Self-Potential Survey Results from the Beowawe KGRA, Nevada

Abstract

A dipolar self potential anomaly of about 500 mV peak to peak amplitude and about 500 m peak to peak wavelength has been measured over an area of near surface geothermal activity at the Beowawe KGRA, Nevada. The anomaly does not appear to be cause by topographic effects, and shows little correlation to changes in surface soil properties such as moisture content, conductivity, pH, or temperature. A source mechanism by which surface self potential anomalies are generated by subsurface flow of fluid or heat along faults that separate regions different electro kinetic or thermoelectric coupling coefficients was used to model Beowawe anomaly. The model study results indicated that the measured anomaly could be generated by geothermal activity along a set of nine steeply dipping faults extending from about 50 to 250 m deep. Six of the faults lie along the trend of the Malpais fault zone, a major structural feature of the region, and two modeled faults running perpendicular to this trend may represent significant near surface offsets of shallow geothermal activity along the Malpais fault zone. However, the data sampling density was not sufficient for reliable determination of the existence of these cross faults.