Redox evolution during peridotite alteration

Formation of oxidizing and simultaneously reducing metals such as Fe and Ni during serpentinization are key processes that control the total H₂ emissions of peridotite-hosted hydrothermal systems and the redox budgets of diverse geotectonic settings, effectively impacting the reduction capacity of Earth systems and controlling a potential metabolic energy source. One major factor controlling the efficiency of H₂ production is the partitioning of Fe²⁺ and Fe³⁺ into secondary phase assemblages (e.g., magnetite, serpentine, brucite) during specific stages of serpentinization, and the reaction rates and fluid properties that lead to the stabilization of these secondary phases (e.g., role of Al during olivine hydration). In this project we use µ-XANES spectroscopy to determine the Fe3+ distribution within serpentine. Similarly, in continental sites of active serpentinization biogenic activity is most likely active within the subsurface and facilitated by methane- and hydrogen-rich vents. Our current research focuses on the impact of such reducing fluids on the stability of sulfide minerals and how their decomposition potentially serves as an additional sulfur and metal source for biogenic communities living in these systems.