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B. Marty - One of the best experts on this subject based on the ideXlab platform.

  • The I-Pu-Xe age of the Moon-Earth system revisited
    Philosophical transactions. Series A Mathematical physical and engineering sciences, 2014
    Co-Authors: G Avice, B. Marty
    Abstract:

    From iodine-plutonium-xenon isotope systematics, we re-evaluate time constraints on the early evolution of the Earth-atmosphere system and, by inference, on the Moon-forming event. Two extinct radioactivites (129 I, T 1/2 = 15.6 Ma, and 244 Pu, T 1/2 = 80 Ma) have produced radiogenic 129 Xe and fissiogenic 131-136 Xe, respectively, within the Earth, which related isotope fingerprints are seen in the compositions of mantle and atmospheric Xe. Recent studies of Archean rocks suggest that xenon atoms have been lost from the Earth's atmosphere and isotopically fractionated during long periods of geological time, until at least the end of the Archean Eon. Here we build a model that takes into account these results. Correction for Xe loss permits to compute new closure ages for the Earth's atmosphere that are in agreement with those computed for mantle Xe. The minimum Xe formation interval for the Earth-atmosphere is 40-10 +20 Ma after start of solar system formation, which may also date the Moon-forming impact.

  • Coupled noble gas-hydrocarbon evolution of the early Earth atmosphere upon solar UV irradiation
    Earth and Planetary Science Letters, 2014
    Co-Authors: Emmanuel Hébrard, B. Marty
    Abstract:

    Using a new photochemical model of the Earth's early atmosphere, the relationship between noble gas photoionization and organic photochemistry has been investigated from the Archean Eon to the present day. We have found that the enhanced UV emission of the young Sun triggered a peculiar atmospheric chemistry in a CH4-rich early atmosphere that resulted in the increased formation of an organic haze, similar to the preliminary results of a previous study (Ribas et al., 2010). We have investigated the interaction between this haze and noble gases photoionized by the UV light from the younger Sun. Laboratory experiments have shown indeed that ionized xenon trapping into organics (1) is more efficient that other ionized noble gases trapping and (2) results in a significant enrichment of heavy xenon isotopes relative to the light ones (e.g., Frick et al., 1979; Marrocchi et al., 2011). We find moreover preferential photoionization of xenon that peaks at an altitude range comparable to that of the organic haze formation, in contrast to other noble gases. Trapping and fractioning of ionized xenon in the organic haze could therefore have been far more efficient than for other noble gases, and could have been particularly effective throughout the Archean Eon, since the UV irradiation flux from the young Sun was expected to be substantially higher than today (Ribas et al., 2010; Claire et al., 2012). Thus we suspect that the unique isotopic fractionation of atmospheric xenon and its elemental depletion in the atmosphere relative to other noble gases, compared to potential cosmochemical components, could have resulted from a preferential incorporation of the heaviest xenon isotopes into organics. A fraction of atmospheric xenon could have been continuously trapped in the forming haze and enriched in its heavy isotopes, while another fraction would have escaped from the atmosphere to space, with, or without isotope selection of the lightest isotopes. The combination of these two processes over long periods of time provides thereby a key process for explaining the evolution of its isotopic composition in the atmosphere over time that has been observed in Archean archives (Pujol et al., 2011).

Bernard Marty - One of the best experts on this subject based on the ideXlab platform.

  • Archean kerogen as a new tracer of atmospheric evolution: Implications for dating the widespread nature of early life.
    Science advances, 2018
    Co-Authors: David V. Bekaert, Frédéric Delarue, François Robert, Michael W. Broadley, Guillaume Avice, Bernard Marty
    Abstract:

