The Tuscarora Geothermal Area is located at the north end of Independence Valley, approximately 80 km north-northwest of Elko, Nevada. Independence Valley is a structural basin between the Independence Mountains on the east and the Tuscarora and Bull Run Mountains to the west and northwest. Independence Valley contains 35-39 Ma tuffs and tuffaceous sediments which overlie Paleozoic clastic and volcanic rocks and are overlain by Miocene lava and pyroclastic flows. The rocks have been deformed by normal faults trending north-south and northwest and by folds trending north-south which have been active in the Pleistocene (Sibbett, 1982, p. 1264). Bowman and Cole (1982) determined that the Independence Mountains were the source of recharge for the hydrothermal fluids associated with the Tuscarora Geothermal Area. A closer highland area was ruled out as the source because it did not contain sufficiently depleted non-thermal fluids. Geothermal evidence also suggested that fluid flow in the area trended from the south-east to northwest (Flynn and Buchanan, 1990, p. 55). Sibbett (1982) further discussed the geology of the area.
Hot Sulphur Springs are located along Hot Creek near the east edge of the Tuscarora Mountains, at the north end of Independence Valley, in SE¼ Sec. 5 and Sec. 8, T41N, R52E. The area is about 17 km north of the community of Tuscarora. The springs have reported temperatures of 50-95°C (Bowman and Cole, 1982), and an estimated reservoir temperature of 128°C based on a silica geothermometer (Mariner and others, 1974). AMAX exploration geothermometry indicated a reservoir temperature of 216ºC, and Goranson and van de Kamp (2005) reported an estimated geothermometer reservoir temperature of 165.6ºC. A few small thermal springs occur to the south and southwest of the main thermal area, in NE¼ Sec. 17. A thermal spring on the west side of Hot Creek issues from the top of a low calcite and sediment mound. Two siliceous sinter mounds about 40 cm high are present on the calcareous mound. An intermittently flowing thermal spring occurs 900 m south of the main sinter mound, and a spring with a flow of 75 to 100 L/min, 3 km south-southwest of the main sinter mound, has a temperature of 21ºC (Sibbett, 1982, p. 1264, 1270).
Over 25 hot springs are found along a north-northeast 4.8-km linear zone and sinter deposits are present for about 1.6 km along the zone (Pilkington and Lange, 1980). Deposits include an inactive opaline sinter mound 35 m high and about 1 km long at the southern springs, and a small area of travertine at the northern springs. The northern springs, some of which are boiling, have the greater discharge rate. The springs are depositing both siliceous and calcareous deposits (Sibbett, 1982, p. 1264). The geochemistry of the Tuscarora area is discussed by Bowman and Cole (1982).
The surface expression of the Hot Sulphur Springs thermal system is controlled by a fault zone trending N20ºE. This fault is interpreted to be on the east side of a ~750 m-wide graben defined by a seismic reflection survey (Goranson and van de Kamp, 2005). Exposed argillic alteration produced by the thermal system is limited to the spring area. Quartz-sericite alteration, which predates the present thermal system, is present along the fault zone. (Sibbett, 1982, p. 1272).
In the late 1970s, Amax Exploration drilled 38 temperature-gradient drill holes in the area; the maximum temperature reported from this drilling was 117°C at 522 m. A large-diameter well drilled in 1980 to 1,662 m encountered relatively low-temperature geothermal fluids. Probably most flow was from about 900 m in the Ordovician Valmy Formation, with temperatures in the 107°C range (Pilkington, 1980). A slim hole (HSS-2), drilled in 2004 to 1162 m (NE¼ NW¼ SE¼ Sec. 8, T41N, R52E) encountered a geothermal reservoir below 760 m in fractured Tertiary volcanic rocks. The maximum temperature was 170.6°C at 1126 m in fractured Paleozoic rocks.