Crust-mantle interactions during subduction of oceanic & continental crust. 10th International Eclogite Conference, Courmayeur (Aosta, Italy) - Post-conference excursions: September 9-10, 2013

This excursion is aimed at illustrating oceanic and continental tectonometamorphic sequences and their interactions with ultramafics during Alpine subduction at (U)HP conditions. The first day is dedicated to the visit of the tectonometamorphic sequences of the Monviso meta-ophiolitic massif. The Monviso Massif is one of the best preserved relics of oceanic crust in the western Alps that formed during opening of the Mesozoic western Alpine Tethys and that underwent HP metamorphism during Alpine subduction. This fieldtrip gives the almost unique chance to see and appreciate different portions of the ancient ocean floor along a mountain trail. Among the various lithologies, we will see serpentinite, Mg-Al and Fe-Ti metagabbro, eclogite, metabasite, metasediments and minor metaperidotite. The fieldtrip itinerary is located in a high mountain landscape in front of the pyramid of Monviso (3841 m), which is the symbol of the Cottian Alps. The excursion starts from the spring of the Po river at Pian del Re and reaches three spectacular mountain lakes (Lago Fiorenza, Lago Chiaretto and Lago Superiore), through a typical glacial landscape. The second day excursion proposes a “petrographic” itinerary in the core of the world-famous UHP Brossasco- Isasca Unit (Dora-Maira Massif), allowing to observe the most spectacular evidence of both its pre-Alpine and Alpine metamorphic evolution. We will visit the famous pyrope-bearing whiteschist outcrop of Case Ramello (south of Case Parigi) where coesite was first discovered in continental crust, a spectacular metagranite with UHP coronitic mineral assemblage and an exceptionally well preserved relict of pre-Alpine igneous intrusive contact (basement xenoliths within metagranitoids).