Gas Isotope Research Articles

Simulation of radioactive fission gas release from defective PWR fuel rod using the MFPR/R mechanistic code

A software package was elaborated by coupling the mechanistic code MFPR/R with a recently developed advanced model of mass exchange in defective fuel rods, to simulate the release of radioactive gaseous fission products into the coolant during operation of a thermal reactor. To simulate the oxidation of UO2 fuel, the processes of steam dissociation and radiolysis in the rod free volume were additionally considered. The package was validated by calculating the release of krypton, iodine and xenon isotopes into the coolant from defective rods under irradiation in the pressurized light water loop of the NRX reactor at Chalk River Nuclear Laboratories. It is shown that a reasonable overall agreement between calculations and experiment for noble gas isotopes can be obtained by introducing a single fitting parameter that takes into account uncertainties in the rod geometry and the rate of hydrogen production in the rod free volume.

Selective production of hydrogen isotope gases via PdAg-catalyzed dehydrogenation of formic acid in D2O assisted by surface-grafted amine groups

Hydrogen isotope gases are widely used as deuterium sources in industrial manufacturing processes. It would therefore be beneficial to develop a facile, simple means of selective producing molecular deuterium (D2) and hydrogen deuteride (HD), although reasonable heterogeneous catalytic methodologies are still missing. We previously demonstrated that the hydrogen isotope gases was selectively obtained from formic acid (HCOOH, FA) and D2O using PdAg nanoparticles supported on mesoporous silica (SBA-15) on which amine functional groups had been grafted. In the present work, amine-functionalized carbon was used as an efficient support material to provide a catalyst with improved activity. Employing weakly basic phenylamine groups, D2 was predominantly evolved and the reaction rate was doubled compared with that for our previously reported system. A high degree of correlation between D2 selectivity and the basicity of the grafted amine groups was also observed. The applicability of the present catalytic system was highlighted by in situ deuteration of diphenylacetylene in a solution of FA in D2O, during which deuterated products were obtained with high efficiency.

Origin of the Ultra-Deep Hydrocarbons from the Shunbei No. 1 Fracture Zone in the North of Shuntuoguole Low Uplift, Tarim Basin, North-Western China

In order to have a deeper insight into the accumulation mechanism of ultra-deep hydrocarbons, in this paper, the recently discovered ultra-deep Ordovician light oil and gas deposits (>7200 m) in the Shunbei No. 1 fracture zone are studied intensively, including maturity, source kitchens, the extent of secondary alterations, and possible migration directions, based on an analysis of the molecular compositions and stable carbon isotopes of crude oils and natural gases. The average equivalent vitrinite reflectance (Rc) of these oils, estimated from light hydrocarbons (H versus I), MDI, DNR, and MDR, are about 1.50%, 1.58%, 1.48%, and 1.51%, respectively, which suggests that most of the oils are in the late stages of crossing the oil window. The two maturity grades (1.06–1.25% and 1.36–1.67%) of the oil samples calculated from the aromatic compounds indicate the presence of at least two stages of hydrocarbon charge. In addition, the positive correlation plot of DNR and MDR (y = 3.59x − 12.84; R2 = 0.96) indicates that oils in the southwestern region of the F1 (S1-11–S1-16) are slightly more mature than oils in the northeastern region of the F1 and the well at SL1, far from the No. 1 main fault zone. In addition, the study shows that these hydrocarbons belong to the same source kitchen of a reduced marine sedimentary environment with mixed organic matter comprising benthic and planktonic algae, based on biomarker parameters, light hydrocarbons, and carbon isotope compositions. The oil–oil correlation analyses suggest that the studied oil samples are probably derived from the in situ Lower Cambrian Yuertusi formation source rocks. Various geochemical parameters consistently show limited significant hydrocarbon alteration processes, indicating favorable preservation conditions in the study area. The integrated geochemical characteristics of the hydrocarbons allow us to infer that they mainly migrate vertically from the in situ Lower Cambrian Yuertusi formation source rocks toward the Ordovician reservoirs, followed by a certain degree of lateral migration from southwest to northeast.

Selecting resonances in molecular scattering by anti-Zeno effect.

