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Aqueous geochemical and microbial variation across discrete depth intervals in a peridotite aquifer assessed using a packer system in the Samail Ophiolite, Oman
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  • Daniel Nothaft,
  • Alexis S Templeton,
  • Eric Boyd,
  • Juerg Matter,
  • Martin Stute,
  • Amelia N Paukert Vankeuren
Daniel Nothaft
University of Colorado - Boulder, University of Colorado - Boulder

Corresponding Author:daniel.nothaft@colorado.edu

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Alexis S Templeton
University of Colorado Boulder, University of Colorado Boulder
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Eric Boyd
Montan State University, Montan State University
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Juerg Matter
University of Southampton, University of Southampton
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Martin Stute
Columbia University, Columbia University
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Amelia N Paukert Vankeuren
Sacramento State University, Sacramento State University
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The potential for molecular hydrogen (H-OH- groundwaters bearing up to 4.05 μmol⋅L-1 H2 , 3.81 μmol⋅L-1 methane (CH4) and 946 μmol⋅L-1 sulfate (SO42-) revealed an ecosystem dominated by Bacteria affiliated with the class Thermodesulfovibrionia, a group of chemolithoheterotrophs supported by H2 oxidation coupled to SO42- reduction. In shallower, oxidized Mg2+-HCO3- groundwaters, aerobic and denitrifying heterotrophs were relatively more abundant. High δ13C and δD of CH4 (up to 23.9 ‰ VPDB and 45 ‰ VSMOW , respectively), indicated microbial CH4 oxidation, particularly in Ca2+-OH- waters with evidence of mixing with Mg2+-HCO3- waters. This study demonstrates the power of spatially resolving groundwaters to probe their distinct geochemical conditions and chemosynthetic communities. Such information will help improve predictions of where microbial activity in fractured rock ecosystems might occur, including beyond Earth.
Sep 2021Published in Journal of Geophysical Research: Biogeosciences volume 126 issue 9. 10.1029/2021JG006319