifting, such as the eastern side of the South Mountain of Qinghai and the eastern and western sides of the Waliguan Mountain. [ABSTRACT FROM AUTHOR]

Geochemical investigations carried out on thermal waters over the Erzin-Hatay area allowed the collection of a suite of 9 samples from natural springs and one well characterized by outlet temperatures in the range from 19.6 to 31.5 °C. All of the springs have slightly acidic pH (in the range of 6) but one sample was marked by a pH value >11 as a consequence of serpentinization processes. The water chemistry denotes water/rock interactions with either magmatic or carbonatic rocks in a water reservoir equilibrated at temperatures estimated to be in the range of 58-162 °C. The stable isotope composition of the collected waters, in terms of dD and d18O, denotes a recharge from local meteoric waters. The dissolved gases denote the contribution of no atmospheric components. CO2 is the dominant dissolved component for most of the sample, while methane is the major component for the thermal water involved in serpentinization. Besides the main components CO2 and CH4, the dissolved gases show significant concentrations of He, H2, and CO. The isotopic composition of helium shows ³He/4He ratios well above that of Air Saturated Waters (ASW = 1.39 x 10-6) clearly indicating a significant contribution of 3He of mantle origin. Taking into account the location of some sampling sites nearby the Düziçiİskenderun Active Fault Zone and the associated mantle helium contribution, we propose that fluids/faults relationships have to be considered as responsible for the feeding of deep-originated fluids to the shallow groundwater. As mantle-derived fluids are also carriers of thermal energy, the collected results strongly suggest improving the knowledge of the study area, where hydrological and geochemical considerations coupled with the tectonic setting of the area should focus on the geothermal potential of the circulating waters. [ABSTRACT FROM AUTHOR]

Beta‐decay half‐lives for the free neutron, for 6He and 8He, and for 8Li are calculated ab initio from geometrical thermodynamics arguments, independently of any quantum mechanics. Half‐lives for the decay of 8Be to two alphas and for the disintegration of the tetraneutron are also calculated. The calculated values are close to those experimentally observed. [ABSTRACT FROM AUTHOR]

Identification of methane origins remains a challenging work as current diagnostic signals are often not sufficient to resolve individual formation and post‐formation processes. To address such a knowledge gap in a tectonically active and fragmented terrain, samples from mud volcanoes, gas seeps, and springs distributed along structural features onshore and offshore of Taiwan were analyzed for their isotopic compositions of methane, nitrogen, helium, dissolved inorganic carbon, CO2, and water. Our analyses yielded Δ13CH3D and Δ12CH2D2 values ranging between +1.9‰ and +7.8‰ and between +3.0‰ and +19.9‰, respectively. A portion of the samples were characterized by values that represent the thermodynamic equilibrium at temperatures of 99°–260°C. These temperature estimates, together with the bulk isotopic compositions and local geothermal gradients (25°–30°C/km), suggest that methane was formed by thermal maturation of organic matter at depths of 2–9 km below the land surface and channeled upward along faults. Other samples were found to deviate from equilibrium by varying degrees. Considering the geological background, helium isotopic ratios, and nitrogen isotopologue compositions, and methanogens detected at some sites, these gases are either abiotic in origin or a mixture of microbial and thermogenic sources. Regardless of whether the equilibrium of methane isotopologues was reached, few sites hosted by sedimentary formations were characterized by mantle‐like helium signatures, indicating decoupled origins and potential degassing of helium from the relic igneous source. Overall, these results suggest the extraction of methane and other gases from multiple depths from strata fragmented by fault displacement in an active orogenic belt. Plain Language Summary: Mud volcanoes and gas seeps are distributed primarily in active tectonic regimes and represent the surface expression of subsurface fracture networks. They provide rapid access to probing subsurface characteristics for the generations of methane, other gases, and water. Identifying the exact mechanisms of methane formation remains a challenging work due to the lack of diagnostic signals with sufficient resolving power. This study employed a wide range of isotopic tools to constrain the origins of gases and water from mud volcanoes and seeps in Taiwan, where dual subductions and associated arc‐continent collision between the Philippine Sea and Eurasian plates have enabled the plumbing of gases and water in accordance with structure development and stratum deformation. Our results reveal a spectrum of geochemical characteristics that point to diverse formation mechanisms and conditions. In particular, deeply sourced thermogenic methane (from depths of 2–9 km) appears to constitute a major gas component at most sites, and is mixed by various degrees with abiotic methane pertinent to igneous bodies emplaced during subduction/collision, or microbial methane generated at shallow depths. Overall, the results address the temporal and spatial variations in gas origins prone to terrain fragmentation and dynamic structural control associated with mountain building. Key Points: Mud volcanoes and gas seeps provide rapid access to probing subsurface fluid characteristics in tectonically active regionsThermogenic methane constitutes a major component of hydrocarbons and forms at temperatures of 99°–260°CA wide spectrum of geochemical characteristics indicates diverse formation mechanisms and conditions that constrain gas and water origins [ABSTRACT FROM AUTHOR]

