The crater lake of Copahue volcano (Argentina): geochemical and thermal changes between 1995 and 2015

AGUSTO M.; - CASELLI, A.T.; DAGA R.; VAREKAMP J; TRINELLI A; DOS SANTOS AFONSO M.; VELEZ M.L.; EUILLADES P

Geochemistry and Geophysics of Active Volcanic Lakes

Lyell

Lugar: London; Año: 2017;

The crater lake and associated hydrothermal features of Copahue volcano have beenstudied intensively over the last 20 years (1995?2015). The geochemical and isotopic compositionsof the waters provide insights into the processes occurring in the volcanic?hydrothermal system,the crater lake and the thermal springs. Variations in the temperature and chemicalcomposition of the waters reveal fundamental changes in the system that precede and accompanythe magmatic and phreatic eruptive events at Copahue. A conceptual model of the summit systemwas developed involving the intrusion of slivers of magma in the hot acidic hydrothermal cell, thesaturation of waters with secondary minerals leading to reduced permeability, the blocking of fluidpathways by liquid sulphur during heating events and the transport of gas from the magma throughthe ductile?brittle transition into the hydrothermal system. Geophysical data were integrated withthe chemical data to provide new insights into the behaviour of the deep magmatic system thatfeeds the volcano edifice. Multidisciplinary studies were used to identify precursory signals oferuptive activity to give an early warning of pending volcanic hazards. Several geochemical ratiosin river water were identified as potential indicators of upcoming volcanic activity, which could beused in co-operation with the community and local authorities to deal with these volcanic hazards.