Global presence of H₂_GR indicated on a topographic map (ESRI National Geographic USA Topo Maps). (a) The spatial distribution of ophiolites from Vaughan and Scarrow (2003). (b) Cratonic and proterozoic zones (Furnes et al., 2015) combined with fairy circles location (Larin et al., 2015; Zgonnik et al., 2015) and BIFs (Aftabi et al., 2021). (c). Distribution of uranium provinces differentiated by lithologies from the International Atomic Energy Agency (2021). (d) Spatial distribution of coal deposits. Note that dots from the study of Zgonnik (2020) correspond to H₂ detections in various environments at concentrations >10 vol.%.