    Understanding the composition of the Archean atmosphere is vital for unraveling the origin of volatiles and the environmental conditions that led to the development of life. The isotopic composition of xenon in the Archean atmosphere has evolved through time by mass-dependent fractionation from a precursor comprising cometary and solar/chondritic contributions (referred to as U-Xe). Evaluating the composition of the Archean atmosphere is challenging because limited amounts of atmospheric gas are trapped within minerals during their formation. We show that organic matter, known to be efficient at preserving large quantities of noble gases, can be used as a new archive of atmospheric noble gases. Xe isotopes in a kerogen isolated from the 3.0–billion-year–old Farrel Quartzite (Pilbara Craton, Western Australia) are mass fractionated by 9.8 ± 2.1 per mil (‰) (2σ) per atomic mass unit, in line with a progressive evolution toward modern atmospheric values. Archean atmospheric Xe signatures in kerogens open a new avenue for following the evolution of atmospheric composition through time. The degree of mass fractionation of Xe isotopes relative to the modern atmosphere can provide a time stamp for dating Archean kerogens and therefore narrowing the time window for the diversification of early life during the Archean Eon.

  • Coupled noble gas-hydrocarbon evolution of the early Earth atmosphere upon solar UV irradiation
    Earth and Planetary Science Letters, 2014
    Co-Authors: Emmanuel Hébrard, Bernard Marty
    Abstract:

    Using a new photochemical model of the Earth’s early atmosphere, the relationship between noble gas photoionization and organic photochemistry has been investigated from the Archean Eon to the present day. We have found that the enhanced UV emission of the young Sun triggered a peculiar atmospheric chemistry in a CH4-rich early atmosphere that resulted in the increased formation of an organic haze, similar to the preliminary results of a previous study (Ribas et al., 2010). We have investigated the interaction between this haze and noble gases photoionized by the UV light from the younger Sun. Laboratory experiments have shown indeed that ionized xenon trapping into organics (1) is more efficient that other ionized noble gases trapping and (2) results in a significant enrichment

  • Reply to comment on “Chondritic-like xenon trapped in Archean rocks: A possible signature of the ancient atmosphere” by Pujol, M., Marty, B., Burgess, R., Earth and Planetary Science Letters 308 (2011) 298–306 by Pepin, R.O.
    Earth and Planetary Science Letters, 2013
    Co-Authors: Magali Pujol, Bernard Marty, Ray Burgess
    Abstract:

    We thank Pepin (2013) for pointing-out an interesting issue concerning the interpretation of the xenon isotope data that we recently published (Pujol et al., 2011). We have analyzed noble gases trapped in quartz fluid inclusions from the 3.5 Ga-old Dresser Formation (Western Australia). Ar–Ar dating of the quartz yielded an age of 3.0±0.2 Ga, slightly younger than the formation age, but still clearly within the Archean Eon. This study focused on the Xe isotopic signature of these fluids: the non-fissiogenic isotopes of xenon appear isotopically fractionated, with about 1% amu−1 enrichment in light isotopes. This isotopic mass fractionation was interpreted to represent an intermediate stage of atmosphere evolution.

  • Reply to comment on "Chondritic-like xenon trapped in Archean rocks: A possible signature of the ancient atmosphere" by Pujol, M., Marty, B., Burgess, R., Earth and Planetary Science Letters 308 (2011) 298-306 by Pepin, R.O.
    Earth and Planetary Science Letters, 2013
    Co-Authors: Magali Pujol, Bernard Marty, Ray Burgess
    Abstract:

    We thank Pepin (2013) for pointing-out an interesting issue concerning the interpretation of the xenon isotope data that we recently published (Pujol et al., 2011). We have analyzed noble gases trapped in quartz fluid inclusions from the 3.5 Ga-old Dresser Formation (Western Australia). Ar–Ar dating of the quartz yielded an age of 3.0±0.2 Ga, slightly younger than the formation age, but still clearly within the Archean Eon. This study focused on the Xe isotopic signature of these fluids: the non-fissiogenic isotopes of xenon appear isotopically fractionated, with about 1% amu−1 enrichment in light isotopes. This isotopic mass fractionation was interpreted to represent an intermediate stage of atmosphere evolution.

