Sébastien Merkel

In case, you are wondering: you will not see me at the AGU Fall Meeting this year. I attended 22 out of the latest 26 AGU Fall Meeting. I felt that this year was a good one to take a break and not be travelling in December. Enjoy the meeting, I'm sure it will be great.

New publication in American Mineralogist! former TIMEleSS student Estelle Ledoux present an In-situ study of microstructures induced by the olivine to wadsleyite transformation at conditions of the 410 km depth discontinuity. We study the microstructures produced by the olivine-wadsleyite transformation using in situ laboratory experiments at pressures and temperatures relevant for the Earth's mantle transition zone, measure the orientation and size distribution of individual sample grains using multigrain crystallography, and find that the olivine to wadsleyite transformation is incoherent at the conditions of the mantle transition zone. Thus, we expect that seismic anisotropy near 410 km would drop significantly due to the randomized lattice preferred orientation of newly nucleated wadsleyite induced by the incoherent transformation.

New publication in AGU’s Geochemistry, Geophysics, Geosystems by former TIMEleSS student Estelle Ledoux today: Deformation Mechanisms, Microstructures, and Seismic Anisotropy of Wadsleyite in the Earth’s Transition Zone. Wadsleyite is the high pressure polymorph of olivine and the major phase of the upper part of the mantle transition zone (at 410–520 km depth) and then is suspected to control the deformation of that region of the mantle. In this work, se use in-situ deformation experiments, multigrain X-ray crystallography, literature results, and numerical simulations to propose a new view of plastic deformation of wadsleyite in the Earth’s mantle transition zone. We show that it will be strongly affected by both temperature and water content. We then provide models that could be used for the seismic detection of its anisotropic behavior and mapping mantle flow using seismic measurements. More details online at https://doi.org/10.1029/2023GC011026.

Twitter has yet again suggested another video of someone's death. Learning about new science, keeping in touch, etc. was fun for years, but I now get suggested awful posts and content all day long. I just posted my 910th and last post. Goodbye, Twitter.

Went to Paris-Saclay for the PhD defense of Robin Fréville on tin and iron properties at high pressure. I did not consider that today was the first day of the fall holidays for schools in France. The train was really busy! It was a nice PhD defense with methodological developments for experiments in the diamond anvil cell, multigrain XRD experiments to study phase transformations mechanisms in Fe and Sn, and a new phase diagram for Sn over a megabar.

Coming soon: Deformation mechanisms, microstructures, and seismic anisotropy of wadsleyite in the Earth's transition zone. A new paper by E. Ledoux in press in AGU's Geochemistry, Geophysics, Geosystems. Preprint available upon request.

Just in: I will be attending Rayons X et Matière in Novembre 2023 in Bordeaux. I will be presenting a short wrap-up talk about our work on multigrain crystallography and phase transition microstructures in Earth mantle materials from the ANR-DFG TIMEleSS project. I will also show some preliminary XFEL measurements from the starting ERC HotCores project. Stay tuned for more!

News on my homepage are back! I was using a twitter timeline which stopped working after changes in policies with twitter. Running of a home-built and independent news features from now on. Let's see how this goes.