ORIGINAL PAPER T. Zack Æ R. Moraes Æ A. Kronz Temperature dependence of Zr in rutile: empirical calibration of a rutile thermometer Received: 14 April 2004 / Accepted: 29 August 2004 / Published online: 1 October 2004 Ó Springer-Verlag 2004 Abstract Rutile is an important carrier of high field strength elements (HFSE; Zr, Nb, Mo, Sn, Sb, Hf, Ta, W). Its Zr content is buffered in systems with quartz and zircon as coexisting phases. The effects of temperature (T) and pressure (P) on the Zr content in rutile have been empirically calibrated in this study by analysing rutile–quartz–zircon assemblages of 31 metamorphic rocks spanning a T range from 430 to 1,100°C. Electron microprobe measurements show that Zr concentrations in rutile vary from 30 to 8,400 ppm across this temper- ature interval, correlating closely with metamorphic grade. The following thermometer has been formulated based on the maximum Zr contents of rutile included in garnet and pyroxene: T (in  C) = 127.8  ln (Zr in ppm)  10 No pressure dependence was observed. An uncertainty in absolute T of ±50°C is inherited from T estimates of the natural samples used. A close approach to equilib- rium of Zr distribution between zircon and rutile is suggested based on the high degree of reproducability of Zr contents in rutiles from different rock types from the same locality. At a given locality, the calculated range in T is mostly ±10°C, indicating the geological and ana- lytical precision of the rutile thermometer. Possible applications of this new geothermometer are discussed covering the fields of ultrahigh temperature (UHT) granulites, sedimentary provenance studies and meta- morphic field gradients. Introduction The advent of analytical tools for in situ trace element measurements (electron microprobe, laser ablation ICP- MS, ion microprobe) has sparked an interest in trace element systematics in metamorphic petrology, particu- lary with respect to the role of accessory phases for trace element budgets (Sorensen and Grossman 1989; Her- mann 2002), the delineation of reaction sequences (Carlson 2002; Zack et al. 2002a), relating datable accessory minerals to PT paths (Degeling et al. 2001, 2002; Mo¨ller et al. 2002; Rubatto 2002; Hermann and Rubatto 2003) and the use of trace elements for geo- thermobarometry (Heinrich et al. 1997; Yang and Rivers 2000; Pyle et al. 2001). In this respect, it has been noted by Ferry (2000) that systematics of accessory minerals at medium-grade metamorphic conditions often indicate a close approach to equilibrium, even for the refractory elements. Consistent with this observation, the Y incorporation in garnet coexisting with monazite has revealed a strong temperature dependence (Pyle et al. 2001), therefore encouraging the search for thermome- ters that are based on elements occurring only in trace amounts (<1 wt%) in crystal structures. Despite its abundance in nature, surprisingly few studies on the geochemistry of rutile exist. The studies available indicate that rutile is a carrier of high field strength elements (HFSE) in subduction-related systems (e.g. Saunders et al. 1980). The behavior of the ‘‘ex- tended HFSE family’’ (Zr, Nb, Mo, Sn, Sb, Hf, Ta, W) with respect to rutile has been reviewed by Zack et al. (2002b). There it was noted that in zircon-buffered assemblages, Zr incorporation in rutile appears to be Editorial Responsibility: J. Hoefs T. Zack (&) Mineralogisches Institut, Universita¨t Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg, Germany E-mail: tzack@min.uni.heidelberg.de Tel.: +49-6221-546038 R. Moraes Departamento de Mineralogia e Geotectoˆnica, Instituto de Geocieˆncias, Universidade de Sa˜o Paulo, Sa˜o Paulo, 05508-080, Brazil E-mail: moraes@igc.usp.br A. Kronz Geowissenschaftliches Zentrum der Universita¨t Go¨ttingen, Abteilung Geochemie, Goldschmidtstrasse 1, 37077 Go¨ttingen, Germany E-mail: akronz@gwdg.de Contrib Mineral Petrol (2004) 148: 471–488 DOI 10.1007/s00410-004-0617-8