  • Nitrogen Isotopic Composition and Density of the Archean Atmosphere
    Science, 2013
    Co-Authors: Bernard Marty, Laurent Zimmermann, Magali Pujol, Ray Burgess, Pascal Philippot
    Abstract:

    Understanding the atmosphere's composition during the Archean Eon is a fundamental issue to unravel ancient environmental conditions. We show from the analysis of nitrogen and argon isotopes in fluid inclusions trapped in 3.0-3.5 Ga hydrothermal quartz that the PN2 of the Archean atmosphere was lower than 1.1 bar, possibly as low as 0.5 bar, and had a nitrogen isotopic composition comparable to the present-day one. These results imply that dinitrogen did not play a significant role in the thermal budget of the ancient Earth and that the Archean PCO2 was probably lower than 0.7 bar.

Emmanuel Hébrard - One of the best experts on this subject based on the ideXlab platform.

  • Coupled noble gas-hydrocarbon evolution of the early Earth atmosphere upon solar UV irradiation
    Earth and Planetary Science Letters, 2014
    Co-Authors: Emmanuel Hébrard, Bernard Marty
    Abstract:

    Using a new photochemical model of the Earth’s early atmosphere, the relationship between noble gas photoionization and organic photochemistry has been investigated from the Archean Eon to the present day. We have found that the enhanced UV emission of the young Sun triggered a peculiar atmospheric chemistry in a CH4-rich early atmosphere that resulted in the increased formation of an organic haze, similar to the preliminary results of a previous study (Ribas et al., 2010). We have investigated the interaction between this haze and noble gases photoionized by the UV light from the younger Sun. Laboratory experiments have shown indeed that ionized xenon trapping into organics (1) is more efficient that other ionized noble gases trapping and (2) results in a significant enrichment

  • Coupled noble gas-hydrocarbon evolution of the early Earth atmosphere upon solar UV irradiation
    Earth and Planetary Science Letters, 2014
    Co-Authors: Emmanuel Hébrard, B. Marty
    Abstract:

    Using a new photochemical model of the Earth's early atmosphere, the relationship between noble gas photoionization and organic photochemistry has been investigated from the Archean Eon to the present day. We have found that the enhanced UV emission of the young Sun triggered a peculiar atmospheric chemistry in a CH4-rich early atmosphere that resulted in the increased formation of an organic haze, similar to the preliminary results of a previous study (Ribas et al., 2010). We have investigated the interaction between this haze and noble gases photoionized by the UV light from the younger Sun. Laboratory experiments have shown indeed that ionized xenon trapping into organics (1) is more efficient that other ionized noble gases trapping and (2) results in a significant enrichment of heavy xenon isotopes relative to the light ones (e.g., Frick et al., 1979; Marrocchi et al., 2011). We find moreover preferential photoionization of xenon that peaks at an altitude range comparable to that of the organic haze formation, in contrast to other noble gases. Trapping and fractioning of ionized xenon in the organic haze could therefore have been far more efficient than for other noble gases, and could have been particularly effective throughout the Archean Eon, since the UV irradiation flux from the young Sun was expected to be substantially higher than today (Ribas et al., 2010; Claire et al., 2012). Thus we suspect that the unique isotopic fractionation of atmospheric xenon and its elemental depletion in the atmosphere relative to other noble gases, compared to potential cosmochemical components, could have resulted from a preferential incorporation of the heaviest xenon isotopes into organics. A fraction of atmospheric xenon could have been continuously trapped in the forming haze and enriched in its heavy isotopes, while another fraction would have escaped from the atmosphere to space, with, or without isotope selection of the lightest isotopes. The combination of these two processes over long periods of time provides thereby a key process for explaining the evolution of its isotopic composition in the atmosphere over time that has been observed in Archean archives (Pujol et al., 2011).

Ray Burgess - One of the best experts on this subject based on the ideXlab platform.

Pascal Philippot - One of the best experts on this subject based on the ideXlab platform.