Utilizing the anti-Zeno effect, we demonstrate that the resonances of ultracold molecular interactions can be selectively controlled by modulating the energy levels of molecules with a dynamic magnetic field. We show numerically that the inelastic scattering cross section of the selected isotopic molecules in the mixed isotopic molecular gas can be boosted for 2-3 orders of magnitude by modulation of Zeeman splittings. The mechanism of the resonant anti-Zeno effect in the ultracold scattering is based on matching the spectral modulation function of the magnetic field with the Floquet-engineered resonance of the molecular collision. The resulting insight provides a recipe to implement resonant anti-Zeno effect in control of molecular interactions, such as the selection of reaction channels between molecules involving shape and Feshbach resonances, and external field-assisted separation of isotopes.

Kinetic hydrogen isotope effects and flow compensation strategy of the ZrCo-based chemical beds in full-scale SDS demo-system

ZrCo-based bed, commonly exploited to efficiently process large quantities of mixed hydrogen isotope gases, is one of crucial component in the storage and delivery system (SDS) of the tritium plant in fusion reactor. However, the hydrogen isotope effect on the desorption and adsorption processes of the ZrCo based assemblies has not yet clearly addressed, especially for a full-scale (100 g of Tritium) bed assembly. Herein, the kinetic hydrogen isotope effect of the full-scale ZrCo-based chemical beds, including ZrCo, Zr0.8Ti0.2Co, Zr0.8Hf0.2Co, with different hydrogen isotope ratios in SDS demo-system are investigated in detail. This work shows that the kinetic adsorption isotope effect of all ZrCo based beds are independent of pressure, temperature, and hydrogen isotope ratio. Conversely, the kinetic hydrogen isotope fluctuation is prominent during hydrogen desorption, where the proportion of protium is relatively high at the initial stage. After that, deuterium is easier to release. Finally, the protium gradually increases. The fluctuating degree is in the sequence of Zr0.8Ti0.2Co > ZrCo > Zr0.8Hf0.2Co for types of chemical beds, and 50%D + 50%H > 90%D + 10%H > 10%D + 90%H for isotope components. Based on experimental details, a flow compensation approach to ensure a stable ratio of hydrogen isotope gas is proposed. This work is of crucial significance for practical-scale SDS system operation, which is the prerequisite for the steady-state running of the fusion reactor.

Ultrahigh-precision noble gas isotope analyses reveal pervasive subsurface fractionation in hydrothermal systems.

Mantle-derived noble gases in volcanic gases are powerful tracers of terrestrial volatile evolution, as they contain mixtures of both primordial (from Earth's accretion) and secondary (e.g., radiogenic) isotope signals that characterize the composition of deep Earth. However, volcanic gases emitted through subaerial hydrothermal systems also contain contributions from shallow reservoirs (groundwater, crust, atmosphere). Deconvolving deep and shallow source signals is critical for robust interpretations of mantle-derived signals. Here, we use a novel dynamic mass spectrometry technique to measure argon, krypton, and xenon isotopes in volcanic gas with ultrahigh precision. Data from Iceland, Germany, United States (Yellowstone, Salton Sea), Costa Rica, and Chile show that subsurface isotope fractionation within hydrothermal systems is a globally pervasive and previously unrecognized process causing substantial nonradiogenic Ar-Kr-Xe isotope variations. Quantitatively accounting for this process is vital for accurately interpreting mantle-derived volatile (e.g., noble gas and nitrogen) signals, with profound implications for our understanding of terrestrial volatile evolution.

