Papers by Laurent Zimmermann
Geochemical Perspectives Letters, 2018
The atmospheric helium isotope composition (R A = 3 He/ 4 He air = 1.39 × 10-6) could have varied... more The atmospheric helium isotope composition (R A = 3 He/ 4 He air = 1.39 × 10-6) could have varied over recent times due to anthropogenic activities. In order to check this possibility, we conducted high-precision helium isotope measurements of air trapped in various stainless steel containers from France (pétanque balls, a float carburettor; 1910-2016) and Cape Grim, Tasmania (archived air tanks; 1978, 1988). We used a double collector mass spectrometer at the Centre de Recherches Pétrographiques et Géochimiques (CRPG, Nancy, France). We found a similar composition between the French and Cape Grim air samples. The temporal variation estimated from all samples including data previously published is not significant, with a trend of +0.002 ± 0.024 ‰/yr over 106 years (2σ). We suspect that the release of radiogenic 4 He by fossil fuel exploitation could have been at least partly offset by the production of 3 He (via the decay of 3 H) from nuclear tests. This study supports the suitability of atmospheric helium as an inter-laboratory isotope standard.
Investigations on the composition of the ancient atmosphere have relied so far on indirect approa... more Investigations on the composition of the ancient atmosphere have relied so far on indirect approaches based on geochemical proxies (eg., S isotopes), or on modelling. However, remnants of Archean atmospheric gases are still preserved in ancient rocks. Our group is investigating the composition of the Archean atmosphere, by analysing gases in well characterized and dated barite and quartz fluid inclusions from the Dresser Formation (North Pole, Pilbara, NW Australia). 3.5 Ga ago, the 40Ar/36Ar atmospheric ratio was 143±24 (modern value : 298) [1]. The xenon isotopic composition was isotopically intermediate between extraterrestrial and modern atmospheric [2]. The density of N2 and the nitrogen isotope composition of the Archean atmosphere were comparable to that of the modern atmosphere, but the PCO2 could have been as high as 0.7 bar [3]. These results are consistent with: (i) an Archean atmosphere already shielded from interaction with the solar wind by a significant (>50% moder...
Goldschmidt2021 abstracts, 2021
Opérations unitaires. Génie de la réaction chimique, 2015
Cet article presente les materiaux (vanne, jauge primaire et secondaire, pompe,...) pour developp... more Cet article presente les materiaux (vanne, jauge primaire et secondaire, pompe,...) pour developper des lignes de purification sous ultravide dans les laboratoires de recherche afin de purifier, dans les meilleures conditions analytiques, les gaz rares extraits des echantillons geologiques, tels que des roches ou des mineraux. Differents systemes pour etuver les lignes jusqu'a 300 °C sont aussi presentes afin de reduire la contamination atmospherique (N2, O2, gaz rares) et le degazage des especes interferentes comme les hydrocarbures. Enfin, differentes mesures pour proteger le vide des augmentations accidentelles de la pression sont proposees.
Earth and Planetary Science Letters, 2020
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NonCommercial-NoDerivatives| 4.0 International License
In order to better understand condensation processes in the primitive solar nebula, we have set u... more In order to better understand condensation processes in the primitive solar nebula, we have set up a new apparatus which allows to perform condensation experiments at high temperature and low vacuum from refractory complex gases.
The EGU General Assembly, 2016
The rates and chronologies of valley incision are closely modulated by the tectonic uplift of act... more The rates and chronologies of valley incision are closely modulated by the tectonic uplift of active mountain ranges and were controlled by repeated climate changes during the Quaternary. The continental collision between the Iberian and Eurasian plates induced a double vergence orogen, the Pyrenees, which has been considered as a mature mountain range in spite of significant seismicity (e.g. Chevrot et al., 2011) and evidence of neotectonics (e.g. Goula et al., 1999). Nevertheless, recent studies indicate that the range may have never reached a steady state (Ford et al., in press). One option for resolving this controversy is to quantify the incision rates since the Miocene by reconstructing the vertical movement of geometric markers such as fluvial terraces. However, the few available ages from the Pyrenean terrace systems do not exceed the middle Pleistocene. Thus, to enlarge the time span of this dataset, we studied alluvium-filled horizontal epiphreatic passages in limestone ka...
The ability of discriminating the various forcing parameters controlling the growth of mountain r... more The ability of discriminating the various forcing parameters controlling the growth of mountain ranges depends on the knowledge of the deformation, exhumation and sedimentation chronologies and on accurate constraints on the orogen geometry necessary to quantify accretion and erosion fluxes. The Pyrenees, an intraplate collision range, built by the shortening of continental thinned margins during the convergence between Iberia and Eurasia lasting from Late Cretaceous to Early Miocene, are a particularly well-suited study area to examine the coupling and retroactions between climate and tectonics. Indeed, consisting in a doubly vergent asymmetric orogenic wedge, the northeastern foreland basin underwent particular conditions from the Miocene to the Pliocene due to the closure of all oceanic connections resulting from the continuing convergence between Iberia and Eurasia. In addition, the orogenic growth and its sedimentary evolution occurred during the Cenozoic climatic cooling. To i...
