Examining the Effect of Heat from the Yellowstone Plume on the Release of Helium from the Crust

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Helium (He), which is an irreplaceable resource in low-carbon technologies, medical applications, and various science and engineering sectors, is currently being explored as a primary resource. The correlation between crustal helium (He) release and heat flow in certain geologic environments (e.g., mid-ocean ridge and continental hydrothermal systems) is well established, but few studies have evaluated how past igneous processes influence current gas release/storage from crustal rocks. Here, we report bulk gas and noble gas geochemistry data (n = 43) gathered from thermal springs in and around the Yellowstone National Park (YNP), USA. Samples outside the YNP (near the plume track) are dominantly N 2 -rich, while most samples collected within the active caldera area are CO 2 -rich. Samples outside the YNP typically have much lower 3 He/ 4 He than those within the caldera (i.e., near the current plume head). We explore the relationship between thermal aureoles and He isotopic signatures using heat flow data coupled with bulk gas and noble gas geochemistry data. Data are used to determine gas origins, to understand fluid flow in a regional context, and to assess how different environments impact He release from crustal minerals. Models indicate that advection is the dominant process controlling heat and volatile loss from mantle to crustal systems from the Yellowstone Caldera. In contrast, the influence of conduction/boiling of crustal hydrothermal fluids is more substantial for samples outside of the Yellowstone Caldera. Helium-4 is enriched in the samples which are frontal and near the eruptive center, likely due to recent crustal degassing of 4 He accumulated over long periods in the underlying craton. Ultimately, He and other volatiles are released due to tectonic activity and/or they are enriched as other gases partition out of groundwater (i.e., gas stripping from groundwater). However, elevated heat flow zones likely constitute poor He retention zones. We propose a twofold approach to help identify preferential zones of He release: 1) focusing on areas that are distal from active igneous zones (i.e., areas that have not been fully degassed) with localized moderate heat flow to release trapped crustal He, and 2) utilizing isotope models to constrain groundwater interactions (i.e., migration and accumulation potential).

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