Hydrothermal Alteration in the Nevados de Chillan Geothermal System, Southern Andes: Multidisciplinary Analysis of a Fractured Reservoir

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dc.catalogadordfo
dc.contributor.authorMorata, Diego
dc.contributor.authorGallardo, Romina
dc.contributor.authorMaza, Santiago
dc.contributor.authorArancibia Hernández, Gloria Cecilia
dc.contributor.authorLópez Contreras, Camila Andrea
dc.contributor.authorMura Toledo, Valentina Rossana
dc.contributor.authorCannatelli, Claudia
dc.contributor.authorReich, Martin
dc.date.accessioned2024-05-07T13:35:14Z
dc.date.available2024-05-07T13:35:14Z
dc.date.issued2023
dc.description.abstractThe interplay between a heat source, primary plus secondary permeability, and hydrothermal fluids makes geothermal systems a highly dynamic environment where evolving physico-chemical conditions are recorded in alteration mineralogy. A comprehensive characterization of hydrothermal alteration is therefore essential to decipher the major processes associated with geothermal system development. In this study, we defined the hydrothermal mineralogical evolution of the Nevados de Chillan Geothermal System (NChGS), located in the Southern Volcanic Zone (SVZ) of the central Andes, where the regional framework of the system is formed by a direct association with a currently active volcanic complex, a favorable structural control, and vertically inhibited fluid circulation. To characterize the secondary mineralogy present in the NChGS, we integrated optical petrography, Scanning Electron Microscopy (SEM) observations, X-ray Diffraction (XRD) analysis, and microthermometric measurements along a drill core with a depth of 1000 m at the Nieblas-1 well. These mineralogical approaches were combined with a structural field analysis to highlight the relevance of multidisciplinary study in understanding active geothermal systems. The results indicated that the evolution of the system involved four paragenetic stages, with the main processes in each phase being the heating, boiling, and mixing of fluids and re-equilibration to new physico-chemical conditions. Additionally, three hydrothermal zones were recognized: an upper argillic section, an intermediate sub-propylitic zone, and a deep propylitic domain. Sampled thermal springs are characterized by pH values of 2.4-5.9 and high SO4= concentrations (>290 ppm). These acid-sulfate steam-heated waters suggest the contribution of primary magmatic volatiles to the hydrothermal system. Alunite recorded in the alteration halos of veinlets presents at depths of 170-230 m denote the circulation of acidic fluids at these levels which were favored by reverse faults. These findings indicate that, at this depth range, the condensation of magmatic volatiles into shallow aquifers controls the recharge area of the superficial thermal manifestations. Conversely, deep-seated hydrothermal fluids correspond to near-neutral chloride fluids, with salinities ranging from 0.1 to 6.9 wt.% NaCl eq. The distribution of illite/smectite and chlorite/smectite mixed-layered minerals outline the presence of a significant clay cap, which, in this system, separates the steam-heated domain from the deep hydrothermal realm and restricts fluid circulation to existing permeable channels. Our mineralogical and structural study provides critical data for the interpretation of heat-fluid-rock interaction processes in the NChGS. The interplay between hydrothermal fluids and active faults is also discussed in the context of the complex of geological processes in active geothermal systems along the Chilean Southern Volcanic Zone.
dc.fuente.origenWOS
dc.fuente.origenORCID
dc.identifier.doi10.3390/min13060722
dc.identifier.eissn2075-163X
dc.identifier.urihttps://doi.org/10.3390/min13060722
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/85473
dc.identifier.wosidWOS:001017460300001
dc.information.autorucEscuela de Ingeniería; Arancibia Hernandez Gloria Cecilia; 0000-0003-2860-1302; 1008583
dc.information.autorucEscuela de Ingeniería; Lopez Contreras Camila Andrea; S/I; 1049388
dc.information.autorucEscuela de Ingeniería; Mura Toledo Valentina Rossana; S/I; 1186439
dc.issue.numero6
dc.language.isoen
dc.nota.accesoacceso abierto
dc.pagina.final33
dc.pagina.inicio1
dc.revistaMinerals
dc.rightsacceso abierto
dc.rights.licenseAtribución 4.0 Internacional (CC BY 4.0)
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/deed.es
dc.subjectHydrothermal evolution
dc.subjectBoiling
dc.subjectMixing
dc.subjectClay cap
dc.subjectPermeability
dc.subjectStructural control
dc.subjectSouthern Andes
dc.subject.ddc620
dc.subject.deweyIngenieríaes_ES
dc.titleHydrothermal Alteration in the Nevados de Chillan Geothermal System, Southern Andes: Multidisciplinary Analysis of a Fractured Reservoir
dc.typeartículo
dc.volumen13
sipa.codpersvinculados1008583
sipa.codpersvinculados1049388
sipa.codpersvinculados1186439
sipa.trazabilidadWOS;2023-07-30
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