Application of rutile thermometry to eclogites

Metamorphic temperatures can be derived from the Zr content in rutiles coexisting with quartz and zircon. To evaluate how well this recently calibrated rutile thermometer can be applied to eclogites, we analysed 8 samples that cover the whole temperature range of naturally-occurring eclogites (400-900 degrees C). Due to low concentrations expected at only 400 degrees C, very high precision (better than 5 percent on a 10ppm level) secondary ion mass spectrometry (SIMS) is used in this study. In general, temperatures calculated from rutiles agree favourably with literature data as well as with our own estimates, based on several geothermobarometers and phase assemblages. However, the most important result of this study is the observation that temperatures calculated from 4-8 rutiles within a single sample always agree to within better than 25 degrees C, hence enforcing the claim that rutile thermometry is a powerful tool for relative temperature determinations.