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We have performed path-integral Monte Carlo calculations to study the adsorption of 4He atoms on two different C36 isomers with the D6h and the D2d symmetries. The radial 4He density distributions reveal layer-by-layer growth with the first layer being located at a distance of ∼5.5 Å from the C36 molecular center and the second layer at ∼8.3 Å. From the angular density profiles of 4He, we find different quantum states as the number of 4He adatoms N varies. For N = 20, we observe commensurate solid structures on both D6h and D2d isomers, where each of 8 hexagon and 12 pentagon centers of the fullerene surfaces is occupied by a single 4He atom. The second-layer promotion starts beyond N = 38 on both isomers, where a compressible incommensurate structure is observed on the D6h isomer and another commensurate structure on D2d. Between N = 20 and N = 38, the 4He monolayer on D6h shows several distinct rings of delocalized 4He atoms along with strongly anisotropic superfluid responses at low temperatures, while isotropic but weak superfluid responses are observed in the 4He layer on D2d. [ABSTRACT FROM AUTHOR]

We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 104 ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 104/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies. [ABSTRACT FROM AUTHOR]

Singlet dihydroxycarbene (HOCOH) is produced via pyrolytic decomposition of oxalic acid, captured by helium nanodroplets, and probed with infrared laser Stark spectroscopy. Rovibrational bands in the OH stretch region are assigned to either trans, trans- or trans, cis-rotamers on the basis of symmetry type, nuclear spin statistical weights, and comparisons to electronic structure theory calculations. Stark spectroscopy provides the inertial components of the permanent electric dipole moments for these rotamers. The dipole components for trans, trans- and trans, cis-rotamers are (μa, μb) = (0.00,0.68(6)) and (1.63(3), 1.50(5)), respectively. The infrared spectra lack evidence for the higher energy cis, cis-rotamer, which is consistent with a previously proposed pyrolytic decomposition mechanism of oxalic acid and computations of HOCOH torsional interconversion and tautomerization barriers. [ABSTRACT FROM AUTHOR]

Summary: Replicable experimental results about low‐energy nuclear fusion reactions based on initially reacting deuterium nuclei giving cold nuclear fusion synthesis of helium (both isotopes 3He and 4He) and energy release as final products are reported in this article. These final products are results of interaction of deuterium with the solids in experimental system including two specimens: molybdenum metal and palladium nanowires. Experimental proofs about cold nuclear fusion synthesis of both 3He and 4He are provided. It reported a correlation between concentration of the generated helium and the measured temperature of the sample holder. It is found that the concentrations of both 3He and 4He increase with increase of the kinetic energies of the interacting deuterium nuclei and also with increase of the temperature of the sample holder. [ABSTRACT FROM AUTHOR]

Magma plumbing systems underlying subduction zone volcanoes extend from the mantle through the overlying crust and facilitate protracted fractional crystallisation, assimilation, and mixing, which frequently obscures a clear view of mantle source compositions. In order to see through this crustal noise, we present intracrystal Secondary Ion Mass Spectrometry (SIMS) δ18O values in clinopyroxene from Merapi, Kelut, Batur, and Agung volcanoes in the Sunda arc, Indonesia, under which the thickness of the crust decreases from ca. 30 km at Merapi to ≤20 km at Agung. Here we show that mean clinopyroxene δ18O values decrease concomitantly with crustal thickness and that lavas from Agung possess mantle-like He-Sr-Nd-Pb isotope ratios and clinopyroxene mean equilibrium melt δ18O values of 5.7 ‰ (±0.2 1 SD) indistinguishable from the δ18O range for Mid Ocean Ridge Basalt (MORB). The oxygen isotope composition of the mantle underlying the East Sunda Arc is therefore largely unaffected by subduction-driven metasomatism and may thus represent a sediment-poor arc end-member. Subduction zone volcanoes are underlain by extensive magma plumbing systems, which can obscure original mantle source signals. Here, the authors show that intra-crystal oxygen isotope analysis of clinopyroxenes from the Sunda arc (Indonesia) reveal the δ18 O value of the sub-arc mantle. [ABSTRACT FROM AUTHOR]

Porous and fractured aquifers exist in the area of Hurghada, Eastern Desert of Egypt, whose recharge processes through the common flash floods are not identified. Hydrochemical parameters, stable isotopes 18O, 2H and tritium in floodwater and groundwater were applied in the area subject to study. Additionally, He isotopes were investigated in the deep wells in the faulted zone at the Abu Shaar Plateau. 3H activity in all sampled points lies below the detection limit excluding a recent recharge component in groundwater. However, the hydrochemical ratios and the stable isotope signature confirm that the shallow wells and springs (Red Sea Hills group) are being recharged from modern precipitation. The hydrochemical parameters of the deep wells at the Abu Shaar Plateau (coastal plain group) confirm another origin for the ions rather than the modern precipitation. Together with the 18O and 2H values, the Br/Cl ratio of this group confirms the absence of seawater intrusion component and the role of the fault as a hydraulic barrier. These 18O and 2H values deviate from the GMWL confirming an evaporation effect and colder infiltration conditions and reveal strongly a possible mixing with the Nubian Sandstone in the region. The 3He/4He ratio confirms a mantle contribution of 2% from the total He components. [ABSTRACT FROM AUTHOR]