Incorporation of wet gases to kerogen in petroleum formation and evolution

The formation mechanism for thermogenic gas remains unresolved. Disputes are focused on: (1) stability barrier for decomposition of oil to gas and wet gas to methane, and (2) inconsistence in dryness ratio (C1/ΣC1–5) between gases produced in pyrolysis experiments and in natural reservoirs. Here, we demonstrate the variation trend of dryness ratio (C1/ΣC1–5) with temperatures and thermal stress levels, and the correlation of dryness ratios with the yields of liquid components (ΣC8+) in confined pyrolysis experiments (gold capsules) of twenty coals. At both heating rates of 2 and 20 °C/h, dryness ratios of gaseous hydrocarbons at first decrease, and then increase with increasing temperatures and thermal stress levels. Dryness ratios of produced gases can be very high in the range of 66.3–95.7 wt% at initial temperature about 334 °C and heating rate of 20 °C/h, corresponding to EASY%Ro 0.56. We suggest that these gases are not the original products released from kerogen, but have been altered via wet gas incorporation to kerogen. Larger oil molecules (C8+) are more competitive in incorporating to kerogen compared with wet gases, and therefore, prohibit wet gas incorporation, leading to the observed trend of gas dryness ratios with increasing temperature and maturity and the negative correlation between dryness ratios and the yields of liquid components (ΣC8+). The conflicting results between the yields and carbon isotopes of wet gases produced in the isothermal confined pyrolysis experiments for coal plus oil can be well interpreted using the reaction mechanism that wet gases incorporate to kerogen while oil components retard this incorporation. Once free oil and wet gas molecules are reincorporated to kerogen, the bound molecules can easily decompose to smaller molecules due to substantial reduction of activation energy for carbon-carbon bond rupture. Petroleum formation from kerogen can be a recycling process: kerogen first releases oil compounds, and then free molecules reincorporate to kerogen and further decompose to smaller molecules, and finally to methane.

Effect of rearing conditions on fatty acid allocation during flight in nectivorous lepidopteran Mythimna unipuncta

Insect species that are nectivorous as adults acquire essential fatty acids almost exclusively from host plants during larval development. Thus, as essential fatty acids are important for a number of different biological processes, adult allocation of this limited resource may result in important trade-offs. Most lepidopteran species that migrate do so as sexually immature adults, so essential fatty acids used for migratory flight would not be available for subsequent reproduction. Using the true armyworm, Mythimna unipuncta, as a model system we analyzed fat body samples to test the hypothesis that environmental cues would influence the use of essential fatty acids during migratory flight. We used diets manipulated isotopically to trace origins and use of stored lipids and used chromatographic analyses to determine fatty acid composition. In the first experiments, 5-day old moths that had been reared in summer or fall (migratory) conditions and were force flown for different lengths of time (0–6 h) after which samples of the fat body were analyzed. Rearing conditions did not affect fatty acid loading however patterns of use during flight differed with essential fatty acids being conserved under fall but not summer conditions. As migratory flight can take several days, we repeated the experiment when 5-day old moths were flown for 8 h each day for up to 5 days. Some moths were provided access to sugar water after each flight while others were only given water or only given sugar water once. When sugar water was readily or sporadically available, moths reared under fall conditions conserved their essential fatty acids indicating that the environmental cues responsible for the onset of migratory flight result in physiological changes that modify lipid use. However, when moths had only water, the essential fatty acids were not conserved, highlighting the importance of nectar availability at stopovers for the conservation essential fatty acids during migration. Isotopic analysis of the moth fat body indicated a large contribution of adult-derived diet to lipids used as fuel. The implications of using isotopic approaches to other flight studies and future research on differential resource allocation in winged monomorphic migratory insects are discussed. Summary statement: Isotopic tracing methods and gas chromatography were used to demonstrate that environmental cues can impact patterns of fatty acid use in true armyworm moths. In particular, essential fatty acids are conserved during migratory flight. However, availability of adult food sources will determine the degree to which essential fatty acids are conserved.

Origin and hydrogeochemical formation processes of geothermal fluids from the Kibiro area, Western Uganda

