Plate 2 Topography, resistivity, and chargeability cross-sections along dipole-dipole line 1 on Fumarole Butte

Interest is rapidly increasing in geothermal energy as an economic and plentiful energy source. Because of the anomalous resistivities characteristically found in a geothermal environment, direct current exploration methods can be used to delineate hot, saline waters within more resistive ground rock, or resistive volcanic rocks within less resistive ground rock. Resistivity surveying was employed at Fumarole Butte, Utah, to delineate the contact between a basalt extrusive and underlying lacustrine sediments, and possibly delineate source waters of a near­ by hot spring that may be present under the basalt. Because geothermal investigation at Fumarole Butte is in a preliminary stage, the geology and hydrology of the area are reported in some detail. The results of dipole-dipole resistivity and induced polarization profiles across the basalt, and Schlumberger resistivity soundings on the basalt and on the sediments, are presented. Basalt and sediment resistivity values of around 2000 ohm-meters and 10-12 ohm-meters, respectively, are indicated. An increase in water, salt, and clay with depth is believed to cause the decrease in resistivity and increase in induced polar­ ization with depth, apparent from the resistivity-IP data.