INITIAL ASSESSMENT OF FAVORABLE STRUCTURAL SETTINGS FOR HIDDEN GEOTHERMAL POTENTIAL IN SOUTHERN IDAHO

Southern Idaho hosts the only geothermal plant in the state, and has the potential for significant additional energy output. A set of unique attributes favor geothermal activity in this region: 1) active Basin and Range extension, 2) overall high-heat flow, 3) dense seismicity within the Yellowstone seismic parabola, 4) late Pleistocene volcanism, and 5) northward termination of the Wasatch Fault system. However, many systems may be hidden due to the lack of surface features (e.g., hot springs, sinter deposits). Recent studies have illustrated the utility of play fairway (PF) models in discovering unknown systems in the Great Basin, and that a set of common favorable structural settings (FSS) are a fundamental input for such models. As part of the INGENIOUS project, we developed the first comprehensive FSS catalog for the Great Basin portion of southern Idaho. We utilized published geologic maps, young fault databases, lidar, and regional gravity data to define young fault systems' orientation, distribution, and internal patterns. We identified 141 areas that may have a FSS: 65 fault step-overs, 51 fault intersections, and 25 accommodation zones. We also identified three subregions that may have an influence on overall favorability. The western region includes the topographically distinct Owyhee Plateau, which lacks major range-bounding faults and is instead defined by a dense network of apparently young NW striking low-offset structures. Fault location and geometry are assessed with high degree of confidence due to lidar access, but recency of fault activity with low confidence due to a paucity of detailed mapping. The central region includes the Raft River geothermal plant. However, location, geometry, and recency of young faulting are assessed with low confidence due to a lack of lidar and published detailed geologic maps. In the eastern region, fault geometry, location, and recency are assessed with high confidence due to lidar and recent large-scale geologic mapping. This region also overlaps with the northern terminus of the Wasatch Fault system, late Pleistocene volcanism (Blackfoot field), and pervasive seismic activity associated with the Yellowstone hotspot. This new FSS catalog and identifying subregions of the Great Basin of Idaho are important first steps in building a regional PF model.