  • iron and sulfur isotope constraints on redox conditions associated with the 3 2 ga barite deposits of the mapepe formation barberton greenstone belt south africa
    Geochimica et Cosmochimica Acta, 2017
    Co-Authors: Vincent Busigny, Pierre Cartigny, Johanna Marincarbonne, Elodie Muller, Claire Rollionbard, Nelly Assayag, Pascal Philippot
    Abstract:

    Abstract The occurrence of Early Archean barite deposits is intriguing since this type of sediment requires high availability of dissolved sulfate (SO 4 2− ), the oxidized form of sulfur, although most authors argued that the Archean Eon was dominated by reducing conditions, with low oceanic sulfate concentration ( vs metasomatic processes, in particular using Al, Ti and K interrelations. Bulk rock Fe isotope compositions are linked to mineralogy, with δ 56 Fe values varying between −2.04‰ in Fe sulfide-dominated barite beds, to +2.14‰ in Fe oxide-bearing cherts. δ 34 S values of sulfides vary between −10.84 and +3.56‰, with Δ 33 S in a range comprised between −0.35 and +2.55‰, thus supporting an O 2 -depleted atmosphere ( −5  PAL). Iron isotope variations together with major element correlations show that, although the sediments experienced a pervasive stage of hydrothermal alteration, the rocks preserved a primary/authigenic signature predating subsequent hydrothermal stage. Highly positive δ 56 Fe values recorded in primary Fe-oxides from ferruginous cherts support partial Fe oxidation in a reducing oceanic environment (O 2 −4  μM), but are incompatible with a model of complete oxidation at the redox boundary of a stratified water column. Iron oxide precipitation under low O 2 levels was likely mediated by anoxygenic photosynthesis, and/or abiotic photo-oxidation processes. Our results are consistent with global anoxic conditions in the 3.2 Ga-old sediments, implying that the barite deposits were most likely sourced by atmospheric photolysis of S gases produced by large subaerial volcanic events, and possibly SO 4 2− produced by magmatic SO 2 disproportionation in hydrothermal systems.

  • Nitrogen Isotopic Composition and Density of the Archean Atmosphere
    Science, 2013
    Co-Authors: Bernard Marty, Laurent Zimmermann, Magali Pujol, Ray Burgess, Pascal Philippot
    Abstract:

    Understanding the atmosphere's composition during the Archean Eon is a fundamental issue to unravel ancient environmental conditions. We show from the analysis of nitrogen and argon isotopes in fluid inclusions trapped in 3.0-3.5 Ga hydrothermal quartz that the PN2 of the Archean atmosphere was lower than 1.1 bar, possibly as low as 0.5 bar, and had a nitrogen isotopic composition comparable to the present-day one. These results imply that dinitrogen did not play a significant role in the thermal budget of the ancient Earth and that the Archean PCO2 was probably lower than 0.7 bar.

  • Early traces of life investigations in drilling Archean hydrothermal and sedimentary rocks of the Pilbara Craton, Western Australia and Barberton Greenstone Belt, South Africa
    Comptes Rendus Palevol, 2009
    Co-Authors: Pascal Philippot, Martin J. Van Kranendonk, Mark A. Van Zuilen, Kevin Lepot, Nicolas Rividi, Yoram Teitler, Christophe Thomazo, Marie-madeleine Blanc-valleron, Jean-marie Rouchy, Eugene G. Grosch
    Abstract:

    Abstract The Pilbara Craton of Western Australia and the Barberton Greenstone Belt of the Kaapvaal Craton, South Africa, contain some of the oldest and best preserved Archaean rocks and microfossils in the world. Two stratigraphic horizons in the Pilbara Craton were drilled as part of a collaborative effort between France and Australia (the Pilbara Drilling Project) during August 2004, including the 3481 Ma Dresser Formation (Warrawoona Group) and 2724 Ma Tumbiana Formation (Fortescue Group). A new diamond drill hole was cored in August 2008 through part of the ∼3250 Ma Fig Tree Group in the Barberton Greenstone Belt as part of a joint project between France and South Africa. These pristine diamond drill cores present a unique opportunity to constrain the chemistry of the earliest ocean, the composition of the atmosphere, and the settings and types of microbial ecosystems spanning the Archean Eon. These drill core samples can also provide new clues on the earliest metabolic pathways.