• geological mapping
• granitic intrusion
• magmatic plumbing system
• Sesia Magmatic System

The geological sector of Val Sesia represents a tilted crustal section in which crop out the plumbing system of a Permian rhyolitic caldera, up to a depth of about 25 Km. The mid to upper crustal portion of this plumbing system is represented by Valle Mosso pluton, a granitic body 250 km3 in extension characterized by different textural and compositional facies which is supposed to be the primary source for the caldera eruptions. Just 10 km NE from Valle Mosso pluton there is Alzo-Roccapietra pluton. These two plutons were initially jointed but during Alpine orogenesis they have been dismembered by a right-strike slip fault, the Cremosina Line.
This thesis first aim is to produce a geologic map of Alzo-Roccapietra pluton which can characterize the intrusion in different textural and compositional facies and understand the geochemistry of the facies.
Alzo-Roccapietra pluton is composed by three different facies: 1) an inequigranular quartz-monzonite in the western-central portion of the pluton; 2) an equigranularwhite monzogranite in the eastern portion; 3) a fine-grained two mica leucogranite which crop out in small sub-horizontal lenses 100-200m in size. Because of a) the sub-horizontal attitude of the two mica leucogranite; b) the weak angular contact (<40°) between the pluton and his host rocks in south-eastern portion and c) the lack of a summit facies SiO2-rich and fluid-rich, it is suggested that Alzo-Roccapietra pluton could be tilted of about 15-30° E-SE.