Geothermal play fairway analysis, Phase 3: A provisional conceptual model of the Camas Prairie, Snake River Plain, Idaho

The Snake River Plain (SRP) Geothermal Play Fairway Analysis team identified two regions of interest during Phase 2 studies: the western SRP near Mountain Home, Idaho and Camas Prairie, Idaho. New geological, geochemical, and geophysical (gravity, magnetic, MT, seismic) studies of both areas led to a focus on Camas Prairie for validation during Phase 3. Camas Prairie is an EW-trending half-graben bounded on the north by the Idaho Batholith and on the south by the Mount Bennett Hills. Camas Prairie is bisected by a major NW-trending fault system (The Pothole fault) that separates NW-trending faults to east from ENE-trending faults to the west. The Camas Prairie geothermal system is indicated by warm springs and wells, geophysical evidence of buried faults and basins, mapped faults, elevated ³ He/ ⁴ He ratios, moderate calculated reservoir temperatures, and the occurrence of young basalt vents and lava flows along the range front. High permeability is suggested by the confluence of intersecting faults, including the range front system and the Pothole fault system, the presence of springs along mapped structural features, and dilational stress along major NW-trending fault systems. Basaltic vents as young as 692 ka along the range front are offset by late Pleistocene faults, indicating relatively recent magmatic flux and tectonic activity. Prolonged heat flux is inferred to result from mid- to shallow crustal sills, similar to those observed farther south. Magnetotelluric studies suggest the presence of a clay seal over the prospective target area that may result in part from hydrothermal alteration. Our model is similar to that proposed for the western SRP but is less energetic due to the smaller volume of magma inferred. It is also similar to Basin-and-Range geothermal systems, but differs by including a distinct magmatic heat component.