Abstract Mantle‐derived volatile degassing lacks quantitative evaluation in continental regions without active magmatism, such as the Tibetan Plateau. Ten new gas abundance and helium isotope data points combined with 286 hydrothermal volatile literature data points in India–Asia continental collision settings demonstrate widespread mantle‐derived volatiles across the thick (∼70 km) crust. The mantle‐derived 3He is best explained by direct mantle volatile input from subcontinental lithospheric mantle (1%–36.5%) or the asthenospheric wedge (1%–27.8%) instead of fossil residual magmatic fluids or Quaternary mantle‐derived melt intrusion into crustal depth. Mantle‐derived 3He is transported from the deep mantle to the surface at an upflow rate of 30–11,700 mm/year based on a newly developed steady‐state one‐dimensional flow model, corresponding to a mantle‐derived 3He flux of 17 to 1.5 × 107 atoms m−2 s−1 (81.7%–99.4% of the total 3He flux) and a mantle‐derived 4He flux from 2.0 × 106 to 1.8 × 1012 atoms m−2 s−1 (1.4%–36.5% of the total 4He flux). The mantle‐derived helium fluxes in the study area are comparable to those of other nonvolcanic hydrothermal systems in the tectonically active regions but lower than those of volcanic fields. The helium transit time ranges from 5.3 ka to 2.3 Ma, indicating that the spatial pattern of 3He/4He ratios in the India‐Asia continental collision settings can provide a snapshot of the state of the Indian mantle lithosphere between those revealed by potassic‐rich mafic rocks (25–8 Ma) and seismic methods (present).

In recent decades, phenomenological methods known as Recognition of Earthquake-Prone Areas (REPA) were set up for identifying potential sites of powerful earthquakes. The information on potential earthquake sources provided by the REPA method is an essential part of seismic hazard assessment methodology. For the first time, we have combined global-scale information on the geographic occurrence of geofluids with global-scale information on earthquake occurrence, heat flow distribution, and S-wave dispersion, to gain insights into the evolution of local stress-strain fields. We focused on areas characterized by the occurrence of thermal waters and/or by the release of deep-seated gases, as traced by the isotope composition of associated helium. We noticed that the geographic distribution of these geofluids could serve as an indirect indicator of crustal permeability anomalies generated by crustal deformation procedures. This study proposes adding geofluids to the list of fundamental geological parameters to be considered in hazard assessment research.

This paper explores the operational performance parameter range for inertial confinement fusion propulsion systems under the assumption of best case and worst case mission scenarios. This includes the spacecraft thrust, jet power and specific power. We show the derivation of the key driving equations and then simplify these with approximations for ease of domain space analysis. This includes a consideration of minimum and maximum values for jet efficiency, momentum weighting factor, nozzle divergence angle, fuel burn-up fraction, capsule mass and detonation pulse frequency. It is estimated that the range of parameter values may be of order 0.001 N–100 MN thrust, 1000 W–1,000 TW jet power, 0.01 W/kg–10 GW/kg specific power. Although this range includes values that are likely outside the realistic design space of applicability and to show this data from published designs is also examined. The analysis is considered for reaction isotopes of low mass hydrogen and helium nuclei only and does not take into account the possibility of propellant expellant augmentation, vehicle staging, design optimality or enhanced fuel reactions. • Attempt to examine inertial fusion propulsion theory from a broad perspective. • Derivation of driving equations for various inertial fusion propulsion parameters. • Analysis of min-max range inertial fusion propulsion performance space missions. • Analysis of inertial fusion propulsion performance data from concept designs. • Map of fusion propulsion parameters to derive the requirements for missions. [ABSTRACT FROM AUTHOR]

