Insitut University Of France

Tremblay-en-France, France

Insitut University Of France

Tremblay-en-France, France
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Tan Z.,CAS Institute of Geology and Geophysics | Tan Z.,CNRS Paris Institute of Earth Sciences | Tan Z.,University of Chinese Academy of Sciences | Agard P.,CNRS Paris Institute of Earth Sciences | And 9 more authors.
Lithos | Year: 2017

The Chinese Southwestern Tianshan high- to ultra-high pressure low temperature (HP–UHP/LT) metamorphic belt exhibits well-preserved mafic layers, tectonic blocks/slices and boudins of different sizes and lithology embedded within dominant meta-volcanosedimentary rocks. Despite a wealth of previous studies on UHP relicts, P–T path estimates and age constraints for metamorphism, controversies still exist on P–T–t assessments and regional exhumation patterns (i.e., tectonic mélange versus internally coherent “sub-belt” model). This study focuses on a group of coesite-bearing eclogite samples from a thick (~ 5 m) layered metabasalt outcrop in order to unravel its detailed tectono-metamorphic evolution through space and time (both prograde, peak and exhumation). Using SIMS zircon U–Pb and oxygen isotope analyses, TIMS Sm–Nd multi-point isochron dating, in situ laser-ICP-MS trace-element analyses, classical thermobarometry and thermodynamic modeling, we link the multistage zircon growth to garnet growth and reconstruct a detailed P–T–time-isotopic evolution history for this UHP tectonic slice: from UHP peak burial ~ 2.95 ± 0.2 GPa, 510 ± 20 °C around 318.0 ± 2.3 Ma to HP peak metamorphism ~ 2.45 ± 0.2 GPa, 540 ± 20 °C at 316.8 ± 0.8 Ma, then, with eclogite-facies deformation ~ 2.0 ± 0.15 GPa, 525 ± 25 °C at 312 ± 2.5 Ma, exhumed to near surface within ca. 303 to ca. 280 Ma. Our P–T-time-isotopic results combined with the compilation of regional radiometric data and P–T estimates notably point to the existence of a short-lived period of rock detachment and exhumation (< 10 Ma, i.e. at ca. 315 ± 5 Ma) with respect to subduction duration. © 2017 Elsevier B.V.

Magna T.,Czech Geological Survey | Zak K.,Academy of Sciences of the Czech Republic | Pack A.,University of Gottingen | Moynier F.,CNRS Paris Institute of Global Physics | And 7 more authors.
Nature Communications | Year: 2017

Chemical fingerprints of impacts are usually compromised by extreme conditions in the impact plume, and the contribution of projectile matter to impactites does not often exceed a fraction of per cent. Here we use chromium and oxygen isotopes to identify the impactor and impact-plume processes for Zhamanshin astrobleme, Kazakhstan. e54Cr values up to 1.54 in irghizites, part of the fallback ejecta, represent the 54Cr-rich extremity of the Solar System range and suggest a CI-like chondrite impactor. Δ17O values as low as -0.22% in irghizites, however, are incompatible with a CI-like impactor. We suggest that the observed 17O depletion in irghizites relative to the terrestrial range is caused by partial isotope exchange with atmospheric oxygen (Δ17O = -0.47%) following material ejection. In contrast, combined δ17O-e54Cr data for central European tektites (distal ejecta) fall into the terrestrial range and neither impactor fingerprint nor oxygen isotope exchange with the atmosphere are indicated. © The Author(s) 2017.

Gautier T.,University of Versailles | Carrasco N.,University of Versailles | Carrasco N.,Insitut University Of France | Schmitz-Afonso I.,CNRS Natural Product Chemistry Institute | And 4 more authors.
Earth and Planetary Science Letters | Year: 2014

Influx of solar photons and heavy charged particles from Saturn's magnetosphere on Titan's atmosphere - mainly comprised of methane and nitrogen - induce an intense organic photochemistry which leads to the formation of a large amount of aerosols in suspension in the atmosphere. In order to infer the role of nitrogen in aerosol formation processes we produced laboratory analogs of Titan's aerosols. In this work, we compare the composition of different analogs by using high resolution mass spectrometry and propose an additional study using gas-chromatography coupled to mass-spectrometry for a new kind of analog produced by polymerization of cryogenically trapped gaseous neutral species. The comparison of these materials emphasizes the importance of ion chemistry processes for the inclusion of nitrogen in molecules constituting Titan's tholins. A statistical approach is also used for the treatment of high resolution mass spectra of these highly complex organic materials. This method allows distinguishing molecular families that can be reconstructed by an ideal copolymer. We investigate several copolymer reconstructions, and we suggest that an HCN (or CH3CN)/C2H4 based copolymer agrees well with the polymeric structure of tholins produced with 5% of methane in nitrogen. © 2014 Elsevier B.V.

