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

Abstract The parent geothermal water proposed for the Chachimbiro geothermal area has calculated values of 2250 mg/L Cl and approximately 5 bar P C O 2 . 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–HCO 3 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.