TRACKING SHIFTS IN BIOGEOCHEMICAL INTERACTIONS IN ULTRAMAFIC ROCK SYSTEMS

Serpentinization is the aqueous alteration of iron- and magnesium-rich primary minerals into serpentine-dominated secondary mineral assemblages, and is a water-rock reaction that evolves H₂, CH₄, diverse carbon compounds, and distinctive fluid chemistries known to host unusual microbial communities in deep-sea vent and continental aquifer settings. Modern environments impacted by serpentinization range from relatively young systems, where unaltered primary minerals dominate the solid phases, to mature systems, where secondary minerals dominate the solids; related fossil systems are those in which serpentinization has ceased, and subsequent dissolution and weathering processes transform/have transformed the solid phases and co-evolving waters. In this study, (1) sets of co-occurring minerals are presented as indicators of characteristic stages in the transformation of ultramafic rocks, and (2) simultaneously changing H₂ yields are charted, providing a tentative proxy for chemosynthetic habitability.