Micro-PIXE determination of Zr in rutile: An application to geothermometry of high-P rocks from the western Alps (Italy)

An application of rutile Zr-geothermometer to continental and oceanic rocks of the Western Alps, pervasively re-equilibrated under low-P conditions, is presented. The selected rutile crystals were analysed by PIXE using a microbeam set-up at the LABEC laboratory of INFN in Florence. The FIXE spectra and maps were processed by Geopixe software package. Micro-PIXE analyses allowed determining the concentration and the distribution of Zr. Results obtained by applying the rutile Zr-geothermometer gave a more precise indication about the temperatures of the metamorphic conditions suffered by Alpine metamorphic rocks with respect to phase relations and conventional geothermometry, showing that determination of Zr concentration by micro-PIXE technique is a useful tool to reconstruct metamorphic events.