Publications by authors named "Jean-Alix Barrat"

14 Publications

  • Page 1 of 1

A 4,565-My-old andesite from an extinct chondritic protoplanet.

Proc Natl Acad Sci U S A 2021 Mar 8;118(11). Epub 2021 Mar 8.

Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France.

The age of iron meteorites implies that accretion of protoplanets began during the first millions of years of the solar system. Due to the heat generated by Al decay, many early protoplanets were fully differentiated with an igneous crust produced during the cooling of a magma ocean and the segregation at depth of a metallic core. The formation and nature of the primordial crust generated during the early stages of melting is poorly understood, due in part to the scarcity of available samples. The newly discovered meteorite Erg Chech 002 (EC 002) originates from one such primitive igneous crust and has an andesite bulk composition. It derives from the partial melting of a noncarbonaceous chondritic reservoir, with no depletion in alkalis relative to the Sun's photosphere and at a high degree of melting of around 25%. Moreover, EC 002 is, to date, the oldest known piece of an igneous crust with a Al-Mg crystallization age of 4,565.0 million years (My). Partial melting took place at 1,220 °C up to several hundred kyr before, implying an accretion of the EC 002 parent body ca. 4,566 My ago. Protoplanets covered by andesitic crusts were probably frequent. However, no asteroid shares the spectral features of EC 002, indicating that almost all of these bodies have disappeared, either because they went on to form the building blocks of larger bodies or planets or were simply destroyed.
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http://dx.doi.org/10.1073/pnas.2026129118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7980472PMC
March 2021

Determination of rare earth elements in gadolinium-based contrast agents by ICP-MS.

Talanta 2021 Jan 3;221:121589. Epub 2020 Sep 3.

Univ Brest, CNRS, UMR 6539 (Laboratoire des Sciences de L'Environnement Marin), LIA BeBEST, Institut Universitaire Européen de La Mer (IUEM), Place Nicolas Copernic, 29280, Plouzané, France.

A simple ICP-MS procedure for the determination of trace element concentrations in GBCAs is described here. Abundances of most of the REEs, Y, Ba and Pb concentrations were determined. We confirm that GBCAs contain traces of non-Gd REEs, Y, Ba and Pb. REE patterns of the five GBCAs actually administered in France have been obtained. They display specific shapes that make it possible to identify the different Gd oxides oxides used by pharmaceutical laboratories to produce them. Our method enables us to quickly evaluate the quantities of impurities in these products and, if necessary, to follow the evolution of their quality in the future. The presence of small but not negligible quantities of Y and REEs other than Gd cannot be ignored in these products, and their behaviour in the human body must be considered. The concentrations measured for Pb and Ba, on the other hand, are much lower and do not pose any particular problems.
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http://dx.doi.org/10.1016/j.talanta.2020.121589DOI Listing
January 2021

A new chemical separation procedure for the determination of rare earth elements and yttrium abundances in carbonates by ICP-MS.

Talanta 2020 Nov 13;219:121244. Epub 2020 Jun 13.

LaTIM (INSERM UMR 1101) Université de Bretagne Occidentale, 22, Avenue C. Desmoulins, 29238, Brest Cedex 3, France.

The determination of rare earth elements (REEs) and Y in carbonates can be complicated by low REE abundances and the presence of significant amounts of Ba resulting in problematic interferences when analysed by ICP-MS. We describe here a novel ion-exchange method using the DGA resin (TODGA), combined with addition of a Tm spike, which allows the separation of the REEs+Y as a whole prior to analysis using an Element XR ICP-MS. This method was validated with results obtained on three different reference carbonate materials (CAL-S, JLs-1 and BEAN, an in-house standard), yielding reproducibility levels better than 3% (RSD) in most cases. This new separation scheme is particularly well suited for carbonate samples having very low REE contents, but could be equally applied to various rock types and organic-rich sample matrices whenever quantitative Ba removal is required.
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http://dx.doi.org/10.1016/j.talanta.2020.121244DOI Listing
November 2020

Gadolinium footprint: Cradle to cradle?

J Neuroradiol 2020 Jun 21;47(4):247-249. Epub 2020 Mar 21.

Laboratoire de Traitement de L'Information Médicale - LaTIM (INSERM UMR 1101), université de Bretagne Occidentale, 22, avenue C.-Desmoulins, 29238 Brest cedex 3, France.

