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  • 1
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    Hydrothermal 15N15N abundances constrain the origins of mantle nitrogen (2020)
    Nature P. G.
    Details
    Publication Date: 2020-10-19
    Description: Nitrogen is the main constituent of the Earth's atmosphere, but its provenance in the Earth's mantle remains uncertain. The relative contribution of primordial nitrogen inherited during the Earth's accretion versus that subducted from the Earth's surface is unclear1-6. Here we show that the mantle may have retained remnants of such primordial nitrogen. We use the rare 15N15N isotopologue of N2 as a new tracer of air contamination in volcanic gas effusions. By constraining air contamination in gases from Iceland, Eifel (Germany) and Yellowstone (USA), we derive estimates of mantle δ15N (the fractional difference in 15N/14N from air), N2/36Ar and N2/3He. Our results show that negative δ15N values observed in gases, previously regarded as indicating a mantle origin for nitrogen7-10, in fact represent dominantly air-derived N2 that experienced 15N/14N fractionation in hydrothermal systems. Using two-component mixing models to correct for this effect, the 15N15N data allow extrapolations that characterize mantle endmember δ15N, N2/36Ar and N2/3He values. We show that the Eifel region has slightly increased δ15N and N2/36Ar values relative to estimates for the convective mantle provided by mid-ocean-ridge basalts11, consistent with subducted nitrogen being added to the mantle source. In contrast, we find that whereas the Yellowstone plume has δ15N values substantially greater than that of the convective mantle, resembling surface components12-15, its N2/36Ar and N2/3He ratios are indistinguishable from those of the convective mantle. This observation raises the possibility that the plume hosts a primordial component. We provide a test of the subduction hypothesis with a two-box model, describing the evolution of mantle and surface nitrogen through geological time. We show that the effect of subduction on the deep nitrogen cycle may be less important than has been suggested by previous investigations. We propose instead that high mid-ocean-ridge basalt and plume δ15N values may both be dominantly primordial features.
    Description: Published
    Description: 367–371
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Identification of chondritic krypton and xenon in Yellowstone gases and the timing of terrestrial volatile accretion (2020)
    PNAS
    Details
    Publication Date: 2020-10-19
    Description: Identifying the origin of noble gases in Earth's mantle can provide crucial constraints on the source and timing of volatile (C, N, H2O, noble gases, etc.) delivery to Earth. It remains unclear whether the early Earth was able to directly capture and retain volatiles throughout accretion or whether it accreted anhydrously and subsequently acquired volatiles through later additions of chondritic material. Here, we report high-precision noble gas isotopic data from volcanic gases emanating from, in and around, the Yellowstone caldera (Wyoming, United States). We show that the He and Ne isotopic and elemental signatures of the Yellowstone gas requires an input from an undegassed mantle plume. Coupled with the distinct ratio of 129Xe to primordial Xe isotopes in Yellowstone compared with mid-ocean ridge basalt (MORB) samples, this confirms that the deep plume and shallow MORB mantles have remained distinct from one another for the majority of Earth's history. Krypton and xenon isotopes in the Yellowstone mantle plume are found to be chondritic in origin, similar to the MORB source mantle. This is in contrast with the origin of neon in the mantle, which exhibits an isotopic dichotomy between solar plume and chondritic MORB mantle sources. The co-occurrence of solar and chondritic noble gases in the deep mantle is thought to reflect the heterogeneous nature of Earth's volatile accretion during the lifetime of the protosolar nebula. It notably implies that the Earth was able to retain its chondritic volatiles since its earliest stages of accretion, and not only through late additions.
    Description: Published
    Description: 13997–14004
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Keywords: Yellowstone; accretion; mantle plume; noble gases; origin of Earth’s volatiles ; noble gases ; mantle geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: Geochemical and cosmochemical implications (2020)
    Elsevier
    Details
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marty, B., Almayrac, M., Barry, P. H., Bekaert, D., V., Broadley, M. W., Byrne, D. J., Ballentine, C. J., & Caracausi, A. An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: Geochemical and cosmochemical implications. Earth and Planetary Science Letters, 551, (2020): 116574, doi:10.1016/j.epsl.2020.116574.