In active volcanoes, magmatic fluids rising toward the surface may interact with shallow waters, thereby forming hydrothermal systems that record variations in magma dynamics at depth. Here, we report on a data set comprising the chemical and isotopic composition of thermal waters and dissolved gases from Stromboli Island (Aeolian Volcanic Arc, Southern Italy) that spans 14 years (2004–2018) of continuous observations. We show that the shallow thermal aquifer of Stromboli results from variable mixing between meteoric water, seawater and magmatic fluids. Gas‐water‐rock interactions occur, which induce a large spectrum of variation in both water and gas chemistry. These shallow processes do not affect the 3He/4He of helium dissolved in thermal waters, which records a magmatic signature that varies in response to changes in magma supply at depth. We show that in periods of more intense volcanic activity, the helium isotopic composition of thermal waters approaches that of the gas emitted from the magma residing at 7–10 km depth. Investigation of hydrothermal waters at active volcanoes is a promising tool to examine magmatic fluids and their shallow circulation, as well as to evaluate the state of activity of a volcano, particularly when summit areas are inaccessible. Key Points: The composition of thermal water and dissolved gases results from the mixing of meteoric marine water and the input of volcanic gasesCompositional variation is due to the extent of mixing, the solubility‐driven fractionation of dissolved gas speciesThe gas dissolved in the aquifer has a 3He/4He range of 3–4.5 Ra, similar to that measured in olivines and pyroxenes [ABSTRACT FROM AUTHOR]

Play Fairway Analysis (PFA) methodology was adapted for geothermal exploration at Camas Prairie, Idaho. Geophysical data, structural and geologic mapping, volcanic rock ages and vent locations, and the distribution of thermal springs and wells all indicated a relatively high geothermal potential along the southern margin of the Prairie. An exploration well (USU Camas-1) was drilled to a depth of 618.3 m to validate the PFA. A permeable zone was encountered at ~ 357.5 m with a maximum measured temperature of ~ 80 °C, which was suppressed following the injection of cold water. A moderate transmissivity of ~ 0.25–1 cm2/s estimated from an injection test as well a seasonal artesian flow at ~ 0.7 L/s corroborate the presence of a permeable zone. The existence of a lacustrine clay seal was confirmed near the bottom of the basin-fill sediment occupying the upper 314 m of the well. Geothermometers suggest the USU Camas-1 well water equilibrated at a reservoir temperature of ~ 120 °C. Based on the locations of both thermal and cold wells, geothermal fluids appear to be flowing upward along one or both of two fault systems. The presence of young basalts and elevated helium isotope ratios suggest that the heat source of Camas Prairie is magmatic. However, the faults may be acting as a conduit for geothermal fluids to rise from great depth without a shallow magmatic source being present. Camas Prairie is a promising area for geothermal development, but the relatively low reservoir temperatures indicate this resource may not be suitable for electric generation. Perhaps the best use would be for heating. [ABSTRACT FROM AUTHOR]

The formation of the unbound heavy helium isotopes He was studied in the reactions of stopped pion absorption by light nuclei. Measurements were carried out using two-arm multilayer semiconductor spectrometer. The data on the level structures obtained in different reaction channels are consistent with each other. Our results on the energies and widths of the low-lying states of the He are consistent with the world data. Record values of resonance energies were obtained for highly excited states of He (24.5 MeV) and He (10.5 MeV). [ABSTRACT FROM AUTHOR]

This paper deals with the isotope composition of helium (3Не/4Не = R) in the groundwater of the Southern Baikal volcanic area (SBVA) and Southern Khangai volcanic area (SKhVA) during the Late Cenozoic Period. We have found differences in the behavior and value of that parameter. It was found that the differences in the concentrations of 3Не/4Не in the SBVA and the SKhVA resulted from mantle reservoirs that have different isotope compositions of helium. This confirms that the Late Cenozoic volcanism in the SBVA and SKhVA is controlled by mantle sources related to mantle plumes of the Central Asian hot mantle field. [ABSTRACT FROM AUTHOR]

Trace gases have demonstrated their strength for oceanographic studies, with applications ranging from the tracking of glacial meltwater plumes to estimates of the abyssal overturning duration. Yet measurements of such passive tracers in the ice-covered Arctic Ocean are sparse. We here present a unique data set of trace gases collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, during which the R/V Polarstern drifted along with the Arctic sea ice from the Laptev Sea to Fram Strait, from October 2019 to September 2020. During the expedition, trace 5 gases from anthropogenic origin chlorofluorocarbon 12 (CFC-12), sulfur hexafluoride (SF6), and tritium, along with noble gases helium and neon and their isotopes were collected at a weekly or higher temporal resolution throughout the entire water column and occasionally in the snow, from the ship and from the ice. We describe the sampling procedures along with their challenges, the analysis methods, the data set, and present case studies in Fram Strait and the Central Arctic Ocean to illustrate possible usage for the data along with their robustness. Combined with simultaneous hydrographic measurements, this trace 10 gases data set can be used for process studies and water mass tracing throughout the Arctic in subsequent analyses. [ABSTRACT FROM AUTHOR]

