Radioparagenese von Mn2O3 durch Transmutation von 55Fe-haltigem Hämatit

• Antragsteller: Professor Dr. Björn Winkler
• Fachliche Zuordnung: Mineralogie, Petrologie und Geochemie
• Förderung: Förderung von 2012 bis 2017
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 233454910

Recently, a novel method has been described by which crystalline metastable compounds far from equilibrium can be obtained due to the transmutation of one element. This synthesis route has been called 'radioparagenesis' and its distinguishing feature is that an unstable isotope decays into a stable one, which is incompatible with its local environment while the crystal structure remains unchanged. Due to experimental difficulties, this has been a theoretical concept up to now. Now, we have the unique opportunity to experimentally study radioparagenesis induced by the transmutation of Fe, as we have been able to obtain a few micrograms of 55Fe, recently manufactured at the isotope production facility in Los Alamos. The iron has been separated and purified in April and May 2012 and was then oxidized to hematite, 55Fe2O3. The 55Fe will decay to Mn with a half-life of 2.7 years. As no rhombohedral manganese oxide is known, as the solubility of Mn in hematite is small and as the transmutation occurs at ambient temperature and hence there is insufficient energy for exsolution/precipitation of a Mn-rich phase, it is not obvious what will happen to the structure during the transmutation of 55Fe in hematite. Hence, the scientific question we want to solve is 'What happens to rhombohedral hematite when more and more iron ions are changed into Mn ions?'. The objective of the project is therefore to experimentally demonstrate and understand radioparagenesis, i.e. to determine and explain how a structure changes when one radioactive element transforms into a new element, which is incompatible with the structural environment in which it is formed. Hence, it is planned to characterize the sample every few months by diffraction and spectrosscopy. Beam time for synchrotron diffraction experiments has already been granted. Beam time for IR synchrotron experiments has been requested. Micro-Raman spectroscopic measurements will be performed in house.

• DFG-Verfahren: Sachbeihilfen