The Geothermal Resource in the Guanacaste Region (Costa Rica): New Hints From the Geochemistry of Naturally Discharging Fluids

The Guanacaste Geothermal Province (GGP) encompasses the three major volcanoes
of northern Costa Rica, namely from NW to SE: Rincón de la Vieja, Miravalles, and
Tenorio. The dominant occurrence of (i) SO4-rich acidic fluids at Rincón de la Vieja,
(ii) Cl-rich mature fluids at Miravalles, and (iii) HCO−
3 -rich and low-temperature fluids at
Tenorio was previously interpreted as due to a north-to-south general flow of thermal
waters and a magmatic gas upwelling mostly centered at Rincón de la Vieja, whereas
Miravalles volcano was regarded as fed by a typical geothermal reservoir consisting
of a highly saline Na-Cl aquifer. The uniformity in chemical and isotopic (R/Ra and
d34S) compositions of the neutral Cl-rich waters suggested to state that all the thermal
discharges in the GGP are linked at depth to a single, regional geothermal system. In this
scenario, the thermal manifestations related to Tenorio volcano were regarded as a distal
and diluted fluid outflow. In this study, a new gas geochemical dataset, including both
chemical and isotopic (d13C-CO2 and R/Ra) parameters of fluid discharges fromthe three
volcanoes, is presented and discussed. Particular attention was devoted to the Tenorio
thermal manifestations, since they were poorly studied in the past because this area
has been considered of low geothermal potential. The aim is to provide insights into the
magmatic-hydrothermal fluid circulation and to verify the spatial distribution of the heat
fluid source feeding the fluid manifestations. According to this new dataset, CO2, i.e.,
the most abundant dry gas in the fluid manifestations, is mostly produced by limestone,
whereas the mantle CO2 contribution is ≤3.3%. Strongly acidic gas compounds from
magma degassing were absent in the discharged fluids, being scrubbed by secondary
processes related to prolonged fluid-rock interactions and mixing with shallow aquifers.
Our results only partially confirmthe previously depictedmodel, because the geochemical
and isotopic features (e.g., relatively high concentrations of temperature-dependent
gases and high R/Ra values) shown by fluids seeping out from the southern sector of
Tenorio volcano are more representative of medium-to-high enthalpy volcanic systems
than those typically occurring in distal areas. This implies that the geothermal potential
in the south of the GGP is higher than previously thought.

Alvarado, G. E. (2000). Los Volcanes de Costa Rica: Geología, Historia y Riqueza
Natural. San José: Universidad Estatal a Distancia, UNED.
Alvarado, G. E. (1993). Costa Rica: Land of Volcanoes. Cartago: Gallo Pinto Press.
Alvarado, G. E., and Cárdenes, G. (2016). “Geology, tectonics, and geomorphology
of costa rica: a natural history approach,” in Costa Rican Ecosystems, ed M.
Kappelle (Chicago, IL: The University of Chicago Press), 30–63.
Alvarado, G. E., and Gans, P. B. (2012). Síntesis geocronológica del magmatismo,
metamorfismo y metalogenia de Costa Rica, América Central. Rev. Geol. Am.
Central 46, 7–122. doi: 10.15517/rgac.v0i46.1836
Alvarado, G. E., Kussmaul, S., Chiesa, S., Gillot, P. Y., Appel, H., Worner, G.,
et al. (1992). Resumen cronoestratigrafico de las rocas igneas de Costa Rica
basado en dataciones radiometricas. J. South Am. Earth Sci. 6, 151–168.
doi: 10.1016/0895-9811(92)90005-J
Barquero, J. H., and Segura, J. (1983). La actividad del volcán Rincón de la Vieja.
Bol. Vulcanol. 13, 5–10.
Benavente, O., Tassi, F., Gutiérrez, F., Vaselli, O., Aguilera, F., and Reich, M.