We measured He and Ar in fresh peridotites from the Twin Sisters massif, Washington USA. 3He/4He ratios measured on >35 samples are highly variable (∼0.8 to ∼6 times the atmospheric ratio, R A). Step-heating of a subset of these samples in every case reveals a low 3He/4He component (∼1 R A) released at <1000 °C and a high 3He/4He component (>3 R A) above that temperature, but these components are not effectively isolated by crushing and powder fusion analysis. He-Ar systematics indicate an intimate association of two fluid-inclusion hosted components in the peridotites. The first is a ∼6 R A mantle component that is released at higher temperatures during step heating and is more abundant in dunite bands than surrounding harzburgites. The second component, released at low temperatures, has a 3He/4He ratio of 1.0 ± 0.5 R A, atmospheric 40Ar/36Ar, and 4He/40Ar far above atmospheric. It appears to be a mixture of mantle and radiogenic He sources introduced during obduction-related serpentinization, sometimes invisible, by surface-derived waters enriched with deeply-sourced helium. These data indicate that mantle noble gas signatures can be retained in lithospheric peridotites against both diffusive loss and radiogenic ingrowth over at least 108 year timescales, likely due to concentration and immobilization of He in fluid inclusions. However, the mantle signature can be greatly modified by pervasive and potentially cryptic fluid alteration during emplacement. [ABSTRACT FROM AUTHOR]

We use the path-integral Monte Carlo (PIMC) method and state-of-the-art two-body and three-body potentials to calculate the fourth virial coefficients D(T) of 4He and 3He as functions of temperature from 2.6 K to 2000 K. We derive expressions for the contributions of exchange effects due to the bosonic or fermionic nature of the helium isotope; these effects have been omitted from previous calculations. The exchange effects are relatively insignificant for 4He at the temperatures considered, but for 3He, they are necessary for quantitative accuracy below about 4 K. Our results are consistent with previous theoretical work (also with some of the limited and scattered experimental data) for 4He; for 3He, there are no experimental values, and this work provides the first values of D(T) calculated at this level. The uncertainty of the results depends on the statistical uncertainty of the PIMC calculation, the estimated effect of omitting four-body terms in the potential energy, and the uncertainty contribution propagated from the uncertainty of the potentials. At low temperatures, the uncertainty is dominated by the statistical uncertainty of the PIMC calculations, while at high temperatures, the uncertainties related to the three-body potential and omitted higher-order contributions become dominant. [ABSTRACT FROM AUTHOR]

The breaking of molecular bonds during exposure to ionizing radiation and electron beams creates irreversible damage in the molecular structure. In some cases, such as lithography, controlled damage of a molecular resist is a desirable process and is the basis for the entire semiconductor industry. In other cases, such as environmental exposure or probing of the molecular structure, the induced damage is a major problem that has limited advances in science and technology. We report here the use of an in situ probe that is minimally invasive to detect real-time damage induced in organic materials. Specifically, we use metastable excited helium atoms in the 3S1 state to characterize the damage caused by a low-energy electron beam ∼30 eV on an organic self-assembled monolayer of 11-bromo-1-undecanethiol on a gold substrate. We were able to monitor the damage caused by the electron beam without introducing any additional observed damage by the probing metastable atoms. [ABSTRACT FROM AUTHOR]

