Almost all natural H2 seepages identified over the last 30 years, both on the continents and on the seafloors, are from ultramafic geological environments where olivine and pyroxene serpentinization is the source of H2. There is, however, another very different geological context where spectacular enrichments of H2 are documented, both in fluid inclusions and as free gas migration through rock fractures, mine galleries, and soils. These are peralkaline/agpaitic igneous intrusions, among which those of the Kola Peninsula in Russia (Khibiny and Lovozero) are the two world’s largest known occurrences. These two plutons host giant deposits of strategic metals (REE, Nb, Ta, Zr, Ti), and the emission of explosive gases (H2 and HCs) is a major hazard for miners. To this day, the sources and fluxes of H2 and associated gases are still unknown. Similarly, the role that these volatiles may have played in the genesis of the giant ore deposits associated with these plutons remains undocumented. This research project aims at investigating the behavior of H2, CH4 and other gases in these igneous intrusions, from their deep sources to the atmosphere into which they finally escape. The outcomes of this study will contribute to unravel many aspects that still remain controversial or altogether obscure on the origin and behavior of these gases, their relationship with the rare metal mineralizations, as well as their environmental impacts. Our ambition, through this case study, is to lay the foundation of H2 exploration, and to provide a global overview of H2 geochemical cycle from sources to seeps. To achieve this goal, we will combine: 1) Analytical developments: The aim is to i) set up a portable mass spectrometer to perform on-site measurements of the stable isotopic (C, O, H) composition of CH4, CO2, and to obtain He partial pressure; ii) develop new type of passive gas sensors based on gas physisorption, and iii) deploy a Cavity Ring-Down CH4 spectrometer on a drone. 2) Field studies of H2 and associated gas migration: This aspect will deal with: i) tracing the source and migration pathways of H2, CH4 and associated gases (He, Rn, CO2, N2, HCs); ii) measuring spatial and temporal variations of surface gas release, which will reveal the geological controls on gas migration. 3) Investigations on the consequences for ore genesis, environmental perturbations and energy resources: This part will focus on i) assessing the role of H2 and associated HCs of putative abiotic origin on ore-forming processes; ii) identifying biogeochemical anomalies in soils, and iii) setting up an exploration guide for natural H2 within an industrial perspective. Our consortium is composed of world-class specialists of these geological objects and H2 migration in the lithosphere. All needed skills and know-how are reunited within an interdisciplinary team to complete this project in a timely and efficient manner. In Russia, Drs. J.A. Mikhailova (PI Russia, mineralogy, petrology expert) and V.A. Nivin (gas geochemistry expert), together with junior researchers from the Kola Scientific Center, will lead the field investigations. In France, Prs. L. Truche (PI France, IUF Junior member) and F-V. Donzé (geomechanics) at ISTerre laboratory (Univ. Grenoble) are specialists in the abiotic reactivity of H2 and gas drainage in fault systems. They know Russia very well and have already established a collaboration with the KSC-RAS thanks to the CNRS-INSU project HyNa. Dr. S. Salvi (CNRS researcher), GET laboratory (Univ. Toulouse, France) is a world specialist of peralkaline granites and their associated ore deposits. In addition, biogeochemists will provide important savoir-faire for studying the impact of gas migration on surface ecosystems. Finally, 2 postdoc researchers, and 2 Master students will work in joint supervision between our laboratories, which will contribute to strengthen scientific relationships between the partners.