The Alpine metamorphic evolution of the Banchetta-Rognosa and Albergian units (upper Chisone valley, Western Alps)

Alberto Corno^1
1University of Torino, Earth Sciences Department, via Valperga Caluso 35, 10125, Torino.
Corresponding author e-mail: alberto.corno@unito.it
 

This paper deals with the alpine tectono-metamorphic evolution of the Banchetta- Rognosa unit (BRU) and its surrounding Albergian unit (AU), outcropping in the upper Chisone valley (axial sector of the Western Alps). The peak P-T conditions of these two units were defined through the isochemical phase diagram approach. The results of phase equilibria modeling point to eclogite-facies conditions for the BRU (20-23 kbar and 450-520 °C), and lawsonite blueschist-facies conditions for the AU (18-21 kbar and 380-430 °C). Within the Alpine axial sector, where a decrease of the metamorphic condition is recorded form east to west, the BRU could be one of the westernmost eclogite-facies unit. Moreover, its occurrence embedded within the blueschist-facies AU could be the result of complex exhumation processes.

petrography, thermodynamic modeling, Chisone valley, Ligurian-Piedmont Zone, Western Alps.