This study describes an ongoing intense earthquake swarm in the crust of the northeastern Noto Peninsula, Japan, that began around the end of 2019. Fluid movement related to volcanic activity is often involved in earthquake swarms in the crust. However, no volcanic activity has occurred in this region since the Middle Miocene (15.6 Ma). This study investigates the cause of this earthquake swarm based on the spatiotemporal evolution of earthquake hypocenters and seismic reflectors. The hypocenter relocation of 10,940 earthquakes (M > 1) reveals that they are all crustal and migrated upward, activating a complex network of faults at depths shallower than 20 km. The initiation of this earthquake swarm occurred at a locally deep depth (z = 17 km), and the local hypocenter distribution shows a characteristic circular pattern. We find a distinctive S‐wave reflector in the immediate vicinity. A low‐velocity anomaly exists below the reflector, and a high helium isotope ratio and a low‐gravity anomaly were observed at the surface. These observations suggest that the current seismicity is associated with fluids released by ancient or possibly unrecognized modern magmatic activity, although no volcanic activity has been documented in this area for 15 million years. Significant crustal deformation was observed during this swarm and is probably related to the fluid movement and aseismic deformation that contributed to this earthquake swarm. The strongest M5.4 earthquake (as of October 2022) occurred near the migration front on the largest planar structure, leaving the shallow extension unruptured. Plain Language Summary: An intense earthquake swarm is currently occurring in the crust of the northeastern Noto Peninsula, Japan. Fluid movement related to volcanic activity is often involved in earthquake swarms in the crust, but no volcanic activity has occurred in this region since the middle Miocene (15.6 Ma). We investigate the cause of this earthquake swarm using precisely determined earthquake locations and seismic reflectors. We find that the earthquakes moved from deep to shallow depths via many planes, similar to earthquake swarms near volcanoes. The strongest M5.4 earthquake occurred near the migration front on the largest planar structure. Further earthquakes may be possible in the shallow part of this fault. We find a distinctive S‐wave reflector, suggesting a fluid source, in the immediate vicinity of the initiation point of this swarm. The local hypocenters show a circular pattern similar to the ring fault that forms above the magma reservoir. These observations may indicate that the current seismic activity is being impacted by fluids related to ancient or new hidden magmatic activity. The present results suggest that hidden magma‐induced structures and fluids can generate earthquakes even in areas where no volcanic activity has been observed for over 10 million years. Key Points: An intense seismic swarm continues in a non‐volcanic region, with upward earthquake migration through a complex network of faultsA deep S‐wave reflector located near the seismicity initiation point and above the low‐velocity anomaly may represent a fluid sourceThe significant surface deformation observed during this swarm was caused by aseismic deformation activated by fluid migration [ABSTRACT FROM AUTHOR]

The contemporary occurrence of juvenile gas emissions at springs or mofettes in active volcanic areas can be observed worldwide. This correlation is less frequent in areas with dormant or post-volcanic activity. The NW-Bohemia/Vogtland region located at the Eger rift zone (Czech Republic) provides an intriguing example of this correlation between numerous Neogene-aged post-volcanism locations and juvenile fluid emission sites. Newly discovered dikes and diatremes are located close to vents with the highest helium isotope ratios (3He/4He) of about 6 Ra. Our results lend support to the hypothesis that feeder dikes and their fractured wall rocks should be considered the predominant conduits for the continuous upwelling of juvenile fluids. Moreover, 77% of the CO2 gas emission sites are located close to dikes or diatremes, i.e., within a distance of 4 km. Our studies reveal a spatial dependence of the Ra values at the spring sites with the estimated distances to the basaltic bodies. The results confirm the negative trend known from the literature. That is, Ra values decrease with increasing distance from the feeder dikes. [ABSTRACT FROM AUTHOR]

Helium and carbon isotopic data from 12 springs along a -400 km segment of the Denali fault system (Alaska, USA), inform mantle-to-surface connections of this enigmatic structure. Warm springs on the main strand, west of the 2002 M7.9 Denali fault earthquake rupture, have 3He/4He as high as 2.4 RC/RA (air-corrected 3He/4He relative to air ratio) indicating -30% mantle He. Corresponding -13C values are -9.1- to -7.8- (relative to Vienna Peedee belemnite), suggesting that the CO2 at these western springs is partially mantle derived. At the eastern end of the 2002 rupture, Totschunda fault springs have 3He/4He of 0.65-0.99 RC/RA (-8%-12% mantle He), with -13C values (-0-) from carbonates. Results confirm the Denali fault system is a lithosphericscale feature tapping mantle volatiles. Springs along the 2002 rupture yield air-like 3He/4He of 1 R/RA and -13C values from -9.2- to -3.4-, interpreted as representing shallow groundwater circulation through shales and carbonates without mantle contributions. A thrust splay parallel to the rupture zone has air-like 3He/4He, whereas an along-strike high-angle normal splay yields 3He/4He of 1.3 RC/RA (-16% mantle He), implying that flow paths along the ruptured strand are disrupted in the upper 10 km of the fault zone. Because the Denali fault is a lithospheric-scale, transcurrent structure separating North America from independently moving southern Alaska, we suggest that it has characteristics of a transform boundary. The similarity of our results to helium isotope values at analogous tectonic settings suggest that without magmatism influence, there is a maximum mantle fluid flux through continental strike-slip faults. [ABSTRACT FROM AUTHOR]

