Animators : Yves Marrocchi & Evelyn Füri
Permanent investigators :
Guillaume Caro,
François Faure,
Evelyn Füri,
Andrey Gurenko,
Béatrice Luais,
Yves Marrocchi,
Bernard Marty,
Laurent Tissandier
Postdoc fellows :
Isabella Pignatelli (2016-2018)
PhD students :
Précillia Morino (2013-2016)
Léa Florentin (2013-2016)
Lionel Vacher (2015-2018)
Guillaume Florin (2016-2019)
Cosmochemistry
The classical model of solar system formation involves the gravitational collapse of a cloud of gas and dust, its warming, the creation of a central star, the cooling of the cloud by expansion and loss of matter, the formation of increasingly massive bodies, and finally the formation and stabilisation of a succession of planets. This model is based on two approaches, astronomical observations of other star systems and the analysis of material available in the solar system (the Earth and the Moon, Mars via SNCs, meteorites, and certain astronomical measurements of giant planets and comets). Although this model is still widely in use, we do not yet know the exact origin of the matter in the solar system (in particular, whether isotopic anomalies are inherited or result from gas-radiation interactions in the disc), the formation timeline of the central star and first solids, or the role of shocks as an alternative to the evaporation-condensation model. The period covered in this project is that of the accretion disc, during which time the Sun was being built from the mixture of gas and dust inherited from the interstellar environment. The most recent results show that many processes that were previously considered to be hierarchical (condensation, the formation of chondrules, the accretion of chondrites and planetesimals, the differentiation of planetesimals, and the accretion of embryos and, finally, of planets) are, in fact, largely synchronous. This finding significantly changes our view of the early evolution of the solar system. A new understanding of the possible sequence of these processes, of the possible relationships of cause and effect, and of their locations, both temporal and "geographical", within the disc becomes necessary. This understanding is the objective of this study, which will combine mineralogical, chemical, and isotopic studies of extraterrestrial matter ; experimental simulations ; and astrophysical models. One of the essential aspects of this work is the correlation between the young solar system (as described through meteorites) and young stars and their discs (as observed by astrophysicists).
• Formation and evolution of regoliths
• Chondrules as probes of the physico-chemical conditions of the disc
• Simulation and dating of condensation processes
• Radiation-matter interaction in the disc
Earth and Primitive Life
The Hadean (3.8 to 4.5 Gy) and Archean (2.4 to 3.8 Gy) eons represent key periods in the history of the Earth. Our understanding of that time period is obscured by the extreme rarity of rocks older than 3.5 Gy, but we know that it began with the fusion of the mantle during the lunar impact and that it continued with the establishment of a differentiated crust and a proto-atmosphere at 4.45 Gy. It has also been suggested that the Hadean period witnessed the appearance of the first life forms in a relatively warm primitive ocean that could have been formed at 4.3 Gy.
Despite these major advances, the evolution of the young Earth and its fluid envelopes remains subject to numerous uncertainties. On the one hand, our knowledge of Hadean geology is almost exclusively based on the study of zircons from the Jack Hills (<4.4 Gy). While these exceptional specimens have served to establish a geodynamic and compositional model for the Hadean lithosphere, it is unclear whether these constraints can be generalised for the entire planet or whether they represent a mode of crustal growth that would remain marginal until the end of the Archean period. As for the composition of the ocean and atmosphere, these can be understood only through the isotopic and chemical record of the supposedly oldest sediments, which are Banded Iron Formations (BIFS), cherts, or barites. The study of these sediments requires the development of specific tracers to overcome the secondary disturbances that have invariably affected the oldest terrestrial rocks.
Our research focuses on three main areas that aim to better understand and quantify i) the geodynamic processes at work during the first billion years, ii) the physico-chemical parameters (T, PCO2...) of the ocean-atmosphere system, and iii) the early stages of the evolution of life on our planet. These studies are based on the development of innovative isotopic tools that rely on the CRPG analytical facilities (ion probes, noble gas mass spectrometers, TIMS, and next-generation ICP-MS), and on the geological exploration of Archean cratons in search of a geological record from this period of Earth’s history.