Rationale: Due to isotope fractionations during partial nitrogen release from minerals and rocks, the complete extraction of nitrogen for analysis is crucial to ensure high‐quality nitrogen isotopic data. However, the appropriate nitrogen extraction conditions (e.g. temperature, duration) have not been established for most silicate minerals and rocks. Methods: Nitrogen in a number of common minerals and rocks was extracted using the most robust sealed‐tube offline combustion techniques, purified and quantified in a custom‐made metal manifold, and carried by helium gas to an isotope ratio mass spectrometer for isotopic measurement at nanomolar nitrogen level. Each mineral or rock was combusted in a variety of temperature and duration conditions to compare the nitrogen yields and isotopic compositions. Results: The nitrogen yields and isotopic compositions of minerals and rocks are strongly affected by combustion temperature and duration. The optimal combustion temperature is lowest for cyclosilicate minerals, followed by phyllosilicate, tectosilicate and inosilicate minerals. Preheating of samples can induce significant nitrogen loss and δ15N shift. Heating of samples above their optimal temperatures may cause nitrogen re‐assimilation by the residual mineral or rock. Conclusions: Each mineral or rock has a characteristic optimal temperature and duration for complete nitrogen release. Preheating, under‐heating or over‐heating can cause nitrogen loss and isotopic shift. Therefore, we recommend using the offline combustion techniques and the optimal combustion conditions obtained in this study for nitrogen quantification and isotopic analysis of silicate minerals and rocks. [ABSTRACT FROM AUTHOR]

We investigate deformation mechanics of fracture networks in unsaturated fractured rocks from subsurface conventional detonation using dynamic noble gas measurements and changes in air permeability. We dynamically measured the noble gas isotopic composition and helium exhalation of downhole gas before and after a large subsurface conventional detonation. These noble gas measurements were combined with measurements of the subsurface permeability field from 64 discrete sampling intervals before and after the detonation and subsurface mapping of fractures in borehole walls before well completion. We saw no observable increase in radiogenic noble gas release from either an isotopic composition or a helium exhalation point of view. Large increases in permeability were observed in 13 of 64 discrete sampling intervals. Of the sampling intervals which saw large increases in flow, only two locations did not have preexisting fractures mapped at the site. Given the lack of noble gas release and a clear increase in permeability, we infer that most of the strain accommodation of the fractured media occurred along previously existing fractures, rather than the creation of new fractures, even for a high strain rate event. These results have significant implications for how we conceptualize the deformation of rocks with fracture networks above the percolation threshold, with application to a variety of geologic and geological engineering problems. [ABSTRACT FROM AUTHOR]

Wadsleyite can store significant amounts of H2O in its crystal structure as hydroxyl. However, H2O solubility in Fe‐bearing wadsleyite remains poorly constrained at mantle transition zone temperatures. Previous studies (e.g., Demouchy et al., 2005 [https://doi.org/10.2138/am.2005.1751]; Litasov et al., 2011 [https://doi.org/10.1007/s00269-010-0382-3]) focused primarily on Fe‐free systems, which do not represent the Earth's interior because Fe may affect the H2O solubility. Here, we investigated the temperature dependence of H2O solubility in Fe‐bearing and Fe‐free wadsleyite at 1500–2100 K. The results indicate that H2O solubility in Fe‐bearing wadsleyite is higher than in Fe‐free samples at 1800–1900 K, corresponding to transition zone geotherm, but there is no clear Fe content dependence in the Fe‐bearing samples. Wadsleyite can contain approximately 1.0 wt.% H2O at transition zone temperatures. The H2O solubility in wadsleyite is lower than ringwoodite along a plume geotherm, which may result in dehydration melting at the 520‐km discontinuity by upwelling flow in plumes. Plain Language Summary: The mantle transition zone at 410–660 km depth is a H2O sponge because wadsleyite and ringwoodite can contain large amounts of H2O in their crystal structures as hydroxyl defects. However, the solubility of H2O in Fe‐bearing wadsleyite is poorly constrained compared with ringwoodite and Fe‐free wadsleyite, which have been extensively investigated. The exact H2O storage capacity of the mantle transition zone, therefore, remains unknown. Here, we investigated the solubility of H2O in Fe‐bearing wadsleyite as a function of temperature. The results indicate that wadsleyite can store ∼1.0 wt.% H2O at transition zone temperatures and ∼0.65 wt.% along a plume geotherm. H2O solubility in wadsleyite is lower than that in ringwoodite in mantle plumes. A dehydration melting layer at the 520‐km discontinuity near plumes can, therefore, form via the phase transition from ringwoodite to wadsleyite under H2O‐saturated conditions driven by upwelling flow in mantle plumes. Key Points: H2O solubility in Fe‐bearing wadsleyite decreases with increasing temperatureFe‐bearing wadsleyite can contain ∼1.0 wt.% H2O at mantle transition zone temperatureDehydration melting could occur at the 520‐km discontinuity by upwelling flow near plumes [ABSTRACT FROM AUTHOR]

• Hydrothermal helium is mainly from radiogenic production in the crust with 7.52 % is mantle derived. • CO 2 is mainly constrained by both decarbonization of Tethyan marine carbonate rocks and mantle fluid. • The He-CO 2 system is constrained by the regional magmatic intrusions and degassing process. • The contrasting slab subduction style and the south boundary of EHS are constrained by helium isotopes. • Location of mantle suture in EHS is extended and the south boundary is also constrained by helium isotopes. While understanding the origins of volatiles has strong implications on heat and tectonic processes, the relationship has not well understood, especially in the Eastern Himalayan Syntaxis (EHS) in the Tibetan Plateau, where tectonic framework, petrologic properties, stress field, and geomorphic water system changes greatly due to the strongest continental collision. Based on samples from warm/hot springs in the EHS, geothermal fluid is sourced from local precipitation and simultaneously recharged by deeply-sourced mantle volatiles. Volatiles from hydrothermal systems are mixture of crustal and mantle origin, in which helium is mainly from radiogenic production in the crust with only up to 7.52% is mantle derived whereas CO 2 is mainly constrained by both decarbonization of Tethyan marine carbonate rocks and mantle volatiles. The helium fluxes are estimated to be almost 1–2 orders higher than some representative volcanically and tectonically active continental regions. The He-CO 2 system is dominantly constrained by the regional magmatic intrusions and hydrothermal degassing process. The boundary of the Indian plate underplating beneath Tibet is extended eastward to across the EHS by evidences from He isotope and this boundary is probably the south boundary of the EHS. Differences of helium isotopes between the EHS and its southeastern region indicate the contrasting slab subduction style in the deep structure. These results present some quantitative constraints for the interpretations of regional tectonic processes on transportation of deeply-sourced volatiles and its indications on continental collision style and present essential basis for understanding volatiles degassing and cycling in the continental collision settings. [ABSTRACT FROM AUTHOR]

