Séminaire ISTerre

Effects of iron and volatile elements on the local structure and density of deep silicate melts

lundi 23 novembre 2026 - 14h00
Lucie Canet (Thesis defense) - ESRF
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Seismic observations of an ultra-low velocity zone at the Core-Mantle Boundary (2900 km depth) suggest the presence of a dense silicate melt layer. These melt layer could potentially represent a remnant basal magma ocean that was trapped after the metal-silicate differentiation and the partial crystallization of the mantle. Such a melt layer could be a potential reservoir for many incompatible geochemical elements and its existence would have important implications for the chemical and geodynamic evolution of the planet. While the potential existence of the basal magma ocean is supported by geodynamical modelling and geochemical analyses, it remains problematic to explain the stability of silicate melts at such conditions, that due to their lower density compared to the crystalline host rock, would rise to the planet’s surface.

To study the effect of Fe and volatiles elements on the structure and density of silicates melts at lower mantle conditions, we conduct in-situ synchrotron X-ray diffraction experiments in diamond anvil cells, on silicates glasses with compositions of (Mg1-xFex)SiO3 with x = 0, 0.1, 0.2, 0.4, and (Ca,Al,Na,Mg)SiO doped with CO2 and H2O, up to 135 GPa, at the beamline ID27 of the ESRF, in Grenoble. Data were acquired up to a very high Q-range (170 nm-1) using an incoming X-ray beam energy of 55 keV, enabling high real-space resolution and revealing distinct structural features in the pair distribution function at low pressure. Structural evolutions were followed qualitatively using the pair distribution functions, while density was extracted using a minimization of the figure of merit, and optimization of parameters such as the Q-range and a r cutoff value. The extracted data allow to identify the structural and density evolution of silicate glasses, as a function of pressure, iron and volatiles content.

Equipe organisatrice : Géodynamo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

The emergence of proto-plate boundaries from lithospheric drips with grain-damage

mercredi 7 octobre 2026 - 11h00

Pr David Bercovici - Yale University

Equipe organisatrice : Géodynamo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Round-table on natural carbon capture and other climate-related topics

mercredi 7 octobre 2026 - 14h00

Pr David Bercovici - Yale University, Yale Center for Natural Carbon Capture

Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Study of the mantle transition zone by combining earthquake data and seismic noise data: application to the Alps and Massif Central

vendredi 9 octobre 2026 - 10h00

Piel Pawlowski - ISTerre

Equipe organisatrice : Ondes et structures

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Mapping Mantle Wedge Seismicity for Ground Motion Assessment: The Lesser Antilles Subduction Zone Case (Guadeloupe, Martinique)

vendredi 9 octobre 2026 - 14h00

Océane Foix - ISTerre

Equipe organisatrice : Géophysique des risques sismiques et gravitaires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Statistical physics of creep rupture of heterogeneous materials

jeudi 15 octobre 2026 - 11h00

JUAN CARLOS VERANO ESPITIA  - ISTerre - Aalto University (Finlande)

Equipe organisatrice : Mécanique des failles

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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The Seismic Response of Faults to Weak Perturbations: A New Probe Into Earthquake Physics and Fault State

vendredi 6 novembre 2026 - 11h00

Eric Beaucé - ISTerre

Equipe organisatrice : Cycle sismique et déformations transitoires

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 13 novembre 2026 - 14h00

Farzaneh Mohammadi - ENS Paris

Equipe organisatrice : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Effects of iron and volatile elements on the local structure and density of deep silicate melts

lundi 23 novembre 2026 - 14h00

Lucie Canet (Thesis defense) - ESRF

Equipe organisatrice : Géodynamo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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