A deep reservoir for hydrogen drives intense degassing in the Bulqizë ophiolite

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.