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Theme 4: Solid-liquid-interface reactions

(Andreas Lüttge, Torsten Stumpf, Falko Langenhorst)

Session 4.1: Geo-radiochemistry

Thorsten Stumpf (Dresden-Rossendorf)

The behaviour of radionuclides in the environment is determined by interfacial reactions such as adsorption, ion exchange and incorporation processes. In literature such processes are often described by operational solid-liquid distribution ratios (Rd values). Distribution ratios are defined as the ratio of the quantity of a radionuclide sorbed per solid mass and the equilibrium concentration of the radionuclide. They are macroscopic parameters which are strictly valid only for the mineral and solute combination in the experimental system. For reliable and trustworthy long-term predictions of radionuclide transport behaviour, interaction mechanisms and processes occurring at the solid-water interface, they need to be understood at the molecular level. This can only be achieved by the application of spectroscopic methods. The session will be focused on the combination of microscopy, laser and X-ray based techniques to gain process understanding on a molecular level of the interaction of actinides and fission products with mineral surfaces.


Session 4.2: Fluid-rock interactions: from mechanisms to rates – from atom to plate

Oliver Plümper (Utrecht University, NL), Johannes Vrijmoed (University of Berlin), Helen King (Utrecht University, NL), Christof Kusebauch (GFZ Potsdam)

Reactions between fluids and rocks have a fundamental impact on the geodynamics and geochemistry of Earth at all scales. Fluid-rock interactions strongly affect the petrophysical properties and chemical composition of the rocks. Therefore, they play an important role in processes such as plate tectonics and the formation of economic deposits. The fact that fluid has migrated through rocks is evident from field observations such as veins, metasomatic alteration zones, and (de)-hydration reaction fronts occurring on outcrop to regional scales and porosity observed on the micron down to nanometre scale. Metasomatic alteration zones, but also ore deposits point to the chemical effect of fluid flow that facilitated element mobilisation. Mechanical effects of fluid flow are expressed in phenomena such as zones of localised deformation and hydration.
The underlying mechanisms as well as the rates of the processes are still poorly understood, despite the current field, experimental, and theoretical arguments for the importance of fluid-rock interaction for geodynamic and geochemical processes. On the one hand this is due to the fact that rocks provide only a snapshot in time. On the other hand, deformation, reaction, and fluid flow are complex coupled processes which provide a challenge for numerical modelling as well as for interpreting and controlling experiments. Numerical modelling, experiments, and comprehensive field and laboratory studies that focus on the mechanisms, the rates, the interplay between fluid flow, reaction, deformation and mass transport processes, or the connection between small to large scales, will help to improve our understanding of fluid-rock interactions.
We invite contributions that shed light on the coupled processes of fluid flow, reaction, deformation and fluid-mediated mass transport at all scales. We also welcome geochronology and geospeedometry studies related to fluid flow processes, as well as regional and outcrop scale field studies of fluid-rock interaction. Petrology research using state-of-the art analytical equipment with resolutions down to the nanometer scale that focus on the mechanisms documented in rocks that interacted with fluids contributes to the many facets of fluid-rock interaction. Numerical modelling studies that are designed to handle the complexity and coupled nature of fluid-rock interaction are also encouraged. Finally, studies based on laboratory experiments in which mechanisms and rates of fluid-rock interaction can be further constrained will complete the diversity of this session.


Session 4.3: Reactions at mineral-water interfaces in the Earth Sciences: theory and experiment

Mariëtte Wolthers (Utrecht University, NL), Jörn Hövelmann (GFZ Potsdam), Cornelius Fischer (MARUM, Bremen)

Mineral growth, dissolution, replacement as well as the adsorption/desorption of colloids, nanoparticles, molecules, and trace elements and their incorporation and partitioning are all, in essence, solid-liquid-interface reactions and central to a multitude of geological processes. This session will focus on the kinetics and mechanisms of reactions at solid-liquid interfaces, whether from a fundamental or applied perspective. The aim is to convene a session combining presentations with cutting-edge analytical research with experimental and theoretical concepts, with an emphasis on low-temperature processes in aqueous environments.


Session 4.4: Applied materials: Reactions at interfaces

Luc Nicoleau (GMB, BASF, Ludwigshafen)

This session is focused but not limited to reaction kinetics of cement phases. Recent interest from the cement and material science community in the application of kinetic theories utilized in the field of geochemistry yields critical insight and allows for the revision of existing or the development of new concepts. Cement and geoscience communities certainly have more to exchange and to learn from each other. In both fields, the reactivity, i.e., the dissolution and crystallization of alumino-silicate phases are key processes in which a deeper understanding would help to develop better kinetic models. Additional important examples include the analysis of the stability of materials related to nuclear waste management and the impact of inhibitors during reaction of silicate phases. We also invite contributions focusing on new analytical methods, e.g., surface-sensitive approaches. We are looking forward to studies based on modeling approaches – from the atomic scale up to multi-scale approaches. The main goal of the session is to create the opportunity for networking in-between the theoretical and applied communities and the identification of new co-operations.