230-3 Hidden Hydrogen: Quantifying the Potential of Partially Serpentinized Peridotites

Session: The Power of Hard Rocks: Driving the Energy Transition and Serving Society (Posters)

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Abstract:

As interest in sustainable / green energy sources rises rapidly, a new potential source of energy has been identified in serpentinized peridotites that naturally produce hydrogen. Relatively large volumes of mantle peridotites occur at or near the surface of the Earth, in relatively few localities, where they generally alter through serpentinization. This chemical reaction involves water and produces serpentine minerals, magnetite, and hydrogen gas (H₂).

Determining the potential for hydrogen production requires knowledge of the volume of peridotites at depth and their degree of serpentinization. Peridotite density (r) correlates negatively with degree of serpentinization (S%) and is the best proxy for S%. Also, previous investigations have suggested that the magnetic susceptibility (χ) logarithmically increases with increasing S% and therefore χ would correlate positively with S%. This approach is commonly used as well to invert aeromagnetic data and estimate the volume of peridotites at depth, below the surface. The density of peridotites (r) is the keystone needed to invert gravimetric data and when combined with inversion of aeromagnetic data provides unique solutions to define shape, depth and extend of subsurface peridotite bodies. Ultimately both χ and are r essential for geophysical exploration of peridotite bodies and their potential as a source of hydrogen. The quasi-linear relationship between logχ and r varies from peridotite massif to massif as a function of peridotite composition. Here we show that the saturation magnetization (M_s) of serpentinized peridotites is a better proxy for S% than χ because it relates directly to the mass of magnetite produced and is not affected by reaction type or magnetite grain size. Ms is thus used to determine the amount of magnetite and hydrogen already produced. The amount of hydrogen already produced informs on the potential of the rock to produce additional hydrogen.

Most serpentinization investigations have focused on common oceanic peridotite i.e. harzburgites and refractory bodies in ophiolites i.e. dunites. Surprisingly, although the magnetic properties of unaltered lherzolites have been previously studied very few petrophysical investigations have been performed yet on serpentinized lherzolites.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8924

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