• Hadean Geology : From the lunar impact to the creation of the first continents
• Composition and temperature of Archean Oceans
• Evolution of the Precambrian atmosphere
• Biosignatures and Primitive Life
Recent publications
2017 |
Faure, F., L. Tissandier, L. Florentin, and K. Devineau. "A magmatic origin for silica-rich glass inclusions hosted in porphyritic magnesian olivines in chondrules: An experimental study." Geochimica et Cosmochimica Acta 204 (2017): 19–31.
Résumé : Rare silica-rich glass inclusions (69 < SiO2 < 82 wt.%) are described within magnesian olivines of porphyritic Type IA chondrules. These glass inclusion compositions are clearly out of equilibrium with their host Mg-olivines and their presence within the olivines is generally attributed to an unclear secondary process such as a late interaction with nebular gases. We performed dynamic crystallisation experiments that demonstrate that these Si-rich glass inclusions are actually magmatic in origin and were trapped inside olivines that crystallized slowly from a magma with a CI, i.e. solar, composition. Their silicarich
compositions are the consequence of the small volumes of inclusions, which inhibit the nucleation of secondary crystalline phase (Ca-poor pyroxene) but allow olivine to continue to crystallize metastably on the walls of the inclusions. We suggest
that Si-rich glass inclusions could be the only reliable relicts of what were the first magmas of the solar system, exhibiting a CI, i.e. non-fractionated, composition.
Mots-clés : cosmo
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Rouxel, O., and B. Luais. "Germanium isotope geochemistry." Reviews in Mineralogy and Geochemistry 82 (2017): 601–656.
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2015 |
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Bonal, L., R. Brunetto, R. P. Beck, E. Dartois, Z. Dionnet, Z. Djouadi, J. Duprat, E. Füri, Y. Kakazu, P. Oudayer et al. "Visible-IR and Raman micro-spectroscopic investigation of three Itokawa particles collected by Hayabusa: mineralogy and degree of space weathering based on non-destructive analyses." MAPS 50, no. 9 (2015): 1562–1576.
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Füri, E., and B. Marty. "Nitrogen isotope variations in the solar system." Nature Geoscience 8 (2015): 515–522.
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Füri, E., P. H. Barry, L. Taylor, and B. Marty. "Constraints on the origin of nitrogen in lunar basalts: Coupled nitrogen noble gas analyses." Earth and Planetary Science Letters 431 (2015): 195–205.
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Füri, E., M. Chaussidon, and B. Marty. "Evidence for an early nitrogen isotopic evolution in the solar nebula from volatile analyses of a CAI from the CV3 chondrite NWA 8616." Geochimica et Cosmochimica Acta 153 (2015): 183–201.
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Göpel, C., J. L. Birck, A. Galy, J. A. Barrat, and B. Zanda. "Mn–Cr systematics in primitive meteorites: Insights from mineral separation and partial dissolution." Geochimica et Cosmochimica Acta 156, no. 05 (2015): 1–24.
Résumé : Cr isotopic compositions have been measured on carbonaceous chondrites (CC): Tafassasset, Paris, Niger I, NWA 5958, NWA 8157 and Jbilet Winselwan. In bulk samples, the 54Cr/52Cr ratios (expressed as e54Cr) range from 0.93 to 1.58 e units.
These values are in agreement with values characteristic for distinct petrologic types. Despite this 54Cr heterogeneity, the variability in the 53Cr/52Cr ratios (expressed as e53Cr) of 0.2 e units and the Mn/Cr ratios is consistent with the previous finding of an isochron in the Mn–Cr evolution diagram. The Mn/Cr ratio in CC corresponds to variable abundances of high-T condensate formed and separated at the beginning of the solar system, thus the canonical 53Mn/55Mn ratio can be defined. Based on a consistent chronology for U–Pb and Mn–Cr between the earliest objects formed in the solar nebula and the D’Orbigny angrite we define a canonical 53Mn/55Mn ratio and e53Cri of 6.8 ! 10“6 and ”0.177, respectively. The internal Mn/Cr systematics in Tafassasset and Paris were studied by two approaches: leaching technique and mineral separation. Despite variable e54Cr values (up to >30 e) linear co-variations were found between e53Cr and Mn/Cr ratio. The mineral separates as well as the leachates of Tafassasset fall on a common isochron indicating that (1) cooling of the Tafassasset’s parent body occurred at 4563.5 ± 0.25 Ma, and that (2) 54Cr is decoupled from the other isotopes even though temperatures >900 !C have been reached during metamorphism. In the case of Paris, the leachates form an alignment with a 53Mn/55Mn ratio higher than the canonical value. This alignment is not an isochron but rather a mixing line. Based on leachates from various CM and CI, we propose the occurrence of three distinct Cr reservoirs in meteoritic material: PURE54, HIGH53 and LOW53 characterized by a e53Cr and e54Cr of 0 and 25,000, “2.17 and 8, and 0.5 and ”151, respectively.