The ground state density distributions and electron scattering Coulomb form factors of Helium (4,6,8He) and Phosphorate (27,31P) isotopes are investigated in the framework of nuclear shell model. For stable (4He) and (31P) nuclei, the core and valence parts are studied through Harmonic-oscillator (HO) and Hulthen potentials. Correspondingly, for exotic (6,8He) and (27P) nuclei, the HO potential is applied to the core parts only, while the Hulthen potential is applied to valence parts. The parameters for HO and Hulthen are chosen to reproduce the available experimental size radii for all nuclei under study. Finally, the CO component of electron scattering charge form factors are also investigated. Unfortunately, there is no analytic solution to the Hulthen potential except for the states which are harnessed to the current calculation. [ABSTRACT FROM AUTHOR]

The noble gas signature of incoming Pacific Bottom Water (PBW), when compared to North Atlantic Deep Water, indicates the addition of 450 ± 70 GT a−1 glacial melt water to form AABW and subsequently PBW. The downstream evolution of this signature between the southern (20°S to equator) and northern (25°–45°N) bottom waters indicates a decrease in sea level pressure around Antarctica over the past two millennia. Vertical profiles of noble gases in the deep Pacific show exponential relationships with depth with scale heights identical to temperature and salinity. Unlike the other noble gases, helium isotopes show evidence of mid‐depth injection of non‐atmospheric helium. Using observed deviations from exponential behavior, we quantify its magnitude and isotope ratio. There is a clear latitude trend in the isotope ratio of this added helium that decreases from a high exceeding 9 RA (atmospheric 3He/4He ratio) in the south to around 8 RA near the equator. North of 30–40°N, it systematically decreases northward to a low of ∼2 RA north of 50°N. This decline results from a combination of northward decline in seafloor spreading, release of radiogenic helium from increased sediment thickness, and the possible emission of radiogenic helium through cold seeps along the Alaskan and North American margins. Finally, we derive an improved method of computing the excess helium isotope concentrations and that the distributions of bottom water 3HeXS/4HeXS are consistent with what is known about bottom water flow patterns and the input of low 3He/4He sedimentary helium. Plain Language Summary: Dissolved noble gases, because they are inert and span a range of physical characteristics, uniquely record conditions at the sea surface when water masses are formed and sink from polar regions to fill the abyssal ocean. These signatures can be used not only to deduce past changes in sea level pressure and rates of glacial melting but also to disentangle air‐sea exchange and in situ physical processes that affect all gases from subsurface external sources that are unique for helium isotopes. The distribution of helium isotopes in the deep ocean can be used to constrain the patterns and magnitudes of hydrothermal sources at the sea floor as well as the input of sedimentary radiogenic helium and cold seeps to Pacific bottom water. We use these tools to study the various sources of helium isotopes in the abyssal Northeast Pacific. Key Points: Noble gases constrain the rate of basal melting of Antarctic GlaciersNoble gases allow us to constrain the isotopic composition of helium being added to deep watersThe distribution of helium isotopes mirrors important geological and geophysical processes in the Pacific [ABSTRACT FROM AUTHOR]

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

The helium isotope ratio (3He/4He), concentration ratio of neon-20 to helium-4 (20Ne/4He), argon (Ar), krypton (Kr), and xenon (Xe) concentrations were measured in the porewater of surface sediments of several submarine mud volcanoes. From the 3He/4He values (0.18–0.93RA), the estimated He origin is almost 90% crustal He, with little contribution from mantle-derived He. The determined Ar, Kr, and Xe concentrations lie within the solubility equilibrium range expected for temperatures from 83 °C up to 230 °C and are consistent with the temperature range of the dehydration origin of clay minerals. Considering the geothermal gradient in the investigated region (25 °C/km), these gases are considered to have reached dissolution equilibrium at a depth of about 3.3 km to 9.2 km below the seafloor. As the depth of the plate boundary is 18 km below the seafloor, the noble gas signatures are likely to originate from the crust, not from the plate boundary. This is consistent with the results presented by the He isotope ratios. [ABSTRACT FROM AUTHOR]

