The origin of reservoir fluids in the geothermal field of Los Azufres, Mexico — isotopical and hydrological indications

Element mobility during the hydrothermal alteration of rhyolitic rocks of the Los Azufres geothermal field, Mexico

“…The present hydrothermal system at the LAGF is related to a deep aquifer extending over the entire field. The liquid-dominated geothermal reservoir lies at a depth of approximately 3500 m and has a temperature of about 300 • C (Birkle et al, 2001). Permeable faults and fracture systems allow the geothermal fluids to rise towards the surface (Fig.…”

Evolution of the geothermal fluids at Los Azufres, Mexico, as traced by noble gas isotopes, δ18O, δD, δ13C and 87Sr/86Sr

“…The Los Azufres geothermal field has been extensively studied in the past 30 years for its geological and tectonic features (Dobson and Mahood, 1985;Ferrari et al, 1991;Pradal and Robin, 1994), the geochemistry of the fluids (Nieva et al, 1987a;Gonzalez-Partida et al, 2000;Birkle et al, 2001;Gonzalez-Partida et al, 2003;Barragán et al, 2005;Gonzalez-Partida et al, 2005) and the evolution of the power capacity after 25 years of exploitation and re-injection of used brines (Nieva et al, 1987b;Arellano et al, 2005;Barragán et al, 2005;Torres-Rodríguez et al, 2005). Despite the numerous studies carried out, noble gas data are scarce in Los Azufres (Prasolov et al, 1999) with only a few wells having been monitored for He and Ar to study the evolution of fluids as exploitation proceeded (Arriaga, 2002;Barragán et al, 2006).…”

Radium depletion and 210Pb/226Ra disequilibrium of Mar^|^iacute;taro hydrothermal deposits, Los Azufres geothermal field, Mexico

“…The leaching of uranium mill tailings and associated metal oxides ores by acidic waters at pH from 2 to 5, remobilize large quantities of radionuclides creating an important environmental problem. Marítaro effluents are strongly acidic with a measured pH of 3.2 (Birkle et al, 2001) to 3.9 (Gonzales-Partida et al, 2005). Thus, the anomalous depletion of radium in our core could be explained by the occurrence of acidic fluids at Marítaro.…”

“…Vent activity changes continuously in intensity and location as observed during 2007, 2009 and 2010 surveys. Hydrothermal activity is sustained with the direct rise of a "pristine" geothermal liquid and vapor phase to the surface at temperatures of 88-91°C (Birkle et al, 2001;Gonzales-Partida et al, 2005). Fluids are highly mineralized (Birkle et al, 2001) and contain almost pure mantle helium with a measured 3 He/ 4 He ratio of 7.0 Ra (where Ra is the atmospheric ratio) (Pinti et al, 2013).…”