Advertisement

Contributions to Mineralogy and Petrology

, Volume 154, Issue 4, pp 429–437 | Cite as

New thermodynamic models and revised calibrations for the Ti-in-zircon and Zr-in-rutile thermometers

  • J. M. Ferry
  • E. B. Watson
Original Paper

Abstract

The models recognize that ZrSiO4, ZrTiO4,  and TiSiO4, but not ZrO2 or TiO2, are independently variable phase components in zircon. Accordingly, the equilibrium controlling the Zr content of rutile coexisting with zircon is ZrSiO4 = ZrO2 (in rutile) +  SiO2. The equilibrium controlling the Ti content of zircon is either ZrSiO4 + TiO2 = ZrTiO4 + SiO2 or TiO2 + SiO2 = TiSiO4, depending whether Ti substitutes for Si or Zr. The Zr content of rutile thus depends on the activity of SiO2 \((a_{\text{SiO}_{2}})\) as well as T, and the Ti content of zircon depends on \(a_{\text{SiO}_{2}}\) and \(a_{\text{TiO}_{2}}\) as well as T. New and published experimental data confirm the predicted increase in the Zr content of rutile with decreasing \(a_{\text{SiO}_{2}},\) and unequivocally demonstrate that the Ti content of zircon increases with decreasing \(a_{\text{SiO}_{2}}\). The substitution of Ti in zircon therefore is primarily for Si. Assuming a constant effect of P, unit \(a_{\text{ZrSiO}_{4}},\) and that \(a_{\text{ZrO}_{2}}\) and \(a_{\text{ZrTiO}_{4}}\) are proportional to ppm Zr in rutile and ppm Ti in zircon, [log(ppm Zr-in-rutile) + log\(a_{\text{SiO}_{2}}\)] = A1 + B1/T(K) and  [log(ppm Ti-in-zircon) + log\(a_{\text{SiO}_{2}}\) − log\(a_{\text{TiO}_{2}}\)] = A2 + B2/T, where the A and B are constants. The constants were derived from published and new data from experiments with \(a_{\text{SiO}_{2}}\) buffered by either quartz or zircon + zirconia, from experiments with \(a_{\text{SiO}_{2}}\) defined by the Zr content of rutile, and from well-characterized natural samples. Results are A1 = 7.420 ± 0.105;  B1 = −4,530 ± 111;  A2 = 5.711 ± 0.072;  B2 = −4,800 ± 86 with activity referenced to α-quartz and rutile at P and T of interest. The zircon thermometer may now be applied to rocks without quartz and/or rutile, and the rutile thermometer applied to rocks without quartz, provided that \(a_{\text{SiO}_{2}}\) and \(a_{\text{TiO}_{2}}\) are estimated. Maximum uncertainties introduced to zircon and rutile thermometry by unconstrained \(a_{\text{SiO}_{2}}\) and \(a_{\text{TiO}_{2}}\) can be quantitatively assessed and are ≈60 to 70°C at 750°C. A preliminary assessment of the dependence of the two thermometers on P predicts that an uncertainty of ±1 GPa introduces an additional uncertainty at 750°C of ≈50°C for the Ti-in-zircon thermometer and of ≈70 to 80°C for the Zr-in-rutile thermometer.

Keywords

Zircon Rutile Calibration Point Zirconium Titanate Baddeleyite 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

Research supported by National Science Foundation grant EAR-0229267 to J.M.F. and EAR-0440228 to E.B.W. We thank Dave Elbert, Bob Hazen, and David Veblen for advice on the crystal chemistry of Ti substitution in zircon; Jon Price and Dave Wark for assistance with electron microprobe analyses; and two anonymous reviewers for their comments.

References

  1. Berman RG (1988) Internally-consistent thermodynamic data for minerals in the system Na2O−K2O−CaO−MgO−FeO−Fe2O3−Al2O3−SiO2−TiO2−H2O−CO2. J Petrol 29:445–522Google Scholar
  2. Degeling HS (2003) Zr equilibria in metamorphic rocks. Unpublished PhD Thesis, Australian National University, 231 ppGoogle Scholar
  3. Harrison TM, Aikman A, Holden P, Walker AM, McFarlane C, Rubatto D, Watson EB (2005) Testing the Ti-in-zircon thermometer. Trans Am Geophys U 86 (fall meeting supplement, abstract V41F-1540)Google Scholar
  4. Hayden LA, Watson EB (2007) Rutile saturation in hydrous siliceous melts and its bearing on Ti thermometry of quartz and zircon. Earth Planet Sci Lett (in press)Google Scholar
  5. Holland TJB, Powell R (1998) An internally consistent thermodynamic data set for phases of petrological interest. J Metam Geol 16:309–343CrossRefGoogle Scholar
  6. Lee C-T, Rudnick, RL (1999) Compositionally stratified cratonic lithosphere: petrology and geochemistry of peridotite xenoliths from the Labait Volcano, Tanzania. In: Gurney JJ, Richardson SR (eds) Proceedings of seventh international kimberlite conference, Cape Town, pp 503–521Google Scholar
  7. Spear FS, Wark DA, Cheney JT, Schumacher JC, Watson EB (2006) Zr-in-rutile thermometry in blueschists from Sifnos, Greece. Contrib Mineral Petrol 152:375–385CrossRefGoogle Scholar
  8. Speer JA (1982) Zircon. In: Ribbe PH (ed) Orthosilicates. Rev Mineral, vol 5. Mineral Soc Am, Chantilly, Virginia, pp 67–112Google Scholar
  9. Tomkins HS, Powell R, Ellis DJ (2007) The pressure dependence of the zirconium-in-rutile thermometer. J Metam Geol 25 (in review)Google Scholar
  10. Troitzsch U, Ellis DJ (2004) High PT study of solid solutions in the system ZrO2−TiO2: the stability of srilankite. Eur J Mineral 16:577–584CrossRefGoogle Scholar
  11. Troitzsch U, Ellis DJ (2005) The ZrO2−TiO2 phase diagram. J Mat Sci 40:4571–4577CrossRefGoogle Scholar
  12. Troitzsch U, Christy AG, Ellis DJ (2004) Synthesis of ordered zirconium titanate (Zr,Ti)2O4 from the oxides using fluxes. J Am Ceram Soc 87:2058–2063CrossRefGoogle Scholar
  13. Wark DA, Watson EB (2006) TitaniQ: a titanium-in-quartz geothermometer. Contrib Mineral Petrol 152:743–754CrossRefGoogle Scholar
  14. Watson EB, Harrison TM (2005) Zircon thermometer reveals minimum melting conditions on earliest Earth. Science 308:841–844CrossRefGoogle Scholar
  15. Watson EB, Wark DA, Thomas JB (2006) Crystallization thermometers for zircon and rutile. Contrib Mineral Petrol 151:413–433CrossRefGoogle Scholar
  16. Zack T, Moraes R, Kronz A (2004) Temperature dependence of Zr in rutile: empirical calibration of a rutile thermometer. Contrib Mineral Petrol 148:471–488CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Department of Earth and Planetary SciencesJohns Hopkins UniversityBaltimoreUSA
  2. 2.Department of Earth and Environmental SciencesRensselaer Polytechnic InstituteTroyUSA

Personalised recommendations