The study of the relationships between tectonic processes and metamorphism is one of the most active and exciting areas of current research on the Earth's crust. Thanks to new techniques, to whose development the PI contributed, it is now possible to track the pressure (P) - temperature (T) path of specific assemblages of minerals as they are subjected to burial, heating, compression, dehydration, faulting, uplift, and erosion. The application of geochronologic techniques to the same rocks makes it possible to deduce P-T time paths and opens the possibility of building accurate geophysical models of crustal processes. The PI will conduct research on tectonics and metamorphism during the duration of the PYIA but, also, will study the possible role of fluid immiscibility during high pressure, low temperature metamorphism. Field research will be conducted in three areas: (1) the eastern Alps of Austria; (2) west-central Idaho, USA; and (3) the island of Sifnos in the Aegean Sea. Laboratory work will be carried out primarily at Harvard where an electron microprobe analyzer will be used to determine P-T paths from mineral assemblages and a heating/freezing microscope stage will be used to estimate conditions of fluid immiscibility. Geochronological work will be of the 40 Ar/39 Ar-type and will be performed in a laboratory whose identity is not specified.