The Kibiro geothermal field, located in the western branch of the East African Rift Valley System, has many geothermal surface manifestations. Several geochemical research has already been carried out in this area. However, the sources of dissolved ions in geothermal fluids have not been assessed so far. The hydrochemical and gas isotopic characteristics have been examined in this study to identify and determine the sources of the main dissolved components and the geochemical processes involved in the formation of the geothermal fluid. Methods applied in the analysis of the genesis and hydrogeochemical evolution of geothermal fluids include isotope tracers, major ion ratios, graphical methods (stability diagrams, durov diagrams, chloro-alkaline indices, piper diagrams, and HNC-plot), and hydrogeochemical simulations using PHREEQC software. The Kibiro hot springs are high salinity Na–Cl waters. Based on δ18O and δ2H values, the geothermal waters are found to be of meteoric origin. The assessments indicate that Na+ and Cl− are derived from halite dissolution. The dissolution of dolomite, calcite, gypsum, and anhydrite is responsible for the concentration of Ca2+, Mg2+, SO42−, and HCO3−. The main source of K+ is derived from the dissolution of silicate rocks (K-feldspar). The gas isotopes analysis indicates that 97.5% of He with isotope ratio of 0.217 Ra mainly originates from crustal sources and 2.47% is derived from the mantle. 51.39% of CO2 originates from marine limestone, 46.55% from sedimentary organic carbon and 2.06% from the mantle. This evidence further confirms that there are no direct inputs of volatiles from a magma chamber below the Kibiro geothermal field. The evolution of the fluids suggests that most of the common cations and anions found in the Kibiro hot spring waters originated from high-temperature water/rock interaction.

Retention of noble and rare isotope gases in plasma-facing components – Experience from the JET tokamak with the ITER-like wall

Plasma edge cooling, ion cyclotron wall conditioning and disruption mitigation techniques involve massive gas injection (by puffs or pellets) to the torus. A certain fraction remains in plasma-facing components (PFC) due to co-deposition and implantation. An uncontrolled release/desorption of such retained species affects the stability of plasma operation. The aim of this work was to determine the lateral and depth distribution of noble (3He, 4He, Ne, Ar), seeded (N2, Ne, Ar) and tracer gases (15N, 18O) in PFC retrieved from the JET tokamak with the ITER-Like Wall (JET-ILW) after three experimental campaigns (ILW-1, ILW-2, ILW-3). Results regarding the retention of those gases are shown as well as a comparison to the deuterium retention in the studied areas. Heavy ion elastic recoil detection analysis was used, being the only technique capable of detection and quantitative assessment of all elements, especially low-Z isotopes. Helium was found on the divertor Tile 5, locally up to 44·1015 3He cm−2 and 12·1015 4He cm−2, and on the limiters as well. Neon was found in two positions on the limiters, with up to 10·1015 Ne cm−2 and the 15N tracer on Be limiters exposed to ILW-3. A correlation of N retention with the N seeding rates for each campaign has also been found.

Dissolved gases in the deep North Atlantic track ocean ventilation processes

Gas exchange between the atmosphere and ocean interior profoundly impacts global climate and biogeochemistry. However, our understanding of the relevant physical processes remains limited by a scarcity of direct observations. Dissolved noble gases in the deep ocean are powerful tracers of physical air-sea interaction due to their chemical and biological inertness, yet their isotope ratios have remained underexplored. Here, we present high-precision noble gas isotope and elemental ratios from the deep North Atlantic (~32°N, 64°W) to evaluate gas exchange parameterizations using an ocean circulation model. The unprecedented precision of these data reveal deep-ocean undersaturation of heavy noble gases and isotopes resulting from cooling-driven air-to-sea gas transport associated with deep convection in the northern high latitudes. Our data also imply an underappreciated and large role for bubble-mediated gas exchange in the global air-sea transfer of sparingly soluble gases, including O2, N2, and SF6. Using noble gases to validate the physical representation of air-sea gas exchange in a model also provides a unique opportunity to distinguish physical from biogeochemical signals. As a case study, we compare dissolved N2/Ar measurements in the deep North Atlantic to physics-only model predictions, revealing excess N2 from benthic denitrification in older deep waters (below 2.9 km). These data indicate that the rate of fixed N removal in the deep Northeastern Atlantic is at least three times higher than the global deep-ocean mean, suggesting tight coupling with organic carbon export and raising potential future implications for the marine N cycle.