Gillingham M.A.F.,French National Center for Scientific Research | Gillingham M.A.F.,Leibniz Institute for Zoo and Wildlife Research | Cezilly F.,French National Center for Scientific Research | Cezilly F.,Insitut University Of France | Wattier R.,French National Center for Scientific Research
PLoS ONE | Year: 2013

Dispersal can be divided into three stages: departure, transience and settlement. Despite the fact that theoretical studies have emphasized the importance of heterozygosity on dispersal strategies, empirical evidence of its effect on different stages of dispersal is lacking. Here, using multi-event capture-mark-recapture models, we show a negative association between microsatellite multilocus heterozygosity (MLH; 10 loci; n = 1023) and post-fledging dispersal propensity for greater flamingos, Phoenicopterus roseus, born in southern France. We propose that the negative effects of inbreeding depression affects competitive ability and therefore more homozygous individuals are more likely to disperse because they are less able to compete within the highly saturated natal site. Finally, a model with the effect of MLH on propensity of post-fledgling dispersers to disperse to the long-distance sites of Africa was equivalent to the null model, suggesting that MLH had low to no effect on dispersal distance. Variations in individual genetic quality thus result in context-dependent heterogeneity in dispersal strategies at each stage of dispersal. Our results have important implications on fitness since sites visited early in life are known to influence site selection later on in life and future survival. © 2013 Gillingham et al.

Soret M.,CNRS Paris Institute of Earth Sciences | Agard P.,CNRS Paris Institute of Earth Sciences | Agard P.,Insitut University Of France | Dubacq B.,CNRS Paris Institute of Earth Sciences | And 6 more authors.
Lithos | Year: 2016

Despite decades of petrological and geochemical studies, the nature and setting of obducted ophiolites remain controversial: the influence of supra-subduction zone environments on pre-existing oceanic lithosphere is yet to assess, and the processes leading to subduction/obduction initiation are still poorly constrained. Our study documents successive influx of slab-derived fluids and progressive strain localization within the upper mantle in a supra-subduction environment during the first few My of the subduction history. We focus on strongly sheared mafic amphibolites intruding peridotites near the mantle-crust transition of the New Caledonia obducted ophiolite and ~50 to 100m above the basal thrust contact of the ophiolite. These m- to hm-long and several m-thick shear bands are interpreted as inherited small-scale intrusions of mafic melts, probably dikes or sills, which were derived from a moderately refractory mantle source refertilized by supra-subduction zone fluids. 40Ar/39Ar age constraints on pargasite at ca. 90Ma suggest that they could be inherited from the former Pacific west-dipping subduction. Secondary deformation of these mafic intrusions is intimately associated to three major stages of fluid infiltration: (1) the first stage of deformation and metasomatism is marked by syn-kinematic growth of Ca-amphibole (at 700-800°C and 3-5kbar) with a distinctive supra-subduction zone signature, and controlled later channelization of aqueous fluids. 40Ar/39Ar dating on magnesio-hornblende indicates that this deformation episode occurred at ca. 55Ma, coincident with east-dipping subduction initiation; (2) the main metasomatic stage, characterized by the development of a phlogopite-rich matrix wrapping peridotites and amphibolite boudins, points to the percolation of alkali-rich aqueous fluids at still high temperature (650-750°C); (3) the last, low temperature (<600°C) metasomatic stage results in the formation of deformed veinlets containing talc, chlorite and serpentine. © 2015 Elsevier B.V.

Rousset F.,University of Rennes 1 | Tzvetkov N.,Cergy-Pontoise University | Tzvetkov N.,Insitut University Of France
Communications in Mathematical Physics | Year: 2012

We consider the KP-I and gKP-I equations in ℝ × (ℝ/2Πℤ). We prove that the KdV soliton with subcritical speed 0 < c < c* is orbitally stable under the global KP-I flow constructed by Ionescu and Kenig (Ann Math Stud 163:181-211, 2007). For supercritical speeds c > c*, in the spirit of the work by Duyckaerts and Merle (GAFA 18:1787-1840, 2009), we sharpen our previous instability result and construct a global solution which is different from the solitary wave and its translates and which converges to the solitary wave as time goes to infinity. This last result also holds for the gKP-I equation. © 2012 Springer-Verlag.

Abdelrahim M.,Nancy Research Center for Automatic Control | Postoyan R.,Nancy Research Center for Automatic Control | Daafouz J.,Nancy Research Center for Automatic Control | Daafouz J.,Insitut University Of France
Automatica | Year: 2015

Controllers are often designed based on a reduced or simplified model of the plant dynamics. In this context, we investigate whether it is possible to synthesize a stabilizing event-triggered feedback law for networked control systems (NCS) which have two time-scales, based only on an approximate model of the slow dynamics. We follow an emulation-like approach as we assume that we know how to solve the problem in the absence of sampling and then we study how to design the event-triggering rule under communication constraints. The NCS is modeled as a hybrid singularly perturbed system which exhibits the feature to generate jumps for both the fast variable and the error variable induced by the sampling. The first conclusion is that a triggering law which guarantees the stability and the existence of a uniform minimum amount of time between two transmissions for the slow model may not ensure the existence of such a time for the overall system, which makes the controller not implementable in practice. The objective of this contribution is twofold. We first show that existing event-triggering conditions can be adapted to singularly perturbed systems and semiglobal practical stability can be ensured in this case. Second, we propose another technique that combines event-triggered and time-triggered results in the sense that transmissions are only allowed after a predefined amount of time has elapsed since the last transmission. This technique has the advantage, under an additional assumption, to ensure a global asymptotic stability property and to allow the user to directly tune the minimum inter-transmission interval. We believe that this technique is of its own interest independently of the two-time scale nature of the addressed problem. The results are shown to be applicable to a class of globally Lipschitz systems. © 2014 Elsevier. Ltd All rights reserved.

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