Céline Crépisson

• PhD in Geophysics (to end September 2018)
• PhD Student at Sorbonne University

Xenon (Xe), the heaviest of the stable noble gases, is missing by a factor of 20 relatively to other noble gases, when comparing the Earth's and Mars's atmospheres with chondrites. In this work, the possibility of Xe retention in quartz, a major mineral of the continental crust, is tested. The Xe-SiO 2 system is investigated from 0.7 to 2.7 GPa and...

The structure of two Lu doped (4000 ppm) model end member silicate liquids, a highly polymerised haplogranite (Si–Al–Na–K–O) and a less polymerised anorthite–diopside (Si–Al–Mg–Ca–O), have been studied up to 8 GPa using in situ x-ray diffraction techniques. The results are the first to identify trace rare Earth element incorporation in silicate mel...

Br speciation in hydrous silicate melts at high pressure has been investigated up to 7.6 GPa using X-ray Absorption Spectroscopy (XAS) at the Br K-edge in a Paris-Edinburgh press. Br in silicate melts is surrounded by an average of 6 Na cations, a number slightly increasing with pressure (5.8 to 6.6), with a Br-Na distance increasing from 3.49 to 3...

Garnet is a key mineral used to constrain pressure, temperature and age of metamorphic rocks. This contribution reports oxygen isotope measurements in garnet using the SHRIMP-SI ion microprobe. The reproducibility of oxygen isotope analyses on garnet standard UWG2 is ~ 0.3–0.4‰ (2σ) within and across sessions. The correlation between oxygen isotope...

The lithosphere–asthenosphere boundary (LAB) beneath the continents is a key interface in plate tectonics, yet its nature remains elusive. A partial melt layer has been advocated to explain its geophysical characteristics. However, the main counter-argument is that such a layer cannot be stable as melts should rise through the lithosphere. Density...

Hydroxyl defects in pure forsterite are usually ascribed to incorporation of protons fully compensating the electrostatic charge of cationic vacancies. However, partially compensated vacancies have been predicted from theoretical considerations. Here, we theoretically determine the structural, vibrational and infrared spectroscopic properties of pa...

The mechanism and magnitude of fluorine incorporation in H-bearing forsterite were investigated through a combined experimental and theoretical approach. Forsterite samples were synthesized in a piston cylinder press at 2 and 4 GPa, in hydrous conditions, with or without fluorine. High fluorine solubilities of 1715 and 1308 ppm F were measured by p...

The mechanism and magnitude of fluorine incorporation in H-bearing forsterite were investigated through a combined experimental and theoretical approach. Forsterite samples were synthesized in a piston cylinder press at 2 and 4 GPa, in hydrous conditions, with or without fluorine. High fluorine solubilities of 1715 and 1308 ppm F were measured by p...

The structure of molten fayalite was studied up to 7.5 GPa by means of in situ energy-dispersive X-ray diffraction. The pressure-range studied covers the fayalite–spinel–liquid triple point at 6.2 GPa. For pure molten fayalite, Fe–O coordination increases gradually from 4.8(2) at ambient pressure (P) to 7.2(3) at 7.5 GPa. Compressibility of the mel...

The presence of aqueous fluids and/or melts is a necessary condition for the transport of elements during metamorphism, particularly in the relatively cold subduction environment. The major dehydration and melting reactions during subduction are well known from phase equilibria studies. However, it is more difficult to trace the fluid pathways, the...