The mechanism of the alteration of metamict zircon in aqueous solutions: 2H and 18O tracer experiments

• Applicant: Professor Dr. Andrew Putnis, since 1/2012
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 196078038

Zircon is one of the most important mineral in geochronology and has been proposed as a nuclear waste form to safely encapsulate weapons-grade plutonium. However, actinide-bearing zircon becomes increasingly radiation-damaged with time, resulting in an unusually open microstructure that is assumed to make radiation-damaged zircon prone to aqueous alteration. Results of comprehensive hydrothermal experiments with radiation-damaged zircon have led to a phenomenological model for the alteration of radiation-damaged zircon that is based on the inward diffusion of protons that trigger structural recovery processes and are involved in complex ion exchange processes. However, the hypothesis of proton diffusion is based so far only on indirect observations and atomistic details of the alteration process are not known. In this project, it is planed to perform 2H and 18O hydrothermal tracer experiments with a heavily radiation-damaged zircon in the temperature range the temperature range from zeolite to the upper amphibolite facies. The incorporation of deuterium and 18O into the reacted areas shall be analysed by SIMS and NanoSIMS. The experiments will not only provide information about mechanistic aspects of the alteration (proton diffusion, incorporation of OH/H2O), but will also allow to comment on the recent discussion about the value of the utilization of the oxygen isotope composition of zircon as a geochemical indicator for its magmatic and pre-magmatic history.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Thorsten Geisler-Wierwille, until 1/2012