Geochemistry — including chemical and isotopic (e.g., O, H, C, S, Sr, Li, Pb) characterisation of liquid, gaseous and solid phases — is one of the most effective tools for exploring and managing natural resources such as oil, gas and geothermal reservoirs in volcanic and sedimentary basins, critical raw materials, and mineral ore deposits. In addition, geochemistry plays a crucial role in both monitoring and exploration of subsurface hydrogen and carbon storage. By combining natural fluid samples with thermodynamics and experimental studies on water-gas-rock interactions, we can better understand the deep subsurface processes, chemical and isotopic equilibria governing fluid composition under varying pressure-temperature conditions and the distribution, mobilisation, and migration of elements.

The microbial diversity in the Earth’s subsurface — including bacteria, archaea, and fungi — also influences the chemistry of fluids and may control the motion, stability and availability of many raw elements and chemicals commonly used as tracers for natural resources. Moreover, microbial reactions can control the accumulation and release of many compounds, leading either to the formation of mineral deposits or to their dissolution into the surrounding environments. Improving the understanding of biochemical processes would refine consolidated geochemical principles, based only on inorganic reactions, and create new, reliable geo(bio)tracers for natural resource exploration and management.

We invite interdisciplinary studies that bridge geochemistry, biochemistry, biology, hydrology, geology, and geophysics with modelling, fieldwork, or applied resource management aimed at exploring, monitoring, and sustainably managing natural resources. This session particularly encourages innovative approaches, including: (i) advanced analytical techniques, such as non-conventional stable and radiogenic isotopes, chemical and biological tracers, and geo(bio)indicators; (ii) novel sampling protocols; (iii) statistical tools and thermodynamic models for data interpretation; (iv) machine learning techniques for complex datasets. This session aims to advance both the fundamental understanding of fluid–rock systems and the sustainable use of natural resources and, on the other hand, open new frontiers into the development of biomarkers to better understand the fate of elements in the subsoil and unravel the dark secrets of the Earth’s hidden subsurface.