Geothermal Resources in the Black Rock Desert, Utah: MT and Gravity Surveys

Abstract

Recent geothermal studies on sedimentary basins in Western Utah suggest the possibility of significant geothermal reservoirs at depths of 3 to 5 km. Pavant Butte, a volcanic vent in the Black Rock Desert of Utah, is centered in such a basin. Previous geophysical work in the Pavant Butte area includes aeromagnetic, dipole-dipole resistivity and limited gravity surveys. Since 2010, we have added 73 magnetotelluric (MT) stations and 168 new gravity stations. Two-dimensional MT modeling shows a deep, broad corridor of low resistivities (< 10 ohm?m) 10 to 16 km wide at the base and centered in the basin. The complete Bouguer anomaly map indicates a 12 to 20 km wide gravity low of 30 mGal amplitude extending north-south through the entire basin. Results of 2D gravity modeling provide a maximum depth-to-basement estimate of 3 km and reveal an area over 15 km wide with more than 2 km of sediments overlying basement rock. Modeling results of MT and gravity data are consistent and only differ at the deepest portion of the basins where resistivities show no indication of the sediment-basement interface. However, we believe that this difference is due to the presence of hot, saline fluids contained in the pore space of the basement rock. An extended MT survey and drilling program, scheduled for summer 2012, will assist in determining the southern extent of this potential resource.