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http://dx.doi.org/10.1016/j.neurad.2020.03.006DOI Listing
June 2020

Brain MRIs make up the bulk of the gadolinium footprint in medical imaging.

J Neuroradiol 2020 Jun 14;47(4):259-265. Epub 2020 Mar 14.

Service d'imagerie médicale, université de Bretagne Occidentale, centre hospitalier régional universitaire de Brest, boulevard Tanguy-Prigent, 29609 Brest cedex, France; (Inserm UMR 1101), laboratoire de traitement de l'information médicale - LaTIM, université de Bretagne Occidentale, 22, avenue C. Desmoulins, 29238 Brest cedex 3, France.

Background And Purpose: Assess the evolution of gadolinium consumption and magnetic resonance imaging (MRI) scanners in France and Western Brittany (France) and compare regional practices between public and private hospitals for each organ specialty.

Material And Methods: We collected data from national and universal health registries, and Western Brittany's health care structures, between 2011 and 2018, about the number of MR imaging exams and machines, the number of delivered GBCAs (gadolinium-based contrast agents), prescriptions and administration protocols.

Results: Over the last eight years, we observed an increase in the number of MRI machines implemented in France (62%), correlated with the increase of annual gadolinium consumption (amount of delivered GBCAs in kg, 64%), without modification of the annual quantity of gadolinium used per machine (2.7kg in 2018). In Western Brittany, gadolinium impact is assigned to neuroimaging exams (50% CI95% [45;56] of all the contrast-enhanced exams), followed by thorax and abdomen exams (23% CI95% [18;28]). The ratio of injected exams to all exams is greater in public than in private hospitals (respectively 48% CI95% [46;49] versus 29% CI95% [26;30]).

Conclusion: Gadolinium consumption is increasing, correlated with the increase in the number of examinations carried out. Regionally, the main impact comes from neuroimaging exams. No change in practices has been observed in recent years despite some warnings about gadolinium deposits and environmental consequences.
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http://dx.doi.org/10.1016/j.neurad.2020.03.004DOI Listing
June 2020

Compound-specific recording of gadolinium pollution in coastal waters by great scallops.

Sci Rep 2019 05 29;9(1):8015. Epub 2019 May 29.

LaTIM (INSERM UMR 1101) Université de Bretagne Occidentale. 22, avenue C. Desmoulins, 29238, Brest Cedex 3, France.

Gadolinium-based contrast agents (GBCAs), routinely used in magnetic resonance imaging (MRI), end up directly in coastal seawaters where gadolinium concentrations are now increasing. Because many aquatic species could be sensitive to this new pollution, we have evaluated the possibility of using shellfish to assess its importance. Gadolinium excesses recorded by scallop shells collected in Bay of Brest (Brittany, France) for more than 30 years do not reflect the overall consumption in GBCAs, but are largely controlled by one of them, the gadopentetate dimeglumine. Although its use has been greatly reduced in Europe over the last ten years, gadolinium excesses are still measured in shells. Thus, some gadolinium derived from other GBCAs is bioavailable and could have an impact on marine wildlife.
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http://dx.doi.org/10.1038/s41598-019-44539-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6541655PMC
May 2019

A large planetary body inferred from diamond inclusions in a ureilite meteorite.

Nat Commun 2018 04 17;9(1):1327. Epub 2018 Apr 17.

Earth and Planetary Science Laboratory (EPSL), Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.

Planetary formation models show that terrestrial planets are formed by the accretion of tens of Moon- to Mars-sized planetary embryos through energetic giant impacts. However, relics of these large proto-planets are yet to be found. Ureilites are one of the main families of achondritic meteorites and their parent body is believed to have been catastrophically disrupted by an impact during the first 10 million years of the solar system. Here we studied a section of the Almahata Sitta ureilite using transmission electron microscopy, where large diamonds were formed at high pressure inside the parent body. We discovered chromite, phosphate, and (Fe,Ni)-sulfide inclusions embedded in diamond. The composition and morphology of the inclusions can only be explained if the formation pressure was higher than 20 GPa. Such pressures suggest that the ureilite parent body was a Mercury- to Mars-sized planetary embryo.
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http://dx.doi.org/10.1038/s41467-018-03808-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5904174PMC
April 2018

Oxygen isotopic evidence for accretion of Earth's water before a high-energy Moon-forming giant impact.

