GARNET-ORTHO-PYROXENE GEOTHERMOMETRY AND GEOBAROMETRY - ERROR PROPAGATION AND EQUILIBRATION EFFECTS

Garnet-orthopyroxene geothermometry and geobarometry are widely used i n high-grade metamorphic terranes. These techniques may provide an ins ight into pressure-temperature (P-T) paths followed by such terranes, provided various sources of uncertainty are taken into consideration. Analytical uncertainties, particularly with regard to their effect on ferric iron estimation in orthopyroxene, can contribute to the overall uncertainty on the calculated P-T. Additionally, retrograde cation di ffusion can affect the Fe-Mg distribution between coexisting garnet an d orthopyroxene, consequently affecting P-T estimates. Recognizing the importance of these effects, and care with both the choice of the gra ins analysed and analytical techniques, may lead to more reliable P-T estimation.