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This study assessed the potential for a high-temperature blind geothermal system in southeastern Gabbs Valley, an area with no previous geothermal exploration, by utilizing geothermal play fairway analysis. Gabbs Valley is a structurally complex, tectonically active basin occupying a transtensional displacement transfer zone. Multiple lines of evidence suggest the presence of a blind geothermal system, including collocated intersecting gravity gradients, magnetic-low, low-resistivity, 2-m temperature anomaly, and 130–140 °C geothermometers obtained from nearby agricultural wells. Six 150 m-deep temperature-gradient holes were drilled to target the geophysical and thermal anomalies. Two holes produced bottom-hole temperatures of 114.5 °C and 124.9 °C. Drilling results establish the discovery of a blind geothermal system. Power estimates based on resource conceptual models of the geothermal system suggest a median (P50) capacity of ∼16 MWe.

The Clear Lake Volcanic Field in northern California is the youngest and northern-most part of a long-lived volcanic system that has produced recent (~10 ka) eruptions. Adjacent to the Clear Lake Volcanic Field is the world's largest energy producing geothermal field, The Geysers. The hottest part of The Geyser's geothermal field is in the northwest where temperatures reach ~400 °C at 3 km depth. Low permeability, high thermal gradients, and low steam saturation prescribed development of an enhanced geothermal system (EGS) in the Northwest Geysers to increase energy producing capacity. Though the Northwest Geysers is known to be the hottest part of the field, geophysical methods have failed to adequately image any inferred heat source. This project aims to image the heat source of the Northwest Geysers using newly collected gravity and magnetotelluric (MT) measurements. Gravity data were jointly modeled with existing magnetic data along a two-dimensional profile aligned with an existing geologic cross-section. The key feature of the potential field model is a low-density, low-susceptibility body at 5 km depth (bmsl) under the EGS. MT data were modeled in three-dimensions to characterize subsurface resistivity structure, where the upper 3 km of the resistivity model agrees well with existing data. Lithologic and steam saturation are estimated from modeled resistivity values using existing geophysical data. Below 3 km depth (bmsl), the resistivity model images a possible young intrusion under the EGS. A possible zone of partial melt (