M/F Post Doctoral Position : Mineralogical Characterization Of Inclusions In Quaternary Tektites.

Universities and Institutes of France
September 30, 2022
Offerd Salary:Negotiation
Working address:N/A
Contract Type:Temporary
Working Time:Full time
Working type:N/A
Job Ref.:N/A
  • Organisation/Company: CNRS
  • Research Field: Astronomy Environmental science Geosciences
  • Researcher Profile: Recognised Researcher (R2)
  • Application Deadline: 30/09/2022 23:59 - Europe/Brussels
  • Location: France › ST ETIENNE
  • Type Of Contract: Temporary
  • Job Status: Full-time
  • Hours Per Week: 35
  • Offer Starting Date: 01/01/2023
  • The post doc will be mainly located at LGL-TPE (Saint-Etienne/Lyon), with stays at CEREGE (Aix-en-Provence) for the selection and preparation of samples from the tektite collection. Field trips may be proposed. The objective will be to characterize, down to the nanometric scale, the inclusions preserved in tektites. This will provide us information on the pressure and temperature conditions of formation (e.g. polymorphs of silica, zircon), and even sometimes, on the moment of impact (e.g. zircon, monazite). Particular attention will be given to the search for carbonaceous inclusions to characterize thermal metamorphism, and to identify gaseous species trapped in the form of bubbles in glasses. Depending on the size of inclusions (micro to nanometric) different characterization techniques will be used to determine both their chemical and structural information. Raman spectroscopy and SEM-FEG (CL, EDS, EBSD) will be used to identify the nature of polymorphs within inclusions, including glasses, and their structure that depends on cooling rates. In the case of nanometric inclusions (< 1 μm) or strongly heterogeneous samples at the micrometric scale, the Transmission Electron Microscope (TEM BF/DF, SAED, STEM-HAADF, EELS) coupled with a FIB preparation will be necessary for both chemical and structural identification of nano-phases. Electron energy loss spectroscopy (EELS) will be valuable for discriminating the different possible phases of carbon (e.g. graphite/diamond/carbonate), or specifying oxidation states (e.g. Fe, Cr). With regard to Raman, the characterizations will be carried out at the LGL-TPE (ENS-Lyon site) on the spectrometers of the national INSU platform (collaborators: B. Reynard and G. Montagnac). Characterization using SEM-FEG can be carried out on the new equipment located in Saint-Etienne (JEOL JSM IT800 with EDS and EBSD Oxford, and CL Gatan). A recent TEM JEOL NeoARM200F Cold FEG corrected (Cs), equipped with ADF/ABF, EDS detectors, and EELS spectrometer is also available in Saint-Etienne (https: // www. clym.fr/fr/node/336).

    This post doc is part of the ANR Et-Megafires (Tropical megafires triggered by tektite producing extraterrestrial impacts in the Quaternary; led by P. Rochette, CEREGE) which propose to characterize the response of continental biosphere to large extraterrestrial impact craters, in particular the megafires they may have generated, associated with the melting of the Earth surface

    Studying the impact glasses ejected at long distance, called tektite, will be instrumental in the project. Three tektite producing impacts occurring on forested tropical surfaces from Nicaragua, Ghana, and Indochina during the last 1.1 Myr will be investigated. Environmental response to impact, probed by pollen, charcoal and other proxies will be studied in various marine and lacustrine archives. Reaction of impact melt with biomass (elements such as C, P, S) will be traced using compositional variability of tektites explored in a systematic way, as well as nano-scale characterization of inclusions in tektites such as phosphates, metal, etc. (coordinator: A-M Seydoux- Guillaume). This will bring new clues on tektite production processes and response of ecosystems to megafires. Objectives:

    Eligibility criteria

    Formation: PhD in Material or Earth Sciences. Skills: strong knowledges in mineralogy and in material characterization. An excellent experimental skill with electron transmission microscopy is necessary, and an expertise in EELS is highly expected.

    Web site for additional job details

    https: // emploi.cnrs.fr/Offres/CDD/UMR7330-NOEGAR-031/Default.aspx

    Required Research Experiences
  • Geosciences

  • 1 - 4

  • Astronomy

  • 1 - 4

  • Environmental science

  • 1 - 4

    Offer Requirements
  • Geosciences: PhD or equivalent

    Astronomy: PhD or equivalent

    Environmental science: PhD or equivalent

  • FRENCH: Basic

    Contact Information
  • Organisation/Company: CNRS
  • Department: Centre européen de recherche et d'enseignement de géosciences de l'environnement
  • Organisation Type: Public Research Institution
  • Website: https:// www. cerege.fr
  • Country: France
  • City: ST ETIENNE
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