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This work presents the first chemical and isotopic (δ13C-CO2, δ13C-CH4, 3He, 4He, 20Ne, 40Ar, 36Ar, δ18O, and δD) data for fluid discharges from Guallatiri 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 (

This work presents chemical and isotopic (δ13C-CO2, δ13C-CH4 3He, 4He, 20Ne, 40Ar, 36Ar, δ18O and δD) data of fluid discharges from Colpitas-Taapaca volcanic-hydrothermal system, located close to the Taapaca Volcanic Complex, with the aim to investigate the physical-chemical conditions of the fluid source and to provide a preliminary evaluation of the geothermic potential of the study area. Colpitas thermal springs (to 56 °C) and part of the cold springs (≤18°C) from this area have a Na+-Cl- composition and Total Dissolved Solids (TDS) values (from 6,059 to 19,118 mg/L). Putre springs also show a Na+-Cl- composition, TDS values up to 7,887 mg/L, and outlet temperatures from 21 to 31 °C. Colpitas cold springs, with a Ca2+-SO42- composition and relatively low TDS values (≤1,350 mg/L), are likely produced by interaction of shallow water with uprising H2S-rich hydrothermal gases. This process is likely also controlling the chemistry of Jurase thermal springs, which have the highest outlet temperatures of the study area (up to 68 °C), a Ca2+-SO42- composition and TDS values ≤2,355 mg/L. Eventually, Las Cuevas springs have temperatures up to 36 °C, a Na+-HCO3- composition and low TDS values (≤1,067 mg/L), typical features of springs related to a shallow aquifer. The δ18OH2O and δD-H2O values indicate that all waters have a dominant meteoric origin. Enrichments in 18O and D shown by Colpitas and Putre thermal waters are likely due to steam loss and water-rock interaction, masking a possible direct steam contribution from magmatic degassing. Gas emissions from Colpitas bubbling pools are dominated by CO2, with significant concentrations of CH4, H2S and H2. The Rc/Ra values (up to 2.04) of Colpitas gases indicate a significant contribution of magmatic to mantle He, whereas the high CO2/3He ratios, combined with d13C-CO2 values ranging from -7.66 to -5.63 % vs. PDB, imply a dominant crustal CO2 source, mostly involving limestone. Estimated temperatures based on the composition of waters and gases from Colpitas are up to 215 °C. Higher temperatures (240 °C) are estimated for Putre thermal waters, although these waters, as well as those from Jurase and Las Cuevas, are too immature for a reliable application of geothermometric techniques. Based on the theoretical reservoir temperature and the measured Cl total output, the thermal energy released from Colpitas thermal area is estimated at up to 13.9 Mw. Such results suggest the occurrence of a promising heat source, possibly related to Taapaca volcanic complex, and encourage the development of future research based on combined geophysical and ccepted geochemical approaches, in order to provide a reliable evaluation of the geothermal potential of the whole area.

Cerro Tujle is an isolated Quaternary maar located 21 km south-east of the Salar de Atacama basin. It is situated at 3,554 m a.s.l., on the top of the Cordon de Tujle ridge forming a north-south striking morphological element in the Central Volcanic Zone of the Andes, in northern Chile. The material erupted at Cerro Tujle lies over the Tucucaro Ignimbrite (3.2 ± 0.3 Ma), covering the whole area. The origin of the magma source, as well as the evolution and control of the volcanic eruptive styles, were determined by fieldwork, stratigraphic, morphometric, textural (density and vesicularity), petrographic, and geochemical analyses. The Cerro Tujle maar features an elliptical crater (333 × 279 m wide in east-west and north-south directions, respectively) surrounded by lava flow and tephra deposits. The total Dense Rock Equivalent volume of the products was calculated in 1.53 × 105 m3, and mainly correspond to andesites (58.62–59.80 wt% of SiO2). The lava flow can be categorized in at least two types: i) brown-red and green-to-gray andesites located on the north-northwestern flank of the crater, and ii) black andesites with felsic rock clasts distributed around the crater underlying the other lavas. In contrast, the pyroclastic deposit displays breccias of juvenile pyroclasts with xenoliths of rhyolitic composition. These felsic clasts suggest magma assimilation with a shallow magma reservoir during a relatively fast ascent of the magma. This is evidenced by disequilibrium textures in mineral levels, such as reaction rim, and skeletal and sieve textures of the phenocrysts. The field evidence and results of the different analyses suggest a change in the eruptive style from effusive to explosive. This transition is associated with a decrease of the magma flux and a withdrawal of magma below the groundwater table, which has produced a phreatomagmatic eruption by magma-water interaction.

