| Title | Stratigraphy and Hydrothermal Alteration in Well Baca-8, Sulphur Springs Area, Valles Caldera, New Mexico |
|---|---|
| Authors | Hulen, Jeffrey B.; Nielson, Dennis L. |
| Year | 1986 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Geological Survey; Case Studies; USA; New Mexico; Valles Caldera; Caldera; Rhyolites; Tuffs; Epidote Zone; Surface Thermal Activity; Acid-Sulfate Springs; Vapor Dominated; Ring Fractures; Welding; Andesite; Stability Diagrams; Tshirege Tuffs; Microperthit |
| Abstract | Union Oil Company borehole Baca-8 (B-8) is a 1336 m geothermal well in the Sulphur Springs area, near the western "hinge" of the trapdoor Valles-Toledo caldera complex. B-8 penetrates essentially the same Pleistocene intracaldera rhyolite ash flow tuff sequence as the wells along Redondo Creek, on the Valles caldera's resurgent dome; the sequence in B-8, however, is only about half as thick. Alteration zoning in B-8 is characterized by a mixed layer illite/smectite cap above an illite zone in turn overlying a K-feldspar + epidote zone. Comparison of these assemblages with contemporary temperatures in the well suggests that the rocks of Sulphur Springs have undergone a more complex thermal history that those of Redondo Creek, and that fluids responsible for alteration in the two areas were of different compositions. |