• Play Fairway Analysis is adapted for use in geothermal exploration. • An example is developed for Snake River Plain volcanic province in southern Idaho. • Risk maps produced for heat, permeability, and seal using new and published data. • Play Fairway method is shown to be effective paradigm for discovering new resources. The Snake River Plain (SRP) volcanic province overlies the track of the Yellowstone hotspot, a thermal anomaly that extends deep into the mantle. Most of the area is underlain by a basaltic volcanic province that overlies a mid-crustal intrusive complex, which in turn provides the long-term heat flux needed to sustain geothermal systems. Previous studies have identified several known geothermal resource areas within the SRP. For the geothermal study presented herein, our goals were to: (1) adapt the methodology of Play Fairway Analysis (PFA) for geothermal exploration to create a formal basis for its application to geothermal systems, (2) assemble relevant data for the SRP from publicly available and private sources, and (3) build a geothermal PFA model for the SRP and identify the most promising plays, using GIS-based software tools that are standard in the petroleum industry. The study focused on identifying three critical resource parameters for exploitable hydrothermal systems in the SRP: heat source, reservoir and recharge permeability, and cap or seal. Data included in the compilation for heat source were heat flow, distribution and ages of volcanic vents, groundwater temperatures, thermal springs and wells, helium isotope anomalies, and reservoir temperatures estimated using geothermometry. Reservoir and recharge permeability was inferred from the analysis of stress orientations and magnitudes, post-Miocene faults, and subsurface structural lineaments based on magnetics and gravity data. Data for cap or seal included the distribution of impermeable lake sediments and clay-seal associated with hydrothermal alteration below the regional aquifer. These data were used to compile Common Risk Segment maps for heat, permeability, and seal , which were combined to create a Composite Common Risk Segment map for all southern Idaho that reflects the risk associated with geothermal resource exploration and identifies favorable resource tracks. Our regional assessment indicated that undiscovered geothermal resources may be located in several areas of the SRP. Two of these areas, the western SRP and Camas Prairie, were selected for more detailed assessment, during which heat, permeability, and seal were evaluated using newly collected field data and smaller grid parameters to refine the location of potential resources. These higher resolution assessments illustrate the flexibility of our approach over a range of scales. [Display omitted] [ABSTRACT FROM AUTHOR]

• Negligible Ba removal observed in the Rainbow hydrothermal system. • Insignificant modification of Ba isotope composition of the vent fluid endmember. • Rainbow vent introduces isotopically light Ba (−0.17 % 0) to the deep Atlantic Ocean. • Hydrothermal inputs contribute 4.6 ± 2.2 Gmol/yr Ba to the ocean. The marine barium (Ba) cycle is closely connected to the short-timescale carbon cycle, and Ba serves as a valuable paleo proxy for export production, ocean alkalinity, and terrestrial inputs. However, the marine Ba budget is poorly constrained, particularly regarding the fluxes of hydrothermally sourced Ba, which hinders our understanding of the Ba cycle and use of Ba-based proxies. Recent studies have suggested a modern source-sink imbalance of Ba isotopes in the global ocean, with sources being overall isotopically heavier than the sinks, and the hydrothermal Ba inputs were considered isotopically heavy sources. In this study, we present the first investigation of Ba and its isotopes in a non-buoyant hydrothermal plume based on dissolved and particulate samples collected from the Rainbow hydrothermal vent field on the Mid-Atlantic Ridge. Our data reveal strong hydrothermal signals at near-field stations, as evidenced by helium isotopes, accompanied by elevated concentrations of dissolved and particulate Ba. Dissolved Ba isotope compositions (δ138Ba) in hydrothermally influenced deep waters (∼0.3 % 0) are lighter than at similar depths of far-field stations (∼0.45 % 0) in the Atlantic Ocean. The concentrations and isotopic compositions of dissolved and labile particulate Ba in the non-buoyant hydrothermal plume can be explained by conservative mixing between a Ba-enriched hydrothermal component and North Atlantic Deep Water. By extrapolating the correlations to the vent fluid endmember, our results suggest that there is negligible removal of Ba, and insignificant modification of Ba isotopic signatures, from the vent fluid endmember to the non-buoyant hydrothermal plume. This indicates that the Rainbow hydrothermal system introduces isotopically light Ba (−0.17 ± 0.05 % 0) to the deep Atlantic Ocean. We estimate that global hydrothermal inputs of Ba are 4.6 ± 2.2 Gmol/yr. These observations highlight the potential of hydrothermal Ba to be an isotopically light source component of the marine Ba isotope budget. [ABSTRACT FROM AUTHOR]

