Geothermal Copahue Volcano System, Argentina. New Stable Isotope and Geochemical Data.

CASELLI , ALBERTO TOMAS; DAPEÑA, CRISTINA; AGUSTO, MARIANO; DELGADO HUERTAS, ANTONIO

Punta del Este, Uruguay

Simposio; V South American Symposium on Isotope Geology; 2006

The Geothermal Effusive Copahue-Agrio-Caviahue Complex, is composed by the Copahue polygenic fissural-stratovolcano and the Agrio square caldera. It is located on the west border of Argentina, in the Neuquén province, on the Andes Range nearby the boundary with Chile The volcano-tectonic activity begun since the Pliocene with a relatively frequent eruptive activity in recent times. The eastern crater is the active one and is filled with a lake with acid waters and molten sulfur floating on its surface. Other surface expressions of an extensive volcanic-magmatic hydrothermal system geothermal field are two acid hot springs. The Copahue's last eruption took place at July-October 2000, being at present in a fumarolic stage. In this work, we present new isotopic and chemical water data in order to show changes in the composition of the Crater Lake and hot springs of Copahue volcano with the aim to use like an indicator of future volcanic activity. The compositional variation in the Crater Lake and hot-springs samples is related to the mixing between different magnitudes of meteoric and snow meltwater inputs and to changes in the rate of volcanic input, during the sample period. Chemical and isotopic data show that the Crater Lake and hot springs are both of meteoric origin with evaporation and mixing with deep hydrothermal fluids with different percentages. Periodic monitoring of temperature, chemical and isotopic composition of Crater Lake, hot springs and rivers waters may be useful for determination of perturbations of the magmatic hydrothermal system and provide an indicator of future volcanic activity.