Experimental calibration of oxygen isotope fractionation between quartz and zircon Dustin Trail a, * , Ilya N. Bindeman b , E. Bruce Watson a , Axel K. Schmitt c a Department of Earth & Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA b Department of Geological Sciences, University of Oregon, Eugene, OR 97403, USA c Department of Earth and Space Sciences & Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, USA Received 6 January 2009; accepted in revised form 20 August 2009; available online 26 August 2009 Abstract We report the results of an experimental calibration of oxygen isotope fractionation between quartz and zircon. Data were collected from 700 to 1000 °C, 10–20 kbar, and in some experiments the oxygen fugacity was buffered at the fayalite–magne- tite–quartz equilibrium. Oxygen isotope fractionation shows no clear dependence on oxygen fugacity or pressure. Unexpect- edly, some high-temperature data (900–1000 °C) show evidence for disequilibrium oxygen isotope partitioning. This is based in part on ion microprobe data from these samples that indicate some high-temperature quartz grains may be isotopically zoned. Excluding data that probably represent non-equilibrium conditions, our preferred calibration for oxygen isotope frac- tionation between quartz and zircon can be described by: 1000 ln a qtz–zrc ¼ð2:33  0:24Þ 10 6 =T 2 ðin KÞ This relationship can be used to calculate fractionation factors between zircon and other minerals. In addition, results have been used to calculate WR/melt–zircon fractionations during magma differentiation. Modeling demonstrates that silicic mag- mas show relatively small changes in d 18 O values during differentiation, though late-stage mafic residuals capable of zircon saturation contain elevated d 18 O values. However, residuals also have larger predicted melt–zircon fractionations meaning zircons will not record enriched d 18 O values generally attributed to a granitic protolith. These results agree with data from natural samples if the zircon fractionation factor presented here or from natural studies is applied. Ó 2009 Elsevier Ltd. All rights reserved. 1. INTRODUCTION Zircon is a common accessory phase found in many crustal rocks and is often present with quartz. Oxygen iso- tope compositions of quartz in rocks have helped character- ize petrogenetic processes for about half a century (Taylor, 1968; Taylor and Sheppard, 1986). More recently, an increasing number of zircon oxygen isotope data have been used to gain new insight into crustal evolution (e.g., Valley et al., 1994, 2005; Bindeman et al., 2008). In addition, since zircon is resistant to physical and chemical breakdown dur- ing weathering, oxygen isotope ratios of detrital grains have also been used to constrain source melt compositions (e.g., Valley et al., 2005; Cavosie et al., 2005; Trail et al., 2007). The application of d 18 O values in zircon to petrological problems depends upon the characterization of an equilib- rium fractionation behavior. For example, equilibrium fractionation between quartz and zircon at P500 °C is pre- dicted by the following equation: d 18 OðqtzÞ d 18 OðzrcÞ 10 3 ln a qtz–zrc ¼ A qtz–zrc  10 6 T 2 ðin KÞ ð1Þ where a qtz–zrc is the fractionation factor—the 18 O/ 16 O ratio in quartz divided by the 18 O/ 16 O ratio in zircon—and linearity is assumed for 1000 ln a vs. 1/T 2 (Bottinga and Javoy, 1973). 0016-7037/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.gca.2009.08.024 * Corresponding author. Fax: +1 518 276 2012. E-mail address: traild@rpi.edu (D. Trail). www.elsevier.com/locate/gca Available online at www.sciencedirect.com Geochimica et Cosmochimica Acta 73 (2009) 7110–7126