Life and Death of chemical reaction fronts

• Applicant: Professor Dr. Thomas Müller
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549891241

Under our feet and underneath the ocean floor, water continually moves through the rocks of Earth’s crust. As it does so the water interacts with the rock, exchanging elements and altering the minerals in the rock to new compositions. Fluid-rock interaction is a very important process on our planet, controlling the formation of ore deposits, porosity in petroleum reservoirs, and the chemistry of the oceans. This process often creates geochemical fronts between reacted and unreacted rocks. The main aim of this proposal is to understand the propagation and stagnation of these fronts. We propose that this progression is effectively controlled by the transport of fluid to and from reaction sites, which depends on a balance between transport-enabling reaction steps, such as dissolution, and transport-preventing reaction steps, such as recrystallization and pore precipitation, and that the occurrence of these steps can be effectively mapped in the experimental space.As an example of such reactions, we study the replacement of Ca-carbonate rocks by Mg-bearing carbonates, a reaction that is widely known as dolomitization. We will study this carbonate-fluid reaction using state-of-the-art analytical techniques and develop the following:1) an in-depth, quantitative understanding of the links between local fluid chemistry, nucleation and growth processes fluid pathways and reaction dynamics2) a numerical model to predict the spatial and temporal evolution of chemical reactive fronts on mm to cm scales.Our main aim is to develop a theoretical framework to explain the progression and stagnation of chemical fronts. We want to quantitatively understand the internal coupling and feedback between element fluxes, mineral reactions, recrystallization, and evolution of fluid pathways, resulting in a reaction mechanism map. Therefore, we want to relate the nucleation and growth processes within an evolving reaction front to the local composition of pore fluids and their transport properties, which are intimately linked to the dynamic evolution of fluid pathways.At the end of our project, we hope to have developed a new “toolbox” of methods and parameters that will be useful to other scientists studying mineral reactions, element exchange and advancement of chemical fronts. It will show what experimental data are needed in other mineral systems and how that needs to be included in reactive transport models. In future work, this will help to find and evaluate ore deposits, better understand the generation of porosity in carbon sequestration, allow better modelling of hydrothermal systems, and help constrain long-term processes of chemical exchange between the geosphere and the hydrosphere.

• DFG Programme: Research Grants
• International Connection: United Kingdom
• Co-Investigator: Professor Dr. Daniel Koehn
• Cooperation Partners: Professorin Dr. Catherine Hollis; Professorin Dr. Sandra Piazolo