Stratigraphy and Hydrothermal Alteration in Well Baca-8, Sulphur Springs Area, Valles Caldera, New Mexico
- Key words
- 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
- Location
- Valles Caldera, New Mexico
- Conference
- Geothermal Resources Council Transactions
- Year
- 1986
- Session
- Exploration; Geological surveys; Stratigraphy; Hydrothermal
- Language
- English
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.
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