| Title | Shallow Geophysical Investigations on the Redfield Campus, Steamboat Hills, Nevada--Phase One Results |
|---|---|
| Authors | Huebner, L.; Oppliger, G.; Van Gundy, T.; Mankhemthong, N.; McDonald, J.; Robertson, W.; Shoffner, J.; Johnson, G.; Murtagh, A. |
| Year | 2007 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Basin And Range; Steamboat Hills, Redfield, geophysics, gravity, magnetics, resistivity, structural boundary definition |
| Abstract | The University of Nevada Reno’s new and growing Redfield Campus, south of Reno, Nevada directly overlies the northwestern edge of the Steamboat Hills geothermal reservoir. Ormat Technologies and the University of Nevada Reno are currently working to provide the campus’s electrical power needs using geothermal energy from this resource. The Steamboat Hills geothermal field, which currently hosts three large electric generation plants operated by Ormat, has been the focus of several geoscience studies over the past 70 plus years. Large scale geophysical and thermal anomaly patterns defined in these studies suggest that the northwestern edge of the reservoir may be spatially abrupt, first-order linear and continue directly under the Redfield campus, although no surface expression, borehole or detailed geophysical data has existed to confirm this. This study reports on the results of the first phase of detailed gravity, ground magnetic and electrical resistivity sounding work that was designed to trace and characterize this reservoir boundary. Significant results include a gravity-defined down-to-the-northwest ~50 meter basement offset and a closely related zone of strong magnetic susceptibility reduction (consistent with hydrothermal alteration) which correspond spatially to the projection of the northwest edge of the known Steamboat reservoir boundary through the Redfield Campus. Resistivity data also defines an anomaly indicative of clay or hydrothermal fluids more than 80 meters thick extending within 10 to 20 meters of the surface, although no clear resistivity offset was apparent across the previously described gravity and magnetic defined structure. In the geologic framework, the trace of the newly defined geophysical structure intersects two mapped northnortheast trending high-angle faults on the campus’s eastern and western boundaries, where it, respectively, appears to localize low-flux fumaroles in a late Quaternary mud volcano feature and bisect a relatively young phreatic crater. It is hoped that results of this and future surveys will lead to more effective development of the geothermal resource under the Redfield Campus. |