Complex serpentinizing systems and the deep biosphere: metabolic opportunities depend on the geochemistry of mixing waters

A suite of field sites located on or near serpentine associated with a peridotite from Turkey (southern strand of the Northern Anatolian Fault Zone) allow simultaneous evaluation of the geology, mineralogy, aqueous geochemistry, and microbiology. In this work, we present aqueous geochemistry of spring fluids tapping subsurface hydrological regimes impacted to differing extents by serpentinization of regionally important ultramafic blocks and also by ongoing hydrothermal activity and infiltration of meteoric water (see summary table below). We model the feasibility of metabolisms including sulfate reduction, iron oxidation, nitrate reduction, methanogenesis, and methanotrophy based on the geochemistry of spring, seep, and thermal well waters. We predict that microbiology should follow geochemistry in this subsurface environment, and clarify geochemical controls on chemosynthetic metabolisms in serpentinizing systems and systems in which serpentinization co-occurs with other geological processes, in relevant mixing scenarios. The finding that subsurface mafic and ultramafic rock formations can, and apparently do (see companion poster, Meyer-Dombard et al.), host microbial life has direct implications for origin of life debates and astrobiology.