Located in the western part of the India-Asia continental collision zone, the Tian Shan-Pamir range is the currently most active and largest intracontinental orogenic belt worldwide. The uplifting process of the Pamir Plateau and deep structures below the Tian Shan orogen has attracted a lot of attention. The behavior of He in the geothermal systems holds great potential for addressing questions about local deep crustal processes and the Plateau uplifting mechanism. However, there is still a lack of study on volatiles in the Tian Shan-Pamir region, especially, helium, which is a very powerful geochemistry tool to reflect deep structures and processes. Through constraining the fluxes of 3He, we recognized different transportation modes for deep volatiles between Tian Shan and Pamir. The mantle-derived He along the Tian Shan is connected to the main faults at the mountain foot of the North Tian Shan and the South Tian Shan, and the rapid ascent of fluid from the mantle is implied. The relatively high levels of 3He/4He on the Pamir Plateau are indicative of crustal magmatism that is younger than ∼11 Ma, indicating a contribution of mantle-derived melts to the crustal thickening and uplifting of the Pamir Plateau since the middle Miocene. • The mantle-derived He in springs along the main faults on both sides of Tian Shan implied a rapid ascent of fluid from the mantle. • Recent magmatism is proposed to feed the helium degassing on the Pamir Plateau. • Mantle-derived melts shall contribute to the crustal thickening of the Pamir Plateau since the middle Miocene. [ABSTRACT FROM AUTHOR]

This study presents an almost entirely unpublished dataset of 121 samples of groundwater analyzed for helium concentration and its isotopic ratio (3He/4He) in two adjacent watersheds of the St. Lawrence Lowlands, in a region with intensive agricultural activities in the southern Québec Province, Eastern Canada. Most of the samples were collected in the regional bedrock fractured aquifer hosted in mid-Ordovician siliciclastic shales, on a total surface of 7500 km2. Even with this low-density sampling, and in a heterogeneous and fractured aquifer, the helium isotopes bring precious information on the recharge conditions and on chemical evolution of water. The helium spatial interpolation does not show a clear isotopic gradient through the basin. However, it shows progressive enrichment of radiogenic 4He in the confined part of the aquifer. The atmospheric and/or tritiogenic-rich helium occurs at the recharge in the Appalachians and in the middle of the plain, where impermeable cover is limited, and local infiltration of meteoric freshwater reaches the bedrock aquifer. The relation between the total dissolved solids (TDS) and 3He/4He ratios remains elusive. However, on discriminating the samples with the dominant chemistry of water, a clear trend is observed with 3He/4He ratio, suggesting that radiogenic 4He accumulates together with dissolved solids and with increasing time (indicated by progressively older 14C ages). Finally, the noble gas temperatures (NGTs) obtained from concentrations of the other noble gases (Ne, Ar, Kr and Xe) brings constraints on the earlier recharge conditions during the Holocene. Particularly, the NGTs showed that the studied aquifers were continuously replenished, even under ice-sheet cover in the last 10,000 years.

Abstract Noble gas abundance and isotope data from 12 drilling mud gas samples obtained during IODP Expeditions 338 and 348 provide new insights on fluid origin and fluid migration in the inner accretionary prism below the Kumano forearc basin offshore SE Japan. The samples originate from three adjoining boreholes (C0002F, C0002N and C0002P) spanning depths between 950 and 3050 meters below sea floor (mbsf) and are composed of air and variable contributions of mantle-derived and crustal fluids. Air-corrected 3He/4He ratios of samples from Exp. 338 fall between 0.44 ± 0.24 Ra and 3.26 ± 0.28 Ra. Samples #1400 and #1800 (sample number denotes depth in mbsf) are more influenced by radiogenic helium (1.33 ± 0.34 Ra resp. 0.44 ± 0.24 Ra), whereas the air-free helium isotopic composition of sample #950 is clearly higher (3.26 ± 0.28 Ra). Enhanced radon activity around 950 mbsf, 1100 mbsf, 1400 mbsf, and 1800 mbsf suggests active flow of fluids at these depths. The helium isotopic composition of two other samples (#1700 and #1850) collected during Exp. 338 and of all samples obtained during the 1-year-later Exp. 348 are less variable (1.74–2.46 Ra with a mean 3He/4He ratio of ~ 2.4 Ra) and no radon anomalies were observed during sampling. For these samples, we assume migration by diffusive flow of helium-bearing fluids through sediments of the accretionary prism. In contrast, elevated radon activities and the more variable helium isotopic composition of fluids from 950, 1400, and 1800 mbsf from Exp. 338 are better explained by channelized and active fluid flow through temporarily permeable strata, maybe as a short-term episodic flow event caused by reactivation of buried trust faults. The helium isotopic composition of #950 is in good agreement with estimated helium isotope values of the subducting Philippine Sea Plate (PSP) at present (~ 3.4 Ra), whereas fluids from 1400 and 1800 mbsf demonstrate the input of radiogenic helium from a crustal, probably terrestrial source.

The energy aspects of the problem of intraterrestrial heat transfer in various forms are discussed. Endogenous causes of conductive heat flow dispersion − radiogenic heat generation, tectonic movements and magmatism (volcanism), including its latent and open discharge in the form of volcanic and hydrothermal activity are considered. The geological ordering of the heat flow in the continental crust is related to convective discharge of the heat and mass flux from the mantle, marked by the isotopic composition of helium in freely circulating underground fluids. The combined transport of heat and helium, as well as the correlation of He isotopic compositions in volcanic and hydrothermal gases and Sr compositions in young lavas, testify to the silicate nature of the heat and mass flow emanating from the mantle reservoirs of different depths.

Abstract The helium standard of Japan, referred to as HESJ, is an interlaboratory standard for the 3He/4He ratio. While the ratio of 3He and 4He of the HESJ was previously determined by a relative comparison to atmospheric helium, the absolute value of the 3He/4He ratio of the HESJ has not been directly determined yet. Therefore, it relies on the early measurements of that of atmospheric helium. The accuracy of the absolute 3He/4He ratios of the atmosphere and other working standards including HESJ is crucial in some applications of helium isotopes, such as tritium‐3He dating, surface‐exposure age determination based on cosmogenic 3He, and the accurate measurement of the neutron lifetime. In this work, new control samples of helium gases with 3He/4He ratios of 14, 28, and 42 ppm were fabricated with accuracy of 0.25–0.38% using a gas‐handling system for a neutron lifetime experiment at Japan Proton Accelerator Research Complex. The relative 3He/4He ratios of these samples and the HESJ were measured using a magnetic‐sector type, single‐focusing, noble gas mass spectrometer with a double collector system. As a result, the absolute 3He/4He ratio of the HESJ was determined as 27.36 ± 0.11 ppm. The atmospheric 3He/4He ratio was determined as 1.340 ± 0.006 ppm, based on this work.