Sci Adv 2018 03 28;4(3):eaao5928. Epub 2018 Mar 28.

Planetary and Space Sciences, School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK.

The Earth-Moon system likely formed as a result of a collision between two large planetary objects. Debate about their relative masses, the impact energy involved, and the extent of isotopic homogenization continues. We present the results of a high-precision oxygen isotope study of an extensive suite of lunar and terrestrial samples. We demonstrate that lunar rocks and terrestrial basalts show a 3 to 4 ppm (parts per million), statistically resolvable, difference in ΔO. Taking aubrite meteorites as a candidate impactor material, we show that the giant impact scenario involved nearly complete mixing between the target and impactor. Alternatively, the degree of similarity between the ΔO values of the impactor and the proto-Earth must have been significantly closer than that between Earth and aubrites. If the Earth-Moon system evolved from an initially highly vaporized and isotopically homogenized state, as indicated by recent dynamical models, then the terrestrial basalt-lunar oxygen isotope difference detected by our study may be a reflection of post-giant impact additions to Earth. On the basis of this assumption, our data indicate that post-giant impact additions to Earth could have contributed between 5 and 30% of Earth's water, depending on global water estimates. Consequently, our data indicate that the bulk of Earth's water was accreted before the giant impact and not later, as often proposed.
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http://dx.doi.org/10.1126/sciadv.aao5928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5873841PMC
March 2018

Silicon isotopes in angrites and volatile loss in planetesimals.

Proc Natl Acad Sci U S A 2014 Dec 17;111(48):17029-32. Epub 2014 Nov 17.

Université de Brest, Institut Universitaire Européen de la Mer, 29280 Plouzané, France.

Inner solar system bodies, including the Earth, Moon, and asteroids, are depleted in volatile elements relative to chondrites. Hypotheses for this volatile element depletion include incomplete condensation from the solar nebula and volatile loss during energetic impacts. These processes are expected to each produce characteristic stable isotope signatures. However, processes of planetary differentiation may also modify the isotopic composition of geochemical reservoirs. Angrites are rare meteorites that crystallized only a few million years after calcium-aluminum-rich inclusions and exhibit extreme depletions in volatile elements relative to chondrites, making them ideal samples with which to study volatile element depletion in the early solar system. Here we present high-precision Si isotope data that show angrites are enriched in the heavy isotopes of Si relative to chondritic meteorites by 50-100 ppm/amu. Silicon is sufficiently volatile such that it may be isotopically fractionated during incomplete condensation or evaporative mass loss, but theoretical calculations and experimental results also predict isotope fractionation under specific conditions of metal-silicate differentiation. We show that the Si isotope composition of angrites cannot be explained by any plausible core formation scenario, but rather reflects isotope fractionation during impact-induced evaporation. Our results indicate planetesimals initially formed from volatile-rich material and were subsequently depleted in volatile elements during accretion.
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http://dx.doi.org/10.1073/pnas.1418889111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4260610PMC
December 2014

Trachyandesitic volcanism in the early Solar System.

Proc Natl Acad Sci U S A 2014 Sep 18;111(35):12689-92. Epub 2014 Aug 18.

Meteorite Museum, 55430 Oberwesel, Germany.

Volcanism is a substantial process during crustal growth on planetary bodies and well documented to have occurred in the early Solar System from the recognition of numerous basaltic meteorites. Considering the ureilite parent body (UPB), the compositions of magmas that formed a potential UPB crust and were complementary to the ultramafic ureilite mantle rocks are poorly constrained. Among the Almahata Sitta meteorites, a unique trachyandesite lava (with an oxygen isotope composition identical to that of common ureilites) documents the presence of volatile- and SiO2-rich magmas on the UPB. The magma was extracted at low degrees of disequilibrium partial melting of the UPB mantle. This trachyandesite extends the range of known ancient volcanic, crust-forming rocks and documents that volcanic rocks, similar in composition to trachyandesites on Earth, also formed on small planetary bodies ∼ 4.56 billion years ago. It also extends the volcanic activity on the UPB by ∼ 1 million years (Ma) and thus constrains the time of disruption of the body to later than 6.5 Ma after the formation of Ca-Al-rich inclusions.
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http://dx.doi.org/10.1073/pnas.1404799111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4156728PMC
September 2014

A deep crust-mantle boundary in the asteroid 4 Vesta.