    Description: The terrestrial carbon to nitrogen ratio is a key geochemical parameter that can provide information on the nature of Earth's precursors, accretion/differentiation processes of our planet, as well as on the volatile budget of Earth. In principle, this ratio can be determined from the analysis of volatile elements trapped in mantle-derived rocks like mid-ocean ridge basalts (MORB), corrected for fractional degassing during eruption. However, this correction is critical and previous attempts have adopted different approaches which led to contrasting C/N estimates for the bulk silicate Earth (BSE) (Marty and Zimmermann, 1999; Bergin et al., 2015). Here we consider the analysis of CO2-rich gases worldwide for which a mantle origin has been determined using noble gas isotopes in order to evaluate the C/N ratio of the mantle source regions. These gases experienced little fractionation due to degassing, as indicated by radiogenic 4He / 40Ar* values (where 4He and 40Ar* are produced by the decay of U+Th, and 40K isotopes, respectively) close to the mantle production/accumulation values. The C/N and C/3 He ratios of gases investigated here are within the range of values previously observed in oceanic basalts. They point to an elevated mantle C/N ratio (∼350-470, molar) higher than those of potential cosmochemical accretionary endmembers. For example, the BSE C/N and 36 Ar / N ratios (160-220 and 75 x 10-7, respectively) are higher than those of CM-CI chondrites but within the range of CV-CO groups. This similarity suggests that the Earth accreted from evolved planetary precursors depleted in volatile and moderately volatile elements. Hence the high C / N composition of the BSE may be an inherited feature rather than the result of terrestrial differentiation. The C / N and 36 Ar / N ratios of the surface (atmosphere plus crust) and of the mantle cannot be easily linked to any known chondritic composition. However, these compositions are consistent with early sequestration of carbon into the mantle (but not N and noble gases), permitting the establishment of clement temperatures at the surface of our planet.
    Description: M.A, D.V.B, M.W.B, D.J.B and B.M were supported by the European Research Council (PHOTONIS project, grant agreement No. 695618 to B.M.). Samples were collected as part of Study # YELL-08056 - Xenon anomalies in the Yellowstone Hotspot. We would like to thank Annie Carlson and all of the rangers at the Yellowstone National Park for providing invaluable advice and help when collecting the samples. This work was partially supported by a grant (G-2016-7206) from the Alfred P. Sloan Foundation and the Deep Carbon Observatory to P.H.B as well as NSF award 2015789 to P.H.B.. Sampling at Mt. Etna and gas analysis was supported by Instituto Nazionale di Geofisica e Vulcanologia Palermo. Fruitful discussions with Marc Hirschmann helped us to shape the ideas presented in this work. We acknowledge detailed and insightful reviews by Sami Mikhail and an anonymous reviewer, and efficient editing by Frederic Moynier. This is CRPG contribution 2741.
    Keywords: Carbon ; Nitrogen ; Earth ; Mantle ; Gases
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere (2022)
    Elsevier
    Details
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Broadley, M., Byrne, D., Ardoin, L., Almayrac, M., Bekaert, D., & Marty, B. High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere. Earth and Planetary Science Letters, 588, (2022): 117577, https://doi.org/10.1016/j.epsl.2022.117577.
    Description: Determining the composition of the Archean atmosphere and oceans is vital to understanding the environmental conditions that existed on the surface of the early Earth. The analysis of atmospheric remnants in fluid inclusions trapped in Archean-aged samples has shown that the Xe isotopic signature of the Archean atmosphere progressively evolved via mass-dependent fractionation, arriving at a modern atmospheric composition around the Archean-Proterozoic transition. The mechanisms driving this evolution are however not well constrained, and it is not yet clear whether the evolution proceeded continuously or via episodic bursts. Providing further constraints on the evolution of Xe in the Archean atmosphere is hampered by the limited amounts of atmospheric gas trapped within fluid inclusions during mineral formation, which impacts the precision at which the Archean atmosphere can be determined. Here, we develop a new crush-and-accumulate extraction technique that enables the heavy noble gases (Ar, Kr and Xe) released from crushing large quantities of hydrothermal quartz to be accumulated and analysed to a higher precision than was previously possible. Using this new technique, we re-evaluate the composition of atmospheric gases trapped within fluid inclusions of 3.3 Ga quartz samples from Barberton, South Africa. We find that the Xe isotopic signature is fractionated by +10.3 ± 1.0‰u−1 (2 SE) relative to modern atmosphere, which is within uncertainty of, but slightly lower than, the previous determination of 12.9 ± 2.4‰u−1 for this sample (Avice et al., 2017). We show for the first time that the Kr/Xe ratio measured within Archean quartz samples is enriched in Xe compared to the modern atmosphere, demonstrating that the atmosphere has lost Xe since the Archean. This further reinforces the proposal of atmospheric escape as the primary mechanism for Earth's Xe loss. We further show that the atmospheric Kr/Xe and Xe isotope fractionation recorded in the Barberton quartz at 3.3 Ga is incompatible with a model describing atmospheric loss at a continuous rate under a constant fractionation factor. This gives credence to numerical models of hydrodynamic escape, which suggest that Xe was lost from the Archean atmosphere in episodic bursts rather than at a constant rate. Refining the evolution curve of atmospheric Xe isotopes using the new technique presented here has the potential to shed light on discrete atmospheric events that punctuated the evolution of the Archean Earth and accompanied the evolution of life.