A gas blowout during an unauthorized well drilling occurred on June 9, 2020 at the Rome‐Ciampino boundary at the periphery of Colli Albani quiescent volcano. This zone hosts a shallow confined gas‐pressured aquifer, which recently produced further three gas blowouts. Dangerous atmospheric CO2 and H2S concentrations killed some birds, and 12 families were evacuated. The helium isotopic composition indicates that the gas has a magmatic origin. It rises toward the surface along leaky faults, pressurizing the shallow confined aquifer and creating a permanent gas blowout hazard. Colli Albani volcano is characterized by anomalous uplift, release of magmatic gas, and episodic seismic crises. Should a volcanic unrest occur, gas hazard would increase in this densely inhabited zone of Rome city, as the input of magmatic gas into the confined aquifer might create overpressure conditions leading to a harmful phreatic explosion, or increase the emission of hazardous gas through newly created fractures. Plain Language Summary: Rome city is located at the periphery of Colli Albani dormant volcano. Its south‐eastern part hosts a shallow confined gas‐pressurized aquifer, which can produce a gas blowout, that is, a sudden persistent emission of gas and nebulized water, when reached by drillings. Three blowouts were recorded from 2003 to 2016 and a fourth occurred on June 2020. Air concentration of the emitted carbon dioxide and hydrogen sulfide surpassed their Immediately Dangerous to Life and Health limit. Some birds were killed, and 12 families had to be evacuated. The helium isotopic composition confirms that the gas has a deep origin from the Colli Albani magma reservoir. This part of Rome city is permanently exposed to a gas blowout hazard and might be affected either by a phreatic explosion (i.e., without the direct involvement of magma) or by increasing output of hazardous gas through newly created fractures, in case of volcanic unrest at Colli Albani. Key Points: In the SE part of Rome city, a shallow confined gas‐pressurized aquifer produces frequent hazardous gas blowouts from drillingsGas has the highest helium R/Ra of all discharges of the quiescent Colli Albani volcano, indicating a magmatic originIn case of volcanic unrest, a harmful phreatic explosion might occur or the emission of hazardous gas might increase [ABSTRACT FROM AUTHOR]

The atmospheric He/N2 ratio is expected to increase due to the emission of He associated with fossil fuels and is expected to also vary in both space and time due to gravitational separation in the stratosphere. These signals may be useful indicators of fossil fuel exploitation and variability in stratospheric circulation, but direct measurements of He/N2 ratio are lacking on all timescales. Here we present a high-precision custom inlet system for mass spectrometers that continuously stabilizes the flow of gas during sample–standard comparison and removes all non-noble gases from the gas stream. This enables unprecedented accuracy in measurement of relative changes in the helium mole fraction, which can be directly related to the 4 He/N2 ratio using supplementary measurements of O2/N2 , Ar/N2 and CO 2. Repeat measurements of the same combination of high-pressure tanks using our inlet system achieves a He/N2 reproducibility of ∼ 10 per meg (i.e., 0.001 %) in 6–8 h analyses. This compares to interannual changes of gravitational enrichment at ∼ 35 km in the midlatitude stratosphere of order 300–400 per meg and an annual tropospheric increase from human fossil fuel activity of less than ∼ 30 per meg yr -1 (bounded by previous work on helium isotopes). The gettering and flow-stabilizing inlet may also be used for the analysis of other noble-gas isotopes and could resolve previously unobserved seasonal cycles in Kr/N2 and Xe/N2. [ABSTRACT FROM AUTHOR]

Molybdenum isotopes measured in most individual presolar silicon carbide grains are dominated by s-process contributions from the helium intershells of asymptotic giant branch (AGB) stars. The much smaller isotopic variations in molybdenum in meteorites and their components are largely controlled by s-process enrichments or depletions relative to terrestrial composition but lie along two parallel s-process mixing lines separated by what has been suggested to be an r-process contribution. The two mixing lines are populated by carbonaceous-chondrite- and noncarbonaceous-chondrite-related meteorites (CC and NC groups, respectively). We have compared molybdenum isotopic data for presolar grains with those from meteorites and renormalized the meteorite data in a way that is consistent with s-, r-, and p-process contributions observed in presolar SiC grains. The results indicate that (1) there seems to be a fixed ratio between p- and r-process contributions in all data, (2) the dichotomy in molybdenum isotopes between the CC and NC groups can be explained by variations in the isotope makeup of the s-process contribution to the meteoritic samples, (3) this variability is similar to the variations in s-process molybdenum from different AGB stars deduced from presolar grain analyses, and (4) the larger range of isotopic compositions found in refractory inclusions is also consistent with s-process isotope variability. [ABSTRACT FROM AUTHOR]

