Low Temperature Serpentinization: Natural H2 Generation and CO2 Storage by Carbonation within the Semail Ophiolite
Presenter
Dr. Gabriel Pasquet
Postdoctoral Researcher
Bureau of Economic Geology
Jackson School of Geosciences
The University of Texas at Austin
Description
The northern Semail Ophiolite in the United Arab Emirates provides new insights into natural hydrogen (H2) generation. Surface gas surveys in the Emirate of Ras Al Khaimah reveal significant H2 emissions, with concentrations up to 88% after air correction, often associated with alkaline blue pools (pH >9) where ongoing carbonation occurs. Structural features such as faults, lithological contacts, and structural windows exposing the metamorphic sole act as preferential migration pathways. Gas compositions are highly variable, ranging from H2-rich to N2- and CH4-rich emissions, and a marked seasonal fluctuation of the H2/N2 ratio highlights the crucial role of groundwater dynamics in regulating gas production. These observations underline the strong influence of water circulation in sustaining H2 generation.
Mineralogical evidence supports these findings, showing that serpentinization continues at low temperature (<100°C). Unlike high-temperature systems (>200°C), which produce magnetite alongside H₂, these magnetite-poor assemblages host ferrobrucite within mesh textures and as rims around olivine relics. This phase buffers Fe2+ release, allowing redox reactions to proceed and maintain H2 production. The interplay between structural controls, fluid influx, and mineralogical processes emphasizes that both gas variability and mineral transformations are key to understanding natural hydrogen generation in the northern Semail Ophiolite, a promising region for future hydrogen exploration and CO2 storage.
