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This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. GRC Transactions, Vol. 33, 2009 Geothermal Discovery Near Corner Canyon, Salt Lake County, Utah Robert E. Blackett1, J. Lucy Jordan2, Kevin Thomas2, Janae Wallace2, and Robert F. Biek2 1Utah Geological Survey, Cedar City, Utah 2Utah Geological Survey, Salt Lake City, Utah Keywords of the Wasatch Range, up to the east and northeast. The Traverse Resource Assessment, Utah, Salt Lake County, Corner Canyon 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 ABSTRACT Canyon and which has a long history as the northern ramp of the Sevier-age Charleston thrust fault and the middle Tertiary Deer In winter 2008, a water-supply company drilled a pilot test Creek detachment fault. well at Corner Canyon near the southern edge of Salt Lake County, southeast of Draper, Utah. The site is located at the western base Introduction of the north-south oriented Wasatch Range (Wasatch Front) near the intersection with the northeast-southwest oriented Traverse In December 2007, WaterPro, Inc. contracted to drill and com- Mountains. The well was drilled to 1270 feet (387 m). Static plete a water supply well for the growing community of Draper, water level rose to 85.6 feet (26.1 m) below ground level following Utah, located in the southeastern part of Salt Lake County. Mike completion. Air-lifting produced water at temperatures between Zimmerman Well Service began drilling on December 29, 2007. 175° and 185°F (79°-85°C). Temperature measurements during During the early stages of drilling the temperature of the return well logging three months after well completion revealed a maxi- fluid became elevated suggesting a geothermal source at depth. mum temperature of 202°F (94.4°C) from 472 to 499 feet (144 Zimmerman completed the drilling phase of the well in early -152 m), which likely coincides with the zone of most geothermal March 2008, installing a 10-inch- (25-cm-) diameter well to a fluid movement into the well. The bottom-hole temperature was total depth of 1270 feet (387 m). 195°F (90.6°C). Lithologic and geophysical logging show that the well penetrated monzogranite of the 30.5-million-year-old Location and Access Little Cottonwood Stock at 60 feet (18 m) and multiple fracture zones and possible faults are present in the upper 500 feet (152 The City of Draper is situated about 15 miles (24 km) southeast m) of the well. Analyses of fluid samples collected during a of Salt Lake City. The well is located in the SW¼, SE¼, NE¼ sec- 24-hour pump test yielded 300 gallons per minute (1136 L/min) tion 4, T. 4 S., R. 1 E., Salt Lake Base Line and Meridian (SLBM) of water with total dissolved solids content of 7360 mg/kg. The at a latitude of 40°30′4″ N. and longitude of 111°50′18″W. The water is sodium-chloride type and more similar to Ogden Hot approximate land surface elevation at the well head is 4890 feet Spring in Weber County than to other geothermal systems closer +/- 20 feet (1490 m +/- 6 m). The site is in the lower part of Corner to Corner Canyon. Silica concentration (SiO2 = 179 mg/kg) was Canyon near the southern boundary of Salt Lake County. Corner exceptionally high compared to other Wasatch Front geothermal Canyon sits at the southeast edge of the Salt Lake Valley where systems. The chalcedony and K-Mg chemical geothermometers the base of the Wasatch Range intersects the Traverse Mountains suggest equilibrium reservoir temperature ranging between 302° (Figure 1). The Salt Lake County/Utah County line lies about and 358°F (150°-181°C). one mile (1.6 km) to the southeast from the well. Corner Canyon The well was sited along the surface trace of the Wasatch trends southeastward along the juncture of the two mountain fault, near the southern end of the fault’s Salt Lake City segment. ranges eventually turning due east. The site lies at the edge of Near this segment boundary, the Wasatch fault juxtaposes Eocene- the urban areas of Draper and is accessed by traveling on paved Oligocene volcanic rocks and Pennsylvanian sandstone of the roads through new subdivisions encroaching into the foothills of Oquirrh Group in the Traverse Mountains, down to the west and the Wasatch Range, then by dirt track for a few hundred feet into southwest, against rocks of the Tertiary Little Cottonwood Stock Corner Canyon. The well is near the bottom of the canyon. 