Geological Hydrogen Prospectivity of Iron Ore Deposits in India Based on Semiquantitative Analysis

With increasing focus on clean energy, naturally occurring hydrogen in geological reservoirs represents a potentially attractive energy resource. Studies suggest that the quantity of recoverable subsurface hydrogen is potentially abundant and could have contributed substantially to the global energy supply for several decades. However, the exploration and exploitation processes and technologies for identifying and extracting these potential resources, remain poorly developed. This study presents a semiquantitative approach to provisionally identify the target areas suitable for hydrogen-resource exploration based on prospectivity mapping with available data for India. The proposed approach uses ARCGIS software to generate distance classifications based on positive Bouguer gravity anomalies and the presence of fault systems and surface water bodies relative to identified iron ore deposit locations. These basic measurements provide a provisional identification of geological systems likely to be favorable for the existence of subsurface hydrogen reservoirs. As a first step, the map of India was divided into grids and the locations of known iron ore deposits were identified, highlighting the Indian states with the greatest potential for geologic hydrogen resources. For each of the five states identified, three classification maps corresponding to positive Bouguer anomalies, faults, and surface water bodies, were plotted in terms of their Euclidean distances from known iron ore deposit locations. Favorability scores ranging between 0.1 and 1.0, were assigned based on the distances established for each location using these parameters. The maximum favorability score, 1.0 was assigned to the minimum distance on the classification map, whereas a score of 0.1 referred to the maximum distance. An integrated weighted-average favorability index was defined for each location. The applied weighting factors corresponding to positive Bouguer anomalies, faults, and surface waterbodies were 0.6, 0.2, and 0.2 respectively. Furthermore, magnetic anomalies (with data available for only certain locations), the presence of mafic/ultramafic lithologies, and aquifer systems were qualitatively checked for the identified locations, providing additional evidence of high concentrations of iron-bearing magnetic minerals. The results of the analysis suggest that the state of Karnataka has locations displaying the highest average weighted-average favorability index (prospectivity) score (0.921) for geological hydrogen. Tamil Nadu, Odisha, and Jharkhand also possess some locations considered suitable for hydrogen exploration. Andhra Pradesh was identified as having the lowest potential for hydrogen exploration of the five Indian states assessed. Overall, relatively few iron ore deposit sites were identified with high weighted-average favorability indices.