Direct access to the serpentinite subsurface; a biogeochemical investigation to characterize a unique habitat

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Author(s): Lang, Susan Q.; Lilley, Marvin D.; Frueh-Green, Gretchen L.; Orcutt, Beth
Author Affiliation(s): Primary:
University of South Carolina, Columbia, SC, United States
University of Washington at Seattle, United States
Eidgenössische Technische Hochschule Zürich, Switzerland
Bigelow Laboratory for Ocean Science, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The circulation of ocean water through ultramafic rocks generates hydrogen and methane that can sustain microbial communities. The ultramafic subsurface was the target of the International Ocean Discovery Program (IODP)'s first hard rock expedition specifically devoted to identifying subsurface life. Expedition 357 successfully recovered 17 cores along an east-west profile across the top of the Atlantis Massif, the ocean core complex that hosts the serpentinite-dominated Lost City hydrothermal field. In addition to the recovery of 57 m of core, multiple types of fluid samples were collected before, after, and during drilling to characterize the biogeochemical signatures of water that passes through the rocky subsurface. Here we present results focused on using organic molecules in the recovered rocks and fluids to identify subsurface life and metabolism. The concentrations of these molecules can reveal the spatial distribution of microbial communities while the isotopes can provide constraints on the metabolisms and carbon sources that these communities employ. These signatures are compared to elevated concentrations of hydrogen and methane in co-registered samples that demonstrate active serpentinization is widespread across the Atlantis Massif. Helium isotopes indicate the presence of an additional mantle-influenced fluid input that is distinct from the zones of highest hydrogen and methane concentrations. Biomarker concentrations in the rocks demonstrate a high degree of heterogeneity that reflects, in part, the local exposure to water circulation. Ultimately, the goal of this work is to relate physical and geochemical processes, such as detachment faulting, hydrothermal circulation, and water-rock reactions, to zones of microbial activity.
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Atlantic Ocean; Atlantis Massif; Biochemistry; Chemical composition; Expedition 357; Geochemistry; International Ocean Discovery Program; Marine sediments; Mid-Atlantic Ridge; North Atlantic; Sediments; Ultramafic composition
Coordinates: N300728 N301000 W0420350 W0421100
Record ID: 2017068205
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