PURE54 has already been described and is carried by highly refractory nano-spinel; HIGH53 is Mn-rich and most probably carried by sulfides in the matrix, whereas LOW53 is characterized by low Mn/Cr ratios and it is sensitive to metamorphism.
This component could correspond to mineral phases such as refractory oxides and carbide. Variable mixing proportions of HIGH53 and LOW53 would explain the larger-than-expected uncertainty (MSWD of 5.5) on the CC bulk regression line. A Monte Carlo simulation allows us to evaluate the impact of the dispersion of the initial Cr isotopic ratios (as a function of variable HIGH53). The co-variation of the Mn/Cr ratio and the e53Cr defined by the mineral separates from Paris corresponds
to an age of 4566.44 +0.66/"0.75 Ma, while their e54Cr still differ by at least 0.42 e. This age is likely to date the segregation of forsteritic olivines (most probably from type I chondrules) from fayalitic olivines (from type II chondrules) and, given the sampling procedure by handpicking of hundreds of grains, corresponds to the average age of chondrule formation.
Mots-clés : cosmo
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2014 |
Bouquain, S., N. T. Arndt, F. Faure, and G. Libourel. "An experimental study of pyroxene crystallization during rapid cooling in a thermal gradient: application to komatiites." Solid Earth 5 (2014): 641–650.
Résumé : Abstract. To investigate the crystallization of pyroxene in spinifex-textured komatiites, we undertook a series of experiments in which compositions in the CaO-MgO-Al2O3-SiO2 CMAS system were cooled rapidly in a thermal gradient. Cooling rates were generally between 5 and 10 C h−1, but some runs were made at 100–200 C h−1; thermal gradients were between 10 and 20 C cm−1. These conditions reproduced
those at various depths in the crust of komatiite lava flow. The starting composition was chosen to have pigeonite on the liquidus, and most of the experimental charges crystallized zoned pigeonite–diopside crystals like those in komatiite lavas. An intriguing aspect of the experimental results was their lack of reproducibility. Some experiments crystallized forsterite, whereas others that were run under similar conditions crystallized two pyroxenes and no forsterite; some experiments were totally glassy, but others crystallized entirely to pyroxene. The degree of supercooling at the onset of pyroxene crystallization was variable, from less than 25 C to more than 110 C. We attribute these results to the difficulty of nucleation of pyroxene under the conditions of the experiments.
In some cases forsterite crystallized metastably and modified the liquid composition to inhibit pyroxene crystallization in others no nucleation took place until a large degree of supercooling was achieved, and then pyroxene crystallized
rapidly. Pigeonite crystallized under a wide range of conditions, at cooling rates from 3 to 100 C h−1. The notion that this mineral only forms at low cooling rates is not correct.
Mots-clés : cosmo
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Dauphas, N., M. Roskosz, E. E. Alp, D. R. Neuville, M. Y. Hu, C. K. Sio, F. L. H. Tissot, J. Zhao, L. Tissandier, E. Médard et al. "Magma redox and structural controls on iron isotope variations in Earth’s mantle and crust." Earth and Planetary Science Letters 398 (2014): 127–140.