This work presents the first record of boron-rich aqueous solutions in barite-, anhydrite-, and sassolite-hosted fluid inclusions found in the fumarolic deposits of the Guallatiri volcano, an active and quiescently degassing volcano located in northern Chile. These findings offer a unique opportunity to investigate the mineral-forming and depositional processes in fumarolic environments. Chemical and mineral characterization was performed using XRD and SEM-EDS techniques, whereas petrologic and microthermometry methods, in addition to Raman and FTIR spectroscopy, were conducted to the physicochemical characterization of fluid inclusions. Characterizations of these fluid inclusions show high‑boron concentrations associated with crystalline phases of sassolite and boron-rich aqueous solutions in fluid inclusions. Analyses based on fluid inclusions reveal two potentially fluid sources: (i) a deep source with higher temperatures (up to 220 °C) and saline fluids (>8 wt% NaCl equivalent), in the presence of CO2, H2S, SO2, and CH4; and (ii) a shallower source with lower temperatures (between 113 and 163 °C) and salinities (

This paper introduces the first GIS-based volcanic hazard, vulnerability and risk assessment of Guallatiri volcano. Volcanic hazard assessment is based on the study of five key volcanic phenomena observed during Holocene eruptions of Guallatiri volcano: i) tephra transport, dispersal and deposition; ii) flooding by lahars; iii) lava flows; iv) pyroclastic density currents; and v) ballistic projectiles. A qualitative approach is considered, assuming a relative probability of occurrence for each scenario. Hazard maps are constructed via computer modelling based on field data and some volcanic analogues and relative probability values are assigned to each scenario (the lowest magnitude/intensity scenario has the highest probability value and vice versa). After summing them up through the raster calculator tool, the result corresponds to an integrated volcanic hazard map, that shows the areas likely to be adversely affected by different volcanic processes. Vulnerability was assessed through its social, physical and territorial components considered by dividing the study area into basic administrative units (rural entities), according to the 2017 Chilean Census. Social vulnerability is evaluated through density of people, education qualification, and dependence index. Physical vulnerability is evaluated through the number of houses, and territorial vulnerability, through a critical infrastructure cadaster. A vulnerability level is assigned according to the vulnerability indicator intervals using the quantile method. In order to evaluate the overall risk, the integrated hazard map and vulnerability assessments are aggregated through the arithmetic multiplication of the layers. Consequently, three thematic risk maps are obtained: social, physical and territorial. This analysis depicts that ash transport, dispersal and fallout, indeed has the greatest impact because it is more widely distributed. If a high magnitude eruption occurred during autumn, winter or spring/summer, ash cloud movements would be to the NW, E or SE, respectively reaching Chile, Peru, Bolivia, Argentina, Brazil, and Paraguay. For volcanic processes closest to the volcanic edifice, the higher risk areas would be located towards the N, NW, and SW of the volcano affecting areas up 13 km to the localities of Chungara Viejo, Ancuta, and Guallatiri. In the case of explosive events, areas prone to be affected by tephra deposition could be blanketed with layers up to 50 cm thick, while flooding by bulky lahars could extend for up to ~19 km, and pyroclastic density currents up to ~10 km, whereas for effusive events, lava flows would extend for up to ~7 km. Consequently, the places identified here as those being at highest social risk are Nigramalla, Ancuta, and Guallatire. Due to its remoteness, this volcano and their hazards/vulnerability/risks have been underestimated so far. A future eruption will threaten these areas and the local economy mainly related to the tertiary (e.g., tourism), and primary (e.g., livestock) sectors.

