A COMPARISON OF FAULT-CONTROLLED HYDROTHERMAL FLUID FLOW AT FOUR SITES IN THE BASIN AND RANGE PROVINCE OF THE WESTERN USA

The distribution of hydraulic properties in active faults is a topic of great importance for water supply, petroleum and geothermal reservoir engineering, ore emplacement, nuclear waste disposal, and many other fields of investigation. Recent investigations have shed some light on the distribution of permeability in a fault-controlled hydrothermal system in southeast Oregon (e.g., Fairley and Hinds, 2004; Heffner and Fairley, 2006), but it is difficult to evaluate the generality of those findings without a comparison to similar investigations of other fault systems. Here we compare distributions of heat and fluid discharge from three fault-controlled hydrothermal systems in the Nevada and Oregon with the results from earlier studies of the Borax Lake fault (Oregon). All four sites investigated—Borax Lake, Mickey Hot Springs (Oregon), Smith Creek Hot Springs (Nevada), and Leach Hot Springs (Nevada)—show a common underlying pattern of hydraulic properties in which areas of high permeability are largely concentrated in a few discrete zones that are separated by larger areas of moderate to low permeability. The actual distribution of heat and fluid discharge varies from site to site, apparently in response to differences in the local structural setting; this variation is consistent with conceptual models proposed by a number of earlier investigators. Future work will quantify the spatial distribution of inferred hydraulic properties at each of the study sites to identify specifically the relationships between permeability and structural setting.