Structural and petrographic analysis at the north-eastern margin of the Oligocene Traversella pluton (Internal Western Alps, Italy)

Abstract

In this work a new form surface map at 1:5000 scale of the north-eastern margin of the Oligocene Traversella pluton, synthesised from a field structural study assisted by optical petrography, is presented. Relative chronology of superposed foliations and effects of progress of contact metamorphic reactions in the contact aureole are shown on the structural map for each of the country rock-types of the Sesia-Lanzo Zone. The structural and metamorphic evolution was reconstructed across the north-eastern margin of the pluton by separating the pre- and the post-intrusive tectonic history and defining the contact aureole outline. Contact metamorphic assemblages and thermobarometric estimates indicate that this intrusive body emplaced at shallow structural levels (contact metamorphism peak conditions: T < 750°C; P < 0.2 GPa).