• DOI:10.2138/RMG.2013.75.18
• Corpus ID: 8600635

Serpentinization, Carbon, and Deep Life

@article{Schrenk2013SerpentinizationCA,
  title={Serpentinization, Carbon, and Deep Life},
  author={Matthew O. Schrenk and William J. Brazelton and Susan Q. Lang},
  journal={Reviews in Mineralogy \& Geochemistry},
  year={2013},
  volume={75},
  pages={575-606}
}

• M. Schrenk, W. Brazelton, S. Lang
• Published 2013
• Geology
• Reviews in Mineralogy & Geochemistry

The aqueous alteration of ultramafic rocks through serpentinization liberates mantle carbon and reducing power. Serpentinization occurs in numerous settings on present day Earth, including subduction zones, mid-ocean ridges, and ophiolites and has extended far into Earth’s history, potentially contributing to the origins and early evolution of life. Serpentinization can provide the energy and raw materials to support chemosynthetic microbial communities that may penetrate deep into Earth’s subsurface. Microorganisms may also influence the composition and quantity of carbon-bearing compounds in the deep subsurface. However, conditions created by serpentinization challenge the known limits of microbial physiology in terms of extreme pH, access to electron acceptors, and availability of nutrients. Furthermore, the downward transport of surface carbon and subsequent mixing with calcium-rich fluids at high pH contributes to the precipitation and immobilization of carbonate minerals. The following chapter will explore the physiological challenges presented by the serpentinite environment, data from studies of serpentinite-hosted microbial ecosystems, and areas in need of further investigation.

### Physical and chemical consequences of serpentinization

Serpentinization is an alteration process of low-silica ultramafic rocks, characteristic of the lower oceanic crust and upper mantle. These rocks are rich in the minerals olivine and pyroxene. Water-rock reactions result in the oxidation of ferrous iron from olivine and pyroxene, resulting in the precipitation of ferric iron in magnetite (Fe3O4) and other minerals, and in the release of diatomic hydrogen (H2). At low temperatures (< ~150 °C) the reaction results in extremely high pH, commonly above 10. The combination of H2 and CO2 or CO under highly reducing conditions leads to formation of methane and other hydrocarbons through Fischer-Tropsch Type (FTT) synthesis (McCollom and Seewald 2001; Charlou et al. 2002; Proskurowski et al. 2008; McCollom 2013). Serpentinization also results in volume changes in the altered materials, making serpentinites less dense than …