Geothermometry of Thermal Springs in Southwestern Colorado
Mapping of heat flow and geothermal gradients in Colorado indicates an area of both high heat flow and increased geothermal gradient in southwest Colorado centered on the Town of Rico. Seven flowing thermal springs were sampled in this area and all had surface temperatures in a narrow range between 40 and 44°C, except Geyser Warm Spring at 28.5°C. Geothermometer calculations applied to these data estimate subsurface reservoir temperatures ranging from 60°C to 150°C. Isotopic analyses indicate that all the samples are very similar to meteoric waters. Temperature data from mineral exploration drill holes within a 0.75 km radius of Rico yield geothermal gradients of 91 and 92 °C km-1. Therefore, meteoric water circulation depths ranging from about 0.6 to 1.9 km are necessary to meet the range of subsurface reservoir temperatures predicted by the geothermometers.