Constraining influences on trace element diffusion in rutile as petrogenetic indicator and for industry applications

• Applicant: Dr. Mona Lüder
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572038194

Rutile is a common mineral in different metamorphic rocks and can be used to understand the formation of the host rock. This is based on the way that trace elements, such as Nb, Ta, Zr and Al are incorporated into rutile. However, the kinetic processes behind this incorporation need to be better understood. Rutile containing Nb and/or Al can develop properties that make rutile important for different industry application for the generation of renewable energy. I will study diffusion of Nb, Ta, Zr, Hf and Al in rutile to better constrain natural processes and to further the applicability of rutile in industry. I will perform diffusion experiments on rutile with different trace elements. In these experiments, I will control temperature, availability of oxygen and rutile composition. All these variables are expected to influence the diffusion of trace elements in rutile. By changing one variable at a time, it is possible to evaluate their control on diffusion rates. For this, I will perform multiple sets of experiments, with one changing variable each. Two different types of experiments will be done. For some experiments, Nb, Ta, Zr and Hf doped thin films will be deposited on the surface of rutile. For others rutile grains will be put into Nb-Ta-Zr-Hf doped or Al-doped Ti-oxide powder. These samples will be put into a furnace that can be filled with gas. By using CO and CO2 gasses, the amount of available oxygen can be controlled. The products of the experiments will be measured in high resolution at an electron microscope or a mass spectrometer to see how much of the trace elements was incorporated at what depth. These “diffusion profiles” can give us information about the rate at which different trace elements can be incorporated into rutile. By comparing the different rates for the different experiments, we will be able to understand the underlying processes. From this new data, we will develop computer-based models that can be applied to study natural samples. To test this, we will apply these models to a well understood set of natural samples. Additionally, a small number of experiments will be performed using natural rutile samples, to allow us to evaluate to what degree experimental results can be applied to natural rutile. This will help us with using rutile as indicator for the formation of natural rocks. We will also be able to apply this to the understanding of large scale processes on Earth that are currently debated. Finally, these newly determined rates can be used to improve manufacturing of rutile materials for industry.

• DFG Programme: Research Grants