| Title | Implications of Thrust and Detachment Faulting for the Structural Geology of Thermo Hot Springs Region, Beaver County, Utah |
|---|---|
| Authors | Anderson, Warren V.; Bruhn, Ronald L.; Moore, Joseph N. |
| Year | 2012 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Thermo Hot Springs; Sevier geothermal anomaly; Cave Canyon detachment; southern Mineral Mountains; Black Mountains |
| Abstract | This report presents data and conclusions concerning the role of low-angle faulting in the formation of Thermo Hot Springs and the effects it may have on fluid flow and production. The conclusions are that Thermo Hot Springs is formed by a low-angle normal or detachment fault that places Mesozoic and upper Paleozoic sedimentary rock in the upper plate over underlying metamorphic rock and granite. The Mesozoic section is overlain by a sequence of Tertiary to Quaternary volcanic and sedimentary deposits. High-angle normal faults offset the sedimentary and volcanic section, and in some, if not all, cases penetrate and offset the low-angle detachment fault. The high-angle normal faulting has two primary strikes: one is the northern strike of classical Basin and Range faulting, and the other is a roughly east-west striking set of normal faults. These faults may hydraulically compartmentalize the reservoir but also provide pathways for fluids to ascend upwards from beneath the detachment fault. The low-angle detachment fault model for Thermo Hot Springs structure has regional implications for geothermal prospecting in the Basin and Range terrain of southwestern Utah. This region is underlain by several known detachment faults of Middle to Late Tertiary age, which may act to laterally channel hot fluids at depth over large areas with little surface expression except where the low-angle faults are breached by younger faulting. That is, blind geothermal reservoirs may well occur at depth with few if any surface manifestations such as springs or tufa mounds. We suspect that thrust faults of Mesozoic age may also play a similar role to the Tertiary detachment faults in channeling fluids laterally in the Basin and Range region of southwestern Utah, but this is apparently not the case at Thermo Hot Springs. |