Chemical and isotope characteristics of the Chachimbiro geothermal fluids (Ecuador).

The parent geothermal water proposed for the Chachimbiro geothermal area has calculated values of 2250 mg/L Cl and approximately 5 bar Pco2. It comes from a reservoir having an estimated temperature of 225–235 °C, although temperatures somewhat higher than 260 °C may be present at the roots of the system. The geothermal reservoir at Chachimbiro is recharged mainly by meteoric water (about 92%) and secondarily by arc-type magmatic water. Carbon and sulfur isotope data support a magmatic origin for the C and S species entering the geothermal system from below, consistent with indications provided by He isotopes. The thermal springs of Na–Cl to Na–Cl–HCO3 type located in the Chachimbiro area originate through dilution of the parent geothermal water and have reached different degrees of re-equilibration with country rocks at lower temperatures.