Controls on Geothermal Activity in the Sevier Thermal Belt, Southwestern Utah

Abstract

The Sevier Thermal Belt, southwestern Utah, covers 20,000 km2, and it is located along the eastern edge of the Basin and Range, extending east into the transition zone of the Colorado Plateau. The belt encompasses the geothermal production fields at Cove Fort, Roosevelt Hot Springs, and Thermo, scattered hot spring activity, and the Covenant & Providence hydrocarbon fields. Regionally, it is characterized by elevated heat flow, modest seismicity, and Quaternary basalt-rhyolite magmatism. There are at least five large discrete domains (50 to more than 500 km2) with anomalous heat flow, including ones associated with Roosevelt Hot Springs, Cove Fort, Thermo and the Black Rock desert. Helium isotope data indicate connections to the upper mantle are developed over the region of strongest and most concentrated hydrothermal activity. By contrast, stable isotope data demonstrate that most of the convective heat transfer is associated with shallow to deep circulation of local meteoric water. Quartz-silica geothermometry suggests that convective heat transfer is compartmentalized by stratigraphic horizons and sub-vertical faults. In some cases, the regional hydraulic gradient generates large outflow zones of hot water. Despite complex geology, geothermal activity in the Sevier Thermal Belt is developed over a very large area in multiple sites that reflect a diversity of lithologic and structural controls on hydrothermal fluid flow.