Development of geothermal resources would provide reliable baseload power to isolated communities of the Seward Peninsula that currently depend on fossil fuels for energy. Pilgrim Hot Springs (PHS) has been the main geothermal exploration focus in the region, but multiple drilling efforts have not yet successfully targeted the geothermal system. The Kigluaik Mountains lie ~ 5 km south of PHS and are bound by an active normal fault system that has not been assessed as a structural control for geothermal upwelling. This study evaluates the relationship between the Kigluaik fault system (KFS) and PHS through the application of low temperature thermochronology from samples collected along the KFS trace and drill core from geothermal wells at PHS. Thermochronology from rocks collected from the exposed footwall of normal fault systems is a novel and cost-effective approach for discovering areas with blind hydrothermal activity. Samples along the KFS largely yield 40-25 Ma apatite (U-Th)/He (AHe) dates, with two samples yielding anonymously young average (13 Ma) dates. Two samples from drill core sampled directly in the KFS damage zone produced young single AHe grain dates of 9, 6, and 4 Ma. Areas with young AHe dates indicate zones with potential (active or fossil) blind geothermal systems and are considered future exploration targets. Thermochronology results do not indicate that PHS is directly controlled by the KFS. A concealed fault within the basin at a high angle to the KFS is likely the primary structure controlling upflow at PHS. AHe results from drill core in the zone of outflow at PHS are similar to young samples from the KFS and yield anomalously young single-grain ages that range from 13-0.5 Ma. GeoT multicomponent geothermometry estimates indicate 137°C reservoir temperatures for PHS and confirm prior estimates that the region contains moderate temperature geothermal systems that could be economic sources of renewable power once successfully targeted.

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