Le métamorphisme dans les Alpes françaises

The present study was carried out in the french Alps between the western and eastern zones. A certain amount of data were acquired concerning the characteristics of metamorphism and the distribution of mineraIs. Different genetic models, resulting from earlier work, attemted to explain high-pressure, low temperature metamorphism through thrusting or lithospheric plates (F. ELLENBERGER, J. BOCQUET ). It was necessary to apply precise measurements to little-studies sectors of the chain and increase the amount of know data in critical sectors in order to more accurately determine the thermodynamic conditions for Alpine metamorphism genesis. The present study comprises two different aspects. On the one hand, an attempt to represent mineralogical zones determinable by simple petrographic means. On the other hand, a systematic analytical work method bearing upon two mineraI groups, jadeitic pyroxenes considered as critical in high-pressure metamorphism and phengites likely to vary in composition in response to metamorphie variations. Finally, the ehronology of crystallization and the role played by fluids in this type of metamorphism are studied.