(2013). Origin of fumarolic fluids from Tupungatito Volcano (Central Chile):
interplay between magmatic, hydrothermal, and shallow meteoric sources. Bull.
Volcanol. 75, 1–15. doi: 10.1007/s00445-013-0746-x
Benavente, O., Tassi, F., Reich,M., Aguilera, F., Capecchiacci, F., Gutiérrez, F., et al.
(2016). Chemical and isotopic features of cold and thermal fluids discharged in
the Southern Volcanic Zone between 32.5◦S and 36◦S: insights into the physical
and chemical processes controlling fluid geochemistry in geothermal systems
of Central Chile. Chem. Geol. 420, 97–113. doi: 10.1016/j.chemgeo.2015.
11.010
Boudon, G., Rancon, J. P., Kieffer, G., Soto, G. J., Traineau, H., and Rossignol, J. C.
(1996). Les eruptions de 1966-1970 et 1991-1992 du volcan Rincón de la Vieja,
Costa Rica: exemple d’activité réecurrente d’un systéme hydromagmatique. C.
R. Acad. Sci. 322, 101–108.
Brombach, T., Caliro, S., Chiodini, G., Fiebig, J., Hunziker, J., and Raco,
B. (2003). Geochemical evidence for mixing of magmatic fluids with
seawater, Nisyros hydrothermal system, Greece. Bull. Volcanol. 65, 505–516.
doi: 10.1007/s00445-003-0278-x
Carr, M. J. (1984). Symmetrical and segmented variation of physical and
geochemical characteristics of the Central America Volcanic front. J. Volcanol.
Geotherm. Res. 20, 231–252. doi: 10.1016/0377-0273(84)90041-6
Chavarría, L., Mora, O., Hakanson, E., Galvez, M., Rojas, M., Molina, F., et al.
(2010). “Geologic model of the pailas geothermal field, guanacaste, costa rica,”
in ProceedingsWorld Geothermal Congress (Bali).
Chiesa, S., Alvarado, G. E., Pecchio, M., Corrella, M., and Zanchi, A.
(1994). Contribution to petrological and stratigraphical understanding of the
Cordillera de Guanacaste lava flows, Costa Rica. Rev. Geol. Am. Central 17,
19–43.
Chiesa, S., Civelli, G., Gillot, P. Y., Morz, O., and Alvarado, G. E. (1992). Rocas
piroclásticas asociadas a la formación de la Caldera de Guayabo, Cordillera de
Guanacaste, Costa Rica. Rev. Geol. Am. Central 14, 59–75.
Chiodini, G., Cioni, R., and Marini, L. (1993). Reactions governing the
chemistry of crater fumaroles from Vulcano Island, Italy, and implications for
volcanic surveillance. Appl. Geochem. 8, 357–371. doi: 10.1016/0883-2927(93)
90004-Z
Chiodini, G., Marini, L., and Russo, M. (2001). Geochemical evidence
for the existence of high-temperature hydrothermal brines at
Vesuvio volcano, Italy. Geochim. Cosmochim. Acta 65, 2129–2147.
doi: 10.1016/S0016-7037(01)00583-X
D’Amore, F., and Mejia, T. J. (1999). Chemical and physical reservoir parameters
at initial conditions in Berlin geothermal field, El Salvador: a first assessment.
Geothermics 28, 45–73.
D’Amore, F., and Panichi, C. (1980). Evaluation of deep temperatures of
hydrothermal systems by a new gas geothermometer. Geochim. Cosmochim.
Acta 44, 549–556. doi: 10.1016/0016-7037(80)90051-4
Evans, W., White, L., and Rapp, J. (1988). Geochemistry of some gases in
hydrothermal fluids from the southern Juan de Fuca Ridge. J. Geophys. Res.
93, 15305–15313. doi: 10.1029/JB093iB12p15305
Fergurson, R. B., and Alfonso, P. S. (1977). Electrical investigations in the
Guanacaste Geothermal Area (Costa Rica). Geotherm. Resour. Counc. Trans.