Natural gas characteristics and gas-source comparisons of the Lower Triassic Feixianguan Formation, Eastern Sichuan Basin, China

There is great controversy regarding the origin and source of natural gas in the Lower Triassic Feixianguan Formation in the Eastern Sichuan Basin. This seriously restricts the study of natural gas dynamics in the Feixianguan Formation and thus hampers natural gas exploration in the region, so further study is urgently required. Using experimental tests of natural gas composition, stable isotopes, and noble gas isotopes with gas chromatography (GC) and mass spectrometry (MS) studies of source rock and reservoir asphalt saturated hydrocarbons, the natural gas geochemical characteristics, the genetic identification and a gas-source comparison of the Feixianguan Formation were studied. Then, constrained by the thermal history, the histories of gas generation and expulsion were restored by basin simulation technology. Finally, a gas accumulation model was established for the Feixianguan Formation. The results showed that (1) the H2S-rich and H2S-poor gas reservoirs of the Feixianguan Formation are distributed on the east and west sides of the Kaijiang-Liangping trough in the Eastern Sichuan Basin, respectively. The carbon and hydrogen isotope compositions of the natural gas in the gas reservoirs are generally heavy and have typical characteristics of high-maturity dry gas reservoirs. (2) The natural gas of the Feixianguan Formation is organic thermogenic gas, which is mainly oil-type gas generated by the secondary cracking of crude oil. The gas-generating parent material is mainly type II kerogen. (3) The natural gas of the Feixianguan Formation in the Eastern Sichuan Basin was mainly generated by argillaceous source rocks of the Upper Permian Longtan Formation. (4) Natural gas accumulation occurred as follows: the paleo-structure heights were filled with crude oil in the Early Jurassic, and paleo-oil reservoirs were formed in the Feixianguan Formation; during the Middle-Late Jurassic, the paleo-oil reservoirs were cracked when the reservoir temperatures rose above 160 °C, and paleo-gas reservoirs were formed. Since the end of the Late Jurassic, the paleo-gas reservoirs have been adjusted and reformed to form the present-day natural gas reservoirs. These results provide a basis for studying natural gas accumulation dynamics of the Feixianguan Formation in the Eastern Sichuan Basin.

Quantitative analysis of hydrogen isotope gas mixtures by low resolution quadrupole mass spectrometer

Quadrupole mass spectrometry (QMS) has an important application in the field of rapid on-line analysis of hydrogen isotopes. However, due to the interference of isotope fractionation effect and mass overlap peaks, accurate quantitative analysis of hydrogen isotopes by quadrupole mass spectrometry has always been a challenging problem. For the calibration of a low-resolution quadrupole mass spectrometry, standard samples of hydrogen isotopes gas mixtures with different HD contents were prepared by platinum catalyst that accelerated hydrogen isotope exchange reaction. The results show that the fraction of ionized fragments of various hydrogen isotopes in the mixture is stable and less affected by the coexistence of other isotopes. Taking the main fragment peak as the calibration basis, considering the isotope fractionation effect and mass overlap peak interference, the calibration curve between hydrogen isotope abundance and mass spectral signal was obtained by systematic correction method, and the linear correlation coefficient is 0.9991. The average relative errors between the correction values and the standard values of isotope abundance measured are 1.87% (hydrogen content) and 3.43% (deuterium content), respectively. The method developed in this work can be used for rapid on-line quantitative analysis of hydrogen isotope gas mixtures.

Isotope mass dependence of pedestal transport in JET H-mode plasmas

We present a comparative transport analysis of the isotope mass dependence in the pedestal of two pairs of deuterium/hydrogen type I ELMy H-mode discharges in JET with ITER-like wall, one characterized by the same input power, the other one by the same stored energy. The investigation, carried out using the gyrokinetic code GENE, focuses on the steep profile region of the pedestal. While large wavenumber modes mainly contribute to the electron heat flux and are scarcely influenced by the main gas isotope, an effect of the ion mass in agreement with the experimental (so called anti-gyro-Bohm) scaling is revealed in the low wavenumber range. In this context, the major role played by the shear in regulating the ion-temperature-gradient turbulence is analyzed in some detail. The competing level of turbulent and neoclassical transport is quantified to shed light on the experimental features of the pedestal profiles at different ion mass, with the particle transport found to be consistent with a higher pedestal top density for increasing isotope masses, and the heat transport shown to match the roughly unaltered observed temperature profiles.

