| Title | Integrated Geochemical Investigations of Surprise Valley Thermal Springs and Cold Well Waters |
|---|---|
| Authors | Andrew FOWLER, Carolyn CANTWELL, Nicolas SPYCHER, Drew SILER, Patrick DOBSON, Mack KENNEDY, Robert ZIERENBERG |
| Year | 2015 |
| Conference | Stanford Geothermal Workshop |
| Keywords | Surprise Valley, fluid mixing, GeoT, parameter estimation, geothermometry, modeling, multicomponent |
| Abstract | In this study, we explore various fluid dilution and mixing scenarios that might explain the geochemical variability observed in the composition of Surprise Valley hot springs, NE California, with a particular focus on the Lake City area. Building on previous work by the lead authors, our approach involves applying various graphical and geochemical modeling techniques, including multicomponent geothermometry and reaction path computations, using available analyses of thermal and cold waters to infer reservoir temperatures as well as the compositions of potential end-member mixing fluids. This integrated approach is proving useful to estimate deep reservoir temperatures and unravel the chemical evolution of thermal fluids in systems that have undergone fluid mixing, boiling, and/or water-rock interaction along flow paths. Our investigations show that hot spring waters exhibit similar ratios of concentrations for many solutes, with compositions falling between those of cold groundwater and of a deep thermal component. Some thermal springs also appear to be impacted by interaction with alkali lake waters and/or minerals, although distinguishing this influence from that of a deep thermal component is difficult. Our results suggest that traditional geothermometry methods should be applied to Surprise Valley hot spring fluids with caution, as these estimates yield a wide range of reservoir temperatures. Integrated multicomponent geothermometry analyses, taking into account dilution and CO2 loss in hot spring waters, suggest deep reservoir temperatures may reach up to 230°C in the Lake City area and also near Fort Bidwell, even though reported fluid temperatures measured in drill holes have yet to exceed 170°C. |