1, 99–100.
Gardner, M. C., and Corrales, R. (1977). Geochemical investigations of the
Guanacaste Geothermal Project, Costa Rica. Geotherm. Resour. Counc. Trans.
1, 101–102.
Gherardi, F., Panichi, C., Yock, A., and Gerardo-Abaya, J. (2002). Geochemistry of
the surface and deep fluids of the Miravalles volcano geothermal system (Costa
Rica). Geothermics 31, 91–128. doi: 10.1016/S0375-6505(01)00030-X
Giggenbach, W. F. (1980). Geothermal gas equilibria. Geochim. Cosmochim. Acta
44, 2021–2032. doi: 10.1016/0016-7037(80)90200-8
Giggenbach, W. F. (1987). Redox processes governing the chemistry of fumarolic
gas discharges from White Island, New Zealand. Appl. Geochem. 2, 143–161.
doi: 10.1016/0883-2927(87)90030-8
Giggenbach, W. F. (1991). “Chemical techniques in geothermal exploration,”
in Application of Geochemistry in Geothermal Reservoir Development, ed F.
D’Amore (New York, NY: UNITAR), 119–144.
Giggenbach, W. F. (1992). The composition of gases in geothermal and volcanic
systems as a function of tectonic setting. Proc. Int. Symp. Water Rock Inter. 8,
873–878.
Giggenbach, W. F. (1996). “Chemical composition of volcanic gases,” in
Monitoring and Mitigation of Volcano Hazards, eds R. Scarpa and R. I. Tilling
(Berlin: Springer), 222–256.
Giggenbach, W. F., and Corrales, R. S. (1992). Isotopic and chemical composition
of water and steam discharges from volcanic-magmatic-hydrothermal systems
of the Guanacaste Geothermal Province, Costa Rica. Appl. Geochem. 7,
309–332. doi: 10.1016/0883-2927(92)90022-U
Hilton, D. R., Fischer, T. P., and Marty, B. (2002). Noble gases and
volatile recycling at subduction zones. Rev. Miner. Geochem. 47, 319–370.
doi: 10.2138/rmg.2002.47.9
Hoefs, J. (2009). Stable Isotope Geochemistry. Berlin: Springer.
Instituto Costarricense de Electricidad (ICE) (1990). Estudios de Reconocimiento
y Prefactibilidad Geotérmica en la República de Costa Rica. Fase II, Estudio
de Prefactibilidad del área del Tenorio, Informe Geovulcanológico. Proyecto
COS/83/T01 [Inf. Interno].
Instituto Costarricense de Electricidad (ICE) (1991). Evaluación del Potencial
Geotérmico de Costa Rica. Internal Report, Instituto Costarricense de
Electricidad San José, Costa Rica.
Instituto Costarricense de Electricidad (ICE) (2014). Plan de Expansión
de la Generación Eléctrica, Período 2014-2035. Report, Centro Nacional
de Planificación Eléctrica, Proceso de Expansión Integrada; Instituto
Costarricense de Electricidad; San José, Costa Rica.
Kempter, K. A., Benner, S. G., and Williams, S. N. (1996). Rincón de la Vieja
volcano, Guanacaste province, Costa Rica: geology of the south-western
flank and hazard implication. J. Volcanol. Geotherm. Res. 71, 109–127.
doi: 10.1016/0377-0273(95)00072-0
Mainieri, A., Granados, E., Corrales, R., and Vaca, L. (1985).Miravalles geothermal
field, Costa Rica. Technical report. Geotherm. Resour. Counc. Trans. 9, 279–283.
Mamyrin, B. A., and Tolstikhin, I. N. (1984). Helium Isotopes in Nature, Vol. 3.
Amsterdam: Elsevier.
