December 2024
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12 Reads
Earth and Planetary Science Letters
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December 2024
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12 Reads
Earth and Planetary Science Letters
November 2024
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183 Reads
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1 Citation
The Himalaya orogen evolved since the Eocene as the Tethyan‐, Greater‐, Lesser‐ and Sub‐Himalaya thrust sheets were uplifted and exhumed in sequence. Reconstructing the provenance of sediment in Himalayan River systems can inform on stages in the tectonic history of the orogen. Here, we analyze the oxygen, carbon and “clumped” isotope compositions of carbonate minerals from Himalayan bedrock, Ganga River sediments and Bengal Fan turbidite deposits. We demonstrate that river sediments consist of a mixture of Himalayan‐derived and authigenic calcite precipitated in the river system. The relative abundance and clumped isotope apparent temperatures of detrital calcite in turbidite deposits decreased between the Late Miocene and Pliocene, while chemical weathering intensity did not increase during this interval. Considered together, these results reflect the establishment of the Lesser Himalaya as an important carbonate sediment source for Himalayan rivers, driven by the uplift and exhumation of this thrust sheet.
October 2024
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191 Reads
The deep continental crust represents a vast potential habitat for microbial life where its activity remains poorly constrained. Organic acids like acetate are common in these ecosystems, but their role in the subsurface carbon cycle - including the mechanism and rate of their turnover - is still unclear. Here, we develop an isotope-exchange ‘clock’ based on the abiotic equilibration of H-isotopes between acetate and water, which can be used to define the maximum in situ acetate residence time. We apply this technique to the fracture fluids in Birchtree and Kidd Creek mines within the Canadian Precambrian crust. At both sites, we find that acetate residence times are <1 million years and calculated a rate of turnover that could theoretically support microbial life. However, radiolytic water-rock reactions could also contribute to acetate production and degradation, a process that would have global relevance for the deep biosphere. More broadly, our study demonstrates the utility of isotope-exchange clocks in determining residence times of biomolecules with possible applications to other environments.
October 2024
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194 Reads
Earth and Planetary Science Letters
Methane is an economic energy resource and potent greenhouse gas. Distinguishing secondary microbial methane from thermogenic gas is important for natural gas exploration and consideration of subsurface microbial activity in the global carbon cycle, but remains challenging. To understand controls on methane origins in natural gas systems, we investigated the methane clumped isotopologue distributions in the Qinshui Basin high-thermal maturity coal bed methane (CBM) reservoir. Here, near-equilibrium clumped isotopologues distribution (Δ13CH3D and Δ12CH2D2) inferred a temperature interval of 21.6–252.3 °C. The high-temperature thermodynamic equilibrium most likely represents original thermogenic CBM characteristics during coalification. The low-temperature equilibrium clumped isotopologue distributions suggest microbial alteration to CH4 isotopic bond ordering by increased enzymatically catalyzed isotopic exchange. The independent constraints from clumped isotopes, integrated with other geochemical and genomic evidence, confirm notable secondary microbial methane from biodegradation in the highly mature reservoir. Thus, methane clumped isotopes can be used as unequivocal tracers to distinguish secondary microbial methane from thermogenic gases and hence provide the ability to incorporate them separately into global methane budgets.
September 2024
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9 Reads
Talanta
August 2024
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285 Reads
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1 Citation
Proceedings of the National Academy of Sciences
The oxygen isotope ratio ¹⁸ O/ ¹⁶ O (expressed as a δ ¹⁸ O VSMOW value) in marine sedimentary rocks has increased by ~8‰ from the early Paleozoic to modern times. Interpretation of this trend is hindered by ambiguities in the temperature of formation of the carbonate, the δ ¹⁸ O seawater , and the effects of postdepositional diagenesis. Carbonate clumped isotope measurements, a temperature proxy, offer constraints on this problem. This thermometer is thermodynamically controlled in cases where carbonate achieves an equilibrium internal distribution of isotopes and is independent of the δ ¹⁸ O of the water from which the carbonate grew; therefore, it has a relatively rigorous chemical–physics foundation and can be applied to settings where the δ ¹⁸ O of the water is not known. We apply this technique to an exceptionally well-preserved Ordovician carbonate record from the Baltic Basin and present a framework for interpreting clumped isotope results and for reconstructing past δ ¹⁸ O seawater . We find that the seawater in the Ordovician had lower δ ¹⁸ O seawater values than previously estimated, highlighting the need to reassess climate records based on oxygen-isotopes, particularly where interpretations are based on assumptions regarding either the δ ¹⁸ O seawater or the temperature of deposition or diagenesis. We argue that an increase in δ ¹⁸ O seawater contributed to the long-term rise in the δ ¹⁸ O of marine sedimentary rocks since the early Paleozoic. This rise might have been driven by a change in the proportion of high- versus low-temperature water–rock interaction in the earth’s hydrosphere as a whole.