Distribution characteristics and controlling factors of helium-rich gas reservoirs

With the increasing demand for helium and the gradual shortage of proven helium resources, discussing the distribution characteristics and controlling factors of helium-rich reservoirs discovered around the world can not only help us deeply understand the accumulation process of helium in the crust, but also provide guidance for finding helium resources. Based on the compilation of gas chemical composition, stable isotope and noble gas isotope data of helium-rich gas reservoirs found in the world, this paper discusses the distribution characteristics and key controlling factors in combination with geological data. According to the chemical composition, helium-rich gas reservoirs can be divided into three types: helium-rich CH4, helium-rich CO2 and helium-rich N2. Among them, helium-rich CH4 reservoirs are mainly distributed in cratons, while helium-rich CO2 and helium-rich N2 reservoirs are distributed in orogen and fault zones. The gas-producing layers of different types of helium-rich gas reservoirs almost show the characteristics of ancient age and shallow burial. The helium reserves of helium-rich CH4 and helium-rich CO2 reservoirs are similar and significantly larger than those of helium-rich N2 reservoirs, but the helium content shows the opposite characteristics. Helium source, supplying intensity of associated gas, helium accumulation mode, and tectonic-magmatic activity may be the key factors controlling the distribution of helium-rich gas reservoirs in the crust. As far as helium exploration is concerned, the Proterozoic and Paleozoic traps located in uplift structure which has developed Precambrian granite basement, moderate distance from the gas supply center, high geothermal gradient and developed faults are the most effective exploration target. At the same time, the Meso-Cenozoic traps connecting with the Precambrian granite basement through unconformity or deep-seated faults can also be used as potential exploration targets for helium resources.

Geochemistry of thermal fluids and the genesis of granite-hosted Huangshadong geothermal system, Southeast China

The geochemistry of the thermal waters in the granite-hosted Huangshadong geothermal system was studied to characterize the hydrogeology of the system and potential geothermal energy prospects. In recent years, interest in geothermal energy utilization as an alternative and non-fossil fuel energy source has grown in China. The thermal waters have temperatures of 48–99 °C at the surface and are classified as of HCO3-Na type with low total dissolved solids (TDS) content (192–727 mg/L) and neutral pH (7.12–8.15). Based on the isotope (δ2H, δ18O, 87Sr/86Sr) and chemical (Li, Cl, and Sr) compositions, the thermal waters were sourced from local meteoric water, followed by water-rock interaction with the granite host rocks and mixing with non-thermal water upon water ascent to the surface. Applying geothermometry and mixing models, the chemical composition (SiO2, B, Li, Na, K, Rb, Ca, Mg, Sr, Al, F, Cl, Br, HCO3, and SO4) of deep thermal water was assessed and the reservoir temperature was predicted as approximately 150–165 °C. The corresponding thermal water elemental composition was in equilibrium with common secondary minerals. Based on noble gas isotope systematics (3He, 4He, and 20Ne), He is a crustal source (>95%) being accompanied by radiogenic heat, which is presumably the principal source of induced heat observed in the geothermal systems. Other volatiles (CO2, N2, and Ar) were also of crustal and/or atmospheric origin. Based on chemical and isotopic systematics, it was concluded that the Huangshadong geothermal field is a medium-enthalpy geothermal system with thermal water circulated to a depth of approximately 3.5 km, corresponding to a power density of 4.4 MW/km2. Such geothermal systems are potentially suitable for deep drilling (>2–3 km), followed by energy production and the direct use of thermal water. These findings reveal the genesis mechanism of hydrothermal systems in the granite-hosted area of Southeast China and indicate that high-enthalpy geothermal fluids can hardly be expected within a drilling depth of 4 km.

