Magnetotelluric constraints on natural hydrogen potential in the southern Gawler Craton, Australia

Abstract Natural (or ‘gold’) hydrogen is emerging as a cost-effective and transformative renewable energy resource, with South Australia at the forefront of global exploration initiatives. Here, we assess the potential for natural hydrogen prospectivity in the southern Gawler Craton using magnetotelluric, geomagnetic depth sounding and other geophysical data. We present a comprehensive regional-scale three-dimensional resistivity model of an intracontinental natural hydrogen system, delineating crustal resistivity variations that may be linked to generation of geological hydrogen, and its migration to surface. The Eyre Peninsula, situated on Archean to Paleoproterozoic Gawler Craton, has a demonstrated potential for hydrogen generation through serpentinisation of mafic basement rocks, radiolysis from naturally occurring uranium and thorium, and possibly mantle degassing along lithospheric-scale faults. Our results identify mid-crust (5–15 km depth) low-resistivity zones (<10 Ω.m) attributed to carbon-rich Paleoproterozoic sediments deposited in a deep basin setting, which likely host uranium-rich lithologies favourable for hydrogen generation via radiolysis. At greater depths (>15 km), we interpret underlying granulite-facies mafic lower crust, potentially facilitating deep-seated hydrogen production through serpentinisation. Crustal-scale faults, repeatedly reactivated during multiple Proterozoic orogenic events and are seismically active in the current intracontinental stress regime, bound the low-resistive regions and are potential conduits for hydrogen migration. Mapping structural continuity of such faults provides a framework for defining regional-scale hydrogen prospectivity and identifying new exploration targets. KEY POINTS Magnetotelluric imaging identifies mid-crustal low-resistivity zones (<10 Ω·m) within the Hutchison Group, interpreted to reflect graphite-bearing metasediments formed during Paleoproterozoic carbon burial and subsequent metamorphism. The observed resistivity architecture is compatible with lithological and structural environments that may host processes associated with geological hydrogen generation, such as serpentinisation in mafic crust, radiolysis in U–Th-rich granitoids and low-temperature reactions in iron-rich sediments. Crustal-scale fault systems, particularly the Kalinjala Shear Zone, coincide with sharp resistivity contrasts and seismicity, suggesting they may act as potential pathways for deep-to-shallow fluid and gas migration. These results provide geophysical constraints on the subsurface architecture of a prospective natural hydrogen system, offering a framework to guide future exploration and testing in stable cratonic settings.