Sulfur mass-independent fractionation in subsurface fracture waters indicates a long-standing sulfur cycle in Precambrian rocks

The discovery of hydrogen-rich waters preserved below the Earth’s surface in Precambrian rocks worldwide expands our understanding of the habitability of the terrestrial subsurface. Many deep microbial ecosystems in these waters survive by coupling hydrogen oxidation to sulfate reduction. Hydrogen o...

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Bibliographic Details
Published in:Nature communications 2016-10, Vol.7 (1), p.13252-13252, Article 13252
Main Authors: Li, L., Wing, B. A., Bui, T. H., McDermott, J. M., Slater, G. F., Wei, S., Lacrampe-Couloume, G., Lollar, B. Sherwood
Format: Article
Language:English
Subjects:
704/2151/209
704/2151/213/4114
704/47/4112
Earth science
Electrons
Humanities and Social Sciences
Metamorphism
Minerals
multidisciplinary
Oxidation
Science
Science (multidisciplinary)
Sulfur
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Summary:The discovery of hydrogen-rich waters preserved below the Earth’s surface in Precambrian rocks worldwide expands our understanding of the habitability of the terrestrial subsurface. Many deep microbial ecosystems in these waters survive by coupling hydrogen oxidation to sulfate reduction. Hydrogen originates from water–rock reactions including serpentinization and radiolytic decomposition of water induced by decay of radioactive elements in the host rocks. The origin of dissolved sulfate, however, remains unknown. Here we report, from anoxic saline fracture waters ∼2.4 km below surface in the Canadian Shield, a sulfur mass-independent fractionation signal in dissolved sulfate. We demonstrate that this sulfate most likely originates from oxidation of sulfide minerals in the Archaean host rocks through the action of dissolved oxidants (for example, HO · and H 2 O 2 ) themselves derived from radiolysis of water, thereby providing a coherent long-term mechanism capable of supplying both an essential electron donor (H 2 ) and a complementary acceptor (sulfate) for the deep biosphere. Precambrian rocks host a deep hydrosphere, but where dissolved sulfate, crucial for microbial life, comes from is unclear. At 2.4 km depth in the Canadian shield, Li et al . find that oxidation of sulfides in the host rocks creates sulfate thus providing a long-term mechanism for the deep biosphere sulfate.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms13252