Exploring Helium in European Rifts: New Insights from the Upper Rhine Graben

Helium is a critical raw material for medical, industrial, and scientific applications, yet its global supply is largely dependent on hydrocarbon production, linking helium availability to CO₂ emissions and geopolitical constraints. This dependency has driven growing interest in alternative, low-carbon helium sources, particularly radiogenic helium systems associated with N₂-rich and CO₂-poor geological fluids. However, the geological controls on helium generation, migration, and accumulation in such non-hydrocarbon systems remain poorly constrained.

Radiogenic helium systems require the combination of a U–Th-enriched crystalline basement generating helium through alpha decay, sufficient heat to liberate helium from mineral hosts, and fault- and fracture-controlled pathways enabling upward migration while limiting diffusive loss. Where suitable reservoir and seal configurations exist, migrating helium may locally accumulate. Continental rift and geothermal provinces seem especially favourable for these conditions due to elevated heat flow, crustal thinning, and dense fault networks.

In this study, we first compile helium data from the literature to produce a Europe-wide map linking helium occurrence to rifts, sedimentary basins, and Variscan basement exposures, providing a european framework for helium exploration. New helium concentration data from thermal fluids in the Upper Rhine Graben are used to assess the spatial distribution of helium fluxes and their relationship with fault architecture. While near-surface degassing limits shallow accumulation, major fault systems emerge as first-order controls on helium transport. Their deeper continuations beneath sedimentary basins represent promising exploration targets where appropriate reservoir–seal configurations may allow helium retention. This study provides a preliminary framework to guide exploration of helium in European rift and geothermal settings.