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A Concealed Geothermal System Near Corner Canyon, Salt Lake County, Utah
In March 2008, an irrigation company completed a water supply test well along the Wasatch Front at Corner Canyon near the southern edge of Salt Lake County, southeast of Draper, Utah. The well was drilled to 1270 feet (387 m). Static water level rose to 85.6 feet (26.1 m) below ground level. Air-lifting produced water at temperatures between 175° and 185°F (79°–85°C). Temperature measurements during well logging three months after well completion revealed a maximum temperature of 202°F (94.4°C) from 472 to 499 feet (144 to 152 m), which likely coincides with the zone of most geothermal fluid movement into the well. The bottom-hole temperature was 195°F (90.6°C). Lithologic and geophysical logging show that monzogranite of the Tertiary Little Cottonwood Stock was encountered at 60 feet (18 m) and multiple fracture zones and possible faults are present in the upper 500 feet (152 m) of the hole. Analyses of fluid samples collected during a 24-hour pump test yielded 300 gallons per minute (1136 L/min) and water with total dissolved solids content of 7360 mg/kg. The water is sodium-chloride type and more similar to Ogden Hot Spring in Weber County than to geothermal systems much closer to Corner Canyon. Silica concentration (SiO2 = 179 mg/kg) was exceptionally high compared to other Wasatch Front thermal waters (SiO2 ranges from 12 to 41 mg/kg), suggesting that a component of the Corner Canyon well water has equilibrated with one or more SiO2 mineral phases at temperatures above 302°F (150°C). The chalcedony and K-Mg chemical geothermometers suggest equilibrium reservoir temperatures ranging between 302° and 358°F (150°–181°C).
The well was sited along the surface trace of the Wasatch fault, near the southern end of the fault’s Salt Lake City segment, and was drilled into fractured granodiorite of the 30.5-million-year-old Little Cottonwood Stock. The Wasatch fault juxtaposes Eocene-Oligocene volcanic rocks and Pennsylvanian sandstone of the Oquirrh Group in the Traverse Mountains, down to the west and southwest, against rocks of the Tertiary Little Cottonwood Stock of the Wasatch Range, up to the east and northeast. The Traverse Mountains mark the boundary between the Salt Lake City and Provo segments of the Wasatch fault. These segments are linked by the Fort Canyon fault, which trends east-west through Corner Canyon and which has a long history as the northern ramp of the Sevier-age Charleston thrust fault and the middle Tertiary Deer Creek detachment fault.
Based on the chemistry and geologic setting of the well, the fluids encountered at Corner Canyon may be part of a much larger geothermal system that is mixing with fresh ground water encountered as fluids move along fault conduits.
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