The Regional Thermal Regime in Dixie Valley, Nevada, USA

Abstract

A three dimensional model for the regional thermal regime of the Dixie Valley /Stillwater Range has been developed as part of the Dixie Valley EGS project. The model is based on a 3D basement map and the assumption of conductive heat transfer. Major variations in heat flow and temperature are due to (1) elevation differences of ~1400 m that cause topographic effects on the subsurface temperatures and (2) the geometry of the ~2 km thick valley fill that causes refraction of heat due to the thermal conductivity difference of approximately a factor of 100% between valley fill and basement/range rock types. A 3D inversion of gravity data is used to obtain a depth map of valley fill sediments. A pseudogravity transformation of magnetic data is used to model the possible effects of the Humboldt mafic igneous complex in the central and northern part of the Dixie Valley. The temperature distribution due to the refraction of heat flow is quantified as a function of the valley fill geometry. Both refraction and topographic effects tend to enhance geothermal gradient in Dixie Valley. Refraction due to the thermal conductivity contrast and shape of the valley fill sediments causes heat flow variation of about 30% of the 90 ± 30 mWm-2 average regional heat flow. Moderately: high heat flow anomalies along the valley/range contact can be due to refraction of heat flow and may not be caused by geothermal system.