We report the charge state distributions of the pure and mixed (25%, 50%, and 75% with oxygen and helium gases) neon electron cyclotron resonance (ECR) plasma to probe the hitherto unrevealed mechanism of the gas mixing effect and the isotope anomaly [A. G. Drentje, Rev. Sci. Instrum. 63, 2875 (1992) and A. G. Drentje, Rev. Sci. Instrum. 74, 2631 (2003)]. The multiply charged (up to +7) neon plasma was produced using a 10 GHz all-permanent-magnet NANOGAN ECR ion source. The intensities of highly abundant two isotopes, viz., 20Ne (∼90.48%) and 22Ne (∼9.25%), have been measured by extracting the ions from the plasma, accelerating with different potentials and, finally, analyzing them in mass and energy using a high resolution, large acceptance analyzer-cum-switching dipole magnet. The gas mixing studies show that the addition of oxygen with neon is more effective than that of the helium, particularly on the ion intensities of 20Ne. The higher the fractions of mixing gases, the better are the intensities of highly charged neon ions in the plasma. With and without gas mixing, the intensity ratio of 22Ne to 20Ne shows clear evidence of the isotope anomaly. However, the anomalous effect tends to disappear with increasing oxygen and helium gas mixing. Contrary to the behavior of recently studied pure and oxygen mixed krypton plasma [Kumar et al., J. Mass. Spectrom. 51, 1090 (2016)], the present results are in good agreement with the prediction of linear Landau wave damping theory for selective ion heating in a two-component plasma. [ABSTRACT FROM AUTHOR]

The Huailai area is rich in geothermal resources, but the formation mechanism of its deep heat source is still unclear. In this paper, based on 16 broadband magnetotelluric sounding points, the two-dimensional electrical structure of the crust and mantle in the Huailai area was obtained. Combined with deep seismic reflection and P-wave seismic tomography, the geophysical characteristics of deep heat sources and reservoirs in the Huailai area are described. The Huailai area is characterized by low resistivity and layered reflection above 2 km in depth, which shows the distribution of the Cenozoic sedimentary cover layer. The upper crust is characterized by high resistivity without an obvious reflector, corresponding to the crystalline basement of the basin, whose main lithology is Archean gneiss. There is a highly conductive and bright-spot-reflective structure under the basement, which extends to 100 km, indicating the upwelling of mantle-derived material. Combined with the results of helium isotope tracing, a magma-type geothermal model in the Huailai area is proposed. The upwelling mantle-derived magma material is enriched under the basement to form a heat source. The heat is transferred to the upper crust through heat conduction along the crystalline basement. Then, groundwater circulation brings deep heat to the surface, forming hydrothermal resources. [ABSTRACT FROM AUTHOR]

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The Qulong porphyry Cu–Mo deposit, generated in the Miocene post-collisional extension environment of the Gangdese Copper (Molybdenum) Metallogenic Belt, is one of the largest porphyry Cu deposits in China. This study reports the noble gas isotopic compositions of volatiles released from fluid inclusion reserved in pyrite from the Qulong deposit. 3He/4He and 40Ar/36Ar ratios range from 0.54 to 1.015 Ra and 300–359, respectively. Concentrations of 4He and 40Ar range from 1.77 to 2.62 × 10−8 cm3 STP and 1.7–34 × 10−8 cm3 STP, respectively. The isotopic composition of noble gases indicates that the ore-forming fluids of the Qulong Cu–Mo deposit were a mixture of fluid containing mantle component, which is exsolved from the porphyry magma, and crustal fluid characterized by atmospheric Ar and crustal radiogenic He. The δ34S values of pyrite and molybdenite range from − 0.52‰ to 0.31‰, with an average of − 0.12‰, indicating a magmatic origin. More mantle components were involved in the Cu–Mo deposit than in the Mo–Cu deposit in the Qulong-Jiama ore-district. [ABSTRACT FROM AUTHOR]

The structure of levels of the 8He heavy helium isotope has been studied in the 9Be and 10B stopped pion absorption reactions. Measurements have been performed with a two-arm multilayer semiconductor spectrometer at the LANL. Indications to the existence of a soft dipole mode at the excitation energy MeV have been obtained. A state with a high excitation energy of 12.2(5) MeV has been observed for the first time. [ABSTRACT FROM AUTHOR]

Consistent 3He/4He ratios have been measured for >25 years in geothermal fluids and gases from Cumbre Vieja, La Palma (9.4 ± 0.1RA, where RA is the 3He/4He of air), and Teide, Tenerife (6.8 ± 0.3RA), Canary Islands. Both locations are characterized by similar CO2/3He (~2 to 4 × 109), mantle-like d13C (-3.3‰ to -4.4‰) and CO2 output (0.1-0.2 × 1010 mol yr-1). Helium isotopic differences between the islands cannot be explained by differential aging and 4He ingrowth in their mantle sources. Instead, distinct He reservoirs exist, with a high-µ (HIMU)-type mantle source for La Palma and a more enriched mantle, with possible lithospheric mantle influence, for Tenerife. Geothermal samples from the Canary Islands record a present-day He distribution distinct from higher 3He/4He in olivine from older eastern Canary Island lavas, indicating temporal variability in sources. Comparison of geothermal sample data versus olivine, pyroxene, and glass He isotope data for the Canary Islands, Azores, Cape Verde, Hawaiian islands, and Iceland reveals generally good correspondence, even across >1 m.y. of stratigraphy. However, in addition to the Canary Islands, there are examples of inter-island heterogeneity for He isotopes at Hawaii, the Azores, and within Iceland, preserved in hydrothermal samples, minerals, and glasses. In particular, in northwest Iceland, olivine separates from older lavas preserve higher 3He/4He than present-day geothermal samples from the same region. This difference likely reflects a reduced mantle-derived 3He input to Icelandic magmatism since the Miocene. Temporal variability in 3He/4He, assessed using geothermal and geological materials in conjunction, offers a powerful tool for examining heterogeneity and temporal evolution of mantle sources at intraplate volcanoes. [ABSTRACT FROM AUTHOR]

