GEOCHEMICAL ANALYSIS OF HOT SPRINGS AT STEAMBOAT SPRINGS, COLORADO: CONTROLS ON PERIPHERAL HYDROTHERMAL FLUID PATHWAYS

A study was completed for the hot spring fluids in Steamboat Springs, Colorado, to better understand the flow pattern and evolution of this geothermal system. Thirteen hot spring samples and two meteoric samples were collected within the 2.6 km² study area. Field and laboratory geochemical analyses were completed on all samples. Fluid conductivity, Eh, pH, ferrous iron content, and alkalinity measurements were measured in the field. Cation and anion analysis was performed by inductively coupled plasma-optical emission spectrometry with a PerkinElmer 3000 and ion chromatography with a Dionex IC system. Results from the study were integrated with background geological information to form a conceptual model of the hydrothermal system.

Using a Cl-SO₄-HCO₃ ternary diagram, the fluid compositions plot predominantly within the bicarbonate field. The evolved geothermal fluids are interpreted to be influenced by reaction with the local Mesozoic carbonate-bearing sedimentary units and, to a lesser extent, Precambrian crystalline rocks. The upflow of geothermal fluids appears to be mainly controlled by a major north-south trending fault and its intersection with smaller east/northeast trending faults. The low variance in composition of the fluids sampled at Steamboat Springs indicates that the hot spring fluids are well buffered and that chemical evolution of the fluids within the comparably small study area is limited. Results from a previous study of the Routt Springs fluids to the north of Steamboat Springs were compared to the data set of the present study. These fluids are less evolved, possibly suggesting that the hot springs at Steamboat Springs are located at lower elevation and distal to the main upflow zone of the geothermal system.

Also co-authored on this abstract are Erik R. Tharalson, Efrain Ugarte Zarate, and 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.