Fluid geochemistry of a deep-seated geothermal resource in the Puna plateau (Jujuy Province, Argentina)

Abstract

This study focused on the geochemical and isotopic features of thermal fluids discharged from five zones located in the high altitude Puna plateau (Jujuy Province between S 22°20′-23°20′ and W 66°-67°), i.e. Granada, Vilama, Pairique, Coranzulí and Olaroz. Partially mature waters with a Na + -Cl − composition were recognized in all the investigated zones, suggesting that a deep hydrothermal reservoir hosted within the Paleozoic crystalline basement represents the main hydrothermal fluid source. The hydrothermal reservoirs are mainly recharged by meteoric water, although based on the δ 18 O-H 2 O and δD-H 2 O values, some contribution of andesitic water cannot be completely ruled out. Regional S-oriented faulting systems, which generated a horst and graben tectonics, and NE-, NW-and WE-oriented transverse structures, likely act as preferentially uprising pathways for the deep-originated fluids, as also supported by the Rc/Ra values (up to 1.39) indicating the occurrence of significant amounts of mantle He (up to 16%). Carbon dioxide, the most abundant compound in the gas phase associated with the thermal waters, mostly originated from a crustal source, although the occurrence of CO 2 from a mantle source, contaminated by organic-rich material due to the subduction process, is also possible. Relatively small and cold Na + -HCO 3 − -type aquifers were produced by the interaction between meteoric water and Cretaceous, Palaeogene to Miocene sediments. Dissolution of evaporitic surficial deposits strongly affected the chemistry of the thermal springs in the peripheral zones of the study area. Geothermometry in the Na-K-Ca-Mg system suggested equilibrium temperatures up to 200°C for the deep aquifer, whereas lower temperatures (from 105 to 155°C) were inferred by applying the H 2 geothermometer, likely due to re-equilibrium processes during the thermal fluid uprising within relatively shallow Na-HCO 3 aquifers. The great depth of the geothermal resource (possibly N 5000 m b.g.l.) is likely preventing further studies aimed to evaluate possible exploitation, although the occurrence of Liand Ba-rich deposits associated may attract financial investments, giving a pulse for the development of this remote region.

Preliminary conceptual model of the Cerro Blanco caldera-hosted geothermal system (Southern Puna, Argentina): Inferences from geochemical investigations

“…Hilton et al, 1993;Fischer and Chiodini, 2015), the Rc/Ra values of the CBC samples are consistent with the abnormally thick crust of the Southern Puna (Heit et al, 2014), fitting well with those values from hydrothermal systems from the Central Andean Volcanic Zone (e.g. Tassi et al, 2010;Benavente et al, 2016;Peralta Arnold et al, 2017). As far as the δ 13 C-CO 2 values are concerned, they are consistent with those of mantle CO 2 (Rollinson, 1993;Sano and Marty, 1995;Hoefs, 1997;Ohmoto and Goldhaber, 1997).…”

“…Between dashed lines, average values for Andean Volcanic Arc (Hoke et al, 1994) and crustal gases (Hilton et al, 2002), (c) CO 2 / 3 He vs. δ 13 C-CO 2 ‰ binary diagram for the gases from the Cerro Blanco Caldera. Isotopic values from others geothermal systems in the Puna plateau (Peralta Arnold et al, 2017) are shown for comparison. Symbols are: red triangle: bubbling gases from Los Hornitos area; green circle: dissolved gases from El Médano area; green pentagon: fumarolic gas sample; black square: data from Peralta Arnold et al, (2017).…”

Systematic Analysis of Geothermal Resources in the Coastal Bedrock Area of Chunxiao Town (China) by Using Geochemistry and Geophysics Methods

“…Moreover, the SiO 2 geothermometer gives only the minimum temperature of the geothermal reservoir [29]. It should be noted that the SiO 2 geothermometer depends on dilution and steam loss, while the equilibrium temperatures estimated by using other geothermometry techniques, based on the chemical equilibria in Na-K-Mg systems, are less influenced by dilution and steam loss [30].…”

Connections Between Hydrothermal System Geochemistry and Microbiology: Traversing Tectonic Boundaries in the South-Central Peruvian Andes

“…Thermal spring geochemistry is controlled by the depth of fluid circulation, the types of rocks encountered along fluid flow paths, water-rock interactions along these pathways, and the degree of mixing with shallow meteoric groundwater (e.g., Fournier, 1989;Arnold et al, 2017). These factors are closely tied to the overall tectono-magmatic setting, and spring chemical and isotopic composition (e.g., He, C, O, S) can inform the relative contribution from magmatic, crustal, and meteoric sources (Hilton, 1996;van Soest et al, 1998;de Hoog et al, 2001;Hilton et al, 2002;Zimmer et al, 2004;Newell et al, 2008;Sano et al, 2009;Scott et al, 2020).…”

“…High subsurface temperatures and a long flow path will increase the concentrations of ions at the surface. BAS generally have higher concentrations of Na + , K + , total Fe, Ba, and As, indicative of water-rock interaction during fluid flow and interaction with relatively young volcanic rocks (Hilton et al, 1996;Arnold et al, 2017).…”