Hydrogeochemistry of an Acid River and Lake Related to an Active Volcano: The Case of Study. Agrio River—Copahue Volcano in Patagonia, Argentina

Abstract

During the last three decades, Copahue volcano has been one of the most studied volcanoes in Argentina and Chile. Extensive research has been devoted to studying the geochemistry of rocks and fluids of the Copahue-Caviahue volcanic complex, paying particular attention to the geochemical behavior of the water system. In this study, 275 published analyses of water geochemistry were compiled, in order to describe and revise the processes that control it. Thus, different processes that were previously described in the main volcanic-hydrological system were reanalyzed, such as ions and elements dilution along the Agrio River; alunite, jarosite and barite precipitation in the headwaters; schwertmannite and basaluminite precipitation in the Caviahue Lake and the lower Agrio River. Also, processes such as the incorporation of some elements (As, Tl and Pb) into waters through magmatic gases, and the absortion/adsortion of As, V, Cr and rare earth elements in the hydroxysulfates precipitates are described for the first time.