The compilation of water, sediment, rock, and condensed gas data of arsenic (As) in the Altiplano-Puna of Chile reveals a link between its natural enrichment and volcanic activity, high crustal thicknesses, and regional structures. Two zones were studied which encompass the Altiplano-Puna and western lowlands of Chile: the Northern Zone (including Los Pintados, Surire, and Huasco) and Southern Zone (including Pedernales, Grande, and Laguna Verde). A positive correlation was found between average As concentrations in saline and brackish water of salt flats and crustal thicknesses of the two studied zones with heightened values to the east (up to 25 mg∙L−1 of dissolved As in water and a 64 km depth to the Mohorovicic discontinuity). Furthermore, in the studied Altiplano-Puna salt flats, surrounding Mio-Pliocene to Quaternary felsic and intermediate volcanic outcrops are abundant and As is well correlated with other dissolved components (e.g. Li and B). Sediments show extreme As values at punctual locations within the Altiplano-Puna, where the crust is thick, recent volcanic and hydrothermal activity is present, and regional faults are found. Volcanic rocks and condensed gas in the Altiplano-Puna are also enriched with As (up to 221 and 1234 mg∙kg−1 respectively). In this tectonic environment, it is hypothesized that volcanism represents an important source of As and the thick continental crust can provide a large reservoir of As that can be leached by rising thermal fluids. Regional scale fault systems also can allow for preferential upwelling and the heightened concentration of As in fractures. Hydrological processes at the surface transport dissolved As to lower elevation regions through groundwater in aquifers and surface water in perennial rivers, creeks, and gorges, diluting element concentrations where significant evapoconcentration is not present.

A qualitative and quantitative analysis of 13 Landsat TM and ETM+images of Lascar volcano for the 2000-2004 period was performed by applying the three bands and three components method to determine heat and mass flux and understand the magma circulation process in a passive degassing volcano related to permanent fumarolic activity. The behavior and evolution of spectral radiance during the study period suggest that prior to low-to-moderate magnitude eruptions these values reach their localized temporal minimumlevels, corresponding to 1.9-4.38mW/cm2srμmin July 2000 and 4.38-7.11mW/cm2srμmin December 2003 eruptions, respectively. Similar behavior is observed for anomaly area, heat and mass fluxes. During the 2000-2004 period the heat flux was estimated to vary from 75.46 and 10,527 MW, while mass flux ranged between 131 and 18,469 kg s−1. A magma circulation model is proposed to explain these variations, where the thermal anomaly is related to the presence of a fumarolic field and fluids movement from a magma chamber located at ~10-17 km depth. Fil: Gonzalez, C.. Servicio Nacional de Geología y Minería; Chile Fil: Inostroza, M.. Servicio Nacional de Geología y Minería; Chile Fil: Aguilera, F.. Servicio Nacional de Geología y Minería; Chile Fil: González, R.. Universidad Católica del Norte. Departamento de Ciencias Geológicas; Chile Fil: Viramonte, Jose German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía No Convencional; Argentina Fil: Menzies, A.. Universidad Católica del Norte. Departamento de Ciencias Geológicas; Chile

A detailed study on the mineralogy and chemistry of fumarolic deposits with a focus on metals and metalloids is presented. Two active volcanoes in northern Chile, Guallatiri and Lastarria, are characterised by vigorous and persistent fumarolic activity and the formation of zoned fumarolic deposits. Twelve minerals were identified in the studied deposits by X-ray diffraction: anhydrite, barite, gypsum, rhomboclase, orpiment, pyrite, galena, cristobalite, quartz, magnetite, sassolite, and native sulphur. Chemical analyses revealed the presence of 30 chemical elements, including metals and metalloids such as As, Hg, Pb, Sb, Te, and Tl. Backscattered-electron imaging revealed four types of rock textures in the fumarolic deposits: i) massive and poorly vesiculated, ii) highly vesiculated, iii) clastic-like, and iv) flow-like. Micro-chemical analyses showed the presence of cinnabar nataliyamalikite and unidentified mineral assemblages of As S, Te S, Pb S, Hg S, Tl I, and Tl-I-Pb compositions. Based on colour, outlet gas temperature, mineralogy, and chemistry, four distinct zones of fumarolic deposits are identified. (1) Grey zone: sulphide and silicate dominant with minor native elements, high concentrations of Pb and As, and a clastic-like texture (gas outlet temperature > 265 °C). (2) Red zone: sulphide and silicate dominant with minor oxides and native elements, small As, Pb, Tl, I, and Te minerals, and predominance of a flow-like texture (200–280 °C). (3) Yellow-orange zone: dominated by native sulphur and minor borates and sulphur with small As-, Sb-, Hg-, and I-containing minerals, massive and vesiculated texture (80–200 °C). (4) Yellow-white zone: formed by native sulphur, minor borates and As-rich zones, usually displaying a vesiculated texture (