The Lautaro Volcano, Chilean Patagonia, is situated at 49° 01.4' S, 73° 32.5' W, being the closest volcano to the Chile Triple Junction, in which on-going subduction of active ridge takes place. The volcanoes of the Austral Volcanic Zone are characterised by adakitic composition (Stern and Killian, 1996), and their magma origin is attributed to slab-melting. Such typical ridge subduction volcanism can clarify juvenile continental crust formation process, as a modern analogue of Archaean magmatism.
The access to the Lautaro Volcano, 3, 607 m above the sea level, is extremely difficult because of accidental morphology and unfavourable climate conditions. The volcano edifice stands out from the glacial plateau of 2, 400 m high, so-called South Ice Field, therefore, no research group had got rock samples in enough amount and variety. On February 28, 2002, with help of helicopter, the authors' research group accomplished a successful sampling of eruptive materials of this volcano from deposits of the Lautaro Glacier, first target, and the O'Higgins Glacier, second target.
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