Natural hydrogen generated mainly by water–rock interactions, particularly oxydo-reduction of Fe-bearing rocks, is increasingly investigated as both a fundamental geological process and a potential subsurface resource. While geological H₂ generation has been observed, major uncertainties remain regarding production rates, pathways, geochemical and biological sinks, and accumulation in the subsurface.
Addressing these questions requires moving towards an integrated understanding of the natural hydrogen system, from source to accumulation. Bridging fundamental research and exploration is essential: process-based knowledge provides the framework for interpreting subsurface observations, while exploration datasets offer unique opportunities to test hypotheses at the scale of natural systems.
This session invites multidisciplinary contributions addressing the different components of natural hydrogen systems: water sources, circulation and access to reactive rocks; geometry and dynamics of ultramafic source regions; serpentinization mechanisms, reaction kinetics and H₂ generation; structural controls and migration pathways; geochemical and biological sinks; gas–water–rock interactions and gas mixtures; reservoir properties, trapping and sealing mechanisms; and H₂ accumulation and preservation.
We particularly welcome studies integrating geology, structural geology, petrology, geochemistry, microbiology, laboratory experiments, numerical and reactive-transport modelling, and geophysical imaging, including seismic, electromagnetic, gravity, magnetic and multiphysics approaches.
A central objective is to connect processes with observable signatures: What transforms an H₂-generating geological environment into a functioning natural hydrogen system? Which observations can constrain its source, activity, migration pathways and potential accumulation? By connecting fundamental understanding with subsurface observations, this session aims to advance both the science and exploration of natural hydrogen.