Marty, B., and Jambon, A. (1987). C/3He fluxes from the solid earth:
implications for carbon geodynamics. Earth Planet. Sci. Lett. 83, 16–26.
doi: 10.1016/0012-821X(87)90047-1
Mayorga (2009). Mayorga. Available online at: http://www.kinertech.com/yahoo_
site_admin/assets/docs/Geotermia__Caso_de_Costa_Rica.27362721.pdf
Molina, F., and Martì, J. (2016). The Borinquen geothermal system (Canas Dulces
caldera, Costa Rica). Geothermics 64, 410–425. doi: 10.1016/j.geothermics.
2016.07.001
Montegrossi, G., Tassi, F., Vaselli, O., Buccianti, A., and Garofalo, K. (2001).
Sulfur species in volcanic gases. Anal. Chem. 73, 3709–3715. doi: 10.1021/ac00
1429b
Montero, W., Lewis, J. C., and Araya, M. C. (2017). The Guanacaste volcanic
arc sliver of northwestern costa rica. Sci. Rep. 7:1797. doi:10.1038/s41598-017-
01593-8
O’Leary, M. H. (1988). Carbon isotopes in photosynthesis. Bioscience 38, 328–336.
O’Nions, R. K., and Oxburgh, E. R. (1988). Helium, volatile fluxes and the
development of continental crust. Earth Planet. Sci. Lett. 90, 331–347.
Ozima, M., and Posodek, F. A. (1983). Noble Gas Geochemistry. Cambridge:
Cambridge University Press.
OVSICORI-UNA (1995). Actividad Eruptiva del Volcan Rincón de la Vieja Durante
los Dias 6–13 de Noviembre, 1995. Open Report, OVSICORI-UNA, 42.
Frontiers in Earth Science | www.frontiersin.org 11 June 2018 | Volume 6 | Article 69
Tassi et al. Geothermal Resource in Costa Rica
OVSICORI-UNA (1998). Report of the Rincón de la Vieja Volcanic Activity.
Smithsonian Institution, Global Volcanism Network Bulletin.
OVSICORI-UNA (2011). Report of the Rincón de la Vieja Volcanic Activity.
Smithsonian Institution, Global Volcanism Network Bulletin.
OVSICORI-UNA (2012). Report of the Rincón de la Vieja Volcanic Activity.
Smithsonian Institution, Global Volcanism Network Bulletin.
OVSICORI-UNA (2014). Report of the Rincón de la Vieja Volcanic Activity.
Smithsonian Institution, Global Volcanism Network Bulletin.
OVSICORI-UNA (2015). Report of the Rincón de la Vieja Volcanic Activity.
Smithsonian Institution, Global Volcanism Network Bulletin.
OVSICORI-UNA (2016). Report of the Rincón de la Vieja Volcanic Activity.
Smithsonian Institution, Global Volcanism Network Bulletin.
OVSICORI-UNA (2017). Report of the Rincón de la Vieja Volcanic Activity.
Smithsonian Institution, Global Volcanism Network Bulletin.
Patino, L. C., Carr,M. J., and Feigenson,M.D. (2000). Local and regional variations
in Central American arc lavas controlled by variations in subducted sediment
input. Contrib. Miner. Petrol. 138, 265–283. doi: 10.1007/s004100050562
Pineau, F., and Javoy, M. (1983). Carbon isotopes and concentration
in mid-oceanic ridge basalts. Earth Planet. Sci. Lett. 62, 239–257.