    Description: This study was supported by the European Research Council (PHOTONIS project, grant agreement No. 695618). This is CRPG contribution #2820.
    Keywords: Archean atmosphere ; Noble gases ; Xenon ; Atmospheric escape
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Possible discontinuous evolution of atmospheric xenon suggested by Archean barites (2021)
    Elsevier
    Details
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Almayrac, M. G., Broadley, M. W., Bekaert, D. V., Hofmann, A., & Marty, B. Possible discontinuous evolution of atmospheric xenon suggested by Archean barites. Chemical Geology, 581, (2021): 120405, https://doi.org/10.1016/j.chemgeo.2021.120405.
    Description: The Earth's atmosphere has continually evolved since its formation through interactions with the mantle as well as through loss of volatile species to space. Atmospheric xenon isotopes show a unique and progressive evolution during the Archean that stopped around the Archean-Proterozoic transition. The Xe isotope composition of the early atmosphere has been previously documented through the analysis of fluid inclusions trapped within quartz and barite. Whether this evolution was continuous or not is unclear, requiring additional analyses of ancient samples, which may potentially retain remnants of the ancient atmosphere. Here we present new argon, krypton and xenon isotopic data from a suite of Archean and Proterozoic barites ranging in age from 3.5 to 1.8 Ga, with the goal of providing further insights in to the evolution of atmospheric Xe, whilst also outlining the potential complications that can arise when using barites as a record of past atmospheres. Xenon released by low temperature pyrolysis and crushing of two samples which presumably formed around 2.8 and 2.6 Ga show Xe isotope mass dependent fractionation (MDF) of 11‰.u−1 and 3.4‰.u−1, respectively, relative to modern atmosphere. If trapped Xe is contemporaneous with the respective formation age, the significant difference in the degree of fractionation between the two samples provides supporting evidence for a plateau in the MDF-Xe evolution between 3.3 Ga and 2.8 Ga, followed by a rapid evolution at 2.8–2.6 Ga. This sharp decrease in MDF-Xe degree suggests the potential for a discontinuous temporal evolution of atmospheric Xe isotopes, which could have far reaching implications regarding current physical models of the early evolution of the Earth's atmosphere.
    Description: This work was funded by the ERC grant No. 695618 to B.M. We thank the S.A.R.M for providing elemental bulk analyses of the barites. We thank Laurent Zimmerman for technical mentorship and assistance.
    Keywords: Archean barite ; Noble gases ; Xenon anomalies ; Archean atmosphere
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    Identification of chondritic krypton and xenon in Yellowstone gases and the timing of terrestrial volatile accretion (2020)
    National Academy of Sciences
    Details
    Publication Date: 2022-10-26
    Description: © The Author(s), [year]. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Broadley, M. W., Barry, P. H., Bekaert, D. V., Byrne, D. J., Caracausi, A., Ballentine, C. J., & Marty, B. Identification of chondritic krypton and xenon in Yellowstone gases and the timing of terrestrial volatile accretion. Proceedings of the National Academy of Sciences of the United States of America, 117 (25), (2020): 13997-14004, doi: 10.1073/pnas.2003907117.
