HR: 1340h
AN: V43A-1565    [Abstracts]
TI: Application of rutile thermometry to eclogites
AU: * Zack, T
EM: tzack@min.uni-heidelberg.de
AF: Mineralogisches Institut, INF 236, Heidelberg, 69120 Germany
AU: Luvizotto, G L
EM: george.luvizotto@min.uni-heidelberg.de
AF: Mineralogisches Institut, INF 236, Heidelberg, 69120 Germany
AB: To evaluate how well the rutile thermometer (Zr content in rutile coexisting with zircon and quartz; Zack et al. 2004; CMP 148, 471-488) can be applied to eclogites, we measured 8 samples that cover the whole temperature range of naturally-occurring eclogites (400-900oC). SIMS is the method of choice for such a study as the low concentrations expected at only 400oC can be measured with very high precision (better than 5 percent on a 10 ppm level). We calibrated the Heidelberg SIMS by using relatively homogeneous rutiles that span a range of Zr contents (100, 260 and 770 ppm; determined by high-accuracy isotope dilution MC-ICP-MS). The calibration of the Heidelberg SIMS facility through these three rutiles as well as titanites, MPI-DING glasses and NIST-SRM 610 glass show no matrix effect for Zr determination outside 15 percent (2 sigma), thus SIMS analysis of Zr in rutile is straightforward. For all samples except one calculated temperatures agree with independently determined thermometry. However, even more encouraging is the fact that temperatures calculated from 5-10 rutiles within one sample agrees better than 20oC, hence enforcing the claim that rutile thermometry is a powerful tool for relative temperature determinations, as examplified for two UHP provinces (WGR and Erzgebirge).
DE: 1000 GEOCHEMISTRY
DE: 3600 MINERALOGY AND PETROLOGY
DE: 3651 Thermobarometry
DE: 3660 Metamorphic petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005