Decoupling of zircon U-Pb and trace-element systematics driven by U diffusion in eclogite-facies zircon (Monviso meta-ophiolite, W. Alps)

Garber, Smye, Feineman, Kylander-Clark, Matthews, CMP 175, 1-25 (2020). doi: 10.1007/s00410-020-01692-2

The mineral zircon is used extensively for dating metamorphic processes. The U-Pb system is particularly useful; however, understanding U-Pb dates requires a knowledge of their mobility (or lack thereof) during crustal residence and metamorphism.

In this manuscript, data are presented that suggest U diffusion into zircon can be significantly faster than suggested by experiments. This has important implications for the types of process that can be recorded by zircon dating. My contribution to this study was providing an estimate of the redox state of U in the fluids likely to be reacting with the zircons studied here.

The image is Figure 12 from the manuscript. It shows my predictions for the dominant speciation of U in aqueous fluids at elevated temperature and pressure.

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