This paper presents three itineraries in the Aosta valley (Italian Alps), devoted to the eclogitized ophiolite of the Zermatt-Saas unit and its relationships with the underlying Monte Rosa and the overlying Sesia-Lanzo and Dent Blanche continental units. Special attention will be devoted to the relationships and metamorphic features of the different lithologies, which underwent high- to ultrahigh-pressure metamorphism during subduction of the Tethys ocean.
Visit to the Monte Rosa basement (i.e., the European plate) and the overlying Zermatt-Saas meta-ophiolite (i.e., the Tethys ocean), from Rifugio Città di Mantova (3498 m), down to Lago Gabiet (2342 m). Visit of the eclogite-facies rocks of the overlying Sesia-Lanzo continental unit (i.e., the Adria microplate) at Lillianes.
Walk to the Servette Fe-Cu mine, with visit of the ancient foundry and slags, and then to the Praborna Mn mine (high-pressure metamorphism of hydrothermal oceanic deposits). Return through the abandoned mine village of Chuc and the unusual Cu-hydroxide deposit in the river at “Eaux vertes – Acqua verde”.
Visit to Cignana (coesite-bearing occurrence in the Zermatt-Saas meta-ophiolite). Walk from Lago di Cignana (2158 m) down to the eclogitized oceanic metagabbros of Crepin (1577 m). Departure to Cervinia, up to Plateau Rosa, for a breathtaking view of the Cervino (Matterhorn) and the Africa/Europe collisional zone.
Weather can be warm to quite cold (near or below 0°C). Bring warm waterproof clothes and mountain shoes; walks are on signalled paths in a high mountain environment (up to 3500 m); altitude changes up to 900 m in a day.
This excursion was undertaken in summer 2004 by some of the participants to the 32nd International Geological Congress. Further information and photographs can be found at the following link http://www.geocities.com/g_rebay/FI04_01.html.