Serpentinization is the geochemical alteration of rocks that were originally formed in Earth’s mantle. When these mantle rocks are uplifted into the seafloor, hydrothermal systems, like the Lost City hydrothermal field, can be formed. When these mantle rocks are uplifted into continental crust (typically after they had been on the seafloor for millions of years), then products of serpentinization can be seen on land.
The Coast Range Ophiolite Microbial Observatory (CROMO) was established in 2011 with funds provided by the NASA Astrobiology Institute. Eight new boreholes were drilled with ultra-clean methods, including the use of purified water as the only drilling lubricant. Groundwater sampled from the boreholes has an extremely high pH (>12) and contains hydrogen and methane gas, signatures of serpentinization.
Natural serpentinite springs can be seen at the Tablelands Ophiolite in Gros Morne National Park, Newfoundland, Canada. Ultramafic rocks of the Tablelands Ophiolite (also known as the Bay of Islands Ophiolite) were uplifted from the Iapetus Ocean and obducted onto the continental margin of Laurentia approximately 485 million years ago.
Serpentinization remains evident today in the form of highly reducing, ultrabasic springs with extremely high pH (>12.5).
After starting my lab at the University of Utah, Emily Dart and I conducted an experiment at the Tablelands with Penny Morrill to identify potential subsurface microbes. This was Emily’s undergraduate honors thesis, which is available as a preprint:
Penny Morrill’s team has continued to publish excellent work from the Tablelands:
Kohl, L., Cumming, E., Cox, A., Rietze, A., Morrissey, L., Lang, S. Q., … & Morrill, P. L. (2016). Exploring the metabolic potential of microbial communities in ultra‐basic, reducing springs at The Cedars, CA, USA: experimental evidence of microbial methanogenesis and heterotrophic acetogenesis. Journal of Geophysical Research: Biogeosciences, 121(4), 1203-1220. HTML
Morrissey, L. S., & Morrill, P. L. (2017). Flux of methane release and carbon dioxide sequestration at Winterhouse Canyon, Gros Morne, Newfoundland, Canada: a site of continental serpentinization. Canadian Journal of Earth Sciences, 54(3), 257-262. HTML
Cumming, E. A., Rietze, A., Morrissey, L. S., Cook, M. C., Rhim, J. H., Ono, S., & Morrill, P. L. (2019). Potential sources of dissolved methane at the Tablelands, Gros Morne National Park, NL, CAN: A terrestrial site of serpentinization. Chemical Geology, 514, 42-53. HTML
Cook, M. C., Blank, J. G., Suzuki, S., Nealson, K. H., & Morrill, P. L. (2021) Assessing Geochemical Bioenergetics and Microbial Metabolisms at Three Terrestrial Sites of Serpentinization: the Tablelands (NL, CAN), The Cedars (CA, USA), and Aqua de Ney (CA, USA). Journal of Geophysical Research: Biogeosciences, e2019JG005542. HTML
Cook, M. C., Blank, J. G., Rietze, A., Suzuki, S., Nealson, K. H., & Morrill, P. L. (2021) A Geochemical Comparison of Three Terrestrial Sites of Serpentinization: The Tablelands, The Cedars, and Aqua de Ney. Journal of Geophysical Research: Biogeosciences, e2021JG006316.HTML
The Voltri Massif in northern Italy is a geological formation that was originally on the ocean floor 200 - 250 million years ago.
It hosts natural springs (pH 11–12) that have an important role in the local Italian culture, where the extremely alkaline spring water is used for bathing and drinking.
The springs were surveyed and catalogued by Italian scientists, including a key early study by Cipolli et al. (2003).
Gretchen Früh-Green of ETH-Zurich has led recent studies of the Voltri Massif springs, including the Ph.D. dissertation of Esther Schwarzenbach:
Schwarzenbach, E. M., Früh-Green, G. L., Bernasconi, S. M., Alt, J. C., Shanks III, W. C., Gaggero, L., & Crispini, L. (2012). Sulfur geochemistry of peridotite-hosted hydrothermal systems: comparing the Ligurian ophiolites with oceanic serpentinites. Geochimica et Cosmochimica Acta, 91, 283-305. HTML
Schwarzenbach, E. M., Früh-Green, G. L., Bernasconi, S. M., Alt, J. C., & Plas, A. (2013). Serpentinization and carbon sequestration: A study of two ancient peridotite-hosted hydrothermal systems. Chemical Geology, 351, 115-133. HTML
Schwarzenbach, E. M., Lang, S. Q., Früh-Green, G. L., Lilley, M. D., Bernasconi, S. M., & Mehay, S. (2013). Sources and cycling of carbon in continental, serpentinite-hosted alkaline springs in the Voltri Massif, Italy. Lithos, 177, 226-244. HTML
Alt, J. C., Schwarzenbach, E. M., Früh-Green, G. L., Shanks III, W. C., Bernasconi, S. M., Garrido, C. J., … & Marchesi, C. (2013). The role of serpentinites in cycling of carbon and sulfur: seafloor serpentinization and subduction metamorphism. Lithos, 178, 40-54. HTML
The Brazelton lab conducted the first survey of microbial diversity in the Voltri Massif springs, including metagenomic and laboratory investigations of metabolic activity.
We showed that the pH 12 springs of the Voltri Massif are transporting distinct archaeal and bacterial communities, including methanogenic archaea and methanotrophic bacteria, from subsurface habitats where they are likely to be supported by hydrogen gas, methane, and possibly other products of serpentinization-associated reactions.