Résumé : The heavy iron isotopic composition of Earth’s crust relative to chondrites has been explained by vaporization during the Moon-forming impact, equilibrium partitioning between metal and silicate at core–mantle-boundary conditions, or partial melting and magma differentiation. The latter view is supported by the observed difference in the iron isotopic compositions of MORBS and peridotites. However, the precise controls on iron isotope variations in igneous rocks remain unknown. Here, we show that equilibrium iron isotope fractionation is mainly controlled by redox (Fe3+/Fe tot ratio) and structural (e.g., polymerization) conditions in magmas. We measured, for the first time, the mean force of iron bonds in silicate glasses by synchrotron Nuclear Resonant Inelastic X-ray Scattering (NRIXS, also known as Nuclear Resonance Vibrational Spectroscopy – NRVS, or Nuclear Inelastic Scattering – NIS). The same samples were studied by conventional Mössbauer and X-ray Absorption Near Edge Structure (XANES) spectroscopy. The NRIXS results reveal a+0.2to+0.4 equilibrium fractionation on 56Fe/54Fe ratio between Fe 2+ and Fe3+ end-members in basalt, andesite, and dacite glasses at magmatic temperatures. These first measurements can already explain∼1/3 of the iron isotopic shift measured in MORBs relative to their source. Further work will be required to investigate how pressure, temperature, and structural differences between melts and glasses affect equilibrium fractionation factors. In addition, large fractionation is also found between rhyolitic glass and commonly occurring oxide and silicate minerals. This fractionation reflects mainly changes in the coordination environment of Fe2+in rhyolites relative to less silicic magmas and mantle minerals, as also seen by XANES. We provide a new calibration of XANES features vs. Fe3+/Fetot ratio determinations by Mössbauer to estimate Fe 3+/Fe tot ratio in situ in glasses of basaltic, andesitic, dacitic, and rhyolitic compositions. Modeling of magma differentiation using rhyolite-MELTS shows that iron structural changes in silicic magmas can explain the heavy iron isotopic compositions of granitoids and rhyolites. This study demonstrates that iron stable isotopes can help reveal planetary redox conditions and igneous processes. Other heterovalent elements such as Ti, V, Eu, Cr, Ce, or U may show similar isotopic variations in bulk rocks and individual minerals, which could be used to establish past and present redox condition in the mantles of Earth and other planets.
Mots-clés : cosmo
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Füri, E., E. Deloule, A. Gurenko, and B. Marty. "New evidence for chondritic lunar water from combined D/H and noble gas analyses of single Apollo 17 volcanic glasses." Icarus 229 (2014): 109–120.
Résumé : In order to assess the proportion of solar, cosmogenic, and indigenous water (hydrogen) trapped in individual Ti-rich lunar volcanic glasses (LVGs) from the 74002 core obtained during the Apollo 17 mission, we coupled ion microprobe measurements of water abundances and D/H ratios with CO2 laser extraction-
static mass spectrometry analyses of noble gases (He, Ne, Ar). The large (300–400 lm in diameter) LVGs studied here contain a small amount of solar wind (SW) volatiles implanted at the grain surfaces, as indicated by the small concentrations of solar helium and neon that represent 65% of the respective total
noble gas abundances. The large proportion of volume-correlated cosmogenic gases reflects an exposure duration of 28 Ma, on average, of the glasses at the lunar surface. Hydrogen abundances determined in the grain interiors of glassy and partially-crystalline LVGs are equivalent to between 6.5 and 54.3 ppm H2O. Based on the noble gas exposure ages, the correction of the measured hydrogen isotope composition for in situ production of cosmogenic deuterium by spallation reactions varies between 5‰to 254‰for the different grains. Corrected dD values range from +38‰ to +809‰ in the LVGs and are anti-correlated with the water content, consistent with extensive hydrogen isotope fractionation during kinetic H2 loss
from a lunar melt with an inferred initial isotope signature of the order of 100‰ and a water content of 100–300 ppm. The detection of water in these primitive lunar melts confirms the presence of a nonanhydrous mantle reservoir within the Moon. Furthermore, our results reveal that the hydrogen isotope composition of water in the melt source of the 74002 LVGs is similar to that of carbonaceous chondrites. These observations indicate that the contribution of deuterium-enriched cometary water to the Earth– Moon system is negligible.
Mots-clés : cosmo
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