Serpentinites are rocks composed of serpentine group minerals, which are produced by hydrothermal alteration of olivine-rich, ultra-mafic rocks exposed primarily on mid oceanic ridges. Seafloor serpentinite-hosted hydrothermal systems are unique habitats due to the fact that hydrogen and methane produced by serpentinization reactions can be utilized by microorganisms to gain metabolic energy. The abundance of chemical energy makes serpentinites a strong candidate site for the origin of life on Earth, as well as a prime target in the search for extraterrestrial life. Serpentinization reactions produce carbonate minerals, sequestering carbon dioxide. These so-called carbonation reactions occur where peridotites are altered in the subseafloor as well as on land. Despite considerable effort, the processes governing methane formation and carbonate precipitation associated with serpentinization are still not sufficiently understood. The role of microbial methanogenesis and possibly methanotrophy in the cycling of carbon and mineral authigenesis is even less well constrained. This study investigates serpentinization and serpentinite-hosted carbonates of the Ronda ophiolite in Andalusia (Spain), where highly alkaline spring and pool waters trigger carbonate precipitation and harbor a unique consortium of microorganisms.
“Eternal flames” of Cirali (Turkey) linked to onshore methane seepage and serpentinization.