Macfarlanes is a group of small springs and seeps that form a travertine mound (4 m high, 180 m long) in Sec. 27, T37N, R29E. Historically, the reported temperature was 76.6°C (Sinclair, 1963a), and temperatures between 69 and 78°C were measured in August 2002, and two of the hot springs were sampled. Based on these analyses, chalcedony geothermometer temperatures are 103°C, indicating either a relatively cool source reservoir or loss of SiO₂ during fluid ascent by dilution or precipitation. Previously reported estimates indicate reservoir temperatures <140°C using the Na-K-Ca geothermometer, although chemical data were not reported (Sibbett and others, 1982). The Na/K, quartz, and chalcedony geothermometer indicated temperatures in the range of 80 to 120°C, more in line with values calculated with 2002 data. The springs are currently (2002) only flowing out of the west end of the east-west trending travertine mound that has a visible vein running down the middle of the mound. The springs appear to be controlled by a split or bend in a northeast-trending normal fault with >400 m of displacement (Sibbett and others, 1982; Swanberg and Bowers, 1982), and the springs appear to have been active over the last 15,000 to 60,000 years (Sibbett and others, 1982).

The maximum recorded temperature during temperature gradient drilling was 81.1ºC at 610 m. Data from shallow and intermediate-depth gradient drill holes was modeled to predict that the maximum temperature at greater depths will probably be in the 150ºC range (Swanberg and Bowers, 1982). The area of geothermal activity is confined to a structural block between a northeast-striking fault through the hot springs and the north-striking faults that bound the west side of the Jackson Mountains about 4 km to the east. The proposed water flow path is downward along the Jackson Mountains faults and upward along the fault at the hot spring (Swanberg and Bowers, 1982).

Chemistry

Photos
Picture of spring mound.
Picture of spring mound and red bus.
Macfarlanes Hot Springs, red and green algae (78°C).
Spring at west end of travertine mound at Macfarlanes Spring (69°C).
Macfarlanes Hot Springs, red and green algae (78°C).
Macfarlanes Hot Springs, soaking pool below spring.
Macfarlanes Hot Springs, N80E, 75N travertine vein in travertine mound.
Salt Water Spring is actually a flowing artesian salt-water well (12°C).
Sampling at pumping windmill (17°C).
Sampling at pumping windmill (17°C).