Mapping Hydrothermal Upwelling and Outflow Zones: Preliminary Results from Two-Meter Temperature Data and Geologic Analysis at Lee Allen Springs and Salt Wells Basin

Abstract

Two-meter temperature surveys have been conducted at Salt Wells Basin and Lee-Allen Springs geothermal areas with the objective of distinguishing and mapping zones of upwelling and outflow. The ability to do this may help maximize their development potential. Geothermometers of these areas suggest the presence of high temperature reservoirs, but Lee Allen Springs remains undeveloped and geothermometer data at Salt Wells Basin suggests this area is under-developed. At Lee Allen Springs, a strong shallow temperature anomaly has been mapped in the area of Lee Hot Spring. This anomaly consists of temperatures locally exceeding 40°C at two meters depth, covering an east-west trending area approximately one kilometer in length. Preliminary interpretations map this area as an upwelling zone with outflow to the west and east. Also, this zone may reflect an unmapped subsurface east-west trending fault zone. Other, more subtle anomalies, found at Lee Allen springs indicate a possible second upwelling zone near a fault intersection between a north-northeast striking east dipping normal fault and a northwest striking dextral fault. At Salt Wells Basin, a large north-south trending temperature anomaly has been mapped. A group of subtle temperature anomalies along Simpson Pass, south of the current production area, are interpreted as an upwelling zone with a complex outflow to the north along the eastern flank of the Bunejug Mountains. The data suggest there may be additional upwelling zones north of Simpson Pass. Additional temperature survey work, geologic and geophysical surveys, and soil gas surveys may help test the upwelling and outflow interpretations.