Book Description

The Colorado Geological Survey, has been engaged in assessing the nature and extent of Colorado's geothermal resources. The program has included geologic and hydrogeologic reconnaissance, and geophysical and geochemical surveys. In the Animas Valley, in southwestern Colorado, two groups of thermal springs exist: Pinkerton Springs to the north, and Tripp-Trimble-Stratten Springs about 5 miles (8.1 Km) south of Pinkerton. The geothermal resources of the Animas Valley were studied. Due to terrain problems in the narrow valley, a soil mercury survey was conducted only at Tripp-Trimble Stratten, while an electrical D.C. resistivity survey was limited to the vicinity of Pinkerton. Although higher mercury values tended to be near a previously mapped fault, the small extent of the survey ruled out conclusive results. Consistent low resistivity zones interpreted from the geophysical data were mapped as faults near Pinkerton, and compared well with aerial photo work and spring locations. This new information was added to reconnaissance geology and hydrogeology to provide several clues regarding the geothermal potential of the valley. Hydrothermal minerals found in faults in the study area are very similar to ore mined in a very young mountain range, nearby. Groundwater would not need to circulate very deeply along faults to attain the estimated subsurface temperatures present in the valley. The water chemistry of each area is unique. Although previously incompletely manned, faulting in the area is extensive. The geothermal resources in the Animas Valley are fault controlled. Pinkerton and Tripp-Trimble-Stratten are probably not directly connected systems, but may have the same source at distance. Recharge to the geothermal system comes from the needle and La Plata Mountains, and the latter may also be a heat source. Movement of the thermal water is probably primarily horizontal, via the Leadville Limestone aquifer.