    Description: Identifying the origin of noble gases in Earth’s mantle can provide crucial constraints on the source and timing of volatile (C, N, H2O, noble gases, etc.) delivery to Earth. It remains unclear whether the early Earth was able to directly capture and retain volatiles throughout accretion or whether it accreted anhydrously and subsequently acquired volatiles through later additions of chondritic material. Here, we report high-precision noble gas isotopic data from volcanic gases emanating from, in and around, the Yellowstone caldera (Wyoming, United States). We show that the He and Ne isotopic and elemental signatures of the Yellowstone gas requires an input from an undegassed mantle plume. Coupled with the distinct ratio of 129Xe to primordial Xe isotopes in Yellowstone compared with mid-ocean ridge basalt (MORB) samples, this confirms that the deep plume and shallow MORB mantles have remained distinct from one another for the majority of Earth’s history. Krypton and xenon isotopes in the Yellowstone mantle plume are found to be chondritic in origin, similar to the MORB source mantle. This is in contrast with the origin of neon in the mantle, which exhibits an isotopic dichotomy between solar plume and chondritic MORB mantle sources. The co-occurrence of solar and chondritic noble gases in the deep mantle is thought to reflect the heterogeneous nature of Earth’s volatile accretion during the lifetime of the protosolar nebula. It notably implies that the Earth was able to retain its chondritic volatiles since its earliest stages of accretion, and not only through late additions.
    Description: Samples were collected as part of Study YELL-08056: Xenon Anomalies in the Yellowstone Hotspot. We thank Annie Carlson and all of the rangers at the Yellowstone National Park for providing invaluable advice and help when collecting the samples. M.W.B., D.V.B., D.J.B., and B.M. were supported by the European Research Council (PHOTONIS Project Grant 695618). This work was partially supported by Grants G-2016-7206 and G-2017-9696 from the Alfred P. Sloan Foundation and the Deep Carbon Observatory (to P.H.B.) and UK National Environment Research Council Deep Volatile Grant NE/M000427/1 (to C.J.B.). We also thank Laurent Zimmerman for providing help with the analysis. Finally, we thank the editor for efficient handling of our manuscript and the two anonymous reviewers for their insightful comments. This is CRPG contribution 2998.
    Keywords: Origin of Earth’s volatiles ; Accretion ; Mantle plume ; Noble gases ; Yellowstone
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Unknown
    An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: Geochemical and cosmochemical implications (2020)
    Elsevier
    Details
    Publication Date: 2023-10-31
    Description: The terrestrial carbon to nitrogen ratio is a key geochemical parameter that can provide information on the nature of Earth's precursors, accretion/differentiation processes of our planet, as well as on the volatile budget of Earth. In principle, this ratio can be determined from the analysis of volatile elements trapped in mantle-derived rocks like mid-ocean ridge basalts (MORB), corrected for fractional degassing during eruption. However, this correction is critical and previous attempts have adopted different approaches which led to contrasting C/N estimates for the bulk silicate Earth (BSE) (Marty and Zimmermann, 1999; Bergin et al., 2015). Here we consider the analysis of CO2-rich gases worldwide for which a mantle origin has been determined using noble gas isotopes in order to evaluate the C/N ratio of the mantle source regions. These gases experienced little fractionation due to degassing, as indicated by radiogenic ⁎ values (where 4He and 40Ar* are produced by the decay of U+Th, and 40K isotopes, respectively) close to the mantle production/accumulation values. The C/N and ratios of gases investigated here are within the range of values previously observed in oceanic basalts. They point to an elevated mantle C/N ratio (∼350-470, molar) higher than those of potential cosmochemical accretionary endmembers. For example, the BSE C/N and ratios (160-220 and , respectively) are higher than those of CM-CI chondrites but within the range of CV-CO groups. This similarity suggests that the Earth accreted from evolved planetary precursors depleted in volatile and moderately volatile elements. Hence the high composition of the BSE may be an inherited feature rather than the result of terrestrial differentiation. The and ratios of the surface (atmosphere plus crust) and of the mantle cannot be easily linked to any known chondritic composition. However, these compositions are consistent with early sequestration of carbon into the mantle (but not N and noble gases), permitting the establishment of clement temperatures at the surface of our planet.
    Description: Published
    Description: 116574
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Ultrahigh-precision noble gas isotope analyses reveal pervasive subsurface fractionation in hydrothermal systems (2024)
    American Association for the Advancement of Science
    Details
    Publication Date: 2024-01-12
    Description: 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.
    Description: Published
    Description: eadg2566
    Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
    Description: JCR Journal
    Keywords: noble gases ; earth degassing
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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