The Snake River Plain is an area characterized by high heat flow and abundant Quaternary volcanism. While USGS assessments indicate that significant undiscovered geothermal resources are likely to be present in this region, no commercial geothermal development in this region has occurred. Elevated 3He/4He values reflect crustal input of mantle volatiles and may serve as a geochemical indicator of hidden geothermal systems that are masked by the presence of shallow cold water aquifers. This study is part of an integrated geochemical investigation of thermal features in the central and eastern Snake River Plain region. Our project started by compiling existing He isotope data, regional heat flow data, and the locations of thermal wells and springs to develop compositional trends and identify new sampling opportunities where data gaps exist. Our initial field work has resulted in the highest 3He/4He measurements ever reported for the Snake River Plain, with three locations having Rc/Ra values greater than 2.0, suggesting that we can see through the effects of shallow cold water aquifers to indicate the presence of mantle-derived fluid and heat input into the shallow crust. Our new He isotopic results and previously reported data for the Snake River Plain range from 0.05 to 2.36 Rc/Ra. These results will be evaluated in conjunction with the results of conventional, isotopic, and multicomponent geothermometry studies.

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