Publication Date:
2024-05-09
Description:
The Cerro Blanco Caldera (CBC) is the youngest collapse caldera system in the Southern Central Andes (Southern
Puna, Argentina). The CBC is subsiding with at an average velocity of 0.87 cm/year and hosts an active geothermal
system. A geochemical characterization of emitted fluids was carried out based on the chemical and
isotopic compositions of fumaroles, and thermal and cold springs discharged in this volcanic area with the aim of
constructing the first hydrogeochemical conceptual model and preliminary estimate the geothermal potential.
The main hydrothermal reservoir, likely hosted within the pre-caldera basement rocks, has a Na+-Clˉ(HCO3)ˉ
composition with estimated temperatures ≥135 °C. The unconsolidated, fine-grained Cerro Blanco ignimbrite
likely acts as the cap-rock of the hydrothermal system. The presence of phreatic eruption breccias in the surrounding
area of the geothermal fumaroles supports the effectiveness of the pyroclastic deposit as sealing rocks.
The isotopic data of water (δ18O and δD) indicate a meteoric recharge of the hydrothermal reservoir, suggesting
as recharge areas the sectors surrounding the CBC, mainly towards the W and NW where large outcrops of the
pre-caldera basement exist. A fault-controlled hydraulic connection between the hot springs and the hydrothermal
reservoir is proposed for the Los Hornitos area. The fumaroles show the typical compositional features of
hydrothermal fluids, being dominated by water vapor with significant concentrations of H2S, CH4 and H2.
Considering the high geothermal gradient of this area (∼104 °C/km) and the relatively high fraction of mantle
He (∼39%) calculated on the basis of the measured R/Ra values, the hydrothermal aquifer likely receives inputs
of magmatic fluids from the degassing magma chamber. The preliminary geothermal potential at CBC was
evaluated with the Volume Method, calculating up to E = 11.4*1018 J. Both the scarce presence of superficial
thermal manifestations and the occurrence of an efficient cap-rock likely contribute to minimize the loss of
thermal energy from the reservoir. The results here presented constitute the necessary base of knowledge for
further accurate assessment of the geothermal potential and ultimately the implementation of the geothermal
resource as a viable energy alternative for small localities or mining facilities isolated from the National
Interconnected System due to their remote localization.
Description:
Published
Description:
102213
Description:
6A. Geochimica per l'ambiente e geologia medica
Description:
JCR Journal
Keywords:
Hydrothermal system
;
Fluid geochemistry
;
Geothermal prospection
;
Quaternary caldera
;
Northwestern Argentina
;
05.09. Miscellaneous
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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