911 Blackett, et al. (Deer Creek fault) with contemporaneous volcanism and intrusions of the Wasatch igneous belt occurring from about 40 to 20 million years ago (mya), and 2) basin-and-range extension and differential uplift that produced normal faulting beginning in Miocene time and continuing to the present. This second episode, beginning about 17.5 mya (Hintze, 2005) and extend- ing to the present, produced the Basin and Range physiographic province with its numerous north- south-trending, tilted mountain ranges bounded on at least one side by high-angle normal faults. Wasatch Fault Zone The Wasatch fault zone marks the western margin of the Wasatch Range and represents the boundary between the Middle Rocky Mountains province to the east and the Basin and Range province to the west. Hecker (1993) describes Quaternary tectonics in northern Utah as concentrated within a 124-mile- (200-km-) wide zone centered on the Wasatch fault zone and coincident with the Intermountain seismic belt. The Wasatch fault zone extends 211 miles (340 km) from southern Idaho through northern, and into central Utah. It is the most tectonically active structure in this region and exhibits abundant evidence of recurrent surface rupture during the Holocene (Machette and others, 1992; Schwartz and Coppersmith, 1984). Geologists recognize several segments of the Wasatch fault. Each segment is bounded by a bed- rock projection (often called a spur) or a significant step-wise offset to the surface trace. The Salt Lake segment (Figure 1) is bounded on the north by a spur called the Salt Lake salient that projects westward from the Wasatch Front between Salt Lake City and Bountiful. On the south, the Traverse Mountains, extending west from Alpine, separate the Salt Lake Figure 1. General geology of the Jordan River Valley region, northern Utah showing locations segment from the Provo segment (see, for example, and temperatures of selected geothermal wells and springs. Geology from Hintze and others (2000). Hintze, 2005). Between Alpine and Corner Canyon, the Wasatch fault offsets bedrock, down-dropping Geology, Hydrogeology, and Pennsylvanian Oquirrh Group rocks and Tertiary Geothermal Systems (late Eocene to Miocene [?]) volcanic rocks and alluvial deposits of the Traverse Mountains relative to the Tertiary Cottonwood Regional Setting Stock of the Wasatch Range. At Corner Canyon, near the southern end of the Salt Lake Davis (1983) described the geology of the central part of the City segment, the Wasatch fault makes an abrupt bend to the east- Wasatch Front as diverse with rocks representing nearly every southeast, coincident with the trace of the Sevier-age Charleston geologic period from Precambrian to Quaternary. The Wasatch thrust fault. Machette (1992) referred to this east-trending part of Range comprises the westernmost range of the Middle Rocky the Wasatch fault, which links the Salt Lake City and Provo seg- Mountains physiographic province with peaks reaching elevations ments, as the Fort Canyon fault, which dips about 25° south and in excess of 11,000 feet (3350 m). The range has about 7000 feet exhibits a significant amount of down-to-the-southwest oblique (2130 m) of relief. Rocks in the Wasatch Range have undergone slip (Evans and others, 1997; Bruhn and others, 2005). The at least two major episodes of mountain building (orogeny). Biek Charleston thrust fault is the northern boundary fault (edge) of (2005b) describes events leading to the current geologic features the Charleston-Nebo thrust sheet. During the Sevier orogeny, the seen in the study area including 1) Sevier-age compression where Charleston thrust resulted from a protracted period of compression great thicknesses of Pennsylvanian-Permian Oquirrh Group rocks between about 100 and 40 million years ago (early Late Cretaceous were folded and thrust eastward, followed by regional uplift and to late Eocene). The Charleston thrust fault separates allochtho- collapse of the orogenic belt along low-angle detachment faults nous terrain to the south (displaced roughly 50 miles [80 km] from 912 Blackett, et al. the west) from autochthonous terrain to the north exposed in the near Point-of-the-Mountain on the south end of the Salt Lake Val- Wasatch Range near Park City.