GEOCHEMISTRY OF THE LOWER WAUNITA HOT SPRINGS, GUNNISON COUNTY, COLORADO

Water samples were collected from seeps and pools at lower Waunita Hot Springs on the Wagner property, Gunnison County, Colorado. On site measurements were made for temperature, pH, Eh, conductivity, alkalinity, dissolved oxygen, and ferrous iron concentrations in the sampled water. ICP-AES and anion-exchange chromatography were used to identify the cations and major anions in solution. The discharge from the lower Waunita Hot Springs geothermal field was calculated to be 0.179 m³/s. Geochemical modeling, XRD analysis of mineral scalings, and field evidence indicated that clay minerals, calcite, chalcedony, and hydrous ferric oxides were all precipitating. Metal flux in the geothermal waters was significant, including 300 kg/yr of molybdenum and 66 kg/yr of cadmium. All water samples display a unique and consistent geochemical fingerprint reflecting the bulk composition of the passively degassing Tomichi intrusion, which is thought to be the source of the geothermal system. Water chemistry and temperature of the lower Waunita Hot Springs are similar to other geothermal systems in central Colorado, including the Cottonwood Hot Springs and the Mt. Princeton Hot Springs.

Also co-authored on this abstract are Thomas Monecke, Department of Geology and Geological Engineering, Colorado School of Mines, and James F. Ranville, Department of Chemistry and Geochemistry, Colorado School of Mines.