Investigating carbon-rich phases at lower mantle conditions - Eglantine Boulard

Eglantine Boulard - IMPMC

IMPMC - Sorbonne Université - 4 place Jussieu, 75005 Paris, tour 23, 4e étage, couloir 22-23, salle 401

Lundi 12 février 2018 à 10 h 30

Abstract

The deep carbon cycle plays a key role on the evolution of the atmosphere and life on the planet. Surficial observations reveal carbon in a great variety of organic, inorganic, and biological forms which subduct with descending slabs and rises and erupt in volcanoes. Little is known about the nature and the extent of deep carbon reservoirs as well as how carbon moves from one deep reservoir to another. Several questions on the chemistry and physic of carbon at high-pressure and high-temperature remain to be answered: e.g. what is the state of carbon in the deep Earth?  In what form do carbon-bearing materials exist deep within the Earth? With what others materials do they react and how quickly? How is it transported within the planet’s deep interior? To address these types of questions, we need to improve our understanding of carbon-bearing phases at the extreme pressure-temperature conditions existing in Earth.

I will first present results on carbonates at Earth’s mantle conditions. We combined in-situ, ex-situ  techniques  and  theoretical  studies  in  order  to  constrain  carbonate  stability  and structure at these extreme conditions. This led to the discovery of new high pressures phases of carbonates as well as first evidences of tetrahedrally coordinated C at lower mantle conditions. Such a drastic change in the C environment may have implications on the stability of carbonates within silicate phases at high-pressure but also on C-rich melt physical properties, the latter will be discussed on the second part of my talk on which I will present experimental developments of nano and micro x-ray computed tomography at extreme conditions. I used 3D imaging for the measure of melt/amorphous material, such as silicate glass, equation of state for which conventional x-ray diffraction is not suitable. Ultra-fast 3D imaging at extreme conditions was also developped in order to study carbon-rich melt percolation through solid matrix in real time.