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

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

We present a detailed study of inelastic energy-loss collisions of photoelectrons emitted from He nanodroplets by tunable extreme ultraviolet (XUV) radiation. Using coincidence imaging detection of electrons and ions, we probe the lowest He droplet excited states up to the electron impact ionization threshold. We find significant signal contributions from photoelectrons emitted from free He atoms accompanying the He nanodroplet beam. Furthermore, signal contributions from photoionization and electron impact excitation/ionization occurring in pairs of nearest-neighbor atoms in the He droplets are detected. This work highlights the importance of inelastic electron scattering in the interaction of nanoparticles with XUV radiation. [ABSTRACT FROM AUTHOR]

The Fernando de Noronha archipelago (southwest Atlantic, 345 km from the coast of Brazil) is considered as the result of mantle plume activity. However, data on the isotopic composition of helium and neon, which are, perhaps, the only unambiguous geochemical criterion for deep mantle plumes have not been published yet for the region. In this paper, we present the first data on the isotopic composition of helium, neon, argon, and nitrogen, obtained by stepwise crushing of mantle xenoliths from the basanites of the San José Formation. The results obtained may indicate that fluid inclusions contain the very first portions of the exsolved gases—they are ultra-depleted in helium in relation to neon and especially argon. This conclusion is also supported by He–Ar–CO2 systematics. The isotopic composition of helium (4He/3He = 31 879 ± 6796) and neon (21Ne/22Ne(mantle) = 0.0453 ± 0.0012) indicates that it was indeed a mantle plume, identical in noble gas composition to the Kerguelen plume. According to the Ar–Ne isotope systematics 40Ar/36Ar (mantle) = 7455 ± 2290. Nitrogen is characterized by a heavy isotopic composition (δ15N = +5.4 ± 0.2‰), which corresponds to the hypothesis of the subduction nature of nitrogen in deep mantle plumes. [ABSTRACT FROM AUTHOR]

The cross sections for the production of the isotopes Au in Au reactions are calculated based on numerical solution of the time-dependent Schrödinger equation for outer neutrons of colliding nuclei. It is shown that the fusion–evaporation contribution to experimental data is small. By and large, the results of the calculations agree with experimental data. [ABSTRACT FROM AUTHOR]

Deception Island is one of the most active volcanoes in Antarctica with more than twenty explosive eruptions in the past two centuries. Any future volcanic eruption(s) is a serious concern for scientists and tourists, will be detrimental to marine ecosystems and could have an impact to global oceanographic processes. Currently, it is not possible to carry-out low and high frequency volcanic gas monitoring at Deception Island because of the arduous climatic conditions and its remote location. Helium, neon and argon isotopes measured in olivine samples of the main eruptive events (pre-, syn- and post caldera) offer insights into the processes governing its volcanic history. Our results show that: (i) ascending primitive magmas outgassed volatiles with a MORB-like helium isotopic signature (3He/4He ratio); and (ii) variations in the He isotope ratio, as well as intensive degassing evidenced by fractionated 4He/40Ar* values, occurred before the beginning of the main eruptive episodes. Our results show how the pre-eruptive noble gas signals of volcanic activity is an important step toward a better understanding of the magmatic dynamics and has the potential to improve eruption forecasting. [ABSTRACT FROM AUTHOR]

We report 3He and 4He concentrations in 57 sediment samples from the southeast Indian Ocean where 60Fe excesses were previously identified in a subset of the same samples (Wallner et al., 2016). The coupled 60Fe-3He data allow further evaluation of two competing hypotheses: (1) a nearby supernova (SN) showered Earth with exotic radionuclides such as 60Fe during the last 3 million years, or (2) 60Fe in terrestrial archives was generated by reactions of galactic cosmic rays (GCRs) on micrometeorite grains that were irradiated for hundreds of millions of years in the interstellar medium, where 3He production by GCRs is larger than the solar wind 3He flux. Piston core ELT49-53 sediments show no correlation between 3He and 60Fe, and sedimentary 3He appears to be dominated by the presence of interplanetary dust particles (IDPs). Because 3He is not supplied in significant amounts by SN ejecta, the absence of a 3He-60Fe correlation provides additional, although circumstantial evidence for the supernova hypothesis. Large uncertainties in the relatively small number of sediment 60Fe measurements currently limit a firmer conclusion. The extraterrestrial 3He accumulation rate in ELT49-53 from 3.2 to 1.7 Ma was 0.88 ± 0.26 × 10−12 cm3 STP/g/kyr, similar to IDP 3He flux estimates from previous sedimentary and ice core records that span both shorter and longer time scales. 4He and 60Fe accumulation rates during this time interval were 0.11 ± 0.04 × 10−6 cm3 STP/cm2/kyr and 1.9 ± 0.5 × 104 atoms/cm2/kyr. Bulk sediment [4He] is strongly anti-correlated with sediment CaCO 3 content, evidence for modulation of the terrigenous and cosmic sedimentary fractions primarily by changes in biogenic carbonate deposition. Although the dominant terrigenous source has not been uniquely identified at the Indian Ocean deposition site, it resembles eolian material from the continental interior of Australia, and shows a narrow range of 3He/4He (from 2 to 4 × 10−8, 0.015–0.030 R A) over the last ∼3 Myrs. [ABSTRACT FROM AUTHOR]

