Diffusion in common mineral phases. Part 4: Spinel

• Applicant: Professor Dr. Sumit Chakraborty, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405665352

Spinels are common minerals in a wide range of magmatic rocks as well as in samples from the mantle, the Moon or Mars, meteorites from the Asteroid belt, and metamorphic rocks. Chemical compositions of spinels are used as petrogenetic indicators to study crystallization pathways and to determine temperatures, oxygen fugacities, or pressures of formation. Compositional zoning in spinels have been used to determine the rates of changes of these quantities by diffusion modelling, and in addition, diffusion data in spinels are necessary to evaluate the temperatures at which the spinel compositions freeze and record the conditions in the rocks. Finally, spinels find a wide range of applications in various aspects of materials sciences. While a significant body of diffusion data in spinels are available, there remain important gaps which make applications in all of the above areas problematic. Notably, the role of cations on one site and one charge (e.g. 3+, Cr or Al) in affecting the diffusion rates of cations on the other site and charge (e.g. 2+, Fe or Mg) has not been studied until now. The main objective of this project is to make use of the experimental facilities available within this Research Unit and the methodological developments made in the first cycle of funding to close this gap. This would involve experimental studies using the available tools, theoretical analysis involving multicomponent diffusion theory, and making use of the ability to measure isotopic fractionations to better understand diffusion mechanisms. An added benefit would be the ability to study the systematics of isotope fractionation caused by diffusion in silicates (first cycle of funding as well as TP1 and TP3 in this cycle) vs. oxides – this is a fundamental dataset that does not exist until now.

• DFG Programme: Research Units
• Subproject of: FOR 2881: Diffusion Chronometry of magmatic systems
• Co-Investigator: Dr. Ralf Dohmen