Geochemical characteristics and enrichment regularity of bedrock reservoir in the central paleo-uplift, north songliao basin

The Central Paleo-Uplift is a key target for exploration in the deep layers of the Songliao Basin. Our study focused on the systematic analysis of the forming conditions and accumulation patterns of bedrock reservoirs. We conducted this analysis using data such as gas composition, isotopes, slices, and CT scans, while also considering factors such as source rock, hydrocarbon supply window, and transport channels. By analyzing these factors, we were able to gain insights into the geological processes that led to the formation of these reservoirs. Our findings reveal that the gas in the Central Paleo-Uplift is primarily coal-formed and highly mature. These gases originate from two main sources - the Xujiaweizi Fault Depression as the primary source, and the Gulong Fault Depression as the secondary source. We identified two types of gas reservoirs in the area, namely weathering reservoirs and inside bedrock reservoirs. The weathering reservoirs primarily contain gas trapped in erosion pores and fractures, while the inside bedrock reservoirs mainly contain gas in fractures. The Central Paleo-Uplift area is surrounded by favorable source rocks, with greater hydrocarbon supply windows on the east side compared to the west. The efficient transport channels have facilitated the accumulation of gas, while the presence of a steady mudstone cap has been advantageous for the preservation of gas reservoirs. The region contains various traps that are favorable for gas accumulation, with higher concentrations found at elevated positions. Our study identified three distinct accumulation patterns in the north, middle, and south regions of the Central Paleo-Uplift. The Wangjiatun Bulge, Changde Bulge, and Zhaozhou Bulge are particularly promising areas for exploration in this region.

Noble gas mass-spectrometry for extraterrestrial micro-samples: analyses of asteroid matter returned by Hayabusa2 JAXA mission

Mass spectrometry of noble gas isotopes from the asteroid materials delivered by robotic space missions requires high sensitivity, high ion transmission, low detection limit, and other characteristics not readily available in commercial instruments.

Bacterial anomalies associated with deep sea hydrocarbon seepage along the Scotian Slope

Deep sea hydrocarbon seep detection relies predominantly on geochemical analyses of seabed marine sediment cores to identify the presence of gas or oil. The presence of seeping hydrocarbons in these locations alters local redox stratification and microbial community structure. Cultivation-independent biodiversity surveys of microbial communities can offer a proxy for seeping hydrocarbons, but this strategy has not been extensively investigated in deep water settings. In this study, 16S rRNA gene sequencing of bacterial communities was performed on sediment cores obtained in >2500 m water depth at 43 different locations in the Northwest Atlantic Ocean. Cores extending down to 10 m below seafloor (mbsf) were assessed for gas composition, gas isotopes and liquid hydrocarbons. Over 650 bacterial biodiversity libraries were constructed from different sediment depths at these locations. Sites with strong evidence for the presence of thermogenic or biogenic hydrocarbon seepage were reflected in bacterial population analyses that revealed significant differences between hydrocarbon seep and non-seep locations. Specific bacterial indicators were associated with different sediment depth intervals including Caldatribacteriota and Campilobacterota OTUs observed in high relative sequence abundance at 20-50 cmbsf in hydrocarbon seep sediments. These groups were differentially abundant between sites with thermogenic and biogenic hydrocarbon seepage.

Origin and evolution of a CO2-Rich gas reservoir offshore Angola: Insights from the Gas Composition and isotope analysis

The pre-salt sections of the offshore Kwanza Basin, Angola are potentially petroliferous reservoirs like their Brazilian counterparts on the other side of the South Atlantic Ocean. In this study, a pre-salt reservoir of the offshore Kwanza Basin was found to contain solid bitumen and gas of high portions of CO2 (ca. 83%) and methane (ca. 16%). The chemical and isotopic (C, H and He) compositions of the gas indicate that the CO2 is primarily mantle-derived while the gaseous hydrocarbons are mainly late mature thermogenic gas. The Barremian-Aptian Red Cuvo Formation with sapropelic and humic organic matter and an average TOC content of 1.7% could be the principal source of the bitumen and gaseous hydrocarbons in the reservoir. Rapid oil generation since the source rock sedimentation could have occurred as a result of the fast and thick salt deposition or the high thermal gradient created by the crustal thinning and magmatism during the South Atlantic Ocean opening. The δ13C of gaseous hydrocarbons also indicates their mixed origins of sapropelic and humic organic matters and possible abiotic processes.This reservoir is similar in the origin of CO2 and geological background to some pre-salt reservoirs in the Brazilian basins. Such similarities with prolific petroleum systems may imply great petroleum potential in the pre-salt sections of the offshore Kwanza Basin, Angola.