Publication Date:
2020-11-09
Description:
This work presents the first chemical and isotopic (δ13C-CO2, δ13C-CH4, 3He, 4He, 20Ne, 40Ar, 36Ar, δ18O, and δD) data for fluid
discharges fromGuallatiri volcano, a remote and massive stratovolcano, which is considered as the second most active volcano of
the Central Volcanic Zone (CVZ) in northern Chile. Fumarolic gases had outlet temperatures of between 80.2 and 265 °C, and
showed a significant magmatic fluid contribution marked by the occurrence of SO2, HCl, and HF that are partially scrubbed by a
hydrothermal aquifer. The helium isotope ratios (〈 3.2) were relatively low compared to those of other active volcanoes in CVZ,
possibly due to contamination of the magmatic source by 4He-rich crust and/or crustal fluid addition to the hydrothermal
reservoir. Geothermometry in the H2O-CO2-CO-H2-CH4 system suggests equilibrium temperatures of up to 320 °C attained
in a vapor phase at redox conditions intermediate between those typical of hydrothermal and magmatic environments. Thermal
springs located 12 km northwest of the volcano’s summit had outlet temperatures of up to 50.1 °C, neutral to slightly basic pH,
and a sodium bicarbonate composition, typical of distal fluid discharges in volcanic systems. Cold springs at the base of the
volcanic edifice, showing a calcium sulfate composition, were likely produced by interaction of shallow meteoric water with
CO2- andH2S-rich gases. A geochemical conceptual model was constructed to graphically represent these results, which can be
used as an indication for future geochemical monitoring and volcanic hazard assessment.
Description:
Published
Description:
id 57
Description:
2V. Struttura e sistema di alimentazione dei vulcani
Description:
4V. Processi pre-eruttivi
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