Helium isotopes in the ocean are very useful tracers of hydrothermal input and deep-sea circulation. Unlike labile trace elements, noble gases are inert and do not react with other substances in the water column. Previous studies in the Indian Ocean showed that helium isotopes in the region were discharged mainly from the central Indian midocean ridge, convergent boundaries, and the Pacific Ocean via currents that flow through the Indonesian archipelago. These Indonesian waters then exit out as the Indonesian Throughflow (ITF) into the Indian Ocean through shallow sills. The ITF plays a significant role in global climate, because it serves as the main pathway of thermocline waters between the Pacific Ocean and Indian Ocean. We present new helium isotope data from International Indian Ocean Expedition (IIOE-2) at the east Indian Ocean in December 2018. Helium isotopes were measured using a Noble Gas Mass Spectrometer at the Atmosphere and Ocean Research Institute, The University of Tokyo. We compare our data with those from previous expeditions and discuss the source and distribution of helium isotopes near Java. Waters with high excess 3He from the ITF were observed at 1000 m. Application of two-components mixing model enabled us to estimate ITF fraction in the observed area and to clarify the ITF flow in the deep layer. Moreover, flow rate of the deep ITF from Savu sill to Indian Ocean was estimated to be ~ 0.8–1.6 Sv. Based on stations near the Java coast, there could be a deep current or hydrothermal source at 3000 m that advects water enriched in 3He southwards along the Java Island. [ABSTRACT FROM AUTHOR]

The article revisiting the finding of widespread deep seismicity in the upper mantle imaged with a dense, temporary nodal seismic array in Long Beach, California using back-projection to detect candidate events and trace randomization to develop a reliable imaging threshold for candidate detections. It discusses the challenges with the Long Beach dataset.

In the nucleus, a nucleon will have interacted with a remaining core. In previous studies, nucleon interactions in atom nuclei have been simulated using the generalized Woods–Saxon potential with an interaction motion assumed to be a binary system. However, the simulation results are only successful in the nucleus of the Helium atom and its isotopes, while the nucleons interaction in the Lithium atom has not been successfully simulated well. The main purpose of this study is to develop a simulation of the nucleons interaction in the atom nucleus with the mass number of the atom greater than the Helium atom. Therefore, in this study, the interaction potential used is the modified Woods–Saxon potential while the interaction motion model still uses a binary system. The trajectory pattern of nucleon interactions is obtained by the numerical solution of the reduced mass equations of the two masses interacting in a binary system. The numerical solution method used is the fourth-order Runge–Kutta method. The simulations can produce the trajectory pattern of the motion of the nucleons in the nucleus of the Helium atom up to the Beryllium-10 isotope. The simulations were also carried out on the atom nuclei of Boron and Carbon, but the simulation results have not been successful. Based on the simulation results, the characteristics of the mass number of each atom nucleus affect the potential shape and trajectory pattern of the nucleon interactions. The binary system can only be applied to the mass number of the atoms is small. [ABSTRACT FROM AUTHOR]

A general method to study classical scattering in n-dimension is developed. Through classical trajectory calculations, the three-body recombination is computed as a function of the collision energy for helium atoms, as an example. Quantum calculations are also performed for the Jπ = 0+ symmetry of the three-body recombination rate in order to compare with the classical results, yielding good agreement for E ≳ 1 K. The classical threshold law is derived and numerically confirmed for the Newtonian three-body recombination rate. Finally, a relationship is found between the quantum and classical three-body hard hypersphere elastic cross sections which is analogous to the well-known shadow scattering in two-body collisions. [ABSTRACT FROM AUTHOR]

The evolution of continental crust can be directly linked to the first-order supercontinent-superplume cycles. We demonstrate that: (1) a mantle-like oxygen isotopic signature is not a diagnostic feature for distinguishing crustal addition from the reworking of pre-existing continental crust; (2) juvenile continental crust shows a wide range of whole-rock Hf isotopic compositions throughout Earth's history; and (3) detrital zircon Hf model ages cannot reliably determine the growth of continental crust. Thus, the wide use of zircon Hf model ages, based on zircon grains with mantle-like oxygen isotopes, is inappropriate for estimating the timing of continental crustal generation. Based on an analysis of global Hf and O isotope and zircon age databases, we argue that the actual U-Pb crystallization ages of juvenile zircon grains provide the best opportunity to unravel crustal growth through time and to test its relationship with supercontinent-superplume cycles. Furthermore, when the Hf isotopes of these juvenile grains plot within the field of juvenile continental crust, they correlate well with times of global mantle depletion as recorded by Os and He isotopes, plume activity as recorded by LIP events, and periods of crustal growth and the breakup of supercontinents. In contrast, zircon grains crystallized from magmas that were produced by partial melting of pre-existing continental crust show U-Pb age peaks that correspond mainly to times of supercontinent assembly and crustal reworking. Detailed analysis shows the key role played by recycling of mafic crustal components in the generation of juvenile continental crust. [ABSTRACT FROM AUTHOR]

Magnetic resonance mass spectrometers (MRMSs), developed in the second half of the 20th century at the Ioffe Institute, have still possessed such a complex of parameters that they have no alternative for solving many analytical problems, in particular, in the isotopy of helium. With the resolution of one of the devices several thousand at the base of the 3He+ mass peak, its absolute sensitivity is <106 atoms of this isotope in the volume of the mass analyzer chamber (~2.5 L), and the 3He/4He isotope ratio measured in a single experiment can be as low as 109 and even 1010. Another device of this type demonstrated resolution of more than 150 000 at the base of the mass peak, which ensured the detection of a 3He+–3T+ doublet. Excellent analytical characteristics of the MRMSs make it possible to use them to study the isotopy of helium in natural and man-made samples (solid, liquid, or gaseous) in meteorites and lunar soil, ferromanganese nodules from the bottom of seas and oceans, in ice cores from the well of Lake Vostok in Antarctica, in water from mountain streams of Mongolia and geysers of Iceland, in volcanic gases of Kamchatka and gases released from structural materials of a modern thermonuclear installation. In this work, we consider the principle and modes of operation of an MRMS and its design. The focus is on the details that distinguish these instruments from other instruments and ensure extremely high analytical performance, which is partly presented in the article. [ABSTRACT FROM AUTHOR]

