Deep crustal production of hydrogen (H ₂ ) is a potential source of primary energy if recoverable accumulations in geological formations are sufficiently large. We report direct measurements of an elevated outgassing rate of 84% (by volume) of H ₂ from the deep underground Bulqizë chromite mine in Albania. A minimum of 200 tons of H ₂ is vented annually from the mine’s galleries, making it one of the largest recorded H ₂ flow rates to date. We cannot attribute the flux solely to the release of paleo-fluids trapped within the rocks or to present-day active and pervasive serpentinization of ultramafic rocks; rather, our results demonstrate the presence of a faulted reservoir deeply rooted in the Jurassic ophiolite massif. This discovery suggests that certain ophiolites may host economically useful accumulations of H ₂ gas.

Native hydrogen (H₂) may represent a new carbon free‐energy resource, but to date there is no specific exploration guide to target H₂‐fertile geological settings. Here, we present the first soil gas survey specifically designed to explore H₂ migration in a region where no surface seepage has been documented so far. We choose the Pyrenean orogenic belt and its northern foreland basin (Aquitaine, France) as a test site for our strategy. The presence of mantle rocks at shallow depth (<10 km depth) under the Mauléon Basin connected to the surface by major faults is considered as preliminary requisites for H₂ generation and drainage. On this basis, more than 1,100 in situ soil gas analysis (H₂, CO, CO₂, CH₄, H₂S, and ²²²Rn) were performed at ∼1 m depth at the regional scale along a 10 × 10 km grid spanning over 7,500 km². The analysis campaign reveals several areas of high occurrence to the north of the Mauléon Basin where H₂, CO₂, and ²²²Rn concentrations exceed 1,000 ppmv, 10 vol%, and 50 kBq m⁻³, respectively. Most of these hot spots are located along the North Pyrenean Frontal Thrust and other related faults rooted in the mantle body. These results, together with evidence from the literature of fluid migration at depth, suggest that H₂ may be sourced from mantle rocks serpentinization and carried to the surface along major thrusting faults. Traps containing hydrogen remain unidentified up to now but the presence of salt‐related structures (diapirs) near these hot spots is considered encouraging.

Molecular hydrogen (H₂), methane, and hydrocarbons with an apparent abiotic origin have been observed in a variety of geologic settings, including serpentinized ultramafic rocks, hydrothermal fluids, and deep fractures within ancient cratons. Molecular hydrogen is also observed in vapor plumes emanating from the icy crust of Saturn’s moon Enceladus, and methane has been detected in the atmosphere of Mars. Geologic production of these compounds has been the subject of increasing scientific attention due to their use by chemosynthetic biological communities. These compounds are also of interest as possible energy resources. This issue summarizes the geological sources of abiotic H₂ and hydrocarbons on Earth and elsewhere and examines their impact on microbial life and energy resources.