As the world explores alternatives to fossil fuels, hydrogen (H₂) has emerged as a critical element in accelerating the transition to clean and renewable energy sources (Gaucher et al., 2023; Le et al., 2023; Blay-Roger et al., 2024). Unlike gasoline, which emits CO2 when burned, H₂ combustion produces only water vapor, making it a high-quality and environmentally friendly fuel alternative. Hydrogen is primarily produced for industry processes, including green hydrogen, blue hydrogen, and gray hydrogen (IEA, 2019). On the other hand, the so-called natural or white hydrogen is potentially a more cost-effective and environmentally friendly alternative because it is ready to be used for energy production, without the need for polluting processes to obtain it (Smith et al., 2005; Lapi et al., 2022; Gaucher et al., 2023; Blay-Roger et al., 2024). However, H₂ accumulation in the subsurface has been largely overlooked due to assumptions of its rarity or nonexistence, attributed to the hydrogen’s inheritance characteristics (small and reactive molecule). The first fortuitous discoveries in the USA or Mali (West Africa) proved that it was a mistake (Zgonnik, 2020).
Currently, the geological processes that generate natural hydrogen have started to be better understood, but the conditions for its accumulation remain poorly constrained (Lévy et al., 2023). The potential for global extraction of natural hydrogen is significant, so it is critical that we understand how it is generated, transported, and ultimately trapped. Recent discoveries of natural hydrogen in various geological settings, including mid-ocean ridges, ophiolitic nappes, transform faults, convergent subduction margins, and intraplate settings (Zgonnik et al., 2020; Jackson et al., 2024) highlight the increasing interest in this resource. As a result, exploration projects are currently active in several countries such as Australia, the USA, France, Spain, and South America (e.g., Zgonnik et al., 2020, Jackson et al., 2024). Experience in managing H₂ reservoirs is obviously still missing, but the analogies should perhaps rather be sought in the field of geothermal energy (Moretti et al., 2023).
In terms of geotectonic settings of natural hydrogen formation, subduction zones represent the primary geological environment for the large-scale interaction between water and mantle peridotite, i.e., serpentinization processes (Zgonnik et al., 2020). Serpentinization is the most effective and hence important subsurface process for producing and focusing natural hydrogen in potentially commercial volumes (Jackson et al., 2024). Particularly, in the Central Andean Volcanic Zone (CAVZ; 18-28°S; Fig. 1a) only a limited number of investigations have focused on natural hydrogen data. Moretti et al. (2023) confirmed the presence of natural hydrogen in the Bolivian Altiplano (e.g., Pampa Lirima and Sol de Mañana; Fig. 1a) by using geochemical measurements of gasses from hot springs and in-situ analysis of soil gas. Moreover, the 3He/4He ratios in the Altiplano-Puna plateau indicate that the amount of He uprising from the mantle (i.e., 3He content) is very large (Fig. 1b). This indicates that deep gasses are migrating toward the overriding plate surface above subduction (Fig. 1c). Based on the findings of Moretti et al. (2023), it is highly probable to find natural hydrogen in the Chilean portion of the Altiplano. In this context, the proposed research plans to unlock the geological origin and assess the potential of natural hydrogen in northern Chile. Moreover, this project goes one step further than the study of Moretti et al. (2023) and proposes to investigate the potential occurrences of natural hydrogen associated with specific structural arrangements related to volcanic and geothermal systems (Veloso et al., 2019). For that reason, the acquisition of new geological, structural, geochemical, seismological, and geophysical data is crucial to better understand natural hydrogen systems and to determine the prospectivity of new areas in Chile.