August 2024
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29 Reads
Geochimica et Cosmochimica Acta
July 2024
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218 Reads
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3 Citations
We report primordial aqueous alteration signatures in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu by the Hayabusa2 spacecraft of JAXA. Newly identified low-molecular-weight hydroxy acids (HO-R-COOH) and dicarboxylic acids (HOOC-R-COOH), such as glycolic acid, lactic acid, glyceric acid, oxalic acid, and succinic acid, are predominant in samples from the two touchdown locations at Ryugu. The quantitative and qualitative profiles for the hydrophilic molecules between the two sampling locations shows similar trends within the order of ppb (parts per billion) to ppm (parts per million). A wide variety of structural isomers, including α- and β-hydroxy acids, are observed among the hydrophilic molecules. We also identify pyruvic acid and dihydroxy and tricarboxylic acids, which are biochemically important intermediates relevant to molecular evolution, such as the primordial TCA (tricarboxylic acid) cycle. Here, we find evidence that the asteroid Ryugu samples underwent substantial aqueous alteration, as revealed by the presence of malonic acid during keto–enol tautomerism in the dicarboxylic acid profile. The comprehensive data suggest the presence of a series for water-soluble organic molecules in the regolith of Ryugu and evidence of signatures in coevolutionary aqueous alteration between water and organics in this carbonaceous asteroid.
July 2024
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21 Reads
Geochimica et Cosmochimica Acta
June 2024
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11 Reads
Proceedings of the National Academy of Sciences
Nitrous oxide (N 2 O), a potent greenhouse gas, can be generated by multiple biological and abiotic processes in diverse contexts. Accurately tracking the dominant sources of N 2 O has the potential to improve our understanding of N 2 O fluxes from soils as well as inform the diagnosis of human infections. Isotopic “Site Preference” (SP) values have been used toward this end, as bacterial and fungal nitric oxide reductases (NORs) produce N 2 O with different isotopic fingerprints, spanning a large range. Here, we show that flavohemoglobin (Fhp), a hitherto biogeochemically neglected yet widely distributed detoxifying bacterial NO reductase, imparts a distinct SP value onto N 2 O under anoxic conditions (~+10‰) that correlates with typical environmental N 2 O SP measurements. Using Pseudomonas aeruginosa as a model organism, we generated strains that only contained Fhp or the dissimilatory NOR, finding that in vivo N 2 O SP values imparted by these enzymes differ by over 10‰. Depending on the cellular physiological state, the ratio of Fhp:NOR varies significantly in wild-type cells and controls the net N 2 O SP biosignature: When cells grow anaerobically under denitrifying conditions, NOR dominates; when cells experience rapid, increased nitric oxide concentrations under anoxic conditions but are not growing, Fhp dominates. Other bacteria that only make Fhp generate similar N 2 O SP biosignatures to those measured from our P. aeruginosa Fhp-only strain. Fhp homologs in sequenced bacterial genomes currently exceed NOR homologs by nearly a factor of four. Accordingly, we suggest a different framework to guide the attribution of N 2 O biological sources in nature and disease.
... The maximum percentage of Tethys Himalayan detritus is identified in Upper Miocene strata, which is supported by the positive correlation between the percentage of carbonate content and the percentage of δ 18 O values >16 ‰ in turbidites (Fig. 4). This fully supports more significative supply from the Tethys Himalaya to Bengal Fan during the Late and Middle Miocene than during the Pliocene-Pleistocene, already documented by the higher detrital carbonate content of the Upper and Middle Miocene turbidites (Ryb et al., 2024;France-Lanord et al., 2016). No relationship is observed instead between Sr -Nd values and single-grain quartz δ 18 O values (Supplementary Figure S6ab). ...
November 2024
... parent body 21 compared with Bennu's, leading to their evaporation and/ or more extensive aqueous alteration, ultimately decomposing or altering carboxylic acids 28 . The structural diversity of carboxylic acids in Bennu is consistent with an origin through stochastic low-temperature free radical reactions on interstellar dust grains 26 . ...
July 2024
... To address these important scientific questions, the Hayabusa2 soluble organic matter (SOM) team 6 evaluated aggregate fine grain samples from the first and second touchdown sites (hereafter, TD1 and TD2); hence, the bulk chemistry data from these two sample collections are averaged representative values for the surface (A0106) and possibly subsurface (C0107) environments (i.e., TD2 was near the artificial crater, for which the depth was~1.7 meters below ground level 8 ) of Ryugu (Fig. 1). For further insight at the organic molecular level, the SOM team determined the first answers to these questions based on carbon (C), nitrogen (N), hydrogen (H), oxygen (O), sulfur (S) elements and their isotopic profiles 6,9,10 , monocarboxylic acids 6 , amino acids and their molecular chirality 6,11,12 , pyrimidine nucleobase and N-heterocycles 6,9 , primordial salts and sulfur-bearing labile molecules between the organic and inorganic interfaces 10 , aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) 13,14 , comprehensive organic molecular profiles 6,15 , molecular growth signatures 16 , and sub-mm scale spatial imaging for organic homogeneity and heterogeneity in the mineral assemblage 6,17 . According to Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR/MS) analysis, the SOM from Ryugu samples contained highly diverse organic molecules (~20,000 species) in the solvent extracts 6,15 . ...
