DEFORMATION AND METAMORPHISM RELATIONSHIPS IN ACID AND FEMIC PROTHOLITHS OF THE AUSTROALINE CONTINENTAL CRUST SUBDUCTED AND EXHUMED IN THERMAL REGIME SEVERELY DEPRESSED

Intrusives of pre-Alpine age and their high grade country rocks, subducted-exhumed in Alpine times, has been studied with petro-structural methods, applied after quality mapping. In this subduction environment, focus was oriented on interaction of deformation and metamorphic transformation progress, in areas offering a mosaic of different tectonometamorphic steps. Such apparently incoherent distribution of structural imprints, representing various discrete states of the tectonic sequence heterogeneously frozen in adjacent space, has been recomposed into a coherent progression of deformation events by means of foliation trajectory mapping. Such work guaranteed a petrographic analysis of the mineral support of sequentially ordered planar fabrics, used for thermobarometrical estimates of the deformative and metamorphic evolution. This evaluation has been performed in acid and femic protoliths intruded in the continental crust of the Sesia-Lanzio Zone in the internal Western Alps.