doi: 10.1016/0012-821X(83)90087-0
Polyak, B. G., and Tolstikhin, I. N. (1985). Isotopic composition of the Earth’s
helium and the problem of the motive forces of tectogenesis. Chem. Geol. 52,
9–33. doi: 10.1016/0168-9622(85)90005-3
Poreda, R. J., and Craig, H. (1989). Heliumisotope ratios in circum-Pacific volcanic
arcs. Nature 338, 473–478. doi: 10.1038/338473a0
Ray, M., Hilton, D., Muñoz, J., Fischer, T., and Shaw, A. (2009). The effects of
volatile recycling, degassing and crustal contamination on the helium and
carbon geochemistry of hydrothermal fluids from the southern volcanic zone
of Chile. Chem. Geol. 266, 38–49. doi: 10.1016/j.chemgeo.2008.12.026
Rizzo, A., Barberi, F., Carapezza, M. L., Di Piazza, A., Francalanci, L., Sortino, F.,
et al. (2015). New mafic magma refilling a quiescent volcano: evidence from
He-Ne-Ar isotopes during the 2011-2012 unrest at Santorini, Greece. Geochem.
Geophys. Geosyst. 16, 798–814. doi: 10.1002/2014GC005653
Saginor, I., Gazel, E., Condie, C., and Carr, M. J. (2013). Evolution of geochemical
variations along the Central American volcanic front. Geochem. Geophys.
Geosyst. 14, 4504–4522. doi: 10.1002/ggge.20259
Sànchez-Rivera, E., and Vallejos-Ruiz, O. (2015). Costa Rica country update
report,” in ProceedingsWorld Geothermal Congress (Melbourne, VIC), 1–12.
Sano, Y., and Marty, B. (1995). Origin of carbon in fumarolic gases from island
arcs. Chem. Geol. 119, 265–274. doi: 10.1016/0009-2541(94)00097-R
Sano, Y., and Williams, S. N. (1996). Fluxes of mantle and subducted carbon
along convergent plate boundaries. Geophys. Res. Lett. 23, 2749–2752.
doi: 10.1029/96GL02260
Shaw, A. M., Hilton, D. R., Fischer, T. P., Walker, J. A., and Alvarado, G. E.
(2003). Contrasting He-C relationships in Nicaragua and Costa Rica: insights
into C cycling through subduction zones. Earth Planet. Sci. Lett. 214, 499–513.
doi: 10.1016/S0012-821X(03)00401-1
Sherwood Lollar, B., Ballentine, C. J., and O’Nions, R. K. (1997). The fate of
mantle-derived carbon in a continental sedimentary basin: integration of C/He
relationships and stable isotope signatures. Geochim. Cosmochim. Acta 61,
2295–2307.
Shock, E. L. (1993). Hydrothermal dehydration of aqueous organic compounds.
Geochim. Cosmochim. Acta 57, 3341–3349. doi: 10.1016/0016-7037(93)
90542-5
Tassi, F., Vaselli, O., Capaccioni, B., Giolito, C., Duarte, E., Fernandez, et al.
(2005). The hydrothermal-volcanic system of Rincón de la Vieja volcano
(Costa Rica): a combined (inorganic and organic) geochemical approach
to understanding the origin of the fluid discharges and its possible
application to volcanic surveillance. J. Volcanol. Geotherm. Res. 148, 315–333.
doi: 10.1016/j.jvolgeores.2005.05.001
Tedesco, D., and Nagao, K. (1996). Radiogenic 4He, 21Ne and 40Ar in
fumarolic gases at Vulcano island: implication for the subductuted African
continental plate beneath Italy. Earth Planet. Sci. Lett. 144, 517–528.
doi: 10.1016/S0012-821X(96)00196-3
Tristan, J. F. (1921). Apuntes sobre el volcano Rincón de la Vieja. Rev. Costa Rica
II 6, 161–168.
Vallejos-Ruiz, O., Sànchez-Rivera, E., and Gonzàlez-Vargas, C. (2005). “Reservoir
management at the Miravalles geothermal field, Costa Rica,” in Proceedings
World Geothermal Congress (Antalya), 1–8.
Venturi, S., Tassi, F., Bicocchi, G., Cabassi, J., Capecchiacci, F., Capasso, G., et al.
(2017). Fractionation processes affecting the stable carbon isotope signature of
thermal waters from hydrothermal/volcanic systems: the examples of Campi
Flegrei and Vulcano Island (southern Italy). J.