Séminaire ISTerre

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Elemental transfers at mineral interfaces – from mineral weathering to nutrient availability

mercredi 23 novembre 2022 - 10h00

Bastien Wild  - ISTerre-Séminaire Post-doc
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Mineral interfaces constitute the locus of chemical reactions that are key to the evolution of the Earth system. Fluid confined in nanoporous interfaces exhibits singular properties that can control dissolution and precipitation processes involved in metasomatism and metamorphic reactions, and involved in ductile deformation of the upper crust, fault creep and interseismic healing. Electron transfers at mineral interfaces support the metabolism of deep biosphere microbial communities, while in the most surficial layers of our planet, biofilms and thin fluid films adsorbed at mineral interfaces in the regolith carry reactive species in the form of organic molecules, dissolved ions and gases that drive rock weathering, thereby regulating atmospheric CO2, climate, and pedogenesis and thereby generating bio-essential elements that fuel ecosystem development. Common to this broad range of systems is the need to probe experimentally or numerically the properties of complex fluid-mineral(-microorganism) interfaces. This seminar will highlight a set of recent studies conducted in hydrothermal and surface contexts that aim to disentangle processes driving mineral dissolution. I will show how structural changes probed by surface-sensitive synchrotron techniques at fluid-mineral interfaces can impact mass and energy transfer between the mineral and the bulk fluid, as determined using atomic-scale non-equilibrium molecular dynamics simulations. Moving towards surface environments, we incubated a suite of well-characterized single crystals in soil profiles located at several instrumented sites in France and in the United States to assess the impact of the properties of the fluid flow in unsaturated soil media on local dissolution rates. We combined high resolution microscopy and molecular biology tools to quantitatively compare the relative effect of microbial colonization and the evolution of mineral interfaces on weathering. Finally, I will outline how we intend to further develop this framework in synergy with capabilities available at ISTerre to better understand the production of critical nutrients for surface ecosystems at the fluid-mineral-microorganism nexus.

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Equipe organisatrice : Organisation labo

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