Gravity and hydrothermal modeling of the Roosevelt Hot Springs Area, southwestern Utah

Abstract

The geothermal field at Roosevelt Hot Springs, Utah, produces water at temperatures exceeding 230°C. The source of the heat for the geothermal field and the nature of the hydrothermal system have been investigated by analyses of gravity, thermal, and hydrogeologic data. A deep, cylindrically shaped, anomalous mass approximately 10–15 km in diameter is inferred to exist approximately 5 km beneath the geothermal field based on inverse modeling of a −17 mGal gravity anomaly isolated by strike filtering. This body is assumed to be a young intrusion and the heat source for the geothermal field. The configuration of the anomalous body was used in a vertical cross‐sectional model of the hydrothermal system. The results of the modeling indicate (1) the source of the fluid recharge for the field is the Mineral Mountains; (2) the age of the source of the geothermal field may be younger than 500,000 years, the age of nearby rhyolites; (3) water at high temperature may be found beneath the sedimentary basin west of the geothermal field if sufficient permeability can be found; (4) the deep body beneath the field has significant permeability, in excess of 5 × 10−18 m2; and (5) the fault zone which acts as a conduit for upwelling thermal waters and provides the production at the field is probably bounded by low‐permeability material.

Interpretation of hydrothermal conditions, production-injection induced effects, and evidence for enhanced geothermal system-type heat exchange in response to >30 years of production at Roosevelt Hot Springs, Utah, USA

“…The evidence of Pleistocene rhyolite volcanism (Nielson et al, 1986), helium and carbon isotopes (Bowman and Rohrs, 1981;Kennedy and van Soest, 2007), and the N 2 -Ar-He ratios (Fig. 7; Table 2) indicate the existence of a bimodal felsic-mafic magmatic heat source, which is consistent with geophysical evidence of a melt body at mid-crustal depths (Robinson and Iyer, 1981;Becker and Blackwell, 1993;Wannamaker et al, 2020). Based on natural seismicity (Zandt et al, 1982;Pankow et al, 2019;Mesimeri et al, 2021), the deep upflow may originate from ~2 km east of the production field.…”

“…Based on natural seismicity (Zandt et al, 1982;Pankow et al, 2019;Mesimeri et al, 2021), the deep upflow may originate from ~2 km east of the production field. Two-dimensional numerical modeling suggests that hydrothermal circulation extends to 7-10 km depth, which defines the probable base of the convection cell (Becker and Blackwell, 1993). The minimum period of hydrothermal activity extends at least back ~2000 years based on 14 C dating of the Opal Mound silica sinter (Lynne et al, 2005), and perhaps >10,000 years, if the meteoric recharge dates back to the late Pleistocene Buchanan, 1990, 1993).…”

“…Many of the early reports cover geology, heat flow, petrologymineralogy, and preproduction fluid chemistry (Ward et al, 1978;Parry et al, 1980;Wilson and Chapman, 1980;Bowman and Rohrs, 1981;Capuano and Cole, 1982;Nielson et al, 1986). Subsequent studies concentrated on topics of reservoir characterization and fluid-flow modeling, and changes in pressure and temperature induced by geothermal production (Faulder, 1991;Becker and Blackwell, 1993;Faulder, 1994;Yearsley, 1994;Allis and Larsen, 2012).…”

Utah Renewable Energy Zone Task Force phase I report : renewable energy zone resource identification

“…Heat-flow values in excess of 1000 mW/ m 2 enclose an area roughly 1.2 miles wide by 5 miles long that is thought to coincide with the near-surface part of the geothermal system. Becker and Blackwell (1993) also inferred a deep, cylindrically shaped, anomalous mass approximately 6 to 9 miles in diameter situated about 3 miles beneath the geothermal field.…”

Final Report: Natural State Models of The Geysers Geothermal System, Sonoma County, California

“…Forster and Smith, 1989;Wisian, 2000) and natural (e.g. Becker and Blackwell, 1993) extensional systems, primarily using the U.S. Basin and Range province as the basis for the models. In particular, Wisian (2000) models a hypothetical system similar to the Figure 29: P-T paths for selected wells, supercritical RFP test using EOS1sc.…”