• Helium isotopes up to 7.9Ra are among the highest in the SVZ, showing mantle-derived fluids. • Soil CO 2 flux > 3000 g m −2 d −1 and temperatures up to 96 °C were measured. • A total CO 2 output of 2.37 t⋅ d −1 and a total heat release of ∼3.3 MW was computed. • Gas geothermometers yielded an average value of 249°. • A geothermal potential of 15.6 MWe⋅km−2 for the sollipulli hydrothermal field was estimated. The Alpehue Hydrothermal Field (AHF) near the Sollipulli Volcano in the Southern Volcanic Zone of Chile shows promise as a significant geothermal resource. A comprehensive geothermal exploration survey was conducted, including the evaluation of hydrothermal gases, geothermometer calculations, and CO 2 flux measurements, to assess the AHF's geothermal potential. Our results indicate that the hydrothermal gasses at the AHF primarily originate from primitive, mantle-derived sources, with some contribution from crustal sediments. Two different CO 2 populations of fluxes were identified. One corresponds to the background emission related to the soil biological activity (mean ∼7.7 g·m−2·d−1), and the other, much more significant, emanates from an endogenous source related to the Alpehue hydrothermal reservoir (mean ∼461 g·m−2·d−1). Reservoir temperatures were calculated using gas geothermometry yielding average temperatures of 249 °C. The calculated heat flow rate of the AHF is approximately 3.3 MW and the heat flux corresponds to 156 thermal MW⋅km−2, which could be considered a medium geothermal potential comparable to other systems worldwide. Although further studies are needed to fully address its exploitability, this study presents favorable characteristics of the AHF that make it a promising avenue for further exploration. [ABSTRACT FROM AUTHOR]

Karst springs are one of the most exploited drinking water resources in the world. Isotopic and chemical analyses on these waters reveal essential insights into their hydrodynamics. Valseriana (Northern Italy) is a valley within the Italian Pre-Alps, characterized by high water availability. The main reasons are a bedrock consisting of very permeable carbonate formations and a mean annual precipitation above 1800 mm/y. In this context, the Valseriana spring catchments have become strategically important for the water exploitation and the domestic supply of Bergamo and the neighboring municipalities. This study general aim is to expand the knowledge on the two main karst systems (Nossana and Ponte del Costone), which together include twenty-three major and minor springs, by defining a state-of-the-art that will be useful in future decades to preserve this crucial resource. Specific objectives include i) verifying the applicability of the 3H/3He dating method in karst environments, ii) defining groups of springs according to their chemical and isotopic characteristics for possible safeguard actions, and iii) establishing a conceptual model of the internal dynamics of the two spring systems. A chemical and isotopic sampling campaign was specifically conducted between May 2018 and July 2019. A total of 34 water points were sampled, including natural springs, rivers, wells, karst caves, and nearby mines. Water sampling for 3H/3He isotopic analyses was proved possible through careful selection of the sampling points and the insertion of the pump tubing in the spring fractures. A first classification of springs into uniform hydrochemical groups was obtained by applying the hierarchical cluster analysis technique on major ions contents. These outputs were combined with information from the 3H/3He dating analyses and resulted in three different classes of springs. The three classes showed a clustering for elevations: at high, medium, and valley bottom elevations, respectively. Finally, the elaborations simplified the two karst systems by a hierarchical flow system model, dynamically controlled by different karst network development and infiltration water. [Display omitted] • Valseriana karst springs are strategic for water supply in the Lombardy Pre-Alps. • Three spring groups were defined connecting chemical properties and residence time. • The repetition of 3H–3He analyses proved them robust in a karst environment. • Noble gas air-excess data suggest a tendency towards lower recharge altitudes. • Results will support the sustainable use of water resources in the area. [ABSTRACT FROM AUTHOR]