Nature 2014 Jul;511(7509):303-6

EPSL, Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland.

The asteroid 4 Vesta was recently found to have two large impact craters near its south pole, exposing subsurface material. Modelling suggested that surface material in the northern hemisphere of Vesta came from a depth of about 20 kilometres, whereas the exposed southern material comes from a depth of 60 to 100 kilometres. Large amounts of olivine from the mantle were not seen, suggesting that the outer 100 kilometres or so is mainly igneous crust. Here we analyse the data on Vesta and conclude that the crust-mantle boundary (or Moho) is deeper than 80 kilometres.
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http://dx.doi.org/10.1038/nature13499DOI Listing
July 2014

Determination of rare earth elements and other trace elements (Y, Mn, Co, Cr) in seawater using Tm addition and Mg(OH)₂ co-precipitation.

Talanta 2011 Jul 5;85(1):582-7. Epub 2011 May 5.

Département Géosciences Marines, IFREMER, 29280 Plouzané, France.

This paper reports on a novel procedure for determining trace element abundances (REE and Y, Cr, Mn, Co) in seawater by inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The procedure uses a combination of pre-concentration using co-precipitation onto magnesium hydroxides and addition of thulium spike. The validity of the method was assessed onto 25 ml volumes of certified reference materials (NASS- and CASS-4) and in house seawater standard. Procedural blanks were determined by applying the same procedure to aliquots of seawater previously depleted in trace elements by successive Mg(OH)(2) co-precipitations, yielding estimated contributions to the studied samples better than 1.1% for all elements, with the exception of Cr (<3.3%) and Co (up to 8%). The reproducibility of the method over the six month duration of the study was smaller than 11% RSD for all the studied elements. Results obtained for NASS-5 and CASS-4 agree well with published working values for trace elements.
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http://dx.doi.org/10.1016/j.talanta.2011.04.023DOI Listing
July 2011

A unique basaltic micrometeorite expands the inventory of solar system planetary crusts.

Proc Natl Acad Sci U S A 2009 Apr 6;106(17):6904-9. Epub 2009 Apr 6.

Laboratoire de Minéralogie et de Cosmochimie du Muséum, Muséum National d'Histoire Naturelle, Unité Mixte de Recherche Centre National de Recherche Scientifique-7202, CP52, 57 rue Cuvier, 75005 Paris, France.

Micrometeorites with diameter approximately 100-200 microm dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission.
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http://dx.doi.org/10.1073/pnas.0900328106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2678474PMC
April 2009

First occurrence of early Homo in the Nachukui Formation (West Turkana, Kenya) at 2.3-2.4 Myr.

J Hum Evol 2005 Aug;49(2):230-40

CNRS, UPR 2147, 44 rue de l'Amiral Mouchez, 75014 Paris, France.

Cognitive abilities and techno-economic behaviours of hominids in the time period between 2.6-2.3 Myr have become increasingly well-documented. This time period corresponds to the oldest evidence for stone tools at Gona (Kada Gona, West Gona, EG 10-12, OGS 6-7), Hadar (AL 666), lower Omo valley (Ftji1, 2 & 5, Omo 57, Omo 123) in Ethiopia, and West Turkana (Lokalalei sites -LA1 & LA2C-) in Kenya. In 2002 a new palaeoanthropological site (LA1alpha), 100 meters south of the LA1 archaeological site, produced a first right lower molar of a juvenile hominid (KNM-WT 42718). The relative small size of the crown, its marked MD elongation and BL reduction, the relative position of the cusps, the lack of a C6 and the mild expression of a protostylid, reinforced by metrical analyses, demonstrate the distinctiveness of this tooth compared with Australopithecus afarensis, A. anamensis, A. africanus and Paranthropus boisei, and its similarity to early Homo. The LA1alpha site lies 2.2 m above the Ekalalei Tuff which is slightly younger than Tuff F dated to 2.34+/-0.04 Myr. This juvenile specimen represents the oldest occurrence of the genus Homo in West Turkana.
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http://dx.doi.org/10.1016/j.jhevol.2005.03.009DOI Listing
August 2005