Compositional Changes of Magmatic-Hydrothermal Fluids Related to Anomalous Temperatures at Copahue Crater Lake (Argentina).

.- M. AGUSTO, F. TASSI, A. CASELLI, O. VASELLI.

Tenerife

Congreso; Cities on Volcanoes 6; 2010

ITER

The Caviahue-Copahue Volcanic Complex (CCVC; Argentina-Chile), is composed by the Copahue polygenic fissural-stratovolcano (37º45’S-71º10.2’W, 2977 m a.s.l.) and the Caviahue squared caldera (Fig. 1). It is located on the west border of Argentina, in the Neuquén province, on the Andes Range nearby the boundary with Chile, and belongs to the Southern Andean Volcanic Zone (SVZ: 33.3º- 46ºS). The volcano-tectonic activity in this area started in the Pliocene and it was mainly characterized by intense eruptions producing andesitic to basaltic-andesitic pyroclastic and lava flows. Copahue is an active stratovolcano, whose summit is composed by nine NEoriented craters, that lies in the western sector of the Caviahue caldera. During the last 250 years, this volcano has experienced at least 12 low-magnitude phreatic and phreato-magmatic eruptions. The last eruptive cycle (phreatic and phreato-magmatic) took place from the easternmost crater in July 1992 and was marked by major eruptions in August 1992, September 1995 and July-October 2000, being at present in a fumarolic stage. There are two small villages within the caldera, Copahue and Caviahue, located 5 and 9 km from the active volcano