Le soulevement tectonique des chaines de montagnes actives controle a priori les rythmes et les t... more Le soulevement tectonique des chaines de montagnes actives controle a priori les rythmes et les taux d’incision des vallees fluviales, lesquels sont a leur tour modules par les changements cli-matiques repetes du Quaternaire. Une option pour contraindre les mouvements verticaux a long terme est de quantifier les taux d’incision par le biais de marqueurs geometriques passifs du soulevement tels que les terrasses alluviales. Cependant, selon les contextes geo-morphologiques, il n’est pas toujours possible de contraindre les mouvements verticaux de la lithosphere a partir de tels marqueurs. Dans les massifs calcaires les reseaux karstiques peuvent constituer une alternative : ils offrent en effet l’opportunite de determiner a partir de la concentration en cosmonucleides produits in situ dans les quartz la duree d’enfouissement d’alluvions fluviatiles produits par la partie amont des bassins versants et pieges a la traversee des chainons calcaires peripheriques. En effet, au fur et a me...
Meteoritics & Planetary Science, 2021
Cosmic ray exposure (CRE) ages of rocks that were ejected by the impacts that created Cone and No... more Cosmic ray exposure (CRE) ages of rocks that were ejected by the impacts that created Cone and North Ray craters provide two crucial calibration points at <100 Ma for the lunar cratering chronology function, which relates the crater density of geological units on the Moon to their absolute age. To reassess the formation ages of these two craters, we determine here the accumulated abundances of 'cosmogenic' noble gas nuclides (3 He cosm , 21 Ne cosm , 38 Ar cosm), as well as the corresponding CRE ages, in six Apollo 14 rocks (i.e., one breccia and five basalts) and two Apollo 16 anorthosites that were collected near the rims of Cone and North Ray craters, respectively. Although noble gas concentrations allow CRE ages to be derived, the calculated 21 Ne and 38 Ar exposure ages of a given sample cover a significant range of values because published empirical or theoretical production rates of cosmogenic nuclides are highly variable. Nonetheless, it is evident that mare basalts 14053 and 14072 as well as breccia 14068, which were collected near the rim of Cone Crater, were exposed at the lunar surface more recently than the three KREEP basalts (14073, 14077, 14078) collected further away. The 38 Ar exposure ages of anorthosites 67075 and 67955 from North Ray Crater slightly exceed those of samples 14053, 14068, and 14072. These results confirm that Cone Crater is younger than North Ray Crater. However, the formation ages of Cone and North Ray craters have larger uncertainties than previously acknowledged. This implies that the uncertainties of noble gas exposure ages should be taken into account when remotely dating young surfaces on the Moon and on other planetary bodies in the solar system.
Geochimica et Cosmochimica Acta, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Geomorphology, 2020
Abstract Despite increasing knowledge on the orogenic phases of the Pyrenees, the Neogene evoluti... more Abstract Despite increasing knowledge on the orogenic phases of the Pyrenees, the Neogene evolution of the range remains poorly constrained. The central Pyrenees, particularly the Ariege River valley and its terrace systems and glacial extensions, are key to reconstructing Pyrenean evolution during the Neogene. However, few terrace relics remain on the piedmont edges. To overcome this limitation and temporally extend the dataset obtained from terraces, we focus on alluvium-filled horizontal epiphreatic passages developed in limestone karstic networks. These landforms record the transient position of former local base levels during the process of valley deepening, similar to fluvial terraces. The alluvium fills of the studied caves in the Tarascon-sur-Ariege area, in the transition zone between the upper range and the piedmont, therefore enable the reconstruction of the geodynamic evolution of the Ariege River valley. All studied caves are developed on at least eight levels. Based on burial durations determined by 26Al/10Be and 10Be/21Ne terrestrial cosmogenic nuclide dating of samples from epiphreatic levels, our results indicate Langhian to Messinian (~13–5 Ma) incision rates averaging 48 m Myr−1. However, the obtained record does not allow us to accurately retrace the Pliocene evolution of the area due to the lack of known caves at corresponding levels. Moreover, raised local base levels during glacial phases both make the record more complex and call into question the methodological approach in terms of potential internal sediment remobilization and mixing related to implied re-flooding periods.
Opérations unitaires. Génie de la réaction chimique, 2020
Chemical Geology
A new all-metal induction furnace for extraction of all noble gases from pyroxenes, olivines, qua... more A new all-metal induction furnace for extraction of all noble gases from pyroxenes, olivines, quartz or barites has been developed at CRPG. It differs in design from other induction furnaces in that the totality of the vacuum vessel is metallic and the induction coil, normally located outside the furnace, has been placed inside the vacuum vessel, with a special radio frequency power feedthrough welded onto a flange. The volume of the crucible is ≈15 cm 3 and permits fusion of samples with a mass of up to 1 g. Samples are packed into a metal foil, loaded into a carousel, baked out before analysis, and then sequentially dropped into the Ta-
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Papers by Laurent Zimmermann