We discuss an ion-optical system (IOS) of a mass spectrometer designed for isotopic measurements of light gases, containing a magnetic prism with plane-parallel pole tips and two sector-wise, cylindrical-capacitor identical in geometry, symmetrically located relative to the prism. The relationships between the geometric parameters of the capacitors and the prism are given, which are necessary to ensure achromatic focusing of the ion beam in the plane of the detector receiving slit. We assessed numerically the effect of IOS aberrations on the mass resolution of the IOS and determined the optimal emittance of the ion beam at the source output, which enables achieving a resolution at the level of 3000–3500 with an output slit of the ion source of approximately 50 μm, high transmittance of the mass analyzer, small dimensions of the magnetic prism, and a moderate total length of the central ion trajectory (less than 1 m). The IOS is characterized by a high dispersion in masses, which is much larger than the dispersion of conventional sector magnetic mass spectrometers of the same dimensions. The IOS consists of simple geometry elements, which reduces the costs of its implementation and makes the mass spectrometer technologically advanced and convenient to set up and operate. [ABSTRACT FROM AUTHOR]

Rare high-3He/4He signatures in ocean island basalts (OIB) erupted at volcanic hotspots derive from deep-seated domains preserved in Earth's interior. Only high-3He/4He OIB exhibit anomalous 182W--an isotopic signature inherited during the earliest history of Earth-- supporting an ancient origin of high 3He/4He. However, it is not understood why some OIB host anomalous 182W while others do not. We provide geochemical data for the highest-3He/4He lavas from Iceland (up to 42.9 times atmospheric) with anomalous 182W and examine how Sr-Nd-Hf-Pb isotopic variations--useful for tracing subducted, recycled crust--relate to high 3He/4He and anomalous 182W. These data, together with data on global OIB, show that the highest-3He/4He and the largest-magnitude 182W anomalies are found only in geochemically depleted mantle domains--with high 143Nd/144Nd and low 206Pb/204Pb--lacking strong signatures of recycled materials. In contrast, OIB with the strongest signatures associated with recycledmaterials have low 3He/4He and lack anomalous 182W. These observations provide important clues regarding the survival of the ancient He and W signatures in Earth's mantle. We show that high-3He/4He mantle domains with anomalous 182W have lowW and 4He concentrations compared to recycled materials and are therefore highly susceptible to being overprinted with low 3He/4He and normal (not anomalous) 182W characteristic of subducted crust. Thus, high 3He/4He and anomalous 182Ware preserved exclusively in mantle domains least modified by recycled crust. This model places the long-term preservation of ancient high 3He/4He and anomalous 182W in the geodynamic context of crustal subduction and recycling and informs on survival of other early-formed heterogeneities in Earth's interior. [ABSTRACT FROM AUTHOR]

Methods for measuring the composition of a binary gas mixture using the dependence of the speed of sound in a gas on its molecular weight, in particular, using an acoustic resonator, are considered. The described atmospheric hydrogen sensor target station for the cyclotron of the S-70 accelerator, which allows the production of medical isotopes, as well as a sensor for the content of neon in helium during its liquefaction, was developed based on this principle at the Kurchatov Institute IHEP SIC. Optimization of the resonator characteristics allowed a resolution of 10–5. [ABSTRACT FROM AUTHOR]

In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly efficient nanoadsorbent for H2S gas removal. Temperature optimization within the range of 30–90 °C was set which significantly improved the adsorption capacity of the nanoadsorbent. The operational conditions including the initial concentration of H2S (60,000 ppm) with CH4 (15 vol%), H2O (10 vol%), O2 (3 vol%) and the rest by helium gas and gas hour space velocity (GHSV) 4000–6000 h−1 were examined on adsorption capacity. The results of the removal of H2S after 180 min by RGO-N-(piperazine), reduced graphene oxide (RGO), and graphene oxide (GO) were reported as 99.71, 99.18, and 99.38, respectively. Also, the output concentration of H2S after 180 min by RGO-N-(piperazine), RGO, and GO was found to be 170, 488, and 369 ppm, respectively. Both chemisorption and physisorption are suggested as mechanism in which the chemisorption is based on an acid–base reaction between H2S and amine, epoxy, hydroxyl functional groups on the surface of RGO-N-(piperazine), GO, and RGO. The piperazine augmentation of removal percentage can be attributed to the presence of amine functional groups in the case of RGO-N-(piperazine) versus RGO and GO. Finally, analyses of the equilibrium models used to describe the experimental data showed that the three-parameter isotherm equations Toth and Sips provided slightly better fits compared to the three-parameter isotherms. [ABSTRACT FROM AUTHOR]

We present Mayer-sampling Monte Carlo calculations of the quantum Boltzmann contribution to the virial coefficients Bn, as defined by path integrals, for n = 2 to 4 and for temperatures from 2.6 K to 1000 K, using state-of-the-art ab initio potentials for interactions within pairs and triplets of helium-4 atoms. Effects of exchange are not included. The vapor-liquid critical temperature of the resulting fourth-order virial equation of state is 5.033(16) K, a value only 3% less than the critical temperature of helium-4: 5.19 K. We describe an approach for parsing the Boltzmann contribution into components that reduce the number of Mayer-sampling Monte Carlo steps required for components with large per-step time requirements. We estimate that in this manner the calculation of the Boltzmann contribution to B3 at 2.6 K is completed at least 100 times faster than the previously reported approach. [ABSTRACT FROM AUTHOR]

The article talks about the systematics and parametrization of the significance of geofluids hosted in the deep crust. Topics covered include the significance of studies about the occurrence of geofluids in faulted areas, how geofluids may contribute to define a more effective description of the studied area like Probabilistic Seismic Hazard Assessment (PSHA) and Deterministic Seismic Hazard Assessment (DSHA), and concentration and pressure gradients that geofluids are subjected to.