Geochemistry and isotopic characteristics of the Caviahue-Copahue volcanic complex, Province of Neuquén, Argentina

During the last two decades, Copahue and its active acidic crater lake have shown different magmatic, phreatomagmatic, and hydrothermal manifestations. Geochemical data of waters from Copahue springs, lakes and rivers provide new insights into the behavior of its volcano-hydrothermal system. Temporal variations in the chemical (major anions and cations) compositions, element fluxes, and isotopic fluctuations (δD and δ 18 O; stable Pb isotopes, 129 I/ 127 I, δ 37 Cl, δ 7 Li, δ 34 S) of surface waters from Copahue for the period 1997-2012 can be related to processes in the underlying hydrothermal system. The 2000 and 2012 eruptive periods and the 2004 thermal anomaly showed increases in SO 4 , Cl and F contents in the waters as a result of ascending magmatic fluids. The changing chemical compositions also showed evidence for enhanced water/rock interaction during these magmatic periods, with increased concentrations of the major rock forming elements such as Al, K and Mg. Soon after the magmatic events, the elemental fluxes from the hydrothermal system decreased strongly, especially for K and Al. The latter is related to a decrease in permeability in the system through crystallization of alunite. Stable isotopic data (δD and δ 18 O) indicate that the hydrothermal fluids consist of a mixture of meteoric and magmatic waters that are affected by evaporation and water/rock interaction processes. The δ 7 Li values, polythionate concentrations and water stable isotope ratios indicate that the hot spring M. Agusto

Section: δ 34 S and Sulfur Speciationmentioning

confidence: 66%

Section: Recommendations For Monitoring Of Volcanic Activity At Copahmentioning

confidence: 92%

See 1 more Smart Citation

The Copahue Volcanic-Hydrothermal System and Applications for Volcanic Surveillance

Agusto

Varekamp

2015

“…lithostratigraphic (Pesce 1989;Mazzoni and Licitra 2000;Melnick et al 2006;Sruoga and Consoli 2011), structural (Folguera and Ramos 2000), petrological (Delpino and Bermudéz 2002), and geochemical (Varekamp et al 2006;Agusto et al 2013, Agusto and Varekamp this volume;Tassi et al this volume). The 1992 eruption (Delpino and Bermúdez 1993) gave a strong pulse for the creation of the Volcano Studies Group (Neuquino Geological Survey) who drew the map of potential hazards for this Argentine sector (Bermúdez and Delpino 1995).…”

Section: Hazard Mapmentioning

confidence: 95%

Risk Assessment and Mitigation at Copahue Volcano

Caselli

Liccioli

Tassi

2015

Abstract"Risk assessment" is a relatively new concept in Argentina, since the very first hazard map was only recently constructed on the basis of the 1992 eruption of Copahue volcano (Patagonia). Copahue is considered a very active volcanic system since 13 eruptive events have been recognized over the last 260 years. Most the events are phreatic and phreato-magmatic with VEI ≤ 2; nevertheless such eruptions represent a threat for the communities living in the surrounding areas of the emission centre, not only because of pyroclastic flows and tephra fall (the nearby villages, Caviahue and Copahue, have so far only experienced ash fallout), but also due to the possible formation of mud flows and flank collapse triggered by the volcanic activity. Owing to the frequent eruptions of Copahue, the most recent ones (2000, 2012) showed an increasing explosive character, hazard survey actions, such as thematic maps and contingency plans are constantly, though slowly, modified. The risk assessment described in this chapter calls for the implementation of the monitoring network in the Argentina side of the volcano, since the only currently active seismic stations (OVDAS) are located in the Chilean side of the volcanic edifice, Copahue volcano lying at the border between the two countries. Moreover, the Chilean observatory adopts criteria of alert levels, which

“…The zone east of the caldera contains many Holocene lava flows and cinder cones (Fig. 5.2), forming the back arc suite of Copahue volcano (Muñoz and Stern 1989;Kay et al 2004;Hesse 2007;Varekamp et al 2006). The volcanic stratigraphy and geology of the Caviahue and Copahue Volcano Complex (CCVC) have been characterized by Bermúdez et al (1993Bermúdez et al ( , 2002, Bermúdez and Delpino (1995;, Colvin (2004), Delpino and Bermúdez (1993), deMoor (2003, Merrill (2003), Moreno et al (1986), Goss (2001), Linares et al (1999), Melnick et al (2006), Hesse (2007), Todd (2005), Todd and Ort (2012), Varekamp et al (2006Varekamp et al ( , 2010 and Zareski (2014).…”

Section: Introductionmentioning

confidence: 98%

Copahue Volcano and Its Regional Magmatic Setting

Varekamp

Zareski

Camfield

et al. 2015

Copahue volcano (Province of Neuquen, Argentina) has produced lavas and strombolian deposits over several 100,000s of years, building a rounded volcano with a 3 km elevation. The products are mainly basaltic andesites, with the 2000-2012 eruptive products the most mafic. The geochemistry of Copahue products is compared with those of the main Andes arc (Llaima, Callaqui, Tolhuaca), the older Caviahue volcano directly east of Copahue, and the back arc volcanics of the Loncopue graben. The Caviahue rocks resemble the main Andes arc suite, whereas the Copahue rocks are characterized by lower Fe and Ti contents and higher incompatible element concentrations. The rocks have negative Nb-Ta anomalies, modest enrichments in radiogenic Sr and Pb isotope ratios and slightly depleted Nd isotope ratios. The combined trace element and isotopic data indicate that Copahue magmas formed in a relatively dry mantle environment, with melting of a subducted sediment residue. The back arc basalts show a wide variation in isotopic composition, have similar water contents as the Copahue magmas and show evidence for a subducted sedimentary component in their source regions. The low 206 Pb/ 204 Pb of some backarc lava flows suggests the presence of a second endmember with an EM1 flavor in its source. The overall magma genesis is explained within the context of a subducted slab with sediment that gradually looses water, water-mobile elements, and then switches to sediment melt extracts deeper down in the subduction zone. With the change in element extraction mechanism with depth comes a depletion and fractionation of the subducted