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H/F : Chemical and physical characterization of the lithosphere-asthenosphere boundary (LAB)

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Français - Anglais

Date Limite Candidature : lundi 22 août 2022

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General information

Reference : UMR6524-AUDCHA-015
Workplace : CLERMONT FERRAND
Date of publication : Monday, August 1, 2022
Scientific Responsible name : Nathalie BOLFAN
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 November 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The diamond deposits of the Kimberlite volcanic chimneys are natural boreholes through the earth's crust and mantle. Kimberlite magmas during their ascent to the surface sampled the rocks crossed over more than 300 km. Among the thousands of samples of mantle rock enclaves collected, a small fraction comes from the lithosphere-asthenosphere boundary. This boundary (LAB) located under the very old terrestrial cratons (more than 2.5 billion years ago) between 150 and 250km is a crucial area for the knowledge of the Earth's dynamics and in chemical and thermal exchanges between the convective deep mantle and the conductive lithospheric continental mantle.This limit also reflects a profound rheological change in mantle rocks (from brittle to ductile) where the role of fluids seems crucial (the hydrogen–H– content of minerals plays a decisive role in the mechanisms of deformation, viscosity and electrical conductivity). This boundary is known indirectly by its geophysical properties (seismic and conductimetric). The subject therefore proposes, thanks to the exceptional collections of personal mantle enclaves and the University of Cape Town to study directly petrology, mineralogy, geochemistry (H,∂D, major elements and traces) and the petrophysical characteristics of these rocks (EBSD, modeling of seismic velocities, conductivity, seismic anisotropy and conductivity). All of these geochemical and petrophysical methods are developed at the highest level at the Magmas and Volcanoes laboratory. The objective of this thesis is a better chemical and physical knowledge of this interface and to provide the community of geophysicists with strong constraints for their seismic and conductimetric models.

Work Context

The Magmas and Volcanoes Laboratory (LMV) is a joint research unit of the University of Clermont Auvergne (UCA), the National Center for Scientific Research (CNRS, UMR 6524), and the Institute for Research for Development (IRD, UMR 163).

Constraints and risks

No particular constraints

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