May 2024
Journal of Chromatography Open
... Observations of Io at (sub)millimeter wavelengths previously revealed the distribution of SO 2 , SO, and alkali gases using a variety of single-dish and interferometric facilities (Lellouch et al., 1990(Lellouch et al., , 1992(Lellouch et al., , 1996(Lellouch et al., , 2003Moullet et al., 2010Moullet et al., , 2013Roth et al., 2020;de Pater et al., 2020;Redwing et al., 2022;de Kleer et al., 2024). Moullet et al. (2008) made the first direct measurements of atmospheric winds in Io's SO 2 using the Institut de Radioastronomie Millimétrique (IRAM) Plateau de Bure Interferometer (PdBI). ...
Reference:
Io's SO2 and NaCl Wind Fields From ALMA
April 2024
Science
... While observations are at a relatively low spatial resolution (~350 km/pixel in the near-IR and~750 km/pixel in the mid-IR), infrared spectra have been obtained from 0.7 to 5.3 µm at high spectral resolution (λ/Δλ =~3000), obtaining spectra of gas emission from Io's most powerful volcanoes (de Pater et al. 2023). The Atacama Large (sub-)Millimeter Array (ALMA) can map molecular species in Io's atmosphere with high sensitivity to trace the composition of Io's bulk atmosphere as well as in plumes (de Pater et al. 2020;Redwing et al. 2022;de Kleer et al. 2024); planned upgrades to ALMA in the upcoming decades will increase its ability to map many species simultaneously, and may improve its sensitivity, which would enable detection of new species. ...
April 2024
... In recent years, many scholars have found that CBM can be produced by in situ microorganisms in coal (Tao et al. 2007;Flores et al. 2008;Hamilton et al. 2014;Sechman et al. 2017). The formation and accumulation of biogenic methane in coal seams results from a series of biogeochemical processes facilitated by microorganisms , which are manifested as the synergistic action of living bacteria or fungi and archaea within three major metabolic steps (Susilawati et al. 2015):(1) hydrolysis and fermentation bacteria degrade large components of coal into small molecules, such as fatty acids; (2) vinegar-producing bacteria convert fatty acids, alcohols, some aromatics and amino acids into acetic acid, methanol, H 2 and CO 2 ; (3) simple molecules such as acetic acid are subsequently converted to CH 4 by methanogenic archaea (Wang et al. 2024). Certain methanogenic thermophilic micrococci can directly convert methoxyaromatic compounds (MACs) from coal to CH 4 (Akimbekov et al. 2024). ...
March 2024
Fuel
... In carbonaceous chondrites, insoluble organic matter (IOM) accounts for 70% of all organic matter [39]. Its origin, besides interstellar radical synthesis, might be related to impact-induced reduction reactions, promoted by metal droplets or minerals [40,41]. These metals could act as reductive agents, originating reduced forms of organic matter (e.g., aromatic rings, extensive conjugation, and CO 2 reduction) [42,43]. ...
December 2023
Science
... The supersonic expansion technique introduced the gas-phase molecular complexes into the spectrometer, forming a supersonic molecular beam crucial for well-defined rotational spectra Nasrollahzadeh et al., 2018). Pulsed microwave excitation-induced rotational transitions, and Fourier Transform Infrared (FTIR) detection probed the resulting molecular states, providing information about vibrational and rotational characteristics (Chimiak & Eiler, 2024;Mani, 2018;. The high-resolution capabilities of the PNFTIR spectrometer, both in the time and frequency domains, enabled precise determination of transition frequencies and intensities (Shinggu et nozzle Fourier transform microwave spectroscopy and computational analysis. ...
November 2023
Chemical Geology
... Δ 47-CDES25 = 0.655 ‰ for TV04 and Δ 47-CDES25 = 0.405 ‰ for Carrara (Mangenot et al., 2024). The error related to the standards was used (± 0.014 ‰, 1σ) for samples without 3 replicates. ...
November 2023
Marine and Petroleum Geology
... It could therefore aid in the identification of potential terrestrial contaminants in samples brought back to Earth. Current research also focuses on utilizing ultrahigh-resolution mass spectrometry for stable isotope analysis of larger molecules ( 34 ) providing the possibility for reconstruction of positionspecific and multiply substituted (clumped) isotope abundances, which can give critical insights into the origins of organic materials. ...
November 2023
Analytical Chemistry