Pb, U and Th diffusion in natural zircon

Abstract

Zircon (ZrSiO4) is one of the most widely used minerals for determining the age, origin and thermal history of rocks by U–Th–Pb geochronology. But the parameters describing the solid-state (volume) diffusion rates of these elements in natural zircon, which are themselves important for establishing the limits on the applicability of zircon for geochronological studies, have remained poorly quantified1. This is because of the measurement difficulties associated with the low (p.p.m.) concentrations and low diffusion rates of these elements in natural zircon, and the chemical and physical heterogeneity present in most crystals. Here we present direct measurements of the uranium, thorium and lead loss from a thermally treated gem-quality natural zircon and show that lead diffuses much faster than uranium or thorium. We find that the U–Th–Pb isotopic system in natural zircon will typically have a closure temperature greater than 900 °C, which explains why zircon is apparently such a robust geochrometer and is capable of remaining isotopically closed through extended periods of high-grade metamorphism and partial melting of the host rock.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: a, Typical Pb diffusion profile after heating at 1,100 °C.
Figure 2: Arrhenius diagram of Pb, U and Th diffusion coefficients.
Figure 3: Zircon Pb closure temperature plotted against effective radius of diffusion.

References

  1. 1

    Lee, J. K. W. in Defects and Processes in the Solid State (eds Boland, J. N. &Fitz Gerald, J. D.) 423–446 (Elsevier, New York, (1993)).

  2. 2

    Roddick, J. C. & van Breemen, O. in Radiogenic Age and Isotopic Studies: Report 8, Geol. Surv. Can. Curr. Res. 1994-F, 1–9 (1994).

  3. 3

    Reddy, K. P. R. & Cooper, A. R. Oxygen diffusion in sapphire. J. Am. Ceram. Soc. 65, 634–638 (1982).

  4. 4

    Sinha, A. K., Wayne, D. M. & Essex, R. Flux growth of pure and doped zircons. J. Cryst. Growth 125, 431–439 (1992).

  5. 5

    Crank, J. The Mathematics of Diffusion (Clarendon, Oxford, (1975)).

  6. 6

    Dowty, E. Crystal-chemical factors affecting the mobility of ions in minerals. Am. Mineral. 65, 174–182 (1980).

  7. 7

    Fortier, S. M. & Giletti, B. J. An empirical model for predicting diffusion coefficients in silicate minerals. Science 245, 1481–1484 (1989).

  8. 8

    Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst. A32, 751–767 (1976).

  9. 9

    Cherniak, D. J., Hanchar, J. M. & Watson, E. B. Diffusion of tetravalent cations in zircon. Contrib. Mineral. Petrol. 127, 383–390 (1997).

  10. 10

    York, D. Least squares fitting of a straight line with correlated errors. Earth Planet. Sci. Lett. 2, 479–482 (1969).

  11. 11

    Dodson, M. H. Closure temperature in cooling geochronological and petrological systems. Contrib. Mineral. Petrol. 40, 259–274 (1973).

  12. 12

    Silver, L. T. & Deutsch, S. Uranium–lead isotopic variations in zircons: a case study. J. Geol. 71, 721–758 (1963).

  13. 13

    Silver, L. T. in Nuclear Geophysics (ed. Hurley, P. M.) Natl Acad. Sci.–Nat. Res. Council Publ. 1075, 34–39 (1963).

  14. 14

    Lee, J. K. W. & Tromp, J. Self-induced fracture generation in zircon. J. Geophys. Res. 100, 17753–17770 (1995).

  15. 15

    Goldich, S. S. & Mudrey, M. G. in Recent Contributions to Geochemistry and Analytical Chemistry (ed. Tugarinov, A. I.) 466–470 (Wiley, New York, (1972)).

  16. 16

    Black, L. P., Williams, I. S. & Compston, W. Four zircon ages from one rock: the history of a 3930 Ma-old granulite from Mount Sones, Enderby Land, Antarctica. Contrib. Mineral. Petrol. 94, 427–437 (1986).

  17. 17

    Pidgeon, R. T. Recrystallisation of oscillatory zoned zircon: some geochronological and petrological implications. Contrib. Mineral. Petrol. 110, 463–472 (1992).

  18. 18

    Watson, E. B. & Harrison, T. M. Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types. Earth Planet. Sci. Lett. 64, 295–304 (1983).

  19. 19

    Pidgeon, R. T., O'Neil, J. R. & Silver, L. T. Uranium and lead isotopic stability in a metamict zircon under experimental hydrothermal conditions. Science 154, 1538–1540 (1966).

  20. 20

    Krogh, T. E. & Davis, G. L. Alteration in zircons with discordant U-Pb ages. Ann. Rep. Dir. Geophys. Lab. Carnegie Inst. Washington Ybk 73, 560–567 (1973).

  21. 21

    Sinha, A. K., Wayne, D. M. & Hewitt, D. A. The hydrothermal stability of zircon: preliminary experimental and isotopic studies. Geochim. Cosmochim. Acta 56, 3551–3560 (1992).

  22. 22

    Kinny, P. D., Compston, W., Bristow, J. W. & Williams, I. S. in Kimberlites and Related Rocks, vol. 2(eds Ross, J. et al.) Geol. Soc. Austral. Spec. Pub. 14, 833–842 (Blackwell, Melbourne, (1989)).

Download references

Acknowledgements

We thank W. Compston and D. H. Green (Director, RSES) for supporting this project. We thank the following RSES technical personnel for assistance and advice: R. Willison for electron-beam welding; and R. Waterford, K. Massey, R. Willis and B. Hibberson for sample preparation. Numerous people provided guidance and assistance with equipment: J. Fitz Gerald (TEM), T. Senden and A. Hyde (AFM), R. Headey (SEM), S. Eggins (ICP-MS) and D. Tilley (XRD). We also thank E. B. Watson for advice and discussions about experimental procedures and Pb diffusion, H. O'Neill and S. Chakraborty for discussions about thermodynamics and diffusion, and A. Sinha for providing us with synthetic zircon crystals. This work was supported by the Research School of Earth Sciences and an Australian Research Council grant to D. Ellis for the experimental work carried out in the Geology Department.

Author information

Correspondence to James K. W. Lee†.

Rights and permissions

Reprints and Permissions

About this article

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.