New Mexico Geological Society Annual Spring Meeting — Abstracts

Valles caldera is a 22-km-diameter resurgent cauldron that formed 1.25 Ma with eruption of the upper Bandelier Tuff. Continued post-caldera volcanism to roughly 40 ka provides potent, shallow heat for long-lived hydrothermal activity. A generalized model of the geothermal system includes recharge of cold meteoric water in the north and east caldera moat, convective rise of hydrothermal fluids beneath the southwestern resurgent dome, and lateral discharge of an outflow plume southwest of the caldera. Geochemical studies and drilling data indicate that hydrothermal fluids in the caldera are parent fluids for hot springs discharged in San Diego Canyon. The present geothermal system (260 to 300°C) occupies two structural zones within the resurgent dome. The Redondo Creek subsystem, located in a graben that bisects the resurgent dome, was drilled by 19 wells of which only seven were considered viable for electricity production. Steep terrain and landslides restrict drilling sites. Two geochemically distinct fluids indicate lack of connectivity in the faulted reservoir. The Sulphur Springs subsystem on the west side of the resurgent dome was penetrated by eight subcommercial wells. In 1983, geothermal development of the Redondo Creek subsystem ceased due to insufficient quantities of fluid to supply a planned 50 MWe power plant. Only 20 to 30 MWe of capacity were proven. After the Valles Caldera National Preserve was created in 2000, a “hold out” owner of Baca mineral rights declared an interest in renewing